Hearing loss in dogs: signs, causes and treatment

Overview

Sound conduction and inner ear function

Hearing may decline slightly or be lost completely. The change may affect one ear or both. In conductive hearing loss, sound does not travel normally through the ear canal or middle ear to the cochlea in the inner ear. In sensorineural hearing loss, the problem lies in the cochlea's sensory cells or the auditory pathway. Permanent damage to cochlear sensory cells can cause hearing loss. Hearing also requires a functioning auditory nerve to carry information onwards from the ear. Your dog may still hear some sounds despite no longer responding to every familiar sound.

Causes

Obstruction in the ear canal and middle ear

Longstanding outer ear inflammation can narrow the ear canal. A large build-up of earwax can also impair hearing. A ruptured eardrum may interfere with sound conduction. Fluid in the middle ear can muffle sound. Middle ear infection can develop when longstanding outer ear infection spreads deeper. Ointment remaining in the ear canal can sometimes also form a blockage that obstructs sound. An ear infection may coexist with another condition affecting hearing.

Damage to the inner ear and auditory nerve

Age-related hearing loss, or presbycusis, usually develops gradually. Inner ear inflammation can impair the nerve responsible for hearing and balance. Both a single loud sound and repeated noise exposure can damage hearing. Some medicines can damage the inner ear. Certain aminoglycoside antibiotics can cause this adverse effect, for example. Some ear cleaning products can damage the inner ear if they enter the middle ear. Hearing loss may then become noticeable to you weeks after medication has ended.

Risk factors

Age-related hearing loss often begins in the final third of a dog's lifespan. One longitudinal study followed hearing in 10 dogs for 7 years. Age-related changes began at around 8–10 years in that follow-up. Hearing thresholds rose most markedly at 8–32 kilohertz, representing middle and high frequencies. As age-related loss progresses, it can affect all frequencies.

A form of adult-onset hearing loss recognised in Border Collies may begin at 3–5 years. One breed association's description reports that adult-onset hearing loss may become apparent as early as 2–5 years. Certain USP31 gene variants have been associated with adult-onset hearing loss in Border Collies. Inherited progressive hearing loss in Rhodesian Ridgebacks can result in deafness within 1–2 years of birth. Cavalier King Charles Spaniels can develop a condition that causes middle ear fluid accumulation and conductive hearing loss. Repeated gunshots may gradually impair hearing in hunting and working dogs. A gunfire noise study compared auditory evoked responses in 40 active hunting dogs with measurements from 10 puppies. The hunting dogs had smaller waveform peaks following a click sound than the puppies. In German adverse drug reaction reports, most hearing loss observed after ear medication affected dogs over 10 years old.

Typical symptoms

Gradual hearing loss may initially be apparent only in certain situations.

• Your dog responds to their name or familiar verbal cues less often.
• A sleeping dog no longer wakes to ordinary household sounds.
• When looking for a sound, your dog turns towards the hearing ear.
• Your dog more often stays where they can see you.
• Your dog may bark more than usual.
• An inflamed ear may cause head shaking.

One-sided hearing loss may go unnoticed at home because the other ear can hear. Your dog may follow other dogs' reactions rather than hearing the sound themselves. If an ear infection spreads to the middle ear, opening the mouth or touching the head and neck may be painful.

Complications and consequences

Safety, balance and everyday function

A dog with poor hearing may not notice an approaching vehicle. Unexpected touch can startle a dog that did not hear someone approach. With inner ear inflammation, hearing loss may accompany a head tilt and balance problems. The inflammation can also cause involuntary eye movements. Middle ear inflammation can affect facial nerve function and pull the lip to one side.

In a study of ageing dogs, poorer hearing was associated with owner-reported changes in everyday function. Questionnaire results suggesting cognitive signs were more common in the severe hearing loss group. This study of 39 older dogs tested hearing thresholds using sounds at 50, 70 and 90 decibels. In the 90-decibel group, the relative risk of a questionnaire result indicating moderate or severe cognitive signs was 3.88 compared with the other groups. This association does not show that hearing loss causes cognitive disease.

Diagnosis at the vet

Examining the ear and eardrum

Your vet examines the ear canal and eardrum with an otoscope. A sample from the canal can be checked for inflammatory cells and microbes. Discharge or a narrow canal may prevent a view of the eardrum. A normal-looking eardrum does not rule out middle ear infection. CT can help assess the bony middle ear structures. MRI can show middle ear fluid and changes in surrounding soft tissues. Fluid may also be an incidental imaging finding, so its significance is assessed alongside symptoms. Among 380 dogs undergoing brain MRI, 54 had changes consistent with middle ear inflammation (14.2%). Inflammation in some part of the ear was incidental in 45 of 380 dogs (11.8%).

