Sudden hearing loss

Sudden sensorineural hearing loss is a loss of 30 dB or more over at least 3 contiguous frequencies, developing within 72 hours. It is an emergency because early treatment improves recovery and because it can reveal stroke, tumour, infection or systemic disease.

Clinical relevance. Most cases are idiopathic. Recovery occurs spontaneously in about a third to a half of patients, depends on the severity of loss, age, vertigo and the interval to treatment, and is poorer with severe or profound loss and with vertigo. About 3 to 10 percent of adults have a retrocochlear lesion on MRI.

Mechanisms. Proposed mechanisms include viral cochlear injury, vascular compromise of the labyrinthine artery, rupture of cochlear membranes, immune mediated injury, and cochlear stress response. In stroke, loss arises from ischaemia of the anterior inferior cerebellar artery territory.

Classification.

• Idiopathic.
• Secondary: infective, vascular, haematological, traumatic, ototoxic, autoimmune, neoplastic, neurological and metabolic.
• Unilateral (most) or bilateral (suggests a systemic or toxic cause).
• With or without vertigo and tinnitus.

Temporal patterns. Onset on waking is common. Loss may be complete in minutes or evolve over hours. Fluctuating loss with fullness, tinnitus and vertigo attacks suggests Meniere disease.

Key distinction. Conductive loss (wax, effusion, perforation) must be excluded first, because it is the commonest cause of apparent sudden loss and needs no steroid.

History. Exact time and circumstances of onset, whether it began on waking, rate of progression, laterality, tinnitus, vertigo, aural fullness, otalgia, otorrhoea, preceding upper respiratory infection, head or neck injury, barotrauma or diving, straining, new drugs, noise exposure, previous ear disease or surgery.

Also ask about neurological symptoms (facial droop, limb weakness, diplopia, dysarthria), headache, rash, joint pain, red eyes, visual symptoms, fever, weight loss, HIV and syphilis risk, tick bite, sickle cell disease or leukaemia, and previous episodes.

Drug history. Aminoglycosides, loop diuretics, platinum agents, high dose salicylates, quinine, macrolides, phosphodiesterase inhibitors, vancomycin.

Examination.

• Otoscopy for wax, foreign body, effusion, perforation, vesicles on the pinna or canal (Ramsay Hunt syndrome), haemotympanum, and CSF leak.
• Tuning forks: Rinne positive on the affected side and Weber to the better ear indicate sensorineural loss. A conductive pattern suggests a middle ear cause.
• Cranial nerves (facial weakness, trigeminal and other lower nerves), nystagmus, head impulse test, gait and Romberg test, limb coordination and power.
• Blood pressure, pulse (atrial fibrillation), carotid bruit, skin (rash, purpura), eyes (red eye, interstitial keratitis), joints, and lymph nodes.

Red flags

• Any neurological sign, severe vertigo with inability to walk, new headache, or diplopia
• Bilateral sudden loss
• Facial weakness or vesicles
• Head injury, temporal bone trauma, or CSF otorrhoea
• Fever, neck stiffness, or purulent ear disease
• Systemic features: rash, arthritis, eye inflammation, haematuria, sinus disease
• Sickle cell crisis, leukaemia, or hyperviscosity
• Recent aminoglycoside or cisplatin exposure
• Diabetes with poor control

Special groups. Pregnancy: treat with prednisolone only when the specialist agrees that benefit justifies risk; exclude pre-eclampsia, sickle cell crisis and venous sinus thrombosis. Children: viral infection, meningitis, congenital anomalies such as large vestibular aqueduct and trauma. Older adults: stroke is more probable with vascular risk factors. Region specific: mumps, measles, malaria treatment (quinine), tuberculosis therapy (aminoglycosides), syphilis and HIV.

