Neurologic/Head and Neck ImagingFree Access
Wayne S. Fang , Richard H. Wiggins, III, Anna Illner, Bronwyn E. Hamilton, Gary L. Hedlund, Jason P. Hunt, H. Ric Harnsberger
Author Affiliations
From the Departments of Radiology (W.S.F., R.H.W., H.R.H.) and Otolaryngology (J.P.H., H.R.H.), University of Utah, Salt Lake City, Utah; Department of Diagnostic Imaging, Texas Children's Hospital, Houston, Tex (A.I.); Department of Radiology, Oregon Health & Science University, Portland, Ore (B.E.H.); and Department of Radiology, Primary Children's Medical Center, Salt Lake City, Utah (G.L.H.).
Address correspondence to W.S.F., Seattle Radiologists, 1229 Madison St, Seattle, WA 98040 (e-mail: fang.wayne@yahoo.com).
Published Online:Nov 8 2011https://doi.org/10.1148/rg.317095738
Sections
PDF
Tools
Share
Abstract
In the assessment of the head and neck, differential diagnoses can be formulated by subdividing the anatomy into spaces along identifiable and logical boundaries. In the oral cavity, the root of the tongue is notably unlike adjacent regions due to structural and tissue-specific differences. The majority of lesions found in the root of the tongue are congenital and benign, representing ectopic tissues of thyroidal, epidermal, dermal, foregut, venous, and lymphatic origin. A greater number of acquired neoplasms and infections are seen in the adjacent sublingual, submandibular, and oropharyngeal regions of the base of the tongue, presumably due to their greater exposure to mucosal surfaces and lymphatic tissues. Many lesions of the root of the tongue have clinical and imaging characteristics that can help narrow the differential diagnosis, and surgical management may be required. Familiarity with these lesions and how they differ from other lesions of the oral cavity and oropharynx can significantly aid in their diagnosis and treatment.
© RSNA, 2011
LEARNING OBJECTIVES FOR TEST 3
After completing this journal-based CME activity, participants will be able to:
•.
Identify the boundaries of the root of the tongue.
•.
Describe the defining imaging features of lesions of the root of the tongue.
•.
Discuss the structural attributes of the root of the tongue that help distinguish it from adjacent spaces.
Introduction
What makes the head and neck region so challenging and interesting is its compact geography of small but important structures. Assessment of the head and neck is greatly aided by the generation of differential diagnoses using subdivision of the anatomy into spaces along identifiable and logical boundaries. Tailored space-specific differential diagnoses can be formulated by recalling the anatomic contents of the spaces.
The root of the tongue is an important subregion of the oral cavity, associated with very specific differential diagnoses. It is relatively resistant to primary neoplastic and infectious processes due to its high percentage of skeletal muscle and lack of significant lymphatic tissue (1). In contrast, many acquired lesions are found within adjacent regions such as the base of the tongue and the sublingual and submandibular spaces. Squamous cell carcinoma invariably invades the deep tongue from adjacent mucosal surfaces of the oral cavity and anterior oropharynx and does not originate from the deep tongue structures (2). Accurately localizing a lesion to the root of the tongue can significantly narrow the differential diagnosis.
In this article, we review the normal tongue anatomy, make recommendations for the imaging of lesions of the root of the tongue, discuss the imaging features of a variety of such lesions (congenital nonvascular, congenital vascular, infectious, and benign and malignant neoplastic lesions), and address surgical management issues.
Normal Tongue Anatomy
The terms root of the tongue and floor of the mouth pertain to the oral cavity, whereas the term base of the tongue refers to an area of the oropharynx. Misuse of these terms can lead to misunderstandings between the radiologist and the surgeon, much to the detriment of patients with disease affecting these areas. In addition, more specific differential diagnoses may be formulated once these areas are defined separately.
The tongue is a complex of muscle groups with a fibrous scaffold consisting of the hyoglossal membrane and midline lingual septum. The musculature of the tongue is separated into intrinsic and extrinsic groups. The intrinsic muscles comprise most of the mobile tongue and are named for their orientation: vertical, transverse, inferior longitudinal, and superior longitudinal. They provide the mobile tongue with a wide range of motion. The extrinsic muscles include the genioglossus, geniohyoid, hyoglossus, styloglossus, and palatoglossus muscles. These muscles are responsible for the raising and lowering, as well as the forward and backward motion, of the tongue as a unit. The hyoglossal membrane anchors the inferior posterior edge of the tongue to the hyoid bone. The lingual septum inserts into the hyoglossal membrane and extends superiorly along the midline of the tongue (Figs 1–3). It divides the tongue into halves and provides attachments for the transverse intrinsic muscles (4,5).
Figure 1 Axial drawing (left) and T1-weighted magnetic resonance (MR) image (right) demonstrate the root of the tongue. The high-signal-intensity lingual septum (ls) is clearly seen and is flanked by the genioglossus muscles (gg), which form an inverted V anteriorly before blending into the intrinsic muscles of the mobile tongue. The sublingual spaces (sls) are lateral to the genioglossus and geniohyoid muscles and also show high T1 signal intensity. (Drawing reprinted, with permission, from reference 3.)
Download as PowerPointOpen in Image Viewer
Figure 2 On a coronal drawing (left) and T1-weighted MR image (right), the genioglossus muscles (gg) resemble paramidline vertical pillars. Below the genioglossus muscles, the geniohyoid muscles (gh) appear subtly wider than they do on axial images (cf Fig 1). The sublingual spaces (sls) show high T1 signal intensity. ls = lingual septum. (Drawing reprinted, with permission, from reference 3.)
Download as PowerPointOpen in Image Viewer
Figure 3 Sagittal drawing (left) and T1-weighted MR image (right) demonstrate the geniohyoid muscles (gh) and the fanlike shape of the genioglossus muscles (gg). The mylohyoid muscle (mh) extends from the mandible to the hyoid bone and supports the floor of the mouth. (Drawing reprinted, with permission, from reference 3.)
Download as PowerPointOpen in Image Viewer
The tongue is often divided into the mobile tongue and the base of the tongue. The mobile tongue extends from the frenulum to the circumvallate papillae and is part of the oral cavity. The base of the tongue is posterior to the circumvallate papillae and is part of the oropharynx. However, head and neck subspecialists often refer to the region deep to the mobile tongue and anterior to the base of the tongue as the root of the tongue (3). The root of the tongue includes the lingual septum and bilateral genioglossus and geniohyoid muscles (genioglossus-geniohyoid complex). Both muscle groups originate from the symphysis menti on the back of the mandible and attach to the hyoid bone. Only a small group of inferolateral genioglossal fibers attach to the hyoid bone. The majority of genioglossal fibers fan out superiorly, interdigitating with the intrinsic tongue muscles and attaching to the dorsum of the tongue (Figs 1–3).
The borders of the root of the tongue are well defined anteriorly, laterally, and inferiorly. The anterior border is defined by the mandible and is easily seen at MR imaging and computed tomography (CT). Laterally, the sublingual spaces can be distinguished from the root of the tongue at MR imaging on the basis of their higher T1 and T2 signal from higher fat and connective tissue content. Masses in the root of the tongue will bow the genioglossus-geniohyoid muscle complexes laterally (Fig 4). The sublingual neurovascular bundles, which are especially well visualized at contrast-enhanced imaging, can also provide a good landmark for identifying the sublingual spaces.
Mass effect from lesions of the root of the tongue. (a) Sagittal contrast material–enhanced T1-weighted MR image demonstrates bowing of the mylohyoid muscle (arrow) inferiorly by a lymphatic malformation. (b, c) Coronal (b) and axial (c) contrast-enhanced T1-weighted MR images show lateral displacement of the genioglossus muscles (arrows) by a dermoid cyst.
