Hearing loss in one ear.

Why one-sided hearing loss is treated differently

Age-related hearing loss almost always affects both ears similarly. When loss is meaningfully asymmetric — one ear is much worse than the other, or only one ear has changed — the differential diagnosis is broader, and some of the possibilities require timely action. A pattern that looks like "the ear just gets worse on one side" can be a presenting sign of a treatable medical condition, an urgent inner-ear event, or, occasionally, a benign tumour that grows slowly enough to be missed for years.

The clinical convention is therefore: asymmetric hearing loss warrants more workup than symmetric hearing loss of the same severity.

What causes hearing loss in one ear

Conductive (outer or middle ear)

• Earwax (cerumen) impaction. The most common reversible cause of one-sided hearing loss. Often presents as sudden fullness and muffled hearing in one ear. The 2017 AAO-HNS Cerumen Impaction Clinical Practice Guideline (Schwartz et al.) outlines safe removal options.
• Middle-ear fluid (otitis media with effusion). Fluid behind the eardrum dampens transmission. May follow a cold, allergy, or eustachian tube dysfunction.
• Eardrum perforation. Sudden one-sided loss with pain or after pressure trauma, infection, or insertion of objects into the canal.
• Eustachian tube dysfunction. Often seasonal or after a respiratory infection. Produces fullness and conductive loss that may fluctuate.
• Foreign object in the canal. Cotton-tip remnants, retained hearing aid domes, or other objects.
• Otosclerosis. Abnormal middle-ear bone growth. Usually progressive and may present asymmetrically.
• Cholesteatoma. An abnormal skin growth in the middle ear from chronic infection. Progressive and requires surgical management.

Sensorineural (inner ear or nerve)

• Sudden sensorineural hearing loss (SSNHL). Over 90% of SSNHL cases affect one ear. The 2019 AAO-HNS guideline classifies SSNHL as a medical priority with a 14-day audiometric window and corticosteroids as an option within 2 weeks of onset. See our SSNHL article.
• Vestibular schwannoma (acoustic neuroma). A benign tumour on the vestibulocochlear nerve. Presents with one-sided sensorineural hearing loss, one-sided tinnitus, and/or balance change. About 1–3% of patients with sudden one-sided sensorineural hearing loss have an acoustic neuroma. Standard of care includes MRI of the internal auditory canals for asymmetric sensorineural loss.
• Ménière's disease. Episodic vertigo with fluctuating one-sided hearing loss, tinnitus, and ear fullness.
• Viral or infectious labyrinthitis. Inflammation of the inner ear, often after a viral upper-respiratory infection.
• Trauma. Head injury, temporal-bone fracture, or significant acoustic trauma (single very loud event) can damage one ear preferentially.
• Ototoxic injection or perfusion. Rarely, intratympanic gentamicin used for vertigo control can produce one-sided sensorineural loss.
• Stroke or other central pathology. Very rare, but central causes can affect hearing pathways on one side.

The AAO-HNS workup for asymmetric or sudden one-sided loss

The 2019 AAO-HNS Clinical Practice Guideline on sudden hearing loss outlines the workup most clinicians follow, with adjustments for cases that are not strictly "sudden":

1. History and physical examination — including a check for bilateral involvement, recurrent episodes, focal neurological findings, and ear examination.
2. Distinguish sensorineural from conductive with a tuning-fork test (Weber and Rinne) and audiometry.
3. Audiometry within 14 days for sudden one-sided loss; promptly for any clearly asymmetric loss.
4. MRI of the internal auditory canals to evaluate for retrocochlear pathology (most importantly vestibular schwannoma). Auditory brainstem response testing is an alternative when MRI cannot be performed.
5. Follow-up audiometry at the conclusion of any treatment and within 6 months.

The guideline explicitly recommends against routine head CT (non-targeted), routine laboratory panels, and routine use of antivirals, thrombolytics, vasodilators, or vasoactive substances for sudden sensorineural hearing loss.

Treatment options by cause

Reversible conductive causes

Earwax is removed by irrigation, suction, or curette in a clinician's office — hearing typically returns within minutes. Middle-ear fluid often resolves on its own; persistent cases may need medical or surgical management. Eardrum perforations often heal spontaneously; large perforations may be repaired surgically (tympanoplasty).

Sudden sensorineural hearing loss

Corticosteroids within 2 weeks of onset are an option; intratympanic steroids are recommended as salvage at 2–6 weeks if recovery is incomplete. Hyperbaric oxygen plus steroids is an option. See our SSNHL article for the full picture.

Vestibular schwannoma

Three management paths, chosen based on tumour size, growth rate, and patient factors: observation with serial MRI for small or slow-growing tumours, stereotactic radiosurgery (Gamma Knife / CyberKnife), or microsurgical resection. Hearing preservation is part of the planning conversation.

Permanent single-sided deafness or asymmetric loss

When hearing in one ear is permanently lost or severely reduced and not surgically recoverable, several rehabilitation options exist:

• CROS hearing aid (Contralateral Routing of Signal): a microphone on the deaf ear wirelessly transmits sound to a receiver in the better ear. Does not restore hearing in the deaf ear but eliminates the head-shadow effect when sound comes from the deaf side.
• BiCROS: similar to CROS, but for cases where the better ear also has some hearing loss; the better-ear unit also amplifies its own input.
• Bone-anchored hearing aid (BAHA / osseointegrated). A surgically implanted abutment transmits sound via bone conduction to the cochlea of the better ear.
• Cochlear implant for single-sided deafness. FDA approval expanded in 2019 to include single-sided deafness; the CI directly stimulates the deaf side's auditory nerve. Best candidates have had loss for less than a few years; longer durations are associated with reduced benefit.

Practical issues people with one-sided hearing loss face

Even with normal hearing in one ear, single-sided loss creates predictable daily challenges:

• Sound localisation — the brain uses inter-aural time and level differences to localise sounds; with input from only one ear, localisation is impaired.
• Speech-in-noise difficulty. Two ears help "unmask" speech from background noise. One ear cannot.
• Head-shadow effect. Sound from the deaf side is partially blocked by the head before reaching the good ear, so conversations on the wrong side are unusually difficult.
• Fatigue. Active listening with one ear in noisy settings is cognitively expensive.

CROS, BAHA, and cochlear implant options address subsets of these issues. None fully restore binaural hearing; the choice is about which trade-offs fit best.

The bottom line

Hearing loss in one ear sits between common reversible problems and rare but consequential ones. The pattern alone does not tell you which you have; the workup does. The 2019 AAO-HNS guideline lays out a clear path — distinguish sensorineural from conductive, get audiometry promptly, image with MRI when sensorineural and asymmetric, treat the underlying cause, and rehabilitate any residual loss with CROS, BAHA, or cochlear-implant options as appropriate. The single most important step is to act early enough that the workup actually changes management.