Quietly progressive hearing loss in one ear

A 58-year-old man with gradual left-sided hearing loss, intermittent unsteadiness, and a unilateral abnormal head impulse.

The case

A 58-year-old accountant presents with a 2-year history of slowly worsening hearing in his left ear. He noticed it first at family gatherings, where he found it hard to hear his grandchildren when they sat on his left. There is a constant high-pitched tinnitus on the same side. He has occasional episodes of mild disequilibrium — particularly when walking on uneven ground or in the dark — but no discrete vertigo attacks.

He has had no facial weakness, no facial numbness, no visual symptoms, and no other neurological features. There is no family history of hearing loss or schwannoma.

On examination, his right ear and external auditory canal are normal. There is no spontaneous nystagmus. Head-impulse testing shows a clear catch-up saccade on left head impulse but is normal on the right. Facial sensation and movement are symmetric. Cerebellar examination is unremarkable.

His audiogram is shown.

Investigations

Fig. Right ear: mild presbycusis pattern with high-frequency drop appropriate for age. Left ear: substantially worse loss, downsloping from 30 dB at 500 Hz to 75 dB at 8 kHz. The right-left asymmetry at 4 kHz is 45 dB.

Question

What is the most appropriate next investigation?

Teaching point

Asymmetric sensorineural hearing loss is the single most common presentation of vestibular schwannoma. The Welling criteria and AAO-HNS guidance recommend MRI of the IACs with gadolinium for any unexplained asymmetry of 15 dB or more at any frequency, or 10 dB at 3 kHz. The unilateral abnormal head impulse in this case adds vestibular nerve involvement to the cochlear picture — together they should accelerate, not delay, the imaging decision. Most schwannomas are now diagnosed when small (≤ 1 cm), allowing the full menu of management options: observation, stereotactic radiosurgery, or microsurgery.

References

[1]Welling DB, Glasscock ME, Woods CI, Jackson CG. Acoustic neuroma: a cost-effective approach. Otolaryngology–Head and Neck Surgery 1990;103(3):364–370. doi:10.1177/019459989010300306
[2]Stangerup SE, Caye-Thomasen P, Tos M, Thomsen J. The natural history of vestibular schwannoma. Otology & Neurotology 2010;27(4):547–552. doi:10.1097/01.mao.0000217356.73463.e7
[3]Carlson ML, Link MJ. Vestibular schwannomas. New England Journal of Medicine 2021;384(14):1335–1348. doi:10.1056/NEJMra2020394