Acoustic Shock Disorder

Acoustic shock disorder is a set of symptoms that follows a sudden, unexpected loud sound, usually through a telephone headset, in people who do not have a measurable threshold loss. Symptoms include ear pain, tinnitus, hyperacusis and aural fullness.

Exposure : Call centre and telephone operators, headset users and others in noisy or communication work. The sound is often a loud tone or feedback, and may not exceed levels causing hearing loss.

Epidemiology: Prevalence is not well defined. It affects a small proportion of headset users, and many report anxiety around the incident.

Many recover within weeks to months. Some develop persistent hyperacusis, tinnitus and avoidance of sound.

Associated conditions. Anxiety, depression, sleep disturbance and work disability.

Pathophysiology

Mechanisms are not fully defined. Proposed mechanisms include excessive tensor tympani and stapedius muscle contraction and spasm, cochlear and neural injury, and altered central auditory gain.

Startle responses and heightened anxiety may amplify and perpetuate symptoms through central sensitisation.

• Ear pain or burning, aural fullness, tinnitus, hyperacusis and sensitivity to everyday sounds.
• Fluttering or clicking sensations (tensor tympani syndrome) and dizziness.
• Headache, neck or jaw pain, anxiety and sleep disturbance.
• Avoidance of noisy environments and use of earplugs.

Red flags.

• Sudden hearing loss, vertigo, facial weakness or ear discharge.
• Marked depression, anxiety or suicidal thoughts.

• Incident history: sound type, level, headset equipment, timing and symptoms.
• Otoscopy and tympanometry; acoustic reflex testing.
• Pure tone audiometry, usually normal or showing mild loss; otoacoustic emissions.
• Loudness discomfort levels for hyperacusis.
• Screening for anxiety and depression; audit of headset and telephone system output.

Differential diagnosis. Noise induced hearing loss, acute acoustic trauma, Meniere disease, temporomandibular joint disorder, otitis media, eustachian tube dysfunction, migraine, somatic symptom disorder.

• Remove the source of the injury: headsets with sound level limiters, shorter use and replacement of faulty equipment.
• Avoid overprotection. Continuous earplug use worsens hyperacusis; use graded sound exposure and sound therapy.
• Cognitive behavioural therapy for tinnitus, hyperacusis and anxiety.
• Tinnitus retraining therapy and graded return to work with workplace adjustment.
• No drug has proven benefit. Treat coexisting anxiety or depression by usual practice.
• Hearing rehabilitation and counselling for persistent symptoms.

Monitoring. Review at 4 to 6 weeks, then every 3 months until stable; repeat audiometry if symptoms change.

Referral and escalation. Audiology, ENT and occupational health; psychological therapy for persistent symptoms; urgent review for sudden hearing loss; notification and compensation where required.