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Imaging of pediatric congenital cystic neck masses
Operative Techniques in Otolaryngology (2017) ], ]]]–]]]
Imaging of pediatric congenital cystic neck masses Jennifer A. Vaughn, MD From the Department of Radiology, Boston Children’s Hospital, Boston, Massachusetts KEYWORDS Congenital; Neck masses; Pediatric; Imaging
Congenital neck lesions are a common indication for imaging in the pediatric population. Although the clinical history and physical examination can narrow the differential diagnosis, imaging is often obtained to distinguish among possible entities and provide additional information needed to guide appropriate treatment. In this article, congenital cystic neck masses including thyroglossal duct cysts, dermoid or epidermoids, branchial apparatus anomalies, thymic cysts, and cervical teratomas will be discussed, with a focus on characteristic imaging features and locations that define these lesions. r 2017 Elsevier Inc. All rights reserved.
Introduction When considering which imaging study to order, the clinician has a variety of options, including high-resolution ultrasound (US), computed tomography (CT), and magnetic resonance imaging (MRI). Given the variety of imaging options available today, the American College of Radiology (ACR) has published standards and guidelines to aid in selecting the most appropriate imaging modality for various clinical presentations.1 US is an appropriate initial imaging examination for palpable superficial neck masses in both febrile and afebrile children. US is widely available, relatively inexpensive, can be performed without sedation, and does not expose children to ionizing radiation. Advances in US technology have led to the development of machines that allow for high-quality spatial and contrast resolution and provide the unique advantage of real time assessment.2 The use of US is continuing to increase in the United States, and has been used more extensively in Europe and in the developing world for the workup of a broader range of indications.1,3 US can readily reveal the cystic nature of a mass, allow determination of mass size, and locate many lesions within a Address reprint requests and correspondence: Department of Radiology, Boston Children’s Hospital, 300 Longwood Ave, Boston, MA 02116. E-mail address: [email protected] http://dx.doi.org/10.1016/j.otot.2017.05.011 1043-1810/r 2017 Elsevier Inc. All rights reserved.
specific anatomic neck space. With the use of Doppler, US can provide information on the presence and degree of vascularity, helping to differentiate between high- and lowflow vascular malformations. US can also assist with imageguided biopsy in the cooperative older patient and in the sedated patient.2 Despite the growing awareness and concern of exposure to medical radiation, CT still plays a very important role in the workup of neck masses in pediatric patients. CT provides fast imaging, often without the need for sedation and therefore remains a valuable tool for evaluating patients in the emergency setting. At many institutions, CT equipment is portable, making it an accessible test for children who cannot be transported to the Radiology Department. Additionally, CT serves as the only cross-sectional imaging modality available for patients who cannot undergo MRI secondary to implanted devices or external monitoring hardware. CT of the neck with iodinated contrast (contrast enhanced computed tomography) is recommended in the febrile child suspected of having secondary infection of a congenital cystic neck lesion that may require surgical management. CT and MRI can both be useful to define the extent of more complex lesions that may involve several anatomical spaces within the neck and are not well visualized on US, including lesions located in or around the parotid and thyroid gland, oral cavity lesions, lesions associated with the airway, and deeply located lesions. In addition to characterizing the cystic nature of a mass, both
2 MRI and contrast enhanced computed tomography can detect specific histologic components of the lesion, such as the presence of calcification, fat, and hemorrhage. This information can often point to a single likely diagnosis preoperatively. MRI is being more widely performed in the workup of pediatric neck masses, particularly in the nonemergent setting. MRI avoids the use of ionizing radiation and can provide excellent delineation of soft tissue anatomy. In the case of suspected congenital lymphatic and vascular malformations, MRI is the preferred imaging modality. In many pediatric patients, however, MRI may require sedation and anesthesia, as children have difficulty remaining still in the MR scanner long enough to produce diagnostically useful images. Information is also becoming available on the potential risk of gadolinium-based contrast agents, which are often used in the workup of neck masses. Studies have shown deposition of gadolinium in brain tissue in patients who received numerous administrations.4 Fetal neck masses are uncommon and may be inconspicuous or overlooked on routine second trimester obstetric US.5-7 MRI is now being performed prenatally in fetuses suspected of having a cystic neck mass on US. Accurate antenatal diagnosis is challenging yet essential to distinguish among the various pathologies and assess fetal airway anatomy. This information will affect parental counseling, antenatal, and postnatal management.6 Fetal imaging is performed at 1.5 or 3 T without the use of contrast. Although there is no evidence that MRI is hazardous to the fetus, potential long-term concerns relating to acoustic damage are still unknown.8 Fetal MRI can be especially useful in the workup of obese patients and in instances of unfavorable fetal positioning where US can be very difficult. MRI can delineate the extent of fetal neck masses in terms of the anatomical space(s) involved, the relationship of the mass to the airway, and the presence of intracranial or intrathoracic involvement. Moreover, it can detect any additional fetal anomalies that may be present in syndrome-associated neck masses and warrant consideration of karyotyping.7 The cystic or solid nature of a mass and specific histologic components, such as fat, can also be more readily resolved on MRI than on US. Imaging may be performed at several time points before delivery and can provide crucial information for the clinicians regarding airway management and mode of delivery, including the need for an ex utero intrapartum treatment procedure.5 Given the variety of appropriate imaging modalities available in the workup of neck masses in fetuses and children, it is crucial to understand the appearance of these lesions on US, CT, and MRI. Location within the neck is one of the key features in helping both the clinician and radiologist differentiate among the numerous causes for congenital neck lesions. Broadly, lesions can be defined as: (1) midline—including those in the oral cavity, base of tongue, and perithyroidal visceral space; (2) lateral— including those in the submandibular, parotid, carotid, and parapharyngeal spaces; and (3) those in the posterior
Operative Techniques in Otolaryngology, Vol ], No ], ] 2017 triangle. They may be further classified based on their relation to the hyoid bone as suprahyoid or infrahyoid. Furthermore, cystic lesions can be confined to a single anatomic space or they may be trans-spatial extending between numerous regions of the neck. The purpose of this article is to highlight the key imaging features of the most commonly encountered congenitally acquired neck lesions in children, with a focus on developing a differential diagnosis based on anatomical location, to guide management.
Imaging of midline cystic neck masses Thyroglossal duct cysts Thyroglossal duct cyst (TGDC) is the most common congenital neck mass and the most common midline cystic neck mass.9-11 Imaging is important to confirm the suspected diagnosis, to define the anatomical extent, to evaluate for the presence of thyroid tissue, and to detect the rare instances of malignant degeneration. TGDCs are located in the infrahyoid neck (25%-65%) or in the suprahyoid neck (20%-25%), with 60%-80% being associated with the hyoid bone.11 They are most commonly located within the midline (75%), but may be paramedian in location (25%) and embedded within the strap muscles in the infrahyoid neck.11,12 The embryologic development and descent of the thyroid primordium from the foramen cecum along the midline course of the thyroglossal duct within the neck can predict the common locations of both ectopic thyroid tissue and TGDCs. On cross-sectional imaging, the foramen cecum can be found at the base of tongue at the level of the vallecula—the most common location for the suprahyoid TDCs. The thyroglossal duct descends from this location in the midline and wraps anteriorly, inferiorly, and then posteriorly to the hyoid before continuing into the infrahyoid neck, anterior to the thyroid cartilage, and between the strap muscles (sternothyroid and sternohyoid muscles). In the infrahyoid neck, TGDCs can be found splaying across, embedded within, or deep to the strap muscles.12 On US, TGDCs may appear as simple cysts, which are thin-walled, well circumscribed, homogenous, and anechoic with posterior acoustic enhancement. They may also be pseudosolid in appearance, with central hypoechogenicity consisting of low-level internal echos secondary to proteinaceous fluid or debris. In the setting of infection or hemorrhage, they may appear as more complex cysts with thick walls, septations, and central heterogeneous echoic foci, with surrounding soft tissue edema and associated lymphadenopathy.13 On CT, TGDCs are likewise wellmarginated mucoid density cystic lesions with a thin rim of enhancement. On MRI, TGDCs demonstrate hyperintense signal on T2 weighted imaging, variable signal on T1 secondary to the fluid or protein content, and no central reduced diffusivity. In the setting of acute or prior infection, TGDCs may demonstrate a thick rim of enhancement,
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Congenital Cystic Neck Masses
Figure 1 Axial FSEIR MRI image demonstrates a midline ovoid lesion with central hyperintense T2 signal at the level of the hyoid bone (arrow), characteristic of a thyroglossal duct cyst.