Conductive causes mimicking sensorineural loss

• Cerumen impaction, foreign body
• Otitis media with effusion, acute otitis media, tympanic membrane perforation, haemotympanum
• Ossicular disruption after trauma, barotrauma

Sensorineural, idiopathic and viral

• Idiopathic sudden sensorineural hearing loss
• Viral labyrinthitis and cochleitis: cytomegalovirus, herpes simplex, varicella zoster (Ramsay Hunt syndrome), mumps, measles, rubella, HIV

Sensorineural, vascular and haematological

• Anterior inferior cerebellar artery stroke, vertebrobasilar ischaemia
• Sickle cell disease crisis, polycythaemia, leukaemia, hyperviscosity (Waldenstrom macroglobulinaemia, myeloma)
• Cochlear haemorrhage with anticoagulation

Sensorineural, structural and traumatic

• Vestibular schwannoma, meningioma, other cerebellopontine angle tumours, leptomeningeal malignancy
• Perilymph fistula, superior semicircular canal dehiscence, large vestibular aqueduct
• Temporal bone fracture, labyrinthine concussion, barotrauma, acoustic trauma
• Meniere disease (first attack)

Sensorineural, infective and inflammatory

• Bacterial meningitis, otogenic labyrinthitis, neurosyphilis, Lyme disease, cryptococcal and tuberculous meningitis
• Autoimmune inner ear disease, Cogan syndrome, granulomatosis with polyangiitis, polyarteritis nodosa, systemic lupus erythematosus, Susac syndrome, relapsing polychondritis, sarcoidosis

Toxic and other

• Ototoxic drugs (aminoglycosides, platinum agents, loop diuretics, salicylates, quinine, macrolides)
• Multiple sclerosis, migraine, metabolic disease, functional (non-organic) loss

Reasoning. Confirm that the loss is sensorineural on the same day, start treatment while testing for cause, and then image for retrocochlear and vascular disease.

Same day tests. Otoscopy after wax removal, tuning forks, pure tone audiometry with air and bone conduction and speech audiometry, tympanometry, and blood pressure. Where audiometry is not available the same day, start steroid treatment on the clinical diagnosis of sensorineural loss (tuning forks, normal otoscopy) and arrange audiometry within 2 to 3 days.

Imaging

• MRI of the internal acoustic meatus and cerebellopontine angle with gadolinium within days to 2 weeks for all idiopathic cases (can be done after steroids start).
• MRI brain with diffusion weighted imaging and vessel imaging urgently when vertigo, neurological signs or vascular risk factors suggest posterior circulation stroke (CT can be normal).
• High resolution CT temporal bone for trauma, suspected perilymph fistula, dehiscence or large vestibular aqueduct.

Blood and other tests. Targeted by history:

• glucose or HbA1c
• full blood count and film (leukaemia, sickle cell)
• ESR and C reactive protein
• treponemal serology, HIV, Lyme serology in endemic areas
• antinuclear antibody and ANCA with urine dipstick when vasculitis is suspected
• clotting profile when on anticoagulation
• thyroid stimulating hormone, lipids
• blood viscosity or serum protein electrophoresis for hyperviscosity

Routine large panels have a low yield and delay treatment. Varicella zoster PCR from any vesicle fluid. Lumbar puncture only when meningitis or neurosyphilis is suspected (after imaging).

Interpretation. A difference of 30 dB or more across three adjacent frequencies, with preserved bone conduction in the affected ear, confirms the criteria. Repeat audiometry at 2 weeks to assess recovery and at 3 months for the final level.

Limitations. Spontaneous recovery makes the benefit of steroid treatment difficult to prove and the benefit is modest. Early MRI can be normal in brainstem and labyrinthine infarction. Audiometry within hours of onset can underestimate eventual loss.

Immediate care. Same day ENT assessment. Stop ototoxic drugs when possible, rest, and avoid noise and pressure changes (flying, diving) until reviewed.

Idiopathic sudden sensorineural hearing loss

• Prednisolone 1 mg/kg orally each morning (maximum 60 mg) for 7 to 14 days, started as early as possible and ideally within 72 hours; later treatment up to 2 weeks may still help. A taper is optional.
• Monitor glucose in diabetes, blood pressure, mood and sleep, and give a proton pump inhibitor (omeprazole 20 mg orally daily) when there is peptic ulcer risk.
• Evidence is limited and benefit is modest, so this is a decision made with the patient.
• Contraindications and cautions: uncontrolled diabetes, active infection, peptic ulcer disease, uncontrolled hypertension, psychosis.
• Intratympanic corticosteroid: dexamethasone 10 mg/mL, 0.5 to 1 mL injected into the middle ear by an ENT specialist, 3 to 4 injections over 10 to 14 days.
• Use intratympanic corticosteroid as salvage within 2 to 6 weeks when oral treatment fails, or as primary treatment when systemic steroids are contraindicated.
• Hyperbaric oxygen, for example 90 minute sessions daily for 10 to 20 sessions, may be offered within 2 weeks as an adjunct, but evidence is limited.
• Antiviral drugs (unless varicella zoster), vasodilators, anticoagulants, volume expanders and routine vitamins do not improve outcomes and are not used.

