A 35-year-old man with neurofibromatosis type 2 (NF2) undergoes contrast MRI of the brain. Bilateral enhancing masses are found at the internal auditory meatuses, expanding bilaterally. Which tumor is pathognomonic of NF2?
- A Bilateral optic gliomas
- B Bilateral acoustic neuromas (vestibular schwannomas) ✓
- C Lisch nodules and café-au-lait spots
- D Bilateral posterior fossa meningiomas
Explanation
Bilateral vestibular schwannomas (acoustic neuromas) are pathognomonic of neurofibromatosis type 2 (NF2), caused by mutations in the NF2 gene (merlin protein) on chromosome 22. On MRI, they appear as avidly enhancing masses at the internal auditory meatuses (IAM) that may expand the canal and extend into the cerebellopontine angle cistern (CPA), producing an 'ice cream on cone' appearance. NF1 (chromosome 17, neurofibromin) is associated with unilateral optic pathway gliomas and Lisch nodules. Bilateral posterior fossa meningiomas are associated with NF2 but bilateral schwannomas are the diagnostic criterion.
Reference: Grainger & Allison's Diagnostic Radiology, 7th ed.
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