Download as PowerPointOpen in Image Viewer
Download as PowerPointOpen in Image Viewer
Download as PowerPointOpen in Image Viewer
The inferior border is well defined by the U-shaped mylohyoid muscle under the geniohyoid muscles. Along the midline, the mylohyoid muscle extends from the mandible to the hyoid bone. Posterolaterally, it has a free edge, which allows communication between the sublingual and submandibular spaces. Because it spans the inferior edges of the mandible and encloses the oral cavity inferiorly, it is the true floor of the mouth and is not considered part of the root of the tongue. The mylohyoid muscle is a useful structure because masses of the root of the tongue will displace it inferiorly, which helps distinguish them from submandibular lesions (Fig 4).
Posteriorly, the root of the tongue must be differentiated from the base of the tongue. The tongue musculature is bordered by prominent lymphatic tissues from the lingual tonsils. From an imaging perspective, the root of the tongue includes the visible tongue musculature, whereas the base of the tongue encompasses the posterior lymphatic tissue (Fig 5) (3). As mentioned earlier, the root of the tongue is considered part of the oral cavity, whereas the base of the tongue is included in the oropharynx.
Differentiation of the root of the tongue from the base of the tongue. Axial T2-weighted (a) and T1-weighted (b) MR images demonstrate lymphoid tissue in the base of the tongue with high T2 signal intensity and increased T1 enhancement relative to the muscle tissue in the root of the tongue. Arrows = anatomic border.
Download as PowerPointOpen in Image Viewer
Download as PowerPointOpen in Image Viewer
The superior border of the root of the tongue is the most indistinct, since the genioglossus muscle fans out and blends into the intrinsic tongue muscles within the mobile tongue. The border is difficult to define radiologically; at clinical examination, however, a mass will be seen to cause greater tongue fixation during tongue protrusion the more it involves the root of the tongue.
Recommended Imaging Approach
Many of the congenital lesions in the root of the tongue are found in children. These lesions are more frequently evaluated with MR imaging because it does not make use of ionizing radiation. Moreover, MR imaging provides excellent soft-tissue characterization, which is important in the suprahyoid neck. Diffusion-weighted imaging may be useful for differentiating epidermoid from dermoid cysts, since the former often show diffusion restriction. Sedation is often required in children under 7 years of age, although specific training and the use of audiovisual entertainment systems can significantly reduce this need (6).
In adults, the assessment of masses of the oral cavity and suprahyoid neck is often begun with CT due to its greater speed, lower cost, and wider availability. With modern CT, exceptional anatomic detail can be achieved and then reconstructed in other planes. Adding an additional limited CT sequence with the gantry parallel to the angle of the mandible can significantly reduce metallic artifact from dental amalgam in the inferior oral cavity. MR imaging is reserved for evaluating the extent of involvement in larger lesions and for complicated postsurgical cases.
Imaging Features of Lesions
Lesions involving the root of the tongue can be classified into congenital vascular and nonvascular lesions, infections, and neoplasms (Table).
Lesions of the Root of the Tongue
Congenital vascular and nonvascular lesions make up the largest group of lesions. At our institution, 20 (74%) of 27 lesions involving the root of the tongue were congenital. In contrast, acquired lesions occur much more frequently in the adjacent sublingual and submandibular spaces and the base of the tongue.Acquired inflammatory or neoplastic lesions accounted for 78 of 94 sublingual lesions (83%) in “Anatomic Landmarks and Pathology of the Sublingual Space,” presented by Dr Anna Ilner at the 2003 American Society of Head and Neck Radiology Annual Meeting. Presumably, the higher prevalence of acquired lesions is due to greater exposure to mucosal surfaces and prominent lymphoid tissues. Moreover, the skeletal muscle that composes most of the root of the tongue is relatively resistant to infection and less prone to neoplasms compared with other tissues (1).
Congenital Nonvascular Lesions
Lingual Thyroid.—Ectopic thyroids are found along the thyroglossal duct, which involutes in normal adults but is found between the foramen cecum and the thyroid gland during development. The duct passes through the posterior aspect of the root of the tongue before reaching the hyoid bone (Fig 6). In the suprahyoid neck, the thyroglossal duct is found along the midline, although it diverges laterally in the infrahyoid neck (7). At CT, lingual thyroids are characteristically hyperattenuating relative to muscle due to (a) the iodine content of thyroid tissue and (b) moderate contrast enhancement. At MR imaging, they are usually solid in appearance, mildly T1 hyperintense or isointense relative to muscle, and avidly enhancing (8). High iodine-123 (123I) and technetium-99m uptake on radiotracer studies is very specific (9). Ninety percent of lingual thyroids are found in the tongue (9). Interestingly, at our institution, three of five thyroids involving the root of the tongue were multifocal and demonstrated ectopic tissue in the base of the tongue (Fig 7). In 75% of cases, the lingual thyroid represents the only functioning thyroid tissue (9). Like other thyroid tissue, these lesions can undergo cancerous and goiterous transformation (3% of cases) (9).
Figure 6 Drawing shows the thyroglossal duct traversing the root of the tongue (arrow) along the midline immediately inferior to the base of the tongue. (Reprinted, with permission, from reference 3.)
Download as PowerPointOpen in Image Viewer
Lingual thyroids. Midline sagittal T1-weighted MR image (a) and sagittal reformatted contrast-enhanced CT image (b) obtained in two different patients show soft-tissue masses in the root (arrow) and base (arrowhead) of the tongue. The mylohyoid muscles are bowed inferiorly.
Download as PowerPointOpen in Image Viewer
Download as PowerPointOpen in Image Viewer
Thyroglossal Duct Cyst.—Like ectopic thyroids, thyroglossal duct cysts are found along the thyroglossal duct. They are the most common thyroglossal duct lesion, and approximately 20%–25% are suprahyoid in location (9,10). These lesions have a generic cystic appearance, sometimes with thin septa or lobulations (9). As with most cysts, the attenuation of thyroglossal duct cysts is usually between 0 and 20 HU at CT, with high T2 signal and intermediate T1 signal at MR imaging. The fluid within the lesion can be proteinaceous or hemorrhagic, making the lesion higher in attenuation and higher in T1 signal. Most lesions are well circumscribed with a very thin rim of enhancement. Lesions that are infected or hemorrhagic can appear heterogeneous and complex with profuse surrounding soft-tissue edema. Thyroglossal duct cysts may be distinguished from other cystic lesions when a component closely associated with the hyoid bone is discovered (Fig 8) (11).
Thyroglossal duct cyst. Sagittal T2-weighted (a) and contrast-enhanced T1-weighted (b) MR images show a thyroglossal duct cyst. Part of the lesion is above the mylohyoid muscle (white arrowheads) in the root of the tongue (arrow). The lesion extends through a posterior defect in the mylohyoid muscle into the submandibular space. The lesion appears above the platysma (black arrowheads in b), which separates the submandibular and superficial spaces.
Download as PowerPointOpen in Image Viewer
Download as PowerPointOpen in Image Viewer
Dermoid and Epidermoid Cysts.—Dermoid and epidermoid cysts in the oral cavity have a predilection for the root of the tongue and the floor of the mouth (9,12). It can be difficult to distinguish between dermoid and epidermoid cysts at imaging. Both types of lesions are well circumscribed and have high T2 signal with no enhancement or only rim enhancement. Epidermoid cysts contain only epithelial elements, whereas dermoid cysts have both epithelial elements and a dermal substructure. At imaging, the additional complexity of dermoid cysts is sometimes reflected by greater signal heterogeneity (ie, from the combination of solid and cystic elements). Epidermoid cysts usually lack observable solid components. In dermoid cysts, intralesional fat is a distinguishing feature (Fig 9). This fat may coalesce into globules, creating a “sack of marbles” appearance, which is nearly pathognomonic (13). Epidermoid cysts may show restriction (high diffusion and a low apparent diffusion coefficient) at diffusion imaging, which is a characteristic feature, although the apparent diffusion coefficient values are typically only moderately low (Fig 10) (14).