centrally reduced diffusivity on MRI, and surrounding soft tissue edema and enhancement. Cross-sectional imaging with CT and MRI is helpful in demonstrating the key relationship of the TGDC to the hyoid bone, which as predicted by the embryologic descent, may be located superior, inferior, anterior, or posterior to the TGDC (Figure 1). It is also helpful in demonstrating a characteristic thin connecting stalk coursing from infrahyoid TGDCs toward the midline11 (Figure 2). The rare presence of soft tissue within a TGDC should raise concern for associated functional thyroid tissue or thyroid carcinoma, which is seen in 1% of adult patients.2,12,14 This finding is more readily visible on contrast enhanced CT and MRI.
Dermoids or epidermoids Dermoids and epidermoids are congential cystic masses that occur anywhere in the body, with 7% of dermoids occuring in the head and neck.15 Dermoids or epidermoids
3 are often midline and arise in characteristic locations along the nasal dorsum, oral cavity, and suprasternal notch. Dermoids are also found in the superolateral orbit, the most common location in the head and neck in children.16-18 In the oral cavity, dermoid or epidermoid cysts may occur within the root of tongue as well as within the sublingual space, bound inferiorly by the mylohyoid muscle. More commonly, oral cavity dermoids are located within the midline anteriorly, whereas epidermoid cysts are located laterally.17 Dermoids may also rarely be found at sites of embryologic fusion along the midline of the infrahyoid neck,including thyroidal, suprasternal, and suboccipital locations18 (Figure 3). Imaging characteristics of these lesions are determined by the lining of the cyst and allow one to distinguish between dermoid and epidermoid cysts in some instances. In contrast to the squamous epithelium that lines epidermoid cysts, the epithelial lining of dermal cysts contains hair follicles, sweat glands, and dermal appendages, which make these lesions appear more complex on imaging.15,16 CT and MRI are the preferred imaging modalities for evaluation of suspected oral cavity dermoid or epidermoids, allowing one to characterize the extent of the lesion, its internal appearance, and its relationship to surrounding structures, aiding in the determination of optimal surgical approach. On CT, epidermoids appear as a nonenhancing simple thinwalled fluid density cyst. Dermoids have a more variable appearance and may demonstrate foci of fat density, calcification, or fluid-fluid levels. However, they may also appear as a simple thin-walled fluid density cyst, making them indistinguishable from epidermoids.15,16,19 On MRI, dermoids and epidermoids are nonenhancing and hyperintense on T2 weighted imaging. Epidermoids demonstrate reduced diffusivity and hypointense signal on T1, whereas the signal intensity on T1 weighted imaging in dermoids is variable depending on the fat content. In the presence of macroscopic fat globules, the cyst may appear as a “bag of marbles,” which constitutes a very characteristic visual feature.2,17
Figure 2 Axial FSEIR MRI images at the level of the thyroid cartilage (left) and hyoid bone (right) demonstrate an off-midline infrahyoid ovoid lesion with central hyperintense T2 signal embedded within the strap muscle and contiguous with a T2 hyperintense signal tract coursing superiorly to the level of the hyoid bone.
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Operative Techniques in Otolaryngology, Vol ], No ], ] 2017 within the neck, with cysts being the most common (75%).15,16 Imaging of these masses often begins with US in the case of suspected second branchial cleft cysts. CT and MRI are usually obtained in the workup of first, third, and fourth branchial cleft anomalies, due to their proximity to critical structures and tendency to be more complex.
Figure 3 Axial CECT image demonstrating a well demarcated superficially located nonenhancing low density ovoid mass in the midline at the level of the suprasternal notch, characteristic of a dermoid cyst.
Differential diagnoses of midline cystic neck masses When considering a patient presenting with a midline neck mass, including those that occur at the base of tongue and in the anterior suprahyoid and infrahyoid neck, lesions may often appear similar on imaging. However, certain key features can help point to a specific diagnosis in many cases. As discussed, at the base of tongue, a cystic mass should prompt consideration of TGDCs, vallecular cysts, epidermoids or dermoids, foregut duplication cysts, and lymphatic malformations. On imaging, vallecular cysts may appear very similarly to TGDCs, presenting as a simple cystic mass at the tongue base pushing the epiglottis posteriorly. These lesions are more rare than TGDCs and imaging can occasionally demonstrate the more superficial submucosal nature of the vallecular cyst and the absence of a tail or notch toward the hyoid (with confirmation by direct laryngoscopy).13,20,21 Fat components within a dermoid, in addition to a more superficial location in the neck (Figure 3), as well as lack of any findings to suggest superinfection such as septations and enhancement, can aid in differentiating these cysts from other entities.13 A foregut duplication cyst of the tongue can mimic a dermoid due to its proteinaceous content yielding high signal on T1 weighted images. However, the foregut duplication cysts typically have a thicker wall and more commonly involve the anterior two-thirds of the tongue rather than the tongue base.16,17,22,23 In the infrahyoid neck, a midline infected TGDC that splays the strap muscles may also mimic a necrotic Delphian node. Yet, this is a very atypical location for adenopathy in children without thyroid disease and an atypical location in the adult in the absence of malignancy.24
First branchial cleft cyst The first branchial apparatus anomaly (BAA) is the second most common of the branchial cleft defects and typically presents as a cyst with or without a sinus tract. They are divided into 2 types based on the embryology: type 1— which present as cysts near the pinna and external auditory canal (EAC); and type 2—which is associated with the parotid gland occurring medial or lateral to the facial nerve.15,16,25 On CT, they present as well circumscribed nonenhancing or thin rim enhancing fluid density masses in the periauricular or periparotid region (Figure 4). MRI may demonstrate hyperintense T2 signal within an associated sinus tract to the parotid, EAC, or skin. In the setting of superinfection, the cyst walls will thicken and enhance with surrounding soft tissue edema and cellulitis. First branchial apparatus anomalies are associated with cholesteatomas of the EAC, presenting as a nonenhancing submucosal mass with bony erosion of the tympanic plate. Second branchial cleft cyst The second branchial cleft anomaly is the most common, comprising 95% of the lesions and most frequently presenting as a cyst.15,16,26 The Bailey classification divides these cysts into 4 types with the second type being most common and occurring within the submandibular space posterior to the submandibular gland, lateral to the carotid space, and along the anterior surface of the sternocleidomastoid muscle15,16,26 (Figure 5). On US, they appear as a compressible, well-marginated thin-walled round anechoic
Imaging of lateral cystic neck masses Branchial apparatus anomalies Branchial cleft anomalies present as a combination of cysts, sinuses, and fistulas in characteristic anatomic spaces
Figure 4 Axial CECT image demonstrating a low density peripherally enhancing cystic lesion within the left parotid gland with a tract coursing superiorly and posterior toward the external auditory canal (arrow), characteristic of a first branchial apparatus anomaly.
