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History: 18 year old woman with left sided hearing loss

Findings:

• MRI shows a lobulated mass in the left cerebellopontine angle which is hypointense on T1-weighted images, with homogeneous enhancement. Focal mass effect is present on the pons and cerebellar peduncle, with enlargement of the internal auditory canal. An intracanalicular component of the tumor is present, but the bulk of the tumor is located in the cistern. Also present is a small, enhancing focus within the right internal auditory canal.

Diagnosis:

• Neurofibromatosis II, with bilateral vestibular schwannomas

• Features that distinguish vestibular schwannomas from meningioma (also commonly occurring in this location) are the expansion of the internal auditory canal, acute angulation with the underlying petrous ridge and lack of a dural tail sign

• The finding of bilateral vestibular schwannomas is pathognomonic of neurofibromatosis type TT. Different types of CNS involvement in a patient with neurofibromatosis type II include schwannomas, meningiomas, and ependymomas.