Dermoid cysts. (a) Precontrast T1-weighted MR image shows a well-circumscribed lesion in the inferior aspect of the root of the tongue with mixed high (arrow) and intermediate (arrowhead) signal intensity. (b) Contrast-enhanced fat-saturated T1-weighted MR image shows the lesion (arrow) with a large fatty component. (c) Contrast-enhanced T1-weighted MR image obtained in a different patient shows a dermoid cyst with a more clearly cystic appearance. Mixed solid components are present anteriorly, a finding that indicates increased complexity.
Download as PowerPointOpen in Image Viewer
Download as PowerPointOpen in Image Viewer
Download as PowerPointOpen in Image Viewer
Epidermoid cyst in the root of the tongue. (a) Sagittal contrast-enhanced T1-weighted MR image shows a rim-enhancing unilocular lesion (arrow). (b, c) Axial T2-weighted (b) and diffusion-weighted (c) MR images show the cystic appearance of the lesion more clearly. The lesion demonstrates high signal intensity on the diffusion-weighted image.
Download as PowerPointOpen in Image Viewer
Download as PowerPointOpen in Image Viewer
Download as PowerPointOpen in Image Viewer
Lipoma.—Lipomas are usually easily identified, well-encapsulated lesions with the attenuation or signal intensity of fat. Only 0.1%–5% of benign lesions in the oral cavity are lipomas, but 50% of these lipomas localize to the buccal soft tissues. In a series of 47 lipomas of the oral cavity, five (11%) were located around the floor of the mouth (15). Although the majority of lesions were well encapsulated, four lesions (9%) were intramuscular, with adipose tissue infiltrating the muscle fibers (15).
Foregut Duplication Cyst.—Foregut duplication cysts are rarely seen in the root of the tongue. At our institution, two of 27 lesions were foregut duplication cysts. According to Kong et al (16), 21 duplication cysts of the oral cavity (representing 0.3% of all duplication cysts) have been reported. The CT attenuation of foregut duplication cysts is usually that of fluid but may vary owing to proteinaceous content. At MR imaging, these cysts have high T2 signal and a T1 signal that varies depending on proteinaceous content. They have a uniform enhancing rim and, like thyroglossal duct cysts, can have thin septa or lobulations (Fig 11). Foregut duplication cysts can also become infected or show hemorrhage, leading to a heterogeneous appearance. Usually, these lesions are diagnosed after resection when gastric or intestinal epithelium and a lining of smooth muscle cells are found (17).
Foregut duplication cyst. Axial T2-weighted (a) and sagittal T1-weighted (b) MR images show a foregut duplication cyst (arrow in a) with a thin septum. The high T1-weighted signal intensity in the anterior compartment (arrow in b) likely represents hemorrhagic or proteinaceous material. No chemical shift is noted. Fat-saturated imaging would help exclude fat.
Download as PowerPointOpen in Image Viewer
Download as PowerPointOpen in Image Viewer
Hemangioma.—A discussion of the nomenclature and categorization of hemangiomas is beyond the scope of this article. For our purposes, hemangiomas will be described as congenital nonvascular tumors. Pathologically, they are capillary type hemangiomas consisting of cells of endothelial origin (9).
Hemangiomas of the oral cavity are uncommon but have a predilection for the tongue. Although many lingual hemangiomas are superficial, some lesions may involve the deep tongue or even the majority of the tongue (18,19). At CT, lingual hemangiomas enhance intensely and often have prominent lesional and perilesional vasculature. At MR imaging, lingual hemangiomas have a T2 signal higher than that of muscle and also show intense enhancement. The prominent vasculature may be seen as flow voids at MR imaging.
Congenital Vascular Lesions
Many congenital vascular lesions have a propensity for involving several adjacent anatomic spaces, since they often manifest before fascial boundaries mature. Three of six vascular lesions at our institution were transspatial. Vascular lesions are often infiltrative and multilocular. They are usually classified as slow-flow (lymphatic, venous, venolymphatic) or high-flow (arteriovenous) lesions.
Lymphatic Malformation.—Pure lymphatic malformations are generally nonenhancing or show enhancement only along the rim and in septa. At CT, they often have uniform low attenuation, whereas at MR imaging, they have uniform high T2 signal. Lymphatic malformations can be unilocular or multilocular. A unilocular lesion may be difficult to differentiate from a thyroglossal duct cyst or duplication cyst. Thyroglossal duct cysts are usually found along the midline, whereas this is not necessarily true of lymphatic malformations. Fluid-fluid levels within the loculations are characteristic (Fig 12) (9).
Lymphatic malformations. (a) Axial T2-weighted MR image shows a transspatial lesion with fluid-fluid levels (arrows) involving the root of the tongue and the left sublingual, submandibular, retropharyngeal, and carotid spaces. The genioglossus muscles (arrowheads) are bowed laterally. (b) Coronal contrast-enhanced T1-weighted MR image obtained in a different patient shows a multilocular lesion with thin rim enhancement bowing the genioglossus muscles (arrows).
Download as PowerPointOpen in Image Viewer
Download as PowerPointOpen in Image Viewer
Venous Malformation.—Pure venous malformations usually enhance, and their appearance is largely dependent on the size of the venous channels. Larger channels lead to a septated cystic appearance with greater likelihood of flow voids at MR imaging. Smaller channels have an almost solid appearance, in terms of both enhancement and lower T2 signal (20). Phleboliths are nearly pathognomonic but are not always present (Fig 13).
Venous malformation. (a) Contrast-enhanced CT scan shows a phlebolith (arrow) in the root of the tongue. (b) Contrast-enhanced CT scan demonstrates multiple enhancing abnormal venous channels (arrows) in the root of the tongue, as well as the left sublingual and submandibular spaces. More phleboliths are present in the lateral aspect of the lesion.
Download as PowerPointOpen in Image Viewer
Download as PowerPointOpen in Image Viewer
Venolymphatic Malformation.—Mixed venolymphatic lesions can have a variety of appearances, sharing characteristics of both venous and lymphatic malformations (Fig 14) (9,21). Given their mixed composition, they can be more complex in appearance.
Venolymphatic malformation. Coronal (a) and axial (b) contrast-enhanced T1-weighted MR images show a solid-appearing lesion with nearly solid enhancement, a finding that reflects small rather than large venous channels. The lesion has nearly replaced the root of the tongue and contains a few hypointense cystic areas (arrow in a), which likely represent lymphatic components. The origin of the genioglossus muscles at the genu of the mandible (arrow in b) is marked for reference. The lesion proved to be a venolymphatic malformation at resection.
Download as PowerPointOpen in Image Viewer
Download as PowerPointOpen in Image Viewer
Arteriovenous Malformation.—Arteriovenous malformations are high-flow vascular malformations. There have been only a few reports on lingual arteriovenous malformations, which usually represent part of a transspatial lesion involving other spaces in the head and neck. Arteriovenous malformations are characterized by one or more prominent arterial feeders, often with bilateral involvement. At MR imaging, large convoluted flow voids are typical. Isolated arteriovenous malformations of the tongue are an even rarer entity but are generally characterized by a dominant lingual arterial feeder. Conventional angiography is often used after noninvasive imaging to characterize arterial involvement, identify the nidus, and help guide preoperative treatment with embolization (22).
Infection
Strong defenses against infection exist in the root of the tongue. A thick protective layer of keratinized epithelium covers the surface of the tongue. In addition, the tongue is composed mainly of skeletal muscle, which is relatively resistant to infection (1). The root of the tongue is also well vascularized and possesses efficient lymphatic drainage.In all three cases of tongue infection seen at our institution, the patient presented with traumatic penetrating injury, which resulted in early medical attention (Fig 15). At CT, mature infections (eg, abscess) manifest as thick-rim enhancing fluid-attenuation lesions, whereas immature infections (eg, phlegmon) manifest as ill-defined regions of heterogeneous enhancement. At MR imaging, tongue abscesses manifest as thick-rim enhancing lesions with high T2 signal, whereas phlegmon is ill defined with high T2 signal and mixed enhancement. Prominent localized swelling is often seen.