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Differential diagnoses for lateral cystic neck masses
Figure 5 Axial CECT image demonstrates a well demarcated round low density peripherally enhancing cystic lesion located lateral to the carotid space, posterior to the submandibular gland, and medial to the sternocleidomastoid muscle, a characteristic appearance of a second branchial cleft cyst.
cyst with posterior acoustic enhancement. On CT, they appear similarly as a thin-walled well circumscribed fluid density nonenhancing cyst, and on MRI, they demonstrate hyperintense signal on T2 weighted imaging and hypointense T1 signal. On all imaging modalities, in the setting of infection, the cyst may demonstrate a thicker wall, internal debris, and surrounding edema and cellulitis. Centrally reduced diffusivity may be seen on MRI. Third and fourth branchial apparatus anomalies The third and fourth branchial apparatus anomalies are not reliably distinguished by imaging. Both typically present in the setting of recurrent infection and have a relationship to the pyriform sinus, giving them their alternate names of pyriform sinus tract or pyriform sinus fistula.10,27,28 The third BAA appears as a predominantly left-sided unilocular cyst within the posterior triangle, posterior to the carotid space, and sternocleidomastoid, with a sinus tract to the pyriform sinus that classically opens along the superolateral aspect.10,27,28 A third BAA fistula, if present, will open to the skin anterior to the sternocleidomastoid.10,27,28 In the setting of superinfection, as elsewhere, the cyst may demonstrate thickened mural enhancement, septations, internal debris, and edema along the course of the tract and fistula. The fourth BAA most commonly presents secondary to recurrent suppurative thyroiditis as a sinus tract coursing from the apex of the left pyriform sinus to the left thyroid lobe27,28 (Figure 6). There may be an associated thyroid abscess or diffuse enlargement of the gland with surrounding cellulitis and edema. Cross-sectional imaging may depict the course of the sinus tract in some patients. Alternatively, a barium pharyngogram may be performed to better visualize the tract following a treatment course for infection, as the tract may be acutely obscured by edema and inflammation.2,27
As discussed, the branchial apparatus anomalies occur in characteristic locations within the neck. However, they often present similarly to other infectious and congenital cystic masses, making a single imaging diagnosis challenging. Several unique features can be sought to differentiate among these entities. In the parotid and periauricular spaces where one most commonly finds first BAAs, the differential diagnosis includes infectious nonmycobacterial lymphadenitis, lymphatic malformations, and parotid cysts. Non-TB mycobacterial infection has a predilection to involve the nodes in the periauricular, parotid, and submandibular spaces and can mimic superinfection of a first branchial apparatus anomaly. Often, however, the non-TB mycobacterial nodes will be numerous and directly extend to the skin surface with minimal associated cellulitis—features that would be atypical for infection of a first branchial apparatus anomaly.24,29,30 Parotid cysts, including lymphoepithelial cysts and salivary duct cysts, are rare lesions in children but may be indistinguishable from first BCC based on imaging alone, though a first BCC without an associated sinus tract is a less common presentation.10 In the submandibular space, the classic location for a second branchial cleft cyst, the main differentials to consider are a submandibular space abscess, unilocular lymphatic malformation, cervical thymic cyst, and in an adult, a metastatic lymph node from HPV positive squamous cell carcinoma.15,16 A characteristic feature of second BCCs, which is occasionally depicted on CT and MRI, is a rim of tissue extending from the cyst medially between the internal and external carotid arteries known as the “beak sign.”10,16 In the setting of infection, differentiating superinfection of a second branchial cleft cyst from a submandibular space abscess is often not possible. Follow-up imaging after a course of treatment is advised to evaluate for underlying residual cystic anomaly. Lymphatic malformations in the neck are most commonly found in the posterior cervical space but may occur anywhere.15,16 They have a varied imaging appearance ranging from single space to transspatial, unlocular, to multilocular, and macrocystic to microcystic. When single space and unilocular, they can appear similar to many other cystic neck lesions, however, when trans-spatial and infiltrative, they are more easily differentiated. On MRI, lymphatic malformation (LMs) characteristically demonstrate the presence of fluid-fluid levels secondary to hemorrhage. This is helpful if present, but is not universally seen16,31 (Figure 7). As discussed, the third and fourth BAA are often not distinguishable on imaging alone. A left-sided cystic mass in the region of the thyroid should prompt one to consider a thyroid cyst, a cervical thymic cyst, and an infrahyoid paramedian TGDC. None of these other cysts, however, are associated with recurrent thyroiditis like the BAAs. Thyroidal colloid cysts are rare in young children. A relationship to the strap muscles, either embedded within
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Figure 6 Axial CECT images at the level of the thyroid (left) and at the level of the pyriform sinus (right) demonstrate a low density cystic lesion centered within the left lobe of the thyroid, which is edematous and hyperenhancing. There is a contiguous tract coursing superiorly to the left pyriform sinus. This appearance is characteristic for thyroiditis associated with superinfection of a fourth branchial apparatus anomaly.
or just adjacent, should be sought to distinguish an offmidline TGDC from a fourth BAA, which will be centered more deeply beneath the strap muscles and within the thyroid lobe16,27,28 (Figures 2 and 6).
Imaging of cervical thymic cysts Thymic cysts and ectopic thymic tissue can be found anywhere along the course of the thymopharyngeal duct, which courses from the angle of the mandible parallel to the sternocleidomastoid and into the anterior mediastinum where it medializes. They occur much more commonly in the mediastinum than in the neck,32 and when found in the neck, they are most often infrahyoid on the left side, just inferior to the level of the thyroid.16,32 A connection to the thymus in the mediastinum is seen in 50%, either directly by the cyst yielding a bilobed or dumbbell shape, or by a fibrous stalk that is not resolvable by imaging16,32 (Figure 8). On US, they appear as a large unilocular anechoic elongated cyst closely apposed to the carotid sheath and most often deep to the sternocleidomastoid muscle. Cross-sectional imaging with CT or MRI can more
Figure 7 Axial FSEIR MRI image demonstrates a mulitlocular cystic lesion in the left posterior triangle with multiple fluid-fluid levels characteristic of a lymphatic malformation (arrow).
readily demonstrate any extension into the mediastinum, which is difficult to visualize on US (Figure 8). On CT and MRI, they follow fluid density and signal intensity, respectively. On imaging, one may see a tapered appearance at their ends. The differential diagnosis for thymic cysts includes the other previously discussed lateral cystic neck masses: the BAAs and LMs. LMs rarely extend into the mediastinum and are more often multilocular and posteriorly located within the neck.32 In the suprahyoid neck, thymic cysts may splay the carotid artery and jugular vein, an atypical feature for a second BCC, which occur in a similar location. In the infrahyoid neck, the lesions may appear very similar to third BAAs, and pathology is required for differentiation.10,32
Imaging of cervical teratoma Fetal neck masses are rare, with cervical teratomas being the most common neoplasm.5 When large, they can have significant antenatal, perinatal, and postnatal effects due to
Figure 8 Coronal CECT demonstrates an elongated low density nonenhancing cystic lesion extending from the mediastinum into the right paramedian neck embedded within thymic tissue inferiorly (arrow), characteristic of a thymic cyst.
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Conclusion Congenital neck masses in children and fetuses are relatively rare. However, they are a common indication for neck imaging when encountered. Understanding the clinical presentation in the context of embryology, anatomical neck spaces and key features on US, CT, and MRI can help narrow the list of potential diagnoses, optimize surgical planning, and more accurately prognosticate.
