A 56-year-old woman presents to the clinic with a 9-month history of worsening hearing in her left ear. She reports that she first noticed the deficit when she had trouble hearing her daughter over the telephone. She also describes an intermittent "ringing" in that ear but denies any vertigo, ear pain, or drainage. Past medical history is unremarkable. Physical examination reveals a normal-appearing external auditory canal and tympanic membrane. The Weber test lateralizes to the right ear, and the Rinne test shows that air conduction is greater than bone conduction in both ears. An audiogram confirms a 35 dB sensorineural hearing loss in the left ear at high frequencies, while the right ear is within normal limits.
Which of the following is the most appropriate next step in the management of this patient?
The correct answer is:
B) Gadolinium-enhanced MRI of the internal auditory canals
The patient is presenting with unilateral (asymmetric) sensorineural hearing loss (SNHL). Asymmetric SNHL is considered a red flag that must be investigated to rule out a retrocochlear lesion, most notably a vestibular schwannoma (acoustic neuroma). Even if the patient lacks other symptoms like vertigo or facial numbness, the asymmetry alone warrants definitive imaging. Gadolinium-enhanced MRI of the brain and internal auditory canals (IACs) is the gold standard for diagnosis, as it can detect even small tumors that are limited to the internal auditory canal.
Answer choice A: Formal vestibular rehabilitation therapy, is incorrect. While this is useful for patients with chronic vestibular deficits like those following vestibular neuritis, it does not address the diagnostic necessity of identifying the cause of the asymmetric hearing loss.
Answer choice C: High-resolution CT scan of the temporal bone, is incorrect. CT is excellent for evaluating bony structures, such as in cases of suspected cholesteatoma or temporal bone fractures. However, it is significantly less sensitive than MRI for detecting soft tissue tumors like schwannomas within the IAC.
Answer choice D: Reassurance and repeat audiometry, is incorrect. Asymmetric SNHL should never be ignored or simply monitored without imaging, as early detection of a vestibular schwannoma allows for more management options (e.g., radiation vs. surgery) and better preservation of surrounding cranial nerve function.
Answer choice E: Trial of high-dose oral corticosteroids, is incorrect. This is the treatment for sudden sensorineural Hearing loss (SSNHL), which occurs over a period of 72 hours or less. This patient’s hearing loss has been progressive over 9 months, making an inflammatory or idiopathic sudden etiology unlikely.
Key Learning Point
Asymmetric sensorineural hearing loss is a classic presentation for a vestibular schwannoma (acoustic neuroma) until proven otherwise. Unlike age-related hearing loss (presbycusis), which is symmetric, asymmetric deficits require a gadolinium-enhanced MRI to evaluate the internal auditory canal and cerebellopontine angle.