Figure 15 Abscess of the root of the tongue. Contrast-enhanced CT scan shows a low-attenuation fluid collection with an irregular enhancing rim. Inflammation blurs the fascial planes around the genioglossus muscles (arrows) and causes prominent enhancement of the sublingual and submandibular glands (*). Most tongue infections manifest early and are smaller than the abscess shown in this case.
Download as PowerPointOpen in Image Viewer
Benign Neoplasms
Acquired benign neoplasms in the root of the tongue are rare. A number of case reports discuss these lesions, most of which had a neural or skeletal muscle origin. Our study included a case of rhabdomyoma in a patient with basal cell nevus syndrome (Fig 16) and a case of plexiform neurofibroma in a patient with neurofibromatosis-1. Other reported lesions include leiomyoma, schwannoma, and neurofibroma. Most acquired benign neoplasms in the root of the tongue manifest as well-circumscribed, enhancing soft-tissue lesions at CT and MR imaging (9). Definitive diagnosis usually requires excision or biopsy, since these lesions are difficult to differentiate at imaging. Plexiform neurofibromas are an exception, being amenable to diagnosis at MR imaging, at which they manifest as distinctive infiltrative enhancing lesions with a characteristic swirled high-T2-signal appearance (Fig 17) (9). Because plexiform neurofibromas are found only in neurofibromatosis-1, a search for other stigmata of neurofibromatosis-1 should be undertaken.
Rhabdomyoma in a neonate with basal cell nevus syndrome. Arrowheads = genioglossus muscles. (a) Axial contrast-enhanced T1-weighted MR image shows a solid enhancing mass (arrow) in the root of the tongue and mobile tongue. (b) On a contrast-enhanced T2-weighted MR image, the tongue root component (arrow) has slightly higher signal intensity.
Download as PowerPointOpen in Image Viewer
Download as PowerPointOpen in Image Viewer
Plexiform neurofibroma. (a) Axial contrast-enhanced T1-weighted MR image shows an infiltrative transspatial mass with characteristic whorled internal components. (b) Axial T2-weighted MR image shows high signal intensity throughout the lesion.
Download as PowerPointOpen in Image Viewer
Download as PowerPointOpen in Image Viewer
Malignant Neoplasms
Acquired malignant neoplasms of the root of the tongue are also rare. The majority are rhabdomyosarcomas. Thirty percent of head and neck rhabdomyosarcomas occur in the oral cavity or pharynx but do not commonly involve the tongue. In a series by Cirocco et al (23), three of 63 oral rhabdomyosarcomas (5%) were found in the tongue. Sixty-five percent occur in children less than 6 years old (24).
Alveolar soft part sarcomas have also been reported in the root of the tongue. Although these tumors are very rare (1% of all soft-tissue sarcomas), 27% occur in the head and neck, and 25% of head and neck tumors are found in the tongue (25).
Both rhabdomyosarcoma and alveolar soft part sarcoma frequently exhibit features that indicate an aggressive nature, including irregular indistinct margins, lymph node invasion, distant metastasis, and intense enhancement (Figs 18, 19). Lytic bone change is a hallmark of rhabdomyosarcomas but is only infrequently seen in the root of the tongue, since the region is surrounded by soft tissues. Alveolar soft part sarcomas are comparatively slower-growing angiogenic neoplasms with a high rate of metastasis (26).
Rhabdomyosarcoma. Axial contrast-enhanced T1-weighted MR images (b obtained at a higher level than a) show a rhabdomyosarcoma (arrow). The lesion is relatively well circumscribed in a; in b, the lesion is significantly more infiltrative and may have an exophytic component (arrowhead) that projects into the airway.
Download as PowerPointOpen in Image Viewer
Download as PowerPointOpen in Image Viewer
Alveolar soft part sarcoma. Coronal (a) and axial (b) contrast-enhanced T1-weighted MR images show a lesion with infiltrative margins (arrow) that invades the submandibular and sublingual spaces (arrowhead).
Download as PowerPointOpen in Image Viewer
Download as PowerPointOpen in Image Viewer
Surgical Management
Treatment of lesions involving the root of the tongue varies depending on the disease entity and the extent of the lesion. Some lesions may be managed medically or even with observation. Lingual thyroids may be managed with thyroid suppressive therapy and observation if they remain stable and asymptomatic (27). However, many lesions involving the root of the tongue, including some lingual thyroids, require surgical management.
There are a variety of surgical approaches used to resect lesions involving the root of the tongue. These approaches may be divided into transoral and transcervical approaches. Classic transoral approaches were invasive and left the patient with significant morbidity. An anterior midline labiomandibuloglossotomy involves an osteotomy of the mandible and division of the oral tongue along the lingual septum. An alternative transoral approach is known as a mandibular swing, in which the mandible is reflected laterally after osteotomy. This approach allows access to the root of the tongue through the base of the tongue. Less invasive transoral approaches also exist, including an endoscopic technique. Robotic technology has further advanced these approaches through transoral robotic surgery of the tongue (28). Transcervical approaches include transhyoid and lateral pharyngotomy. These techniques allow somewhat less exposure compared with transoral mandibulotomy approaches but have less morbidity.
When planning surgical resection, the surgeon must take into consideration the type, size, and location of the lesion. Because many of these lesions are benign, a more conservative approach is often used. In addition, combined simultaneous approaches through the mouth and neck may yield the best results.
Summary
The root of the tongue is composed of bilateral genioglossus-geniohyoid muscle complexes and the midline lingual septum. These structures play an important role in tongue mobility and provide support for the mobile tongue. The root of the tongue is deep to the mobile tongue, sublingual and submandibular spaces, and base of the tongue. It contains little mucosal surface or lymphatic tissue. The location and composition of this area make it resistant to acquired lesions; however, a large majority of lesions are congenital.
A few generalizations about lesions involving the root of the tongue may be stated. Many congenital lesions display cystic high signal intensity at T2-weighted MR imaging, and ectopic tissues of epidermal, dermal, venous, and lymphatic origin should be considered. Both thyroglossal duct cysts (common) and foregut duplication cysts (rare) also share this property. Transspatial lesions are more likely vascular or lymphatic in origin.
As a general rule, when lesions are transspatial, three types of lesions should be considered initially: highly aggressive neoplasms, congenital lesions, and aggressive infections (29).
Some specific lesion characteristics can help tailor the differential diagnosis. Solid high-density lesions in the midline are likely lingual thyroids. These lesions may be verified with nuclear medicine imaging. Calcifications may represent goiterous transformation. Phleboliths are highly specific for venous malformations. Multilocular, thin-rim enhancing cystic lesions are classic for lymphatic malformations, especially if fluid-fluid levels are found. Fat within a complex cystic lesion is specific for dermoid cyst, whereas diffusion restriction within a homogeneous-appearing cystic lesion is suggestive of epidermoid cyst. Plexiform neurofibromas have a distinctive infiltrative, transspatial whorled appearance. Patients with infections should have a compelling clinical history of a penetrating injury.
We wish to thank Patricia A. Hudgins, MD, Philip R. Chapman, MD, Joel Cure, MD, and Bernadette L. Koch, MD.
Disclosures of Potential Conflicts of Interest.- B.E.H.:Related financial activities: none. Other financial activities: received royalties from and is a consultant for Amirsys. G.L.H.:Related financial activities: none. Other financial activities: consultant for Amirsys. H.R.H.:Related financial activities: none. Other financial activities: CEO of and holds stock in Amirsys. R.H.W.:Related financial activities: none. Other financial activities: consultant for Amirsys.
For this journal-based CME activity, the authors R.H.W., B.E.H., G.L.H., and H.R.H. have disclosed various financial relationships (see “Disclosures of Potential Conflicts of Interest”); all other authors, the editor, and reviewers have no relevant relationships to disclose.