References
Figure 9 Axial T1 weighted MRI image demonstrates a large right mixed cystic and solid mass causing ventral and leftward deviation of the airway (arrow) and replacing the right thyroid lobe, characteristic of a congenital cervical teratoma.
compression of adjacent critical structures. Obstetric US is often the first imaging study obtained to identify the presence of a mass. On US, teratomas appear as heterogeneous echogenicity mixed solid and cystic multilocular anterior neck masses occurring anywhere from the level of the masticator space to the level of the thoracic inlet. The masses are often large and very extensive, causing hyperextension of the neck and deviation of the head and airway to one side (Figure 9). Calcific components with acoustic shadowing are characteristic, but present in only o20%50% of fetal teratomas.5,33 Color Doppler can demonstrate increased vascularity within the solid portions. Often there will be associated polyhydramnios secondary to impaired fetal swallowing. Fetal MRI is now available at many institutions and allows one to characterize the extent of the mass and degree of airway compression not resolvable by US.5,33–35 The T2 weighted half-Fourier single-shot turbo spin echo and true fast imaging in stready-state procession sequences obtained in multiple imaging planes permit evaluation of airway patency. Furthermore, MRI can demonstrate foci of fat as hyperintense signal on T1 weighted imaging and confirm the cystic and solid nature of these masses. It is important to attempt to distinguish between a teratoma and an anterior LM, the most common fetal neck mass. An LM is more frequently trans-spatial and infiltrative than a teratoma and should not have fat components. However, fat is not reliably a component of fetal teratomas, unlike teratomas occurring later in life. The LM is frequently multilocular and fluid signal intensity. Yet, a microcystic LM may appear solid secondary to numerous septations, mimicking the solid soft tissue components of a teratoma. The relationship to the thyroid gland can be helpful, with teratomas often replacing and involving the thyroid, seen as a claw of tissue around the borders of the mass, whereas LMs displace the thyroid without replacing it34,36,37 (Figure 9).
1. American College of Radiology (ACR) Website. Appropriateness Criteria. http://www.acr.org/Quality-Safety/Appropriateness-Criteria. Accessed September 12, 2016. 2. Wong KT, Lee YY, King AD, et al: Imaging of cystic or cyst-like neck masses. Clin Radiol 63(6):613-622, 2008 3. Sippel S, Muruganandan K, Levine A, et al: Review article: Use of ultrasound in the developing world. Int J Emerg Med 4:72, 2011 4. McDonald RJ, McDonald JS, Kallmes DF, et al: Intracranial gadolinium deposition after contrast-enhanced MR imaging. Radiology 275(3):772-782, 2015 5. Tonni G, De Felice C, Centini G, et al: Cervical and oral teratoma in the fetus: A systematic review of etiology, pathology, diagnosis, treatment and prognosis. Arch Gynecol Obstet 282:355-361, 2010 6. Cass DL: Impact of prenatal diagnosis and therapy on neonatal surgery. Semin Fetal Neonatal Med 16:130-138, 2011 7. Rauff S, Kien TE: Ultrasound diagnosis of fetal neck masses: A case series. Case Rep Obstet Gynecol 2013:1-3. [Article ID 243590], 2013 8. Bulas D, Egloff A: Benefits and risks of MRI in pregnancy. Semin Perinatol 37(5):301-304, 2013 9. Meier JD, Grimmer JF: Evaluation and management of neck masses in children. Am Fam Physician 89(5):353-358, 2014 10. Mittal MK, Malik A, Sureka B, et al: Cystic masses of neck: A pictorial review. Indian J Radiol Imaging 22(4):334-343, 2012 11. Ahuja AT, Wong KT, King AD, et al: Imaging for thyroglossal duct cyst: The bare essentials. Clin Radiol 60:141-148, 2005 12. Zander DA, Smoker WR: Imaging of ectopic thyroid tissue and thyroglossal duct cysts. Radiographics 34(1):37-50, 2014 13. Oyewumi M, Inarejos E, Greer M, et al: Ultrasound to differentiate thyroglossal duct cysts and dermoid cysts in children. The Laryngoscope 125(4):998-1003, 2014 14. Motamed M, McGlashan JA: Thyroglossal duct carcinoma. Curr Opin Otolaryngol Head Neck Surg 12:106-109, 2004 15. Som PM, Smoker WR, Curtin HD, et al: Congenital lesions of the neck. In: Som PM, Curtin HD, editors. Head and Neck Imaging. 5th ed. St Louis, Mo: Mosby; 2011. p. 2235-2286, 2011 16. Koeller KK, Alamo L, Adair CF, et al: Congenital cystic masses of the neck: Radiologic-pathologic correlation. Radiographics 19:121-146, 1999 17. Edwards RM, Chapman T, Horn DL, et al: Imaging of pediatric floor of mouth lesions. Pediatr Radiol 43(5):523-535, 2013 18. Vittore CP, Goldberg KN, McClatchey KD, et al: Cystic mass at the suprasternal notch of a newborn: Congenital suprasternal dermoid cyst. Pediatr Radiol 28(12):984-986, 1998 19. Bluestone CD, Stool SE, Alper CM, et al: Pediatric Otolaryngology— Volume 2. Philadelphia, PA: Saunders; 2003. 20. Gogia S, Agarwal SK, Agarwal A: Vallecular cyst in neonates: Case series —A clinicosurgical insight. Case Rep Otolaryngol 2014:764-860, 2014 21. Cheng SS, Forte V, Shah VS: Symptomatic congenital vallecular cyst in a neonate. J Pediatr 155(3):446, 2009 22. Puvaneswary M, Cassey J: Magnetic resonance imaging findings of a foregut duplication cyst of the floor of the mouth in a fetus. Australas Radiol 49(1):66-68, 2005 23. Eaton D, Billings K, Timmons C, et al: Congenital foregut duplication cysts of the anterior tongue. Arch Otolaryngol Head Neck Surg 127 (12):1484-1487, 2001
8 24. Restrepo R, Oneto J, Lopez K, et al: Head and neck lymph nodes in children: The spectrum from normal to abnormal. Pediatr Radiol 39 (8):836-846, 2009 25. Bailey H: Branchial Cysts and Other Essays on Surgical Subjects in the Facio-Cervical Region. London, England: Lewis; 1929. 26. Mossa-Basha M, Yousem DM: Congenital cystic lesions of the neck. Appl Radiol 42(1):8-22, 2013 27. Wang HK, Tiu CM, Chou YH, et al: Imaging studies of pyriform sinus fistula. Pediatr Radiol 33:328-333, 2003 28. Thomas B, Shroff M, Forte V, et al: Revisiting imaging features and the embryologic basis of third and fourth branchial anomalies. AJNR Am J Neuroradiol 31(4):755-760, 2010 29. Robson CD, Hazra R, Barnes P, et al: Non tuberculous mycobacterial infection of the head and neck in immunocompetent children: CT and MR findings. AJNR Am J Neuroradiol 20:1829-1835, 1999 30. Hanck C, Fleisch F, Katz G: Imaging appearance of nontuberculous mycobacterial infection of the neck. AJNR Am J Neuroradiol 25 (2):349. [author reply 349-350], 2004
Operative Techniques in Otolaryngology, Vol ], No ], ] 2017 31. Güneyli Serkan, Ceylan Naim, Bayraktaroğlu Selen, et al: Imaging findings of vascular lesions in the head and neck. Diagn Interv Radiol 20(5):432-437, 2014 32. Nguyen Q, deTar M, Wells W, et al: Cervical thymic cyst: Case reports and review of the literature. Laryngoscope 106:247-252, 1996 33. Woodward PJ, Sohaey R, Kennedy A, et al: A comprehensive review of fetal tumors with pathologic correlation. Radiographics 25(1): 215-242, 2005 34. Breysem L, Bosmans H, Dymarkowski S, et al: The value of fast MR imaging as an adjunct to ultrasound in prenatal diagnosis. Eur Radiol 13(7):1538-1548, 2003 35. Courtier J, Poder L, Wang Z, et al: Fetal tracheolaryngeal airway obstruction: Prenatal evaluation by sonography and MRI. Pediatr Radiol 40:1800-1805, 2010 36. Martino F, Avila LF, Encinas JL, et al: Teratomas of the neck and mediastinum in children. Pediatr Surg Int 22(8):627-634, 2006 37. Cho JY, Lee YH: Fetal tumors: Prenatal ultrasonographic findings and clinical characteristics. Ultrasonography 33(4):240-251, 2014
Imaging of pediatric congenital cystic neck masses Jennifer A. Vaughn, MD From the Department of Radiology, Boston Children’s Hospital, Boston, Massachusetts KEYWORDS Congenital; Neck masses; Pediatric; Imaging
Congenital neck lesions are a common indication for imaging in the pediatric population. Although the clinical history and physical examination can narrow the differential diagnosis, imaging is often obtained to distinguish among possible entities and provide additional information needed to guide appropriate treatment. In this article, congenital cystic neck masses including thyroglossal duct cysts, dermoid or epidermoids, branchial apparatus anomalies, thymic cysts, and cervical teratomas will be discussed, with a focus on characteristic imaging features and locations that define these lesions. r 2017 Elsevier Inc. All rights reserved.
