Case of the Week
Section Editors: Matylda Machnowska1 and Anvita Pauranik2
1University of Toronto, Toronto, Ontario, Canada
2BC Children's Hospital, University of British Columbia, Vancouver, British Columbia, Canada
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June 11, 2020
Ancient Schwannoma
- Background:
- Ancient schwannomas are rare benign encapsulated tumors of long-standing duration, and the term has been used mainly in extracranial schwannomas.
- These tumors are usually solitary and may grow to a large size.
- The term “ancient schwannoma” is used to describe a schwannoma that has undergone pronounced cystic changes such as relative loss of Antoni type A tissue, perivascular hyalinization, calcification, and cystic necrosis.
- Clinical Presentation:
- Signs and symptoms of intracanalicular schwannomas are often subtle and may take many years to develop. They usually arise from the cochlear and vestibular nerves.
- The common signs and symptoms of intracanalicular schwannoma include hearing loss, tinnitus, dizziness, unsteadiness, and facial numbness.
- Key Diagnostic Features:
- Adjacent bone remodeling when the tumor grows to a large size indicates the benign characteristics of the tumor. Widening of the bony canal of the cochlear nerve is a sign of the tumor extending into the cochlea.
- Ancient schwannomas are usually well-defined with a cystic component due to extensive necrosis. On T1WI, the tumor shows irregular mural wall thickening with enhancement after contrast material administration.
- Differential Diagnoses:
- Petrous apex cholesterol granuloma: Usually hyperintense on both T1- and T2-weighted images
- Cholesteatoma: Appears as nonenhancing, expansile middle ear lesion that may extend to the petrous apex and causes variable degrees of bone destruction. On MR imaging, cholesteatoma generally has intermediate-to-low signal intensity on T1-weighted images. On T2-weighted and FLAIR images, it generally has high signal intensity.
- Mucocele: CT of mucocele shows a smoothly expansile bone lesion that may cause septal erosion. Mucoceles typically have low-to-intermediate signal intensity on T1-weighted images, are hyperintense on T2-weighted images, and do not enhance after contrast material administration.
- Treatment:
- The management of intracanalicular schwannomas includes observation, microsurgery, and radiation treatment.
- Watchful waiting is an important management option for patients with minimal symptoms.
- Surgical removal of the tumor is very effective in regard to relief of the vestibular symptoms.
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