Wayne S. Fang , Richard H. Wiggins, III, Anna Illner, Bronwyn E. Hamilton, Gary L. Hedlund, Jason P. Hunt, H. Ric Harnsberger
Author Affiliations
From the Departments of Radiology (W.S.F., R.H.W., H.R.H.) and Otolaryngology (J.P.H., H.R.H.), University of Utah, Salt Lake City, Utah; Department of Diagnostic Imaging, Texas Children's Hospital, Houston, Tex (A.I.); Department of Radiology, Oregon Health & Science University, Portland, Ore (B.E.H.); and Department of Radiology, Primary Children's Medical Center, Salt Lake City, Utah (G.L.H.).
Address correspondence to W.S.F., Seattle Radiologists, 1229 Madison St, Seattle, WA 98040 (e-mail: fang.wayne@yahoo.com).
Published Online:Nov 8 2011https://doi.org/10.1148/rg.317095738
Sections
Tools
Share
Abstract
In the assessment of the head and neck, differential diagnoses can be formulated by subdividing the anatomy into spaces along identifiable and logical boundaries. In the oral cavity, the root of the tongue is notably unlike adjacent regions due to structural and tissue-specific differences. The majority of lesions found in the root of the tongue are congenital and benign, representing ectopic tissues of thyroidal, epidermal, dermal, foregut, venous, and lymphatic origin. A greater number of acquired neoplasms and infections are seen in the adjacent sublingual, submandibular, and oropharyngeal regions of the base of the tongue, presumably due to their greater exposure to mucosal surfaces and lymphatic tissues. Many lesions of the root of the tongue have clinical and imaging characteristics that can help narrow the differential diagnosis, and surgical management may be required. Familiarity with these lesions and how they differ from other lesions of the oral cavity and oropharynx can significantly aid in their diagnosis and treatment.
© RSNA, 2011
LEARNING OBJECTIVES FOR TEST 3
After completing this journal-based CME activity, participants will be able to:
•.
Identify the boundaries of the root of the tongue.
•.
Describe the defining imaging features of lesions of the root of the tongue.
•.
Discuss the structural attributes of the root of the tongue that help distinguish it from adjacent spaces.
Introduction
What makes the head and neck region so challenging and interesting is its compact geography of small but important structures. Assessment of the head and neck is greatly aided by the generation of differential diagnoses using subdivision of the anatomy into spaces along identifiable and logical boundaries. Tailored space-specific differential diagnoses can be formulated by recalling the anatomic contents of the spaces.
The root of the tongue is an important subregion of the oral cavity, associated with very specific differential diagnoses. It is relatively resistant to primary neoplastic and infectious processes due to its high percentage of skeletal muscle and lack of significant lymphatic tissue (1). In contrast, many acquired lesions are found within adjacent regions such as the base of the tongue and the sublingual and submandibular spaces. Squamous cell carcinoma invariably invades the deep tongue from adjacent mucosal surfaces of the oral cavity and anterior oropharynx and does not originate from the deep tongue structures (2). Accurately localizing a lesion to the root of the tongue can significantly narrow the differential diagnosis.
In this article, we review the normal tongue anatomy, make recommendations for the imaging of lesions of the root of the tongue, discuss the imaging features of a variety of such lesions (congenital nonvascular, congenital vascular, infectious, and benign and malignant neoplastic lesions), and address surgical management issues.
Normal Tongue Anatomy
The terms root of the tongue and floor of the mouth pertain to the oral cavity, whereas the term base of the tongue refers to an area of the oropharynx. Misuse of these terms can lead to misunderstandings between the radiologist and the surgeon, much to the detriment of patients with disease affecting these areas. In addition, more specific differential diagnoses may be formulated once these areas are defined separately.The tongue is a complex of muscle groups with a fibrous scaffold consisting of the hyoglossal membrane and midline lingual septum. The musculature of the tongue is separated into intrinsic and extrinsic groups. The intrinsic muscles comprise most of the mobile tongue and are named for their orientation: vertical, transverse, inferior longitudinal, and superior longitudinal. They provide the mobile tongue with a wide range of motion. The extrinsic muscles include the genioglossus, geniohyoid, hyoglossus, styloglossus, and palatoglossus muscles. These muscles are responsible for the raising and lowering, as well as the forward and backward motion, of the tongue as a unit. The hyoglossal membrane anchors the inferior posterior edge of the tongue to the hyoid bone. The lingual septum inserts into the hyoglossal membrane and extends superiorly along the midline of the tongue (Figs 1–3). It divides the tongue into halves and provides attachments for the transverse intrinsic muscles (4,5).
Figure 1 Axial drawing (left) and T1-weighted magnetic resonance (MR) image (right) demonstrate the root of the tongue. The high-signal-intensity lingual septum (ls) is clearly seen and is flanked by the genioglossus muscles (gg), which form an inverted V anteriorly before blending into the intrinsic muscles of the mobile tongue. The sublingual spaces (sls) are lateral to the genioglossus and geniohyoid muscles and also show high T1 signal intensity. (Drawing reprinted, with permission, from reference 3.)
Download as PowerPointOpen in Image Viewer
Figure 2 On a coronal drawing (left) and T1-weighted MR image (right), the genioglossus muscles (gg) resemble paramidline vertical pillars. Below the genioglossus muscles, the geniohyoid muscles (gh) appear subtly wider than they do on axial images (cf Fig 1). The sublingual spaces (sls) show high T1 signal intensity. ls = lingual septum. (Drawing reprinted, with permission, from reference 3.)
Download as PowerPointOpen in Image Viewer
Figure 3 Sagittal drawing (left) and T1-weighted MR image (right) demonstrate the geniohyoid muscles (gh) and the fanlike shape of the genioglossus muscles (gg). The mylohyoid muscle (mh) extends from the mandible to the hyoid bone and supports the floor of the mouth. (Drawing reprinted, with permission, from reference 3.)
Download as PowerPointOpen in Image Viewer
The tongue is often divided into the mobile tongue and the base of the tongue. The mobile tongue extends from the frenulum to the circumvallate papillae and is part of the oral cavity. The base of the tongue is posterior to the circumvallate papillae and is part of the oropharynx. However, head and neck subspecialists often refer to the region deep to the mobile tongue and anterior to the base of the tongue as the root of the tongue (3). The root of the tongue includes the lingual septum and bilateral genioglossus and geniohyoid muscles (genioglossus-geniohyoid complex). Both muscle groups originate from the symphysis menti on the back of the mandible and attach to the hyoid bone. Only a small group of inferolateral genioglossal fibers attach to the hyoid bone. The majority of genioglossal fibers fan out superiorly, interdigitating with the intrinsic tongue muscles and attaching to the dorsum of the tongue (Figs 1–3).
The borders of the root of the tongue are well defined anteriorly, laterally, and inferiorly. The anterior border is defined by the mandible and is easily seen at MR imaging and computed tomography (CT). Laterally, the sublingual spaces can be distinguished from the root of the tongue at MR imaging on the basis of their higher T1 and T2 signal from higher fat and connective tissue content. Masses in the root of the tongue will bow the genioglossus-geniohyoid muscle complexes laterally (Fig 4). The sublingual neurovascular bundles, which are especially well visualized at contrast-enhanced imaging, can also provide a good landmark for identifying the sublingual spaces.
Mass effect from lesions of the root of the tongue. (a) Sagittal contrast material–enhanced T1-weighted MR image demonstrates bowing of the mylohyoid muscle (arrow) inferiorly by a lymphatic malformation. (b, c) Coronal (b) and axial (c) contrast-enhanced T1-weighted MR images show lateral displacement of the genioglossus muscles (arrows) by a dermoid cyst.
