Sudden Sensorineural Hearing Loss

SSNHL Basics - Hearing's Sudden Halt

• Sudden Sensorineural Hearing Loss (SSNHL): An otologic emergency.
• Definition: Sensorineural hearing loss of ≥30 dB.
  • Across ≥3 consecutive audiometric frequencies.
  • Developing within ≤72 hours (3 days).
• Primarily idiopathic; viral or vascular causes often suspected.
• Requires urgent audiological evaluation and management.

⭐ SSNHL is often defined by the "Rule of 3s": ≥30 dB loss, ≥3 frequencies, within 3 days (72 hrs).

Etiology - The Why Whodunit

• Idiopathic: Most frequent, diagnosis of exclusion (up to 90%).
• Viral Infections: Common culprits.
  • Mumps, Measles, Varicella-Zoster (Ramsay Hunt Syndrome)
  • Influenza, HSV, CMV, HIV.
• Vascular Compromise: Ischemia to cochlea.
  • Labyrinthine artery thrombosis, embolism, hemorrhage, or spasm.
• Autoimmune Inner Ear Disease (AIED):
  • Often bilateral, rapidly progressive; e.g., Cogan's syndrome.
• Neoplastic: Critical to exclude.
  • Vestibular schwannoma (acoustic neuroma), CPA tumors.
• Trauma:
  • Temporal bone #, barotrauma, iatrogenic, perilymphatic fistula.
• Ototoxic agents: Aminoglycosides, cisplatin. (Less common for sudden onset)
• Meniere's Disease: Can present acutely.

⭐ Unilateral SSNHL requires urgent MRI (Gadolinium-enhanced) to rule out retrocochlear lesions like vestibular schwannoma (approx. 3-5% of SSNHL cases).

Clinical Picture - Alarming Audio Alerts

• Onset: Sudden, usually unilateral; develops within 72 hours.
• Hearing Loss: Sensorineural type.
  • Classic definition: ≥30 dB loss over ≥3 consecutive frequencies.
• Associated Symptoms:
  • Tinnitus (very common, ~70-90%).
  • Vertigo/dizziness (frequent, ~30-60%).
  • Ear fullness (sensation of blockage).
• Discovery: Often noted upon awakening or during phone use.

  ⭐ SSNHL accompanied by facial nerve palsy warrants urgent MRI to rule out cerebellopontine angle (CPA) tumors like acoustic neuroma (Vestibular Schwannoma).

Diagnosis - Pinpointing the Problem

• Pure Tone Audiometry (PTA):
  • Confirms SNHL: ≥ 30 dB loss in ≥ 3 contiguous pure-tone frequencies within 72 hours.
  • Establishes severity and pattern.
• Tuning Fork Tests:
  • Rinne: Air Conduction (AC) > Bone Conduction (BC) (Positive), often diminished.
  • Weber: Lateralizes to the better-hearing ear.
• Magnetic Resonance Imaging (MRI):
  • Gadolinium-enhanced MRI of brain & Internal Auditory Canals (IACs).
  • Crucial to rule out retrocochlear pathology (e.g., vestibular schwannoma, stroke).
• Laboratory Tests (Selective):
  • Guided by clinical suspicion (e.g., autoimmune, vasculitis, specific infections).

⭐ MRI is mandatory in all cases of unilateral SSNHL to exclude vestibular schwannoma, which can be present in up to 3-15% of patients.

Management - Sounding the Recovery

• Goal: Maximize hearing recovery, limit permanent deficit.
• First-line: Corticosteroids (start ASAP, ideally <2 weeks of onset).
  • Oral: Prednisolone 1 mg/kg/day (max 60mg) for 7-14 days, then taper.
  • Intratympanic (IT) Steroids: Dexamethasone/Methylprednisolone (primary/salvage).
• Adjunctive: Hyperbaric Oxygen (HBOT).
  • Consider for moderate-severe SSNHL, ideally within 3 months.
• Prognostic Factors: Early treatment (<7 days), younger age, no vertigo, milder loss = better outcome.

⭐ Spontaneous recovery occurs in 32-65% of cases, often within the first 2 weeks.

High‑Yield Points - ⚡ Biggest Takeaways

• Definition: >30 dB SNHL across ≥3 contiguous frequencies within 72 hours.
• Etiology: Mostly idiopathic. MRI Brain with Gadolinium to exclude retrocochlear pathology (e.g., acoustic neuroma).
• Diagnosis: Pure Tone Audiometry (PTA) is key.
• Treatment: Systemic corticosteroids (oral Prednisolone) ASAP, ideally within 2 weeks. Intratympanic steroids for salvage.
• Prognosis: Better with early treatment, mild loss, and no vertigo.
• Tuning Forks: Rinne positive (AC>BC), Weber lateralizes to better ear.