Brainstem auditory evoked response testing: BAER

BAER testing measures the electrical response of the auditory nerve and brainstem to a brief sound. Sound is usually delivered through an earphone to one ear at a time. Small electrodes placed on the head record the response as a waveform. The hearing threshold is the quietest tested sound producing an identifiable response. Several sound levels can be used to establish the threshold. In one study, ears with outer ear inflammation had a mean threshold of 65 dBnHL. Ears classified as normal had a mean threshold of 15 dBnHL. Each ear is tested separately, so one-sided deafness can be detected even if your dog responds to sounds at home. A conventional click test does not describe hearing at each pitch as precisely as frequency-specific testing. Visual cues and floor vibrations can confuse observations of responses to sounds at home.

Hearing screening and official reports

In one official hearing screening scheme, an approved vet must issue the report. Dogs must be permanently identified before an official examination under this scheme. The minimum age for official testing is 35 days. Before measurement, the ear canals and eardrums are checked to ensure they are healthy. If the result is inconclusive, retesting is recommended after about 4 weeks. The official classification is determined by the result of the worse-hearing ear. Adult dogs can also be tested.

Treatment

Treating ear infections and blockages

Your vet chooses treatment according to the cause of hearing loss. If a large amount of discharge has accumulated in the outer ear canal, your vet may flush it. If bacterial middle ear infection is suspected, a sample from that area can be cultured to guide medication selection. A middle ear sample reflects the infection better than outer ear discharge, which may contain other microbes. Discharge can be removed from the middle ear by making a small opening in the eardrum if needed. If an obstruction to sound caused the hearing loss, hearing may return after its removal. After middle ear infection, hearing can return gradually over several weeks.

An otitis study compared 105 inflamed ears with 86 healthy ears. Cleaning the ear canal measurably improved auditory responses in several dogs. Two dogs in the study were completely deaf on the side of the inflamed ear. In a small series of 4 dogs, hearing thresholds improved by an average of 22.3 decibels after ear ointment removal. Improvement ranged from 13 to 41 decibels.

Middle ear mucus plugs and permanent hearing loss

A Cavalier King Charles Spaniel study identified 61 episodes of middle ear inflammation associated with mucus plugs in 43 dogs. Treatment included mucus plug removal and middle ear flushing. Treatment involving plug removal had to be repeated 1–5 times. After severe or longstanding middle or inner ear infection, hearing loss may remain permanent despite resolution of the infection. Medicines cannot reverse permanent loss of inner ear sensory cells. Hearing aids generally provide only limited help for dogs. If a hearing change is noticed during ear medication, your vet assesses whether to change the medicine or clean the canal.

Prevention

Limiting repeated exposure to loud sounds can reduce the risk of noise injury. Hearing protection is available for dogs in situations where noise cannot be avoided. A study of two kennels measured average sound levels of 100–108 decibels. Hearing measurements changed in all 14 tested dogs over 6 months of follow-up. In recurrent ear infections, treating the underlying predisposition helps prevent further episodes. Weekly ear checks help you notice changes in ear condition. Drying the ears after swimming reduces moisture that can predispose dogs to ear infections, particularly those with floppy ears.

Important for dog owners

Teach a clear hand signal alongside a familiar verbal cue. Keep your dog on a lead near traffic because they may not hear a car or horn. A securely fenced area is suitable for off-lead exercise. Approach an awake dog within their field of vision so they see you coming. You can try waking a sleeping dog by tapping the floor nearby. However, floor vibrations do not reach every dog. Scent-based search games provide enrichment for an ageing dog even when hearing or sight declines. Do not put a cotton bud into the ear canal, as it can damage the eardrum.

Frequently asked questions

Can an ear infection cause hearing loss?

Inflammation can narrow the canal or increase middle ear fluid, muffling sound on its way to the inner ear. If sound conduction is obstructed, hearing may improve after infection treatment and discharge removal. Hearing loss can remain permanent after longstanding inner ear infection.

How can I tell if only one ear has lost hearing?

Your dog may hear a familiar sound but turn towards the hearing ear to look for it. Poor hearing in one ear can go unnoticed because the dog learns to compensate. BAER testing can measure the response of each ear separately.

Can an older dog's hearing be tested?

Brainstem auditory evoked response testing can be performed in adult and older dogs. The results show whether sounds at different levels produce a measurable response. Examining the ears also helps find a potentially treatable obstruction to sound, such as discharge in the canal.

What should I do if hearing worsens during ear medication?

Contact the vet treating your dog promptly and explain when the change began in relation to medication. Hearing can deteriorate because of the infection itself, medicine remaining in the canal or inner ear damage. Examining the ear helps your vet decide whether cleaning or other treatment is needed.

How can a dog with poor hearing learn recall?

Your dog can learn that a clear hand signal means to come to you once you have gained their attention. The signal works when your dog can see you and is paying attention. Training is safest on a lead or in a fenced area.