Introduction When considering which imaging study to order, the clinician has a variety of options, including high-resolution ultrasound (US), computed tomography (CT), and magnetic resonance imaging (MRI). Given the variety of imaging options available today, the American College of Radiology (ACR) has published standards and guidelines to aid in selecting the most appropriate imaging modality for various clinical presentations.1 US is an appropriate initial imaging examination for palpable superficial neck masses in both febrile and afebrile children. US is widely available, relatively inexpensive, can be performed without sedation, and does not expose children to ionizing radiation. Advances in US technology have led to the development of machines that allow for high-quality spatial and contrast resolution and provide the unique advantage of real time assessment.2 The use of US is continuing to increase in the United States, and has been used more extensively in Europe and in the developing world for the workup of a broader range of indications.1,3 US can readily reveal the cystic nature of a mass, allow determination of mass size, and locate many lesions within a Address reprint requests and correspondence: Department of Radiology, Boston Children’s Hospital, 300 Longwood Ave, Boston, MA 02116. E-mail address: [email protected] http://dx.doi.org/10.1016/j.otot.2017.05.011 1043-1810/r 2017 Elsevier Inc. All rights reserved.
specific anatomic neck space. With the use of Doppler, US can provide information on the presence and degree of vascularity, helping to differentiate between high- and lowflow vascular malformations. US can also assist with imageguided biopsy in the cooperative older patient and in the sedated patient.2 Despite the growing awareness and concern of exposure to medical radiation, CT still plays a very important role in the workup of neck masses in pediatric patients. CT provides fast imaging, often without the need for sedation and therefore remains a valuable tool for evaluating patients in the emergency setting. At many institutions, CT equipment is portable, making it an accessible test for children who cannot be transported to the Radiology Department. Additionally, CT serves as the only cross-sectional imaging modality available for patients who cannot undergo MRI secondary to implanted devices or external monitoring hardware. CT of the neck with iodinated contrast (contrast enhanced computed tomography) is recommended in the febrile child suspected of having secondary infection of a congenital cystic neck lesion that may require surgical management. CT and MRI can both be useful to define the extent of more complex lesions that may involve several anatomical spaces within the neck and are not well visualized on US, including lesions located in or around the parotid and thyroid gland, oral cavity lesions, lesions associated with the airway, and deeply located lesions. In addition to characterizing the cystic nature of a mass, both
2 MRI and contrast enhanced computed tomography can detect specific histologic components of the lesion, such as the presence of calcification, fat, and hemorrhage. This information can often point to a single likely diagnosis preoperatively. MRI is being more widely performed in the workup of pediatric neck masses, particularly in the nonemergent setting. MRI avoids the use of ionizing radiation and can provide excellent delineation of soft tissue anatomy. In the case of suspected congenital lymphatic and vascular malformations, MRI is the preferred imaging modality. In many pediatric patients, however, MRI may require sedation and anesthesia, as children have difficulty remaining still in the MR scanner long enough to produce diagnostically useful images. Information is also becoming available on the potential risk of gadolinium-based contrast agents, which are often used in the workup of neck masses. Studies have shown deposition of gadolinium in brain tissue in patients who received numerous administrations.4 Fetal neck masses are uncommon and may be inconspicuous or overlooked on routine second trimester obstetric US.5-7 MRI is now being performed prenatally in fetuses suspected of having a cystic neck mass on US. Accurate antenatal diagnosis is challenging yet essential to distinguish among the various pathologies and assess fetal airway anatomy. This information will affect parental counseling, antenatal, and postnatal management.6 Fetal imaging is performed at 1.5 or 3 T without the use of contrast. Although there is no evidence that MRI is hazardous to the fetus, potential long-term concerns relating to acoustic damage are still unknown.8 Fetal MRI can be especially useful in the workup of obese patients and in instances of unfavorable fetal positioning where US can be very difficult. MRI can delineate the extent of fetal neck masses in terms of the anatomical space(s) involved, the relationship of the mass to the airway, and the presence of intracranial or intrathoracic involvement. Moreover, it can detect any additional fetal anomalies that may be present in syndrome-associated neck masses and warrant consideration of karyotyping.7 The cystic or solid nature of a mass and specific histologic components, such as fat, can also be more readily resolved on MRI than on US. Imaging may be performed at several time points before delivery and can provide crucial information for the clinicians regarding airway management and mode of delivery, including the need for an ex utero intrapartum treatment procedure.5 Given the variety of appropriate imaging modalities available in the workup of neck masses in fetuses and children, it is crucial to understand the appearance of these lesions on US, CT, and MRI. Location within the neck is one of the key features in helping both the clinician and radiologist differentiate among the numerous causes for congenital neck lesions. Broadly, lesions can be defined as: (1) midline—including those in the oral cavity, base of tongue, and perithyroidal visceral space; (2) lateral— including those in the submandibular, parotid, carotid, and parapharyngeal spaces; and (3) those in the posterior
Operative Techniques in Otolaryngology, Vol ], No ], ] 2017 triangle. They may be further classified based on their relation to the hyoid bone as suprahyoid or infrahyoid. Furthermore, cystic lesions can be confined to a single anatomic space or they may be trans-spatial extending between numerous regions of the neck. The purpose of this article is to highlight the key imaging features of the most commonly encountered congenitally acquired neck lesions in children, with a focus on developing a differential diagnosis based on anatomical location, to guide management.
Imaging of midline cystic neck masses Thyroglossal duct cysts Thyroglossal duct cyst (TGDC) is the most common congenital neck mass and the most common midline cystic neck mass.9-11 Imaging is important to confirm the suspected diagnosis, to define the anatomical extent, to evaluate for the presence of thyroid tissue, and to detect the rare instances of malignant degeneration. TGDCs are located in the infrahyoid neck (25%-65%) or in the suprahyoid neck (20%-25%), with 60%-80% being associated with the hyoid bone.11 They are most commonly located within the midline (75%), but may be paramedian in location (25%) and embedded within the strap muscles in the infrahyoid neck.11,12 The embryologic development and descent of the thyroid primordium from the foramen cecum along the midline course of the thyroglossal duct within the neck can predict the common locations of both ectopic thyroid tissue and TGDCs. On cross-sectional imaging, the foramen cecum can be found at the base of tongue at the level of the vallecula—the most common location for the suprahyoid TDCs. The thyroglossal duct descends from this location in the midline and wraps anteriorly, inferiorly, and then posteriorly to the hyoid before continuing into the infrahyoid neck, anterior to the thyroid cartilage, and between the strap muscles (sternothyroid and sternohyoid muscles). In the infrahyoid neck, TGDCs can be found splaying across, embedded within, or deep to the strap muscles.12 On US, TGDCs may appear as simple cysts, which are thin-walled, well circumscribed, homogenous, and anechoic with posterior acoustic enhancement. They may also be pseudosolid in appearance, with central hypoechogenicity consisting of low-level internal echos secondary to proteinaceous fluid or debris. In the setting of infection or hemorrhage, they may appear as more complex cysts with thick walls, septations, and central heterogeneous echoic foci, with surrounding soft tissue edema and associated lymphadenopathy.13 On CT, TGDCs are likewise wellmarginated mucoid density cystic lesions with a thin rim of enhancement. On MRI, TGDCs demonstrate hyperintense signal on T2 weighted imaging, variable signal on T1 secondary to the fluid or protein content, and no central reduced diffusivity. In the setting of acute or prior infection, TGDCs may demonstrate a thick rim of enhancement,
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Figure 1 Axial FSEIR MRI image demonstrates a midline ovoid lesion with central hyperintense T2 signal at the level of the hyoid bone (arrow), characteristic of a thyroglossal duct cyst.