Download as PowerPointOpen in Image Viewer
Download as PowerPointOpen in Image Viewer
Download as PowerPointOpen in Image Viewer
The inferior border is well defined by the U-shaped mylohyoid muscle under the geniohyoid muscles. Along the midline, the mylohyoid muscle extends from the mandible to the hyoid bone. Posterolaterally, it has a free edge, which allows communication between the sublingual and submandibular spaces. Because it spans the inferior edges of the mandible and encloses the oral cavity inferiorly, it is the true floor of the mouth and is not considered part of the root of the tongue. The mylohyoid muscle is a useful structure because masses of the root of the tongue will displace it inferiorly, which helps distinguish them from submandibular lesions (Fig 4).
Posteriorly, the root of the tongue must be differentiated from the base of the tongue. The tongue musculature is bordered by prominent lymphatic tissues from the lingual tonsils. From an imaging perspective, the root of the tongue includes the visible tongue musculature, whereas the base of the tongue encompasses the posterior lymphatic tissue (Fig 5) (3). As mentioned earlier, the root of the tongue is considered part of the oral cavity, whereas the base of the tongue is included in the oropharynx.
Differentiation of the root of the tongue from the base of the tongue. Axial T2-weighted (a) and T1-weighted (b) MR images demonstrate lymphoid tissue in the base of the tongue with high T2 signal intensity and increased T1 enhancement relative to the muscle tissue in the root of the tongue. Arrows = anatomic border.
Download as PowerPointOpen in Image Viewer
Download as PowerPointOpen in Image Viewer
The superior border of the root of the tongue is the most indistinct, since the genioglossus muscle fans out and blends into the intrinsic tongue muscles within the mobile tongue. The border is difficult to define radiologically; at clinical examination, however, a mass will be seen to cause greater tongue fixation during tongue protrusion the more it involves the root of the tongue.
Recommended Imaging Approach
Many of the congenital lesions in the root of the tongue are found in children. These lesions are more frequently evaluated with MR imaging because it does not make use of ionizing radiation. Moreover, MR imaging provides excellent soft-tissue characterization, which is important in the suprahyoid neck. Diffusion-weighted imaging may be useful for differentiating epidermoid from dermoid cysts, since the former often show diffusion restriction. Sedation is often required in children under 7 years of age, although specific training and the use of audiovisual entertainment systems can significantly reduce this need (6).
In adults, the assessment of masses of the oral cavity and suprahyoid neck is often begun with CT due to its greater speed, lower cost, and wider availability. With modern CT, exceptional anatomic detail can be achieved and then reconstructed in other planes. Adding an additional limited CT sequence with the gantry parallel to the angle of the mandible can significantly reduce metallic artifact from dental amalgam in the inferior oral cavity. MR imaging is reserved for evaluating the extent of involvement in larger lesions and for complicated postsurgical cases.
Imaging Features of Lesions
Lesions involving the root of the tongue can be classified into congenital vascular and nonvascular lesions, infections, and neoplasms (Table).
Lesions of the Root of the Tongue
Congenital vascular and nonvascular lesions make up the largest group of lesions. At our institution, 20 (74%) of 27 lesions involving the root of the tongue were congenital. In contrast, acquired lesions occur much more frequently in the adjacent sublingual and submandibular spaces and the base of the tongue.Acquired inflammatory or neoplastic lesions accounted for 78 of 94 sublingual lesions (83%) in “Anatomic Landmarks and Pathology of the Sublingual Space,” presented by Dr Anna Ilner at the 2003 American Society of Head and Neck Radiology Annual Meeting. Presumably, the higher prevalence of acquired lesions is due to greater exposure to mucosal surfaces and prominent lymphoid tissues. Moreover, the skeletal muscle that composes most of the root of the tongue is relatively resistant to infection and less prone to neoplasms compared with other tissues (1).Congenital Nonvascular Lesions
Lingual Thyroid.—Ectopic thyroids are found along the thyroglossal duct, which involutes in normal adults but is found between the foramen cecum and the thyroid gland during development. The duct passes through the posterior aspect of the root of the tongue before reaching the hyoid bone (Fig 6). In the suprahyoid neck, the thyroglossal duct is found along the midline, although it diverges laterally in the infrahyoid neck (7). At CT, lingual thyroids are characteristically hyperattenuating relative to muscle due to (a) the iodine content of thyroid tissue and (b) moderate contrast enhancement. At MR imaging, they are usually solid in appearance, mildly T1 hyperintense or isointense relative to muscle, and avidly enhancing (8). High iodine-123 (123I) and technetium-99m uptake on radiotracer studies is very specific (9). Ninety percent of lingual thyroids are found in the tongue (9). Interestingly, at our institution, three of five thyroids involving the root of the tongue were multifocal and demonstrated ectopic tissue in the base of the tongue (Fig 7). In 75% of cases, the lingual thyroid represents the only functioning thyroid tissue (9). Like other thyroid tissue, these lesions can undergo cancerous and goiterous transformation (3% of cases) (9).
Figure 6 Drawing shows the thyroglossal duct traversing the root of the tongue (arrow) along the midline immediately inferior to the base of the tongue. (Reprinted, with permission, from reference 3.)
Download as PowerPointOpen in Image Viewer
Lingual thyroids. Midline sagittal T1-weighted MR image (a) and sagittal reformatted contrast-enhanced CT image (b) obtained in two different patients show soft-tissue masses in the root (arrow) and base (arrowhead) of the tongue. The mylohyoid muscles are bowed inferiorly.
Download as PowerPointOpen in Image Viewer
Download as PowerPointOpen in Image Viewer
Thyroglossal Duct Cyst.—Like ectopic thyroids, thyroglossal duct cysts are found along the thyroglossal duct. They are the most common thyroglossal duct lesion, and approximately 20%–25% are suprahyoid in location (9,10). These lesions have a generic cystic appearance, sometimes with thin septa or lobulations (9). As with most cysts, the attenuation of thyroglossal duct cysts is usually between 0 and 20 HU at CT, with high T2 signal and intermediate T1 signal at MR imaging. The fluid within the lesion can be proteinaceous or hemorrhagic, making the lesion higher in attenuation and higher in T1 signal. Most lesions are well circumscribed with a very thin rim of enhancement. Lesions that are infected or hemorrhagic can appear heterogeneous and complex with profuse surrounding soft-tissue edema. Thyroglossal duct cysts may be distinguished from other cystic lesions when a component closely associated with the hyoid bone is discovered (Fig 8) (11).
Thyroglossal duct cyst. Sagittal T2-weighted (a) and contrast-enhanced T1-weighted (b) MR images show a thyroglossal duct cyst. Part of the lesion is above the mylohyoid muscle (white arrowheads) in the root of the tongue (arrow). The lesion extends through a posterior defect in the mylohyoid muscle into the submandibular space. The lesion appears above the platysma (black arrowheads in b), which separates the submandibular and superficial spaces.
Download as PowerPointOpen in Image Viewer
Download as PowerPointOpen in Image Viewer
Dermoid and Epidermoid Cysts.—Dermoid and epidermoid cysts in the oral cavity have a predilection for the root of the tongue and the floor of the mouth (9,12). It can be difficult to distinguish between dermoid and epidermoid cysts at imaging. Both types of lesions are well circumscribed and have high T2 signal with no enhancement or only rim enhancement. Epidermoid cysts contain only epithelial elements, whereas dermoid cysts have both epithelial elements and a dermal substructure. At imaging, the additional complexity of dermoid cysts is sometimes reflected by greater signal heterogeneity (ie, from the combination of solid and cystic elements). Epidermoid cysts usually lack observable solid components. In dermoid cysts, intralesional fat is a distinguishing feature (Fig 9). This fat may coalesce into globules, creating a “sack of marbles” appearance, which is nearly pathognomonic (13). Epidermoid cysts may show restriction (high diffusion and a low apparent diffusion coefficient) at diffusion imaging, which is a characteristic feature, although the apparent diffusion coefficient values are typically only moderately low (Fig 10) (14).
