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Radiology Quiz Case 3: Diagnosis

Radiology Quiz Case 3: Diagnosis Diagnosis: Hairy (dermoid) cyst originating from the eustachian tube A dermoid cyst originating from the eustachian tube is a rare congenital anomaly, with only 14 cases reported in the literature, to our knowledge.1,2 Most cases occur in females and in the left ear.2 Approximately 7% of all dermoids develop in the head and neck area, and more than 50% of these are found in the periorbital region and 13% in the nasal cavity.3 Although dermoids are considered benign developmental malformations, their location within the relatively inaccessible eustachian tube, with resultant obstruction, can cause significant morbidity.4 The most popular hypothesis regarding histogenesis suggests that dermoids of the eustachian tube originate from errors in ectodermal inclusions at the site of contact of the endodermal surface of the first pharyngeal pouch and the ectodermal surface of the first branchial cleft.5 At approximately the fourth to fifth weeks of gestation, the endodermal lining of the first pharyngeal pouch (from which the tympanic cavity and the auditory tube form) comes in contact with the overlying ectoderm of the first branchial groove (which later deepens to form the external auditory meatus). An inclusion of ectoderm into the endodermal lining during this short period of contact between the 2 layers is the underlying mechanism for the development of dermoids in this region.5 The typical clinical presentation of dermoids involving the eustachian tube consists of chronic ear drainage with recurrent episodes of otitis media.6 This is caused by the obstruction of the eustachian tube by the dermoid. Negative pressure is created within the tympanic cavity and the mastoid air cells, associated with low oxygen and/or high carbon dioxide tension. Such abnormal tension produces alterations of the middle ear mucosa, with an increase of the mucus-secreting cells. Tympanic membrane perforation and inflammatory polyps or granulation tissue may be associated findings. Although the definitive diagnosis is histologic, computed tomography and magnetic resonance imaging may be helpful in diagnosing a dermoid cyst based on the imaging characteristics, anatomical location, and extent of the lesion. Computed tomography is superior in the demonstration of bone changes and can provide excellent visualization of expansion or erosion of the osseous portion of the eustachian canal and involvement of the ossicular chain within the middle ear. It can also demonstrate the characteristic fat component of the lesion, showing a negative attenuation number (Hounsfield unit), which can confirm the diagnosis. According to previous reports, the typical magnetic resonance imaging appearance consists of a well-defined, nonenhancing mass surrounded by a smooth capsule and a relatively homogeneous matrix that follows the signal intensity of fat.5 Also, the anatomical relationship of the lesion with the major intracranial structures, intracranial or parapharyngeal extension, and associated inflammatory changes in the middle ear cavity and mastoid air cells can be detected by computed tomography or magnetic resonance imaging, which can be helpful in preoperative planning. Surgical removal is the key to the successful treatment of dermoids.1 Because these lesions are not associated with malignant change, the prognosis is excellent when complete surgical excision is achieved. In most cases, the surgical method has consisted of a retroauricular approach combined with a simple or modified radical mastoidectomy.1 References 1. Gourin CGSofferman RA Dermoid of the eustachian tube. Otolaryngol Head Neck Surg 1999;120772- 775PubMedGoogle ScholarCrossref 2. Sichel JYDano IHalperin DChisin R Dermoid cyst of the eustachian tube. Int J Pediatr Otorhinolaryngol 1999;4877- 81PubMedGoogle ScholarCrossref 3. Batsakis JG Tumors of the Head and Neck. 2nd ed. Baltimore, Md: Williams & Wilkins; 1979:226-228 4. Resta LSantangelo ALastilla G The s.c. ”hairy polyp” or “dermoid” of the nasopharynx (an unusual observation in older age). J Laryngol Otol 1984;981043- 1046PubMedGoogle ScholarCrossref 5. Kollias SSBall WS JrPrenger ECMeyers CM III Dermoids of the eustachian tube: CT and MR findings with histologic correlation AJNR Am J Neuroradiol 1995;16663- 668PubMedGoogle Scholar 6. Arcand PAbela A Dermoid cyst of the eustachian tube. J Otolaryngol 1985;14187- 191PubMedGoogle Scholar http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Archives of Otolaryngology - Head & Neck Surgery American Medical Association

Radiology Quiz Case 3: Diagnosis

Archives of Otolaryngology - Head & Neck Surgery , Volume 131 (9) – Sep 1, 2005

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Publisher
American Medical Association
Copyright
Copyright © 2005 American Medical Association. All Rights Reserved.
ISSN
0886-4470
eISSN
1538-361X
DOI
10.1001/archotol.131.9.826
Publisher site
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Abstract