centrally reduced diffusivity on MRI, and surrounding soft tissue edema and enhancement. Cross-sectional imaging with CT and MRI is helpful in demonstrating the key relationship of the TGDC to the hyoid bone, which as predicted by the embryologic descent, may be located superior, inferior, anterior, or posterior to the TGDC (Figure 1). It is also helpful in demonstrating a characteristic thin connecting stalk coursing from infrahyoid TGDCs toward the midline11 (Figure 2). The rare presence of soft tissue within a TGDC should raise concern for associated functional thyroid tissue or thyroid carcinoma, which is seen in 1% of adult patients.2,12,14 This finding is more readily visible on contrast enhanced CT and MRI.
Dermoids or epidermoids Dermoids and epidermoids are congential cystic masses that occur anywhere in the body, with 7% of dermoids occuring in the head and neck.15 Dermoids or epidermoids
3 are often midline and arise in characteristic locations along the nasal dorsum, oral cavity, and suprasternal notch. Dermoids are also found in the superolateral orbit, the most common location in the head and neck in children.16-18 In the oral cavity, dermoid or epidermoid cysts may occur within the root of tongue as well as within the sublingual space, bound inferiorly by the mylohyoid muscle. More commonly, oral cavity dermoids are located within the midline anteriorly, whereas epidermoid cysts are located laterally.17 Dermoids may also rarely be found at sites of embryologic fusion along the midline of the infrahyoid neck,including thyroidal, suprasternal, and suboccipital locations18 (Figure 3). Imaging characteristics of these lesions are determined by the lining of the cyst and allow one to distinguish between dermoid and epidermoid cysts in some instances. In contrast to the squamous epithelium that lines epidermoid cysts, the epithelial lining of dermal cysts contains hair follicles, sweat glands, and dermal appendages, which make these lesions appear more complex on imaging.15,16 CT and MRI are the preferred imaging modalities for evaluation of suspected oral cavity dermoid or epidermoids, allowing one to characterize the extent of the lesion, its internal appearance, and its relationship to surrounding structures, aiding in the determination of optimal surgical approach. On CT, epidermoids appear as a nonenhancing simple thinwalled fluid density cyst. Dermoids have a more variable appearance and may demonstrate foci of fat density, calcification, or fluid-fluid levels. However, they may also appear as a simple thin-walled fluid density cyst, making them indistinguishable from epidermoids.15,16,19 On MRI, dermoids and epidermoids are nonenhancing and hyperintense on T2 weighted imaging. Epidermoids demonstrate reduced diffusivity and hypointense signal on T1, whereas the signal intensity on T1 weighted imaging in dermoids is variable depending on the fat content. In the presence of macroscopic fat globules, the cyst may appear as a “bag of marbles,” which constitutes a very characteristic visual feature.2,17
Figure 2 Axial FSEIR MRI images at the level of the thyroid cartilage (left) and hyoid bone (right) demonstrate an off-midline infrahyoid ovoid lesion with central hyperintense T2 signal embedded within the strap muscle and contiguous with a T2 hyperintense signal tract coursing superiorly to the level of the hyoid bone.
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Operative Techniques in Otolaryngology, Vol ], No ], ] 2017 within the neck, with cysts being the most common (75%).15,16 Imaging of these masses often begins with US in the case of suspected second branchial cleft cysts. CT and MRI are usually obtained in the workup of first, third, and fourth branchial cleft anomalies, due to their proximity to critical structures and tendency to be more complex.
Figure 3 Axial CECT image demonstrating a well demarcated superficially located nonenhancing low density ovoid mass in the midline at the level of the suprasternal notch, characteristic of a dermoid cyst.
Differential diagnoses of midline cystic neck masses When considering a patient presenting with a midline neck mass, including those that occur at the base of tongue and in the anterior suprahyoid and infrahyoid neck, lesions may often appear similar on imaging. However, certain key features can help point to a specific diagnosis in many cases. As discussed, at the base of tongue, a cystic mass should prompt consideration of TGDCs, vallecular cysts, epidermoids or dermoids, foregut duplication cysts, and lymphatic malformations. On imaging, vallecular cysts may appear very similarly to TGDCs, presenting as a simple cystic mass at the tongue base pushing the epiglottis posteriorly. These lesions are more rare than TGDCs and imaging can occasionally demonstrate the more superficial submucosal nature of the vallecular cyst and the absence of a tail or notch toward the hyoid (with confirmation by direct laryngoscopy).13,20,21 Fat components within a dermoid, in addition to a more superficial location in the neck (Figure 3), as well as lack of any findings to suggest superinfection such as septations and enhancement, can aid in differentiating these cysts from other entities.13 A foregut duplication cyst of the tongue can mimic a dermoid due to its proteinaceous content yielding high signal on T1 weighted images. However, the foregut duplication cysts typically have a thicker wall and more commonly involve the anterior two-thirds of the tongue rather than the tongue base.16,17,22,23 In the infrahyoid neck, a midline infected TGDC that splays the strap muscles may also mimic a necrotic Delphian node. Yet, this is a very atypical location for adenopathy in children without thyroid disease and an atypical location in the adult in the absence of malignancy.24
First branchial cleft cyst The first branchial apparatus anomaly (BAA) is the second most common of the branchial cleft defects and typically presents as a cyst with or without a sinus tract. They are divided into 2 types based on the embryology: type 1— which present as cysts near the pinna and external auditory canal (EAC); and type 2—which is associated with the parotid gland occurring medial or lateral to the facial nerve.15,16,25 On CT, they present as well circumscribed nonenhancing or thin rim enhancing fluid density masses in the periauricular or periparotid region (Figure 4). MRI may demonstrate hyperintense T2 signal within an associated sinus tract to the parotid, EAC, or skin. In the setting of superinfection, the cyst walls will thicken and enhance with surrounding soft tissue edema and cellulitis. First branchial apparatus anomalies are associated with cholesteatomas of the EAC, presenting as a nonenhancing submucosal mass with bony erosion of the tympanic plate. Second branchial cleft cyst The second branchial cleft anomaly is the most common, comprising 95% of the lesions and most frequently presenting as a cyst.15,16,26 The Bailey classification divides these cysts into 4 types with the second type being most common and occurring within the submandibular space posterior to the submandibular gland, lateral to the carotid space, and along the anterior surface of the sternocleidomastoid muscle15,16,26 (Figure 5). On US, they appear as a compressible, well-marginated thin-walled round anechoic
Imaging of lateral cystic neck masses Branchial apparatus anomalies Branchial cleft anomalies present as a combination of cysts, sinuses, and fistulas in characteristic anatomic spaces
Figure 4 Axial CECT image demonstrating a low density peripherally enhancing cystic lesion within the left parotid gland with a tract coursing superiorly and posterior toward the external auditory canal (arrow), characteristic of a first branchial apparatus anomaly.