Dermoid cysts. (a) Precontrast T1-weighted MR image shows a well-circumscribed lesion in the inferior aspect of the root of the tongue with mixed high (arrow) and intermediate (arrowhead) signal intensity. (b) Contrast-enhanced fat-saturated T1-weighted MR image shows the lesion (arrow) with a large fatty component. (c) Contrast-enhanced T1-weighted MR image obtained in a different patient shows a dermoid cyst with a more clearly cystic appearance. Mixed solid components are present anteriorly, a finding that indicates increased complexity.
Download as PowerPointOpen in Image Viewer
Download as PowerPointOpen in Image Viewer
Download as PowerPointOpen in Image Viewer
Epidermoid cyst in the root of the tongue. (a) Sagittal contrast-enhanced T1-weighted MR image shows a rim-enhancing unilocular lesion (arrow). (b, c) Axial T2-weighted (b) and diffusion-weighted (c) MR images show the cystic appearance of the lesion more clearly. The lesion demonstrates high signal intensity on the diffusion-weighted image.
Download as PowerPointOpen in Image Viewer
Download as PowerPointOpen in Image Viewer
Download as PowerPointOpen in Image Viewer
Lipoma.—Lipomas are usually easily identified, well-encapsulated lesions with the attenuation or signal intensity of fat. Only 0.1%–5% of benign lesions in the oral cavity are lipomas, but 50% of these lipomas localize to the buccal soft tissues. In a series of 47 lipomas of the oral cavity, five (11%) were located around the floor of the mouth (15). Although the majority of lesions were well encapsulated, four lesions (9%) were intramuscular, with adipose tissue infiltrating the muscle fibers (15).
Foregut Duplication Cyst.—Foregut duplication cysts are rarely seen in the root of the tongue. At our institution, two of 27 lesions were foregut duplication cysts. According to Kong et al (16), 21 duplication cysts of the oral cavity (representing 0.3% of all duplication cysts) have been reported. The CT attenuation of foregut duplication cysts is usually that of fluid but may vary owing to proteinaceous content. At MR imaging, these cysts have high T2 signal and a T1 signal that varies depending on proteinaceous content. They have a uniform enhancing rim and, like thyroglossal duct cysts, can have thin septa or lobulations (Fig 11). Foregut duplication cysts can also become infected or show hemorrhage, leading to a heterogeneous appearance. Usually, these lesions are diagnosed after resection when gastric or intestinal epithelium and a lining of smooth muscle cells are found (17).
Foregut duplication cyst. Axial T2-weighted (a) and sagittal T1-weighted (b) MR images show a foregut duplication cyst (arrow in a) with a thin septum. The high T1-weighted signal intensity in the anterior compartment (arrow in b) likely represents hemorrhagic or proteinaceous material. No chemical shift is noted. Fat-saturated imaging would help exclude fat.
Download as PowerPointOpen in Image Viewer
Download as PowerPointOpen in Image Viewer
Hemangioma.—A discussion of the nomenclature and categorization of hemangiomas is beyond the scope of this article. For our purposes, hemangiomas will be described as congenital nonvascular tumors. Pathologically, they are capillary type hemangiomas consisting of cells of endothelial origin (9).
Hemangiomas of the oral cavity are uncommon but have a predilection for the tongue. Although many lingual hemangiomas are superficial, some lesions may involve the deep tongue or even the majority of the tongue (18,19). At CT, lingual hemangiomas enhance intensely and often have prominent lesional and perilesional vasculature. At MR imaging, lingual hemangiomas have a T2 signal higher than that of muscle and also show intense enhancement. The prominent vasculature may be seen as flow voids at MR imaging.
Congenital Vascular Lesions
Many congenital vascular lesions have a propensity for involving several adjacent anatomic spaces, since they often manifest before fascial boundaries mature. Three of six vascular lesions at our institution were transspatial. Vascular lesions are often infiltrative and multilocular. They are usually classified as slow-flow (lymphatic, venous, venolymphatic) or high-flow (arteriovenous) lesions.
Lymphatic Malformation.—Pure lymphatic malformations are generally nonenhancing or show enhancement only along the rim and in septa. At CT, they often have uniform low attenuation, whereas at MR imaging, they have uniform high T2 signal. Lymphatic malformations can be unilocular or multilocular. A unilocular lesion may be difficult to differentiate from a thyroglossal duct cyst or duplication cyst. Thyroglossal duct cysts are usually found along the midline, whereas this is not necessarily true of lymphatic malformations. Fluid-fluid levels within the loculations are characteristic (Fig 12) (9).
Lymphatic malformations. (a) Axial T2-weighted MR image shows a transspatial lesion with fluid-fluid levels (arrows) involving the root of the tongue and the left sublingual, submandibular, retropharyngeal, and carotid spaces. The genioglossus muscles (arrowheads) are bowed laterally. (b) Coronal contrast-enhanced T1-weighted MR image obtained in a different patient shows a multilocular lesion with thin rim enhancement bowing the genioglossus muscles (arrows).
Download as PowerPointOpen in Image Viewer
Download as PowerPointOpen in Image Viewer
Venous Malformation.—Pure venous malformations usually enhance, and their appearance is largely dependent on the size of the venous channels. Larger channels lead to a septated cystic appearance with greater likelihood of flow voids at MR imaging. Smaller channels have an almost solid appearance, in terms of both enhancement and lower T2 signal (20). Phleboliths are nearly pathognomonic but are not always present (Fig 13).
Venous malformation. (a) Contrast-enhanced CT scan shows a phlebolith (arrow) in the root of the tongue. (b) Contrast-enhanced CT scan demonstrates multiple enhancing abnormal venous channels (arrows) in the root of the tongue, as well as the left sublingual and submandibular spaces. More phleboliths are present in the lateral aspect of the lesion.
Download as PowerPointOpen in Image Viewer
Download as PowerPointOpen in Image Viewer
Venolymphatic Malformation.—Mixed venolymphatic lesions can have a variety of appearances, sharing characteristics of both venous and lymphatic malformations (Fig 14) (9,21). Given their mixed composition, they can be more complex in appearance.
Venolymphatic malformation. Coronal (a) and axial (b) contrast-enhanced T1-weighted MR images show a solid-appearing lesion with nearly solid enhancement, a finding that reflects small rather than large venous channels. The lesion has nearly replaced the root of the tongue and contains a few hypointense cystic areas (arrow in a), which likely represent lymphatic components. The origin of the genioglossus muscles at the genu of the mandible (arrow in b) is marked for reference. The lesion proved to be a venolymphatic malformation at resection.
Download as PowerPointOpen in Image Viewer
Download as PowerPointOpen in Image Viewer
Arteriovenous Malformation.—Arteriovenous malformations are high-flow vascular malformations. There have been only a few reports on lingual arteriovenous malformations, which usually represent part of a transspatial lesion involving other spaces in the head and neck. Arteriovenous malformations are characterized by one or more prominent arterial feeders, often with bilateral involvement. At MR imaging, large convoluted flow voids are typical. Isolated arteriovenous malformations of the tongue are an even rarer entity but are generally characterized by a dominant lingual arterial feeder. Conventional angiography is often used after noninvasive imaging to characterize arterial involvement, identify the nidus, and help guide preoperative treatment with embolization (22).
Infection
Strong defenses against infection exist in the root of the tongue. A thick protective layer of keratinized epithelium covers the surface of the tongue. In addition, the tongue is composed mainly of skeletal muscle, which is relatively resistant to infection (1). The root of the tongue is also well vascularized and possesses efficient lymphatic drainage.In all three cases of tongue infection seen at our institution, the patient presented with traumatic penetrating injury, which resulted in early medical attention (Fig 15). At CT, mature infections (eg, abscess) manifest as thick-rim enhancing fluid-attenuation lesions, whereas immature infections (eg, phlegmon) manifest as ill-defined regions of heterogeneous enhancement. At MR imaging, tongue abscesses manifest as thick-rim enhancing lesions with high T2 signal, whereas phlegmon is ill defined with high T2 signal and mixed enhancement. Prominent localized swelling is often seen.Figure 15 Abscess of the root of the tongue. Contrast-enhanced CT scan shows a low-attenuation fluid collection with an irregular enhancing rim. Inflammation blurs the fascial planes around the genioglossus muscles (arrows) and causes prominent enhancement of the sublingual and submandibular glands (*). Most tongue infections manifest early and are smaller than the abscess shown in this case.
