Sudden Sensorineural Hearing Loss (SSNHL)


Introduction

  • Sudden sensorineural hearing loss (SSNHL) is a medical emergency requiring early recognition and treatment.
  • It is estimated to affect between 5 – 30 people per 100,000 each year. 1
  • Hearing loss is unilateral in the majority of cases.
  • There is no sex preference and the condition can affect a wide range of ages, with an average age of 50 – 60 years at presentation. 1

Definition of SSNHL (“Rule of three”)6

Loss of hearing of:

  • At least 30 dB
  • Affecting at least three consecutive frequencies on pure tone audiometry
  • Occurring within 3 days

Aetiology

  • The underlying aetiology and pathogenesis of SSNHL remains unclear but is thought to relate from possible vascular, viral, inflammatory or immune-mediated causes. 2
  • In up to 5% of patients, SSNHL is the first presentation of a benign tumour of the cerebellopontine angle, known as a vestibular schwannoma. 3
  • These tumours usually grow very slowly over many years and do not always require treatment.

History and Examination

History

Presenting Complaint

The most common symptoms include:

  • Unilateral hearing loss
  • Otalgia (50% of cases)
  • Balance disturbance (50% of cases)
  • Tinnitus (70% of cases)
  • Aural fullness

History of Presenting Complaint

Take a focused history asking about the following: 4

  • Onset and progression of symptoms:
    • Unilateral or bilateral symptoms?
    • Sudden change or gradual deterioration over 72 hours?
    • Perceived fluctuation in symptoms?
  • Associated features:
    • Tinnitus (persistent, unilateral, pulsatile or recently changed in nature)
    • Vertigo (an abnormal sensation of motion, usually spinning, while staying still)
    • Otalgia
    • Otorrhoea
    • Aural fullness or pressure in the ear
    • New neurological symptoms

Past medical history

  • History of ear infections, previous ear surgery or hearing loss
  • Recent trauma
  • Chronic conditions including immunosuppression, diabetes, cardiovascular disease, neurological and autoimmune conditions

Medication History

  • Medications including use of ototoxic drugs such as aminoglycosides (ask about admissions to hospital with sepsis)

Family History

  • Family history of hearing loss

Social History

  • Occupation including exposure to excessive noise

Clinical Examination4

Otoscopy

  • There is typically no abnormalities visible on otoscopy in SSNHL however you should rule out other causes of hearing loss (e.g. excessive ear wax).

Hearing Assessment

  • Rinne’s test typically reveals air conduction is better than bone conduction in the affected ear.
  • Weber’s test typically reveals lateralisation to the non-affected ear.
  • Tuning fork tests may be more difficult to interpret in patients with pre-existing hearing loss, and pure tone audiometry is required to confirm the type and severity of the hearing loss

Neurological Assessment

  • A full neurological assessment including upper and lower limbs, cranial nerves and cerebellar examination should be performed.
  • Neurological assessment may reveal balance issues (if the vestibular nerve or cerebellum are involved – e.g. vestibular schwannoma).

General Assessment

  • You should perform a broad assessment of the patient, looking for signs suggestive of possible underling systemic causes (e.g. infective, autoimmune).

Summary

Common findings on clinical examination include:

  • Normal otoscopy
  • Abnormal Rinne’s and Weber’s tests in keeping with sensorineural hearing loss

Investigations

  • Pure tone audiometry is the gold standard investigation and will confirm the type of hearing loss, conductive or sensorineural, and indicate the severity and pattern of hearing loss, providing a baseline for assessment of recovery and efficacy of treatment.
  • An MRI IAM (internal acoustic meatus) should be carried out on an outpatient basis to exclude vestibular schwannoma, even if the hearing loss improves spontaneously.
  • Routine blood testing is not recommended.4

Management

  • Patients with SSNHL should be discussed with the local ENT on-call team to arrange urgent pure tone audiometry and plan review after initial primary care treatment.
  • SSNHL is typically managed acutely in primary care with a short course of high dose oral steroids, though there is no consensus on their effectiveness.5
  • Caution should be taken in elderly patients and those with relative contraindications to steroids, such as diabetes and immunosuppression. Gastric protection should also be considered.
  • If the initial course of oral steroids fails to produce any hearing improvement, a course of three intratympanic steroid injections (over three weeks) may be considered as salvage therapy in secondary care, either alone or in combination with oral steroids.7
  • There is no evidence of the use of other therapies, such as antivirals, thrombolytics, vasodilators or vasoactive substances for patients with SSNHL.6

Follow-up

  • Between 32% and 65% of cases of SSNHL recover spontaneously, usually within two weeks. 8
  • Prognosis is thought to be related to several factors including age, the severity of hearing loss, presence or absence of vertigo, and the delay between hearing loss onset and treatment. 9,10
  • Patients can be followed up in an ENT clinic with audiology support (after liaising with a local ENT team).
  • Hearing aids may be an option for patients with incomplete hearing recovery.

Key Points

  • SSNHL is a medical emergency that requires early recognition and treatment.
  • A thorough history and examination is essential to confirm that the hearing loss is sensorineural and exclude other causes.
  • Early treatment with high dose steroids remains the mainstay of treatment (despite limited evidence).
  • An MRI IAM scan should be requested to exclude vestibular schwannoma.

Reviewer

Louise McMurran

ENT Registrar (ST8)


References

  1. Schreiber BE et al. Sudden sensorineural hearing loss. The Lancet. 2010. Available from: [LINK]
  2. Eisenman DJ, Arts HA. Effectiveness of treatment for sudden sensorineural hearing loss. Archives of Otolaryngology – Head and Neck Surgery. 2000. Available from: [LINK]
  3. Daniels RL et al. Causes of unilateral sensorineural hearing loss screened by high- resolution fast spin echo magnetic resonance imaging: Review of 1,070 consecutive cases. Am J Otol. 2000. Available from: [LINK]
  4. Hearing loss in adults – NICE CKS [Internet]. [cited 2020 Apr 8].  Available from: [LINK]
  5. Wei BPC et al. Steroids for idiopathic sudden sensorineural hearing loss. Cochrane Database of Systematic Reviews. 2009. Available from: [LINK]
  6. Chandrasekhar SS et al l. Clinical Practice Guideline: Sudden Hearing Loss (Update). Otolaryngol – Head Neck Surg (United States). 2019.  Available from: [LINK]
  7. Ahmadzai N et al l. A systematic review and network meta-analysis of existing pharmacologic therapies in patients with idiopathic sudden sensorineural hearing loss. PLoS ONE. 2019. Available from: [LINK]
  8. Mattox DE, Simmons FB. Natural history of sudden sensorineural hearing loss. Ann Otol Rhinol Laryngol. 1977. Available from: [LINK]
  9. Fetterman BL et al. Prognosis and treatment of sudden sensorineural hearing loss. Am J Otol. 1996.  Available from: [LINK]
  10. Byl FM. Sudden hearing loss: eight years’ experience and suggested prognostic table. Laryngoscope. 1984. Available from: [LINK]

 

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