The acute onset of hearing loss of 30 dB in three contiguous frequencies which may have occurred instantaneously or progressively over several days. 1,2
Patients often describe a numbness or blockage as opposed to an obvious hearing loss.
The incidence is 5 to 20 per 100,000 patients per year. 3
Untreated, spontaneous recovery has been reported to range from 30-60%. 4
While a viral or microvascular aetiolgy is proposed, it is essentially a diagnosis of exclusion: cerebellopontine angle tumours, auto-immune disease, multiple sclerosis (MS), infectious aetiologies, intralbyrinthine haemorrhage 5, perilymph fistula and Meniere’s disease must be excluded. 6
Poor prognostic factors include a severe, flat pattern to the hearing loss and associated vestibular dysfunction.
Otoscopic examination is normal. Occasionally a middle ear effusion can result in toxic inner ear damage.
A Weber tuning fork test lateralising to the worst hearing ear is highly suggestive of a sensorineural hearing loss.
Audiometry with speech discrimination
Blood tests: FBC, CRP, Syphilis serology, RF, ANA, ENA, ANCA, serum electrophoresis. The utility of running any blood tests unless there is a history of systemic autioimmune type symptoms is very marginal.2
MRI brain and CPA: urgent if other neurologic signs and symptoms.
Oral Steroids are the only effective therapy shown in randomised controlled trials.7 Varying doses and length of therapy are used. 8,9 However, a recent meta-analysis has questioned the true effectiveness of oral steroids. 10
Generally the benefit to hearing occurs if therapy started within 7 days, with treatment worthwhile out to 14 days. 4
30-50% will show no response. 11
The general approach is to treat for a week and then repeat a hearing test.
High dose Vitamin E, Vitamin C and Magnesium have been reported to add minor benefit to steroids. 12,13
No definitive benefit from antivirals, haemodilution agents or hyperbaric oxygen.7 14,15
Steroid Treatment Regimes
Oral Prednisone: Usually 50mg a day, followed by a taper over the next couple of weeks
Intratympanic Steroid [Dexamethasone, Methylprednisolone]. This can be performed in the office under local anaesthesia, but there are some advantages performing the first injection under a general anaesthetic to maximise absorption through the round window into the inner ear.
Transtympanic, multiple dose. 16,17 This can be administered via a ventilation tube or grommet.
Intratympanic, single dose.
Success of around 40% in selected patients, defined as at least 20dB or 20%. 16,18-20 Although not all studies have reproduced these results. It is important to note that approximately 10% will show some improvement after more than 1 month 21 when analysing results of salvage therapy.
Some evidence to suggest increased benefit is seen if intratympanic steroid is instituted within 7-10 days. 22
Recent reports suggest routine combination oral prednisone and Intratympanic dexamethasone treatment may give the best chance of hearing improvement23 4,20,24,25
It is important to realise that to experience true binaural hearing, that hearing thresholds must be within 15-20dB in both ears.
In rare cases, where there has been a response to steroids, but further decline once the prednisone is reduced, and long term high dose prednisone is required, steroid sparing agents such as methotrexate is considered.
SSNHL is an otologic emergency which requires prompt diagnosis and institution of management in order to optimise the chance of recovery. The patient must be thoroughly informed as to the limitations of current treatments. There is evolving evidence that a subset of patients may benefit from intratympanic steroids. 23 Bilateral sudden sensorineural hearing loss is much rarer, but is more likely to be associated with significant systemic disease.27
Consideration must be given to hearing rehabilitation. Assistive listening devices and hearing aids are useful when there is measurable hearing. BiCross or a bone anchored hearing aid, BAHA is an option when there is a residual severe sensorineural hearing loss. It provides the sensation of binaural hearing in a majority of cases by re-routing a signal to the contra-lateral ear.28,29 The other option is a cochlear implant. This allows stimulation of the damaged cochlear allowing true binaural hearing, and is especially useful if tinnitus is a particular problem.30-33
Vestibular rehabilitation is also an important component in the management of this condition, if the balance is also affected.
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