Download as PowerPointOpen in Image Viewer
Benign Neoplasms
Acquired benign neoplasms in the root of the tongue are rare. A number of case reports discuss these lesions, most of which had a neural or skeletal muscle origin. Our study included a case of rhabdomyoma in a patient with basal cell nevus syndrome (Fig 16) and a case of plexiform neurofibroma in a patient with neurofibromatosis-1. Other reported lesions include leiomyoma, schwannoma, and neurofibroma. Most acquired benign neoplasms in the root of the tongue manifest as well-circumscribed, enhancing soft-tissue lesions at CT and MR imaging (9). Definitive diagnosis usually requires excision or biopsy, since these lesions are difficult to differentiate at imaging. Plexiform neurofibromas are an exception, being amenable to diagnosis at MR imaging, at which they manifest as distinctive infiltrative enhancing lesions with a characteristic swirled high-T2-signal appearance (Fig 17) (9). Because plexiform neurofibromas are found only in neurofibromatosis-1, a search for other stigmata of neurofibromatosis-1 should be undertaken.
Rhabdomyoma in a neonate with basal cell nevus syndrome. Arrowheads = genioglossus muscles. (a) Axial contrast-enhanced T1-weighted MR image shows a solid enhancing mass (arrow) in the root of the tongue and mobile tongue. (b) On a contrast-enhanced T2-weighted MR image, the tongue root component (arrow) has slightly higher signal intensity.
Download as PowerPointOpen in Image Viewer
Download as PowerPointOpen in Image Viewer
Plexiform neurofibroma. (a) Axial contrast-enhanced T1-weighted MR image shows an infiltrative transspatial mass with characteristic whorled internal components. (b) Axial T2-weighted MR image shows high signal intensity throughout the lesion.
Download as PowerPointOpen in Image Viewer
Download as PowerPointOpen in Image Viewer
Malignant Neoplasms
Acquired malignant neoplasms of the root of the tongue are also rare. The majority are rhabdomyosarcomas. Thirty percent of head and neck rhabdomyosarcomas occur in the oral cavity or pharynx but do not commonly involve the tongue. In a series by Cirocco et al (23), three of 63 oral rhabdomyosarcomas (5%) were found in the tongue. Sixty-five percent occur in children less than 6 years old (24).
Alveolar soft part sarcomas have also been reported in the root of the tongue. Although these tumors are very rare (1% of all soft-tissue sarcomas), 27% occur in the head and neck, and 25% of head and neck tumors are found in the tongue (25).
Both rhabdomyosarcoma and alveolar soft part sarcoma frequently exhibit features that indicate an aggressive nature, including irregular indistinct margins, lymph node invasion, distant metastasis, and intense enhancement (Figs 18, 19). Lytic bone change is a hallmark of rhabdomyosarcomas but is only infrequently seen in the root of the tongue, since the region is surrounded by soft tissues. Alveolar soft part sarcomas are comparatively slower-growing angiogenic neoplasms with a high rate of metastasis (26).
Rhabdomyosarcoma. Axial contrast-enhanced T1-weighted MR images (b obtained at a higher level than a) show a rhabdomyosarcoma (arrow). The lesion is relatively well circumscribed in a; in b, the lesion is significantly more infiltrative and may have an exophytic component (arrowhead) that projects into the airway.
Download as PowerPointOpen in Image Viewer
Download as PowerPointOpen in Image Viewer
Alveolar soft part sarcoma. Coronal (a) and axial (b) contrast-enhanced T1-weighted MR images show a lesion with infiltrative margins (arrow) that invades the submandibular and sublingual spaces (arrowhead).
Download as PowerPointOpen in Image Viewer
Download as PowerPointOpen in Image Viewer
Surgical Management
Treatment of lesions involving the root of the tongue varies depending on the disease entity and the extent of the lesion. Some lesions may be managed medically or even with observation. Lingual thyroids may be managed with thyroid suppressive therapy and observation if they remain stable and asymptomatic (27). However, many lesions involving the root of the tongue, including some lingual thyroids, require surgical management.
There are a variety of surgical approaches used to resect lesions involving the root of the tongue. These approaches may be divided into transoral and transcervical approaches. Classic transoral approaches were invasive and left the patient with significant morbidity. An anterior midline labiomandibuloglossotomy involves an osteotomy of the mandible and division of the oral tongue along the lingual septum. An alternative transoral approach is known as a mandibular swing, in which the mandible is reflected laterally after osteotomy. This approach allows access to the root of the tongue through the base of the tongue. Less invasive transoral approaches also exist, including an endoscopic technique. Robotic technology has further advanced these approaches through transoral robotic surgery of the tongue (28). Transcervical approaches include transhyoid and lateral pharyngotomy. These techniques allow somewhat less exposure compared with transoral mandibulotomy approaches but have less morbidity.
When planning surgical resection, the surgeon must take into consideration the type, size, and location of the lesion. Because many of these lesions are benign, a more conservative approach is often used. In addition, combined simultaneous approaches through the mouth and neck may yield the best results.
Summary
The root of the tongue is composed of bilateral genioglossus-geniohyoid muscle complexes and the midline lingual septum. These structures play an important role in tongue mobility and provide support for the mobile tongue. The root of the tongue is deep to the mobile tongue, sublingual and submandibular spaces, and base of the tongue. It contains little mucosal surface or lymphatic tissue. The location and composition of this area make it resistant to acquired lesions; however, a large majority of lesions are congenital.
A few generalizations about lesions involving the root of the tongue may be stated. Many congenital lesions display cystic high signal intensity at T2-weighted MR imaging, and ectopic tissues of epidermal, dermal, venous, and lymphatic origin should be considered. Both thyroglossal duct cysts (common) and foregut duplication cysts (rare) also share this property. Transspatial lesions are more likely vascular or lymphatic in origin. As a general rule, when lesions are transspatial, three types of lesions should be considered initially: highly aggressive neoplasms, congenital lesions, and aggressive infections (29).Some specific lesion characteristics can help tailor the differential diagnosis. Solid high-density lesions in the midline are likely lingual thyroids. These lesions may be verified with nuclear medicine imaging. Calcifications may represent goiterous transformation. Phleboliths are highly specific for venous malformations. Multilocular, thin-rim enhancing cystic lesions are classic for lymphatic malformations, especially if fluid-fluid levels are found. Fat within a complex cystic lesion is specific for dermoid cyst, whereas diffusion restriction within a homogeneous-appearing cystic lesion is suggestive of epidermoid cyst. Plexiform neurofibromas have a distinctive infiltrative, transspatial whorled appearance. Patients with infections should have a compelling clinical history of a penetrating injury.
We wish to thank Patricia A. Hudgins, MD, Philip R. Chapman, MD, Joel Cure, MD, and Bernadette L. Koch, MD.
Disclosures of Potential Conflicts of Interest.- B.E.H.:Related financial activities: none. Other financial activities: received royalties from and is a consultant for Amirsys. G.L.H.:Related financial activities: none. Other financial activities: consultant for Amirsys. H.R.H.:Related financial activities: none. Other financial activities: CEO of and holds stock in Amirsys. R.H.W.:Related financial activities: none. Other financial activities: consultant for Amirsys.
For this journal-based CME activity, the authors R.H.W., B.E.H., G.L.H., and H.R.H. have disclosed various financial relationships (see “Disclosures of Potential Conflicts of Interest”); all other authors, the editor, and reviewers have no relevant relationships to disclose.
Δεν υπάρχουν σχόλια:
Δημοσίευση σχολίου