A 52-year-old man presents with progressive unilateral hearing loss over 18 months and high-pitched tinnitus. Pure-tone audiometry shows the pattern marked **B** in the diagram — unilateral asymmetric sloping sensorineural hearing loss. Speech discrimination score is markedly reduced (28%) despite relatively preserved pure-tone thresholds at low frequencies. Which of the following is the most likely diagnosis?
A. Vestibular schwannoma (acoustic neuroma) arising from the vestibular division of CN VIII
B. Menière disease with low-frequency sensorineural hearing loss
C. Sudden sensorineural hearing loss secondary to viral labyrinthitis
D. Otosclerosis with conductive component masking underlying sensorineural loss
Explanation
Why Vestibular schwannoma (acoustic neuroma) is right
The audiogram pattern marked B — unilateral asymmetric sloping SNHL with markedly reduced speech discrimination out of proportion to pure-tone thresholds — is the pathognomonic retrocochlear signature of vestibular schwannoma. This benign Schwann cell tumor arises from the vestibular division of CN VIII and accounts for 80–90% of cerebellopontine angle tumors. The disproportionate loss of speech discrimination (poor word recognition despite relatively preserved low-frequency thresholds) is a key retrocochlear sign that distinguishes VS from cochlear pathology. The clinical presentation of progressive unilateral hearing loss (95% of cases) with high-pitched tinnitus and the specific audiometric pattern are classic for VS. Per Cummings Otolaryngology 7e and CNS NF2 guidelines 2022, this combination mandates MRI of the internal auditory canal with gadolinium for definitive diagnosis.
Why each distractor is wrong
Sudden sensorineural hearing loss secondary to viral labyrinthitis: While sudden SSNHL can occur in 5–10% of VS presentations and must be ruled out with MRI, the 18-month progressive course and the specific high-frequency sloping pattern with poor speech discrimination are not typical of acute viral labyrinthitis, which usually presents with vertigo and more diffuse SNHL.
Otosclerosis with conductive component: Otosclerosis (marked C in the diagram) presents with conductive or mixed hearing loss, not pure SNHL. The audiogram pattern would show an air-bone gap, not the asymmetric sloping SNHL seen in B. Additionally, otosclerosis does not cause the marked disproportionate speech discrimination loss characteristic of retrocochlear pathology.
Menière disease with low-frequency sensorineural hearing loss: Menière disease (marked D in the diagram) classically causes low-frequency SNHL, not the high-frequency sloping pattern shown in B. Menière also presents with episodic vertigo, fluctuating hearing, and tinnitus, whereas VS causes progressive unilateral loss with dysequilibrium (not true vertigo) due to slow growth allowing central compensation.
High-YieldNEET PG
Asymmetric SNHL + disproportionately poor speech discrimination = retrocochlear pathology (VS) → get MRI IAC with gadolinium; bilateral = NF2.
Cummings Otolaryngology 7e Ch. 177; CNS NF2 guidelines 2022
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