Diagnosis: Hairy (dermoid) cyst originating from the eustachian tube A dermoid cyst originating from the eustachian tube is a rare congenital anomaly, with only 14 cases reported in the literature, to our knowledge.1,2 Most cases occur in females and in the left ear.2 Approximately 7% of all dermoids develop in the head and neck area, and more than 50% of these are found in the periorbital region and 13% in the nasal cavity.3 Although dermoids are considered benign developmental malformations, their location within the relatively inaccessible eustachian tube, with resultant obstruction, can cause significant morbidity.4 The most popular hypothesis regarding histogenesis suggests that dermoids of the eustachian tube originate from errors in ectodermal inclusions at the site of contact of the endodermal surface of the first pharyngeal pouch and the ectodermal surface of the first branchial cleft.5 At approximately the fourth to fifth weeks of gestation, the endodermal lining of the first pharyngeal pouch (from which the tympanic cavity and the auditory tube form) comes in contact with the overlying ectoderm of the first branchial groove (which later deepens to form the external auditory meatus). An inclusion of ectoderm into the endodermal lining during this short period of contact between the 2 layers is the underlying mechanism for the development of dermoids in this region.5 The typical clinical presentation of dermoids involving the eustachian tube consists of chronic ear drainage with recurrent episodes of otitis media.6 This is caused by the obstruction of the eustachian tube by the dermoid. Negative pressure is created within the tympanic cavity and the mastoid air cells, associated with low oxygen and/or high carbon dioxide tension. Such abnormal tension produces alterations of the middle ear mucosa, with an increase of the mucus-secreting cells. Tympanic membrane perforation and inflammatory polyps or granulation tissue may be associated findings. Although the definitive diagnosis is histologic, computed tomography and magnetic resonance imaging may be helpful in diagnosing a dermoid cyst based on the imaging characteristics, anatomical location, and extent of the lesion. Computed tomography is superior in the demonstration of bone changes and can provide excellent visualization of expansion or erosion of the osseous portion of the eustachian canal and involvement of the ossicular chain within the middle ear. It can also demonstrate the characteristic fat component of the lesion, showing a negative attenuation number (Hounsfield unit), which can confirm the diagnosis. According to previous reports, the typical magnetic resonance imaging appearance consists of a well-defined, nonenhancing mass surrounded by a smooth capsule and a relatively homogeneous matrix that follows the signal intensity of fat.5 Also, the anatomical relationship of the lesion with the major intracranial structures, intracranial or parapharyngeal extension, and associated inflammatory changes in the middle ear cavity and mastoid air cells can be detected by computed tomography or magnetic resonance imaging, which can be helpful in preoperative planning. Surgical removal is the key to the successful treatment of dermoids.1 Because these lesions are not associated with malignant change, the prognosis is excellent when complete surgical excision is achieved. In most cases, the surgical method has consisted of a retroauricular approach combined with a simple or modified radical mastoidectomy.1 References 1. Gourin CGSofferman RA Dermoid of the eustachian tube. Otolaryngol Head Neck Surg 1999;120772- 775PubMedGoogle ScholarCrossref 2. Sichel JYDano IHalperin DChisin R Dermoid cyst of the eustachian tube. Int J Pediatr Otorhinolaryngol 1999;4877- 81PubMedGoogle ScholarCrossref 3. Batsakis JG Tumors of the Head and Neck. 2nd ed. Baltimore, Md: Williams & Wilkins; 1979:226-228 4. Resta LSantangelo ALastilla G The s.c. ”hairy polyp” or “dermoid” of the nasopharynx (an unusual observation in older age). J Laryngol Otol 1984;981043- 1046PubMedGoogle ScholarCrossref 5. Kollias SSBall WS JrPrenger ECMeyers CM III Dermoids of the eustachian tube: CT and MR findings with histologic correlation AJNR Am J Neuroradiol 1995;16663- 668PubMedGoogle Scholar 6. Arcand PAbela A Dermoid cyst of the eustachian tube. J Otolaryngol 1985;14187- 191PubMedGoogle Scholar

Journal

Archives of Otolaryngology - Head & Neck SurgeryAmerican Medical Association

Published: Sep 1, 2005

Keywords: diagnostic radiologic examination,radiology specialty,dermoid cyst

References