Vestibular Schwannoma in NF2 — Bilateral MCQ — NEET PG Practice Question | NEETPGAI
Vestibular Schwannoma in NF2 — Bilateral
medium
ear ENT
A 22-year-old man presents with progressive bilateral hearing loss and tinnitus over 18 months. Pure-tone audiometry shows bilateral high-frequency sensorineural hearing loss (40–60 dB at 4–8 kHz), but speech discrimination scores are markedly disproportionately poor (32% right, 28% left). Auditory brainstem response shows delayed wave V latencies and prolonged I–V interpeak intervals bilaterally. MRI with gadolinium reveals bilateral enhancing masses in the cerebellopontine angles. The pattern marked **A** in the diagram — bilateral retrocochlear sensorineural hearing loss with poor word recognition — is characteristic of which genetic condition, and what is the first-line medical intervention?
A. Ménière disease with bilateral involvement and secondary endolymphatic hydrops; salt restriction and diuretics are the primary management
B. Neurofibromatosis type 2 (NF2) with bilateral vestibular schwannomas; bevacizumab is the first-line medical therapy for hearing preservation and tumor stabilization
C. Sporadic unilateral vestibular schwannoma with contralateral noise-induced hearing loss; observation and hearing aids are sufficient
D. Autosomal recessive Usher syndrome type 1 with progressive cochlear degeneration; cochlear implantation is the definitive treatment
Explanation
Why option 1 is correct
The clinical presentation — bilateral high-frequency sensorineural hearing loss with markedly disproportionate poor speech discrimination (rollover phenomenon), delayed ABR wave V latencies, and bilateral enhancing masses in the cerebellopontine angles on MRI — is pathognomonic for neurofibromatosis type 2 (NF2) with bilateral vestibular schwannomas. NF2 is an autosomal dominant phakomatosis caused by loss-of-function mutations in the NF2 gene (chromosome 22q12) encoding the tumor suppressor MERLIN. The bilateral retrocochlear pattern marked A reflects the compressive effect of the schwannomas on the cochlear nerve, causing the characteristic audiometric finding of poor word recognition despite moderate hearing thresholds. According to Plotkin (NEJM 2009) and Dhingra ENT, bevacizumab (anti-VEGF monoclonal antibody) is the first-line medical therapy for NF2-associated vestibular schwannomas, achieving hearing stabilization and tumor shrinkage in 40–50% of patients, thereby preserving hearing and delaying or avoiding surgery in many cases.
Why each distractor is wrong
Option 2 (Usher syndrome): Usher syndrome causes progressive cochlear sensorineural hearing loss, but it is autosomal recessive, presents with congenital or early-onset hearing loss (not progressive over 18 months in adulthood), and does not produce retrocochlear ABR patterns or bilateral cerebellopontine angle masses. The bilateral masses and retrocochlear pattern are absent.
Option 3 (Sporadic unilateral schwannoma + noise-induced loss): Sporadic vestibular schwannomas typically present unilaterally in the 5th–6th decade (much later than age 22), and the combination of unilateral schwannoma with contralateral noise-induced loss would not explain bilateral retrocochlear patterns or bilateral masses on MRI. The family history of cataracts and meningiomas also argues against sporadic disease.
Option 4 (Ménière disease): Ménière disease classically presents with low-frequency fluctuating sensorineural hearing loss, vertigo, and tinnitus, not high-frequency loss. It is not bilateral in typical presentation, does not produce retrocochlear ABR patterns, and does not cause enhancing masses on MRI. Salt restriction and diuretics address endolymphatic hydrops, not tumor burden.
High-YieldNEET PG
In NF2, the retrocochlear pattern (poor word recognition out of proportion to threshold loss) and bilateral ABR delays distinguish vestibular schwannomas from cochlear pathology; bevacizumab is the first-line medical therapy for hearing preservation.
Dhingra ENT 7e Ch 21; Plotkin NF2 NEJM 2009
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