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Differential diagnoses for lateral cystic neck masses
Figure 5 Axial CECT image demonstrates a well demarcated round low density peripherally enhancing cystic lesion located lateral to the carotid space, posterior to the submandibular gland, and medial to the sternocleidomastoid muscle, a characteristic appearance of a second branchial cleft cyst.
cyst with posterior acoustic enhancement. On CT, they appear similarly as a thin-walled well circumscribed fluid density nonenhancing cyst, and on MRI, they demonstrate hyperintense signal on T2 weighted imaging and hypointense T1 signal. On all imaging modalities, in the setting of infection, the cyst may demonstrate a thicker wall, internal debris, and surrounding edema and cellulitis. Centrally reduced diffusivity may be seen on MRI. Third and fourth branchial apparatus anomalies The third and fourth branchial apparatus anomalies are not reliably distinguished by imaging. Both typically present in the setting of recurrent infection and have a relationship to the pyriform sinus, giving them their alternate names of pyriform sinus tract or pyriform sinus fistula.10,27,28 The third BAA appears as a predominantly left-sided unilocular cyst within the posterior triangle, posterior to the carotid space, and sternocleidomastoid, with a sinus tract to the pyriform sinus that classically opens along the superolateral aspect.10,27,28 A third BAA fistula, if present, will open to the skin anterior to the sternocleidomastoid.10,27,28 In the setting of superinfection, as elsewhere, the cyst may demonstrate thickened mural enhancement, septations, internal debris, and edema along the course of the tract and fistula. The fourth BAA most commonly presents secondary to recurrent suppurative thyroiditis as a sinus tract coursing from the apex of the left pyriform sinus to the left thyroid lobe27,28 (Figure 6). There may be an associated thyroid abscess or diffuse enlargement of the gland with surrounding cellulitis and edema. Cross-sectional imaging may depict the course of the sinus tract in some patients. Alternatively, a barium pharyngogram may be performed to better visualize the tract following a treatment course for infection, as the tract may be acutely obscured by edema and inflammation.2,27
As discussed, the branchial apparatus anomalies occur in characteristic locations within the neck. However, they often present similarly to other infectious and congenital cystic masses, making a single imaging diagnosis challenging. Several unique features can be sought to differentiate among these entities. In the parotid and periauricular spaces where one most commonly finds first BAAs, the differential diagnosis includes infectious nonmycobacterial lymphadenitis, lymphatic malformations, and parotid cysts. Non-TB mycobacterial infection has a predilection to involve the nodes in the periauricular, parotid, and submandibular spaces and can mimic superinfection of a first branchial apparatus anomaly. Often, however, the non-TB mycobacterial nodes will be numerous and directly extend to the skin surface with minimal associated cellulitis—features that would be atypical for infection of a first branchial apparatus anomaly.24,29,30 Parotid cysts, including lymphoepithelial cysts and salivary duct cysts, are rare lesions in children but may be indistinguishable from first BCC based on imaging alone, though a first BCC without an associated sinus tract is a less common presentation.10 In the submandibular space, the classic location for a second branchial cleft cyst, the main differentials to consider are a submandibular space abscess, unilocular lymphatic malformation, cervical thymic cyst, and in an adult, a metastatic lymph node from HPV positive squamous cell carcinoma.15,16 A characteristic feature of second BCCs, which is occasionally depicted on CT and MRI, is a rim of tissue extending from the cyst medially between the internal and external carotid arteries known as the “beak sign.”10,16 In the setting of infection, differentiating superinfection of a second branchial cleft cyst from a submandibular space abscess is often not possible. Follow-up imaging after a course of treatment is advised to evaluate for underlying residual cystic anomaly. Lymphatic malformations in the neck are most commonly found in the posterior cervical space but may occur anywhere.15,16 They have a varied imaging appearance ranging from single space to transspatial, unlocular, to multilocular, and macrocystic to microcystic. When single space and unilocular, they can appear similar to many other cystic neck lesions, however, when trans-spatial and infiltrative, they are more easily differentiated. On MRI, lymphatic malformation (LMs) characteristically demonstrate the presence of fluid-fluid levels secondary to hemorrhage. This is helpful if present, but is not universally seen16,31 (Figure 7). As discussed, the third and fourth BAA are often not distinguishable on imaging alone. A left-sided cystic mass in the region of the thyroid should prompt one to consider a thyroid cyst, a cervical thymic cyst, and an infrahyoid paramedian TGDC. None of these other cysts, however, are associated with recurrent thyroiditis like the BAAs. Thyroidal colloid cysts are rare in young children. A relationship to the strap muscles, either embedded within
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Figure 6 Axial CECT images at the level of the thyroid (left) and at the level of the pyriform sinus (right) demonstrate a low density cystic lesion centered within the left lobe of the thyroid, which is edematous and hyperenhancing. There is a contiguous tract coursing superiorly to the left pyriform sinus. This appearance is characteristic for thyroiditis associated with superinfection of a fourth branchial apparatus anomaly.
or just adjacent, should be sought to distinguish an offmidline TGDC from a fourth BAA, which will be centered more deeply beneath the strap muscles and within the thyroid lobe16,27,28 (Figures 2 and 6).
Imaging of cervical thymic cysts Thymic cysts and ectopic thymic tissue can be found anywhere along the course of the thymopharyngeal duct, which courses from the angle of the mandible parallel to the sternocleidomastoid and into the anterior mediastinum where it medializes. They occur much more commonly in the mediastinum than in the neck,32 and when found in the neck, they are most often infrahyoid on the left side, just inferior to the level of the thyroid.16,32 A connection to the thymus in the mediastinum is seen in 50%, either directly by the cyst yielding a bilobed or dumbbell shape, or by a fibrous stalk that is not resolvable by imaging16,32 (Figure 8). On US, they appear as a large unilocular anechoic elongated cyst closely apposed to the carotid sheath and most often deep to the sternocleidomastoid muscle. Cross-sectional imaging with CT or MRI can more
Figure 7 Axial FSEIR MRI image demonstrates a mulitlocular cystic lesion in the left posterior triangle with multiple fluid-fluid levels characteristic of a lymphatic malformation (arrow).
readily demonstrate any extension into the mediastinum, which is difficult to visualize on US (Figure 8). On CT and MRI, they follow fluid density and signal intensity, respectively. On imaging, one may see a tapered appearance at their ends. The differential diagnosis for thymic cysts includes the other previously discussed lateral cystic neck masses: the BAAs and LMs. LMs rarely extend into the mediastinum and are more often multilocular and posteriorly located within the neck.32 In the suprahyoid neck, thymic cysts may splay the carotid artery and jugular vein, an atypical feature for a second BCC, which occur in a similar location. In the infrahyoid neck, the lesions may appear very similar to third BAAs, and pathology is required for differentiation.10,32
Imaging of cervical teratoma Fetal neck masses are rare, with cervical teratomas being the most common neoplasm.5 When large, they can have significant antenatal, perinatal, and postnatal effects due to
Figure 8 Coronal CECT demonstrates an elongated low density nonenhancing cystic lesion extending from the mediastinum into the right paramedian neck embedded within thymic tissue inferiorly (arrow), characteristic of a thymic cyst.
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Conclusion Congenital neck masses in children and fetuses are relatively rare. However, they are a common indication for neck imaging when encountered. Understanding the clinical presentation in the context of embryology, anatomical neck spaces and key features on US, CT, and MRI can help narrow the list of potential diagnoses, optimize surgical planning, and more accurately prognosticate.