Ramsay Hunt syndrome (varicella zoster). Valaciclovir 1 g orally three times daily for 7 days with prednisolone 1 mg/kg orally daily (maximum 60 mg) for 7 days then reduced over 7 days, started within 72 hours. Adjust valaciclovir: creatinine clearance 30 to 49 mL/min, 1 g every 12 hours; 15 to 29 mL/min, 1 g daily; under 15 mL/min, 500 mg daily. Immunocompromised or severe disease: aciclovir 10 mg/kg IV every 8 hours for 7 to 10 days with hydration and adjustment to kidney function.

Bacterial meningitis. Ceftriaxone 2 g IV every 12 hours with dexamethasone 10 mg IV every 6 hours for 4 days (first dose before or with the antibiotic), ampicillin 2 g IV every 4 hours when over age 60 or immunocompromised. Audiology within 4 weeks and early cochlear implant assessment.

Posterior circulation stroke. Emergency stroke care: alteplase 0.9 mg/kg IV (maximum 90 mg, 10 percent as a bolus over 1 minute and the remainder over 60 minutes) within 4.5 hours when haemorrhage is excluded, or tenecteplase 0.25 mg/kg IV as a single bolus (maximum 25 mg).

Blood pressure should be under 185/110 mmHg before and under 180/105 mmHg for 24 hours after thrombolysis. Give aspirin 300 mg orally daily when thrombolysis is not given.

Other causes

• Autoimmune inner ear disease, Cogan syndrome and vasculitis: prednisolone 1 mg/kg orally daily (maximum 60 mg) with specialist immunosuppression. Check ANCA and renal function.
• Syphilis: benzylpenicillin 3 to 4 million units IV every 4 hours (18 to 24 million units daily) for 10 to 14 days, with prednisolone, under specialist care.
• Sickle cell crisis: oxygen, hydration, analgesia and early exchange transfusion by haematology. Leukaemia and hyperviscosity: urgent haematology.
• Perilymph fistula, barotrauma and trauma: bed rest with the head raised, avoidance of straining, and ENT review for exploration when loss persists. Temporal bone fracture with CSF leak: neurosurgical and ENT referral.
• Ototoxicity: stop the drug and discuss alternatives with the prescribing team.
• Vestibular schwannoma: ENT or neurosurgical referral.
• Meniere disease: low salt diet, betahistine 16 mg orally three times daily (evidence limited), and specialist care.

Rehabilitation. Hearing aid or contralateral routing of signal device and bone anchored hearing for persistent unilateral loss, cochlear implant for bilateral profound loss, tinnitus management, balance rehabilitation for vertigo, and counselling.

Monitoring. Repeat audiometry at 2 weeks and 3 months; glucose, blood pressure and mood during prednisolone; MRI follow up; assessment for vestibular recovery.

Referral and escalation. Same day ENT and audiology for all. Stroke team for neurological signs. Neurology, rheumatology, haematology or infectious disease when a systemic cause is found. Neurosurgery for tumour or trauma.

Admission criteria. Suspected stroke, meningitis or other intracranial infection, severe vertigo with vomiting and inability to walk, bilateral loss with systemic illness, sickle cell crisis, temporal bone fracture with CSF leak, immunocompromised zoster, or diabetes needing monitored steroid treatment.

Discharge and safety netting. Review at 2 weeks with repeat audiometry. Return urgently for worsening or contralateral loss, new vertigo, facial weakness, severe headache, drowsiness, fever, neck stiffness, discharge or new neurological symptoms. Advise on ear protection and driving if vertigo persists.