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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December 7, 2017
Geniculate Ganglion Schwannoma
- Background:
- Facial nerve schwannomas (FNSs) are uncommon; they account for <1% of all temporal bone tumors.
- Preferential involvement of geniculate ganglion (GG)
- Among tumors arising from GG, FNSs are the second most common after hemangiomas.
- Clinical Presentation:
- The most common symptom is facial paralysis.
- Extension into greater superficial petrosal nerve (GSPN) and tympanic segment may present with loss of lacrimation and conductive hearing loss, respectively.
- Key Diagnostic Features:
- Benign remodeling and widening of GG on CT
- Avidly enhancing mass on CT or postgadolinium MRI in the GG with possible extension into the GSPN, tympanic or labyrinthine segments, or middle cranial fossa by eroding the roof of the GG
- Cystic degeneration and hemorrhagic components seen in large schwannomas
- Differential Diagnoses:
- Meningioma with cystic degeneration: causes hyperostosis but does not extend into petrous temporal bone
- Dural metastasis: destructive lesion rather than benign bone expansion
- Epidermoid: nonenhancing lesion with restricted diffusion
- Cavernous hemangioma of GG: typically presents an amorphous honeycomb appearance and/or internal bony spicules on CT
- Treatment:
-
Wait-and-scan strategy in the case of nongrowing asymptomatic or minimally symptomatic FNS
-
Microsurgical excision with facial nerve repair
-
Stereotactic radiosurgery
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