References
Figure 9 Axial T1 weighted MRI image demonstrates a large right mixed cystic and solid mass causing ventral and leftward deviation of the airway (arrow) and replacing the right thyroid lobe, characteristic of a congenital cervical teratoma.
compression of adjacent critical structures. Obstetric US is often the first imaging study obtained to identify the presence of a mass. On US, teratomas appear as heterogeneous echogenicity mixed solid and cystic multilocular anterior neck masses occurring anywhere from the level of the masticator space to the level of the thoracic inlet. The masses are often large and very extensive, causing hyperextension of the neck and deviation of the head and airway to one side (Figure 9). Calcific components with acoustic shadowing are characteristic, but present in only o20%50% of fetal teratomas.5,33 Color Doppler can demonstrate increased vascularity within the solid portions. Often there will be associated polyhydramnios secondary to impaired fetal swallowing. Fetal MRI is now available at many institutions and allows one to characterize the extent of the mass and degree of airway compression not resolvable by US.5,33–35 The T2 weighted half-Fourier single-shot turbo spin echo and true fast imaging in stready-state procession sequences obtained in multiple imaging planes permit evaluation of airway patency. Furthermore, MRI can demonstrate foci of fat as hyperintense signal on T1 weighted imaging and confirm the cystic and solid nature of these masses. It is important to attempt to distinguish between a teratoma and an anterior LM, the most common fetal neck mass. An LM is more frequently trans-spatial and infiltrative than a teratoma and should not have fat components. However, fat is not reliably a component of fetal teratomas, unlike teratomas occurring later in life. The LM is frequently multilocular and fluid signal intensity. Yet, a microcystic LM may appear solid secondary to numerous septations, mimicking the solid soft tissue components of a teratoma. The relationship to the thyroid gland can be helpful, with teratomas often replacing and involving the thyroid, seen as a claw of tissue around the borders of the mass, whereas LMs displace the thyroid without replacing it34,36,37 (Figure 9).
1. American College of Radiology (ACR) Website. Appropriateness Criteria. http://www.acr.org/Quality-Safety/Appropriateness-Criteria. Accessed September 12, 2016. 2. Wong KT, Lee YY, King AD, et al: Imaging of cystic or cyst-like neck masses. Clin Radiol 63(6):613-622, 2008 3. Sippel S, Muruganandan K, Levine A, et al: Review article: Use of ultrasound in the developing world. Int J Emerg Med 4:72, 2011 4. McDonald RJ, McDonald JS, Kallmes DF, et al: Intracranial gadolinium deposition after contrast-enhanced MR imaging. Radiology 275(3):772-782, 2015 5. Tonni G, De Felice C, Centini G, et al: Cervical and oral teratoma in the fetus: A systematic review of etiology, pathology, diagnosis, treatment and prognosis. Arch Gynecol Obstet 282:355-361, 2010 6. Cass DL: Impact of prenatal diagnosis and therapy on neonatal surgery. Semin Fetal Neonatal Med 16:130-138, 2011 7. Rauff S, Kien TE: Ultrasound diagnosis of fetal neck masses: A case series. Case Rep Obstet Gynecol 2013:1-3. [Article ID 243590], 2013 8. Bulas D, Egloff A: Benefits and risks of MRI in pregnancy. Semin Perinatol 37(5):301-304, 2013 9. Meier JD, Grimmer JF: Evaluation and management of neck masses in children. Am Fam Physician 89(5):353-358, 2014 10. Mittal MK, Malik A, Sureka B, et al: Cystic masses of neck: A pictorial review. Indian J Radiol Imaging 22(4):334-343, 2012 11. Ahuja AT, Wong KT, King AD, et al: Imaging for thyroglossal duct cyst: The bare essentials. Clin Radiol 60:141-148, 2005 12. Zander DA, Smoker WR: Imaging of ectopic thyroid tissue and thyroglossal duct cysts. Radiographics 34(1):37-50, 2014 13. Oyewumi M, Inarejos E, Greer M, et al: Ultrasound to differentiate thyroglossal duct cysts and dermoid cysts in children. The Laryngoscope 125(4):998-1003, 2014 14. Motamed M, McGlashan JA: Thyroglossal duct carcinoma. Curr Opin Otolaryngol Head Neck Surg 12:106-109, 2004 15. Som PM, Smoker WR, Curtin HD, et al: Congenital lesions of the neck. In: Som PM, Curtin HD, editors. Head and Neck Imaging. 5th ed. St Louis, Mo: Mosby; 2011. p. 2235-2286, 2011 16. Koeller KK, Alamo L, Adair CF, et al: Congenital cystic masses of the neck: Radiologic-pathologic correlation. Radiographics 19:121-146, 1999 17. Edwards RM, Chapman T, Horn DL, et al: Imaging of pediatric floor of mouth lesions. Pediatr Radiol 43(5):523-535, 2013 18. Vittore CP, Goldberg KN, McClatchey KD, et al: Cystic mass at the suprasternal notch of a newborn: Congenital suprasternal dermoid cyst. Pediatr Radiol 28(12):984-986, 1998 19. Bluestone CD, Stool SE, Alper CM, et al: Pediatric Otolaryngology— Volume 2. Philadelphia, PA: Saunders; 2003. 20. Gogia S, Agarwal SK, Agarwal A: Vallecular cyst in neonates: Case series —A clinicosurgical insight. Case Rep Otolaryngol 2014:764-860, 2014 21. Cheng SS, Forte V, Shah VS: Symptomatic congenital vallecular cyst in a neonate. J Pediatr 155(3):446, 2009 22. Puvaneswary M, Cassey J: Magnetic resonance imaging findings of a foregut duplication cyst of the floor of the mouth in a fetus. Australas Radiol 49(1):66-68, 2005 23. Eaton D, Billings K, Timmons C, et al: Congenital foregut duplication cysts of the anterior tongue. Arch Otolaryngol Head Neck Surg 127 (12):1484-1487, 2001
8 24. Restrepo R, Oneto J, Lopez K, et al: Head and neck lymph nodes in children: The spectrum from normal to abnormal. Pediatr Radiol 39 (8):836-846, 2009 25. Bailey H: Branchial Cysts and Other Essays on Surgical Subjects in the Facio-Cervical Region. London, England: Lewis; 1929. 26. Mossa-Basha M, Yousem DM: Congenital cystic lesions of the neck. Appl Radiol 42(1):8-22, 2013 27. Wang HK, Tiu CM, Chou YH, et al: Imaging studies of pyriform sinus fistula. Pediatr Radiol 33:328-333, 2003 28. Thomas B, Shroff M, Forte V, et al: Revisiting imaging features and the embryologic basis of third and fourth branchial anomalies. AJNR Am J Neuroradiol 31(4):755-760, 2010 29. Robson CD, Hazra R, Barnes P, et al: Non tuberculous mycobacterial infection of the head and neck in immunocompetent children: CT and MR findings. AJNR Am J Neuroradiol 20:1829-1835, 1999 30. Hanck C, Fleisch F, Katz G: Imaging appearance of nontuberculous mycobacterial infection of the neck. AJNR Am J Neuroradiol 25 (2):349. [author reply 349-350], 2004
Operative Techniques in Otolaryngology, Vol ], No ], ] 2017 31. Güneyli Serkan, Ceylan Naim, Bayraktaroğlu Selen, et al: Imaging findings of vascular lesions in the head and neck. Diagn Interv Radiol 20(5):432-437, 2014 32. Nguyen Q, deTar M, Wells W, et al: Cervical thymic cyst: Case reports and review of the literature. Laryngoscope 106:247-252, 1996 33. Woodward PJ, Sohaey R, Kennedy A, et al: A comprehensive review of fetal tumors with pathologic correlation. Radiographics 25(1): 215-242, 2005 34. Breysem L, Bosmans H, Dymarkowski S, et al: The value of fast MR imaging as an adjunct to ultrasound in prenatal diagnosis. Eur Radiol 13(7):1538-1548, 2003 35. Courtier J, Poder L, Wang Z, et al: Fetal tracheolaryngeal airway obstruction: Prenatal evaluation by sonography and MRI. Pediatr Radiol 40:1800-1805, 2010 36. Martino F, Avila LF, Encinas JL, et al: Teratomas of the neck and mediastinum in children. Pediatr Surg Int 22(8):627-634, 2006 37. Cho JY, Lee YH: Fetal tumors: Prenatal ultrasonographic findings and clinical characteristics. Ultrasonography 33(4):240-251, 2014