Sudden Hearing Loss - a critical diagnosis
Introduction
Sudden sensorineural hearing loss (SSNHL) is a potentially disabling condition that requires prompt recognition and management.
Early intervention is crucial for optimal recovery, underscoring the importance of understanding its presentation, diagnostic pathway, and current management paradigms.
Definition
• SSNHL is classically defined as a rapid loss of ~30 dB across three consecutive frequencies within 72 hours, confirmed by
audiometry.
• It is commonly unilateral, but bilateral cases can occur.
Presentation
• Key Symptoms:
o Sudden unilateral hearing loss (most common).
o +/- Tinnitus
o +/- Aural fullness
o Sometimes vertigo or dizziness
o No pain or external ear pathology
Clinical Note: You may report difficulty understanding speech, even with normal volume. The onset is often abrupt, and some may notice the change immediately upon awakening or during daily activities.
Causes
The underlying cause of SSNHL is unknown in approximately 60-70% of cases, but potential causes include:
• Viral infections (e.g. herpes simplex virus).
• Vascular compromise affecting the cochlear blood supply
• Autoimmune inner ear disease
• Trauma
• Neoplastic causes, such as vestibular schwannoma
• Other causes: Ménière’s disease, ototoxic medications, Syphilis
Note: Often, no definitive cause is identified (70%).
Epidemiology
• Incidence:
SSNHL affects approximately 5 to 20 per 100,000 people per year in Australia and elsewhere. It accounts for about 1 in 5,000 to 1 in 30,000 individuals annually.
• Age & Demographics:
It occurs across all age groups but is most common between 40-60 years. Slightly more prevalent in males.
• Recovery Rates:
Spontaneous recovery occurs in approximately 30-60% of cases, particularly with early treatment.
Diagnostic Approach
1. High suspicion of Sensorineural Hearing Loss; eliminating causes of Conductive Hearing loss
• Often, examination is normal
• Rule out conductive hearing loss findings ie infections, perforations, effusions, trauma
2. Immediate Referral for Audiometric Evaluation
• Conducted urgently, ideally within 24-48 hours
• Confirms cochlear origin (Sensorineural) of hearing loss
• Helps quantify severity and monitor response to therapy
3. Neuroimaging
• MRI with gadolinium contrast is the gold standard for excluding retrocochlear pathology such as vestibular schwannoma.
• Should be performed as soon as possible, especially if:
o Initial audiometry is inconclusive.
o There is associated vertigo or neurological signs.
o Hearing loss persists despite treatment.
4. Laboratory Tests
• Not routine but may include blood glucose, lipid profile, autoimmune panels, syphilis serology depending on clinical suspicion.
Management Principles
1. Prompt Initiation of Corticosteroids - do not wait for investigation results if suspicious
High-dose corticosteroids are the cornerstone treatment:
• Oral prednisolone: 1 mg/kg/day (up to 60-75 mg/day) for 7-14 days, with gradual tapering.
• The best outcomes are observed when treatment starts within 2 weeks of symptom onset.
2. Salvage Therapy: Intra-tympanic Steroid Injection
Consider referring for intra-tympanic steroids if:
• systemic steroids are contraindicated
• initial therapy is unsuccessful or
• if delayed presentation (>30 days)
melbentgroup.com.au/corticosteroid-therapy-for-inner-ear-disorders/
What is intra-tympanic steroid injection?
• It involves delivering steroids directly into the middle ear via a tympanic membrane (eardrum) perforation or through a minimally invasive technique.
• The steroid solution (commonly Dexamethasone, specially compounded to 24mg/ml) diffuses across the round window membrane into the cochlea, achieving higher local concentrations with fewer systemic effects.
Procedure Details
• Preparation:
The patient is usually seated; local anesthesia is applied and left for 20-30 minutes.
• Injection:
Under microscopic vision, a fine needle is used to inject the steroid solution through the tympanic membrane into the middle ear. There may be some fulness and mild discomfort felt as the middle ear fills, and a small proportion of patients can experience brief dizziness which usually passes quickly.
• Post-procedure:
The patient is left to sit quietly for 30-40 minutes, to allow the steroid to be absorbed optimally. The can usually return home immediately afterwards. The injection may be repeated over several sessions depending on response.
Evidence for intra-tympanic steroids:
• Multiple studies, including randomized controlled trials, demonstrate improved hearing recovery when intra-tympanic steroids are added to systemic therapy.
• Evidence: A 2020 Cochrane review indicates intra-tympanic steroids improve hearing recovery, especially in combination withoral steroids.
• Guidelines: American Academy of Otolaryngology–Head and Neck Surgery (AAO-HNS) 2019 recommends prompt corticosteroid therapy.
What happens after?
• Repeat Audiogram in 6-12 months to check hearing has stabilised
• Consider hearing rehabilitation
o Hearing Aids: Note if age <26 years or >75 years, eligible for government subsidy
o Cochlear Implant - worth considering sooner for patients with viral aetiology, as cochlear sclerosis (scarring) occurs
Summary
• Recognize SSNHL as an urgent condition.
• Initiate prompt corticosteroid therapy.
• Ensure early audiometry within 24-48 hours.
• Consider neuroimaging to exclude retro-cochlear pathology.
• Review by ENT promptly for assessment, including possible intra-tympanic therapy.
References
1. Wilson, W.R., et al. (2019). Clinical Practice Guideline: Sudden Hearing Loss. Otolaryngology–Head and Neck Surgery, 161(1_suppl), S1–S45. [AAO-HNSF, 2019].
2. Mattox, D.E., et al. (2001). Recent studies of medical therapy for sudden hearing loss. Otology & Neurotology, 22(4), 583-589.
3. Conlin AE, Parnes LS. Treatment of sudden sensorineural hearing loss: I. A systematic review. Arch Otolaryngol Head Neck Surg 2007;133(6):573–81. doi: 10.1001/archotol.133.6.573.American Academy of Otolaryngology–Head and Neck Surgery (AAO-HNS) 2019
4. Lin RJ, Krall R, Westerberg BD, Chadha NK, Chau JK. Systematic review and meta-analysis of the risk factors for sudden sensorineural hearing loss in adults. Laryngoscope 2012;122(3):624–35. doi: 10.1002/lary.22480.
5. Wilson WR, Byl FM, Laird N. The efficacy of steroids in the treatment of idiopathic sudden hearing loss. A double-blind clinical study. Arch Otolaryngol 1980;106(12):772–76. doi: 10.1001/ archotol.1980.00790360050013.
6. Spear SA, Schwartz SR. Intratympanic steroids for sudden sensorineural hearing loss: A systematic review. Otolaryngol Head Neck Surg 2011;145(4):534–43. doi: 10.1177/ 0194599811419466.
7. Chandrasekhar SS, Tsai Do BS, Schwartz SR, et al. Clinical practice guideline: Sudden hearing loss (Update). Otolaryngol Head Neck Surg 2019;161 Suppl S1:S1–45. doi: 10.1177/ 0194599819859885.