Sudden Sensorineural Hearing Loss

SSNHL Basics - Deafening Debut

• Definition: Rapid onset hearing loss.
  • ≥ 30dB sensorineural hearing loss.
  • Across ≥ 3 consecutive audiometric frequencies.
  • Developing within 72 hours.
• Epidemiology: Affects ~5-27 per 100,000 annually; incidence may be ↑; peaks in 50s-60s.
• Etiology: Often multifactorial.
  • Idiopathic: Most common.
  • Viral: Mumps, measles, VZV, CMV, HIV.
  • Vascular: Vertebrobasilar insufficiency, TIA, stroke, hypercoagulable states.
  • Autoimmune: e.g., Cogan's syndrome, SLE.
  • Neoplastic: Acoustic neuroma (Vestibular Schwannoma) - must rule out.
  • Traumatic: Head injury, barotrauma, perilymphatic fistula.
• Pathophysiology: Commonly involves cochlear hair cell damage/inflammation or disruption of cochlear microcirculation.

⭐ The majority of SSNHL cases (up to 90%) are idiopathic.

Clinical Picture & Diagnosis - Hear Today, Gone Tomorrow?

• Symptoms:
  • Unilateral, sudden hearing loss (often < 72 hrs).
  • Tinnitus (ringing/buzzing).
  • Vertigo/Dizziness (in ~30-40% of cases).
  • Aural fullness (sensation of pressure in the ear).
• History Taking:
  • Onset: Rapid, often discovered upon waking.
  • Risk factors: Viral prodrome, recent trauma, ototoxic medication use, vascular risk factors (e.g., diabetes, hypertension), autoimmune disease.
• Otoscopy:
  • Typically normal external auditory canal and tympanic membrane.
• Tuning Fork Tests:
  • Rinne: Air Conduction > Bone Conduction (AC>BC) in affected ear (or false negative if profound loss, where BC is perceived by contralateral ear).
  • Weber: Lateralizes to the better hearing ear, indicating SNHL in the poorer ear.
• Audiometry:
  • Pure Tone Audiometry (PTA): Confirms SNHL (≥ 30 dB loss in ≥ 3 consecutive frequencies). Defines type & severity. ⭐> Pure Tone Audiometry (PTA) is the gold standard investigation to confirm SSNHL and quantify the hearing loss.

Workup & Differentials - Rule Out the Rascals

• Further Investigations:
  • MRI Brain with Gadolinium: Mandatory for unilateral SSNHL. Screens for retrocochlear pathology (e.g., vestibular schwannoma, CPA tumors).
  • Blood Tests (if clinically suspected):
    • CBC, ESR, Blood glucose, Lipid profile.
    • Autoimmune markers (e.g., ANA, RF).
    • Viral serology (e.g., HSV, VZV, CMV).
• Differential Diagnosis (Consider these "Rascals"):
  • Meniere's disease (fluctuating HL, vertigo, tinnitus)
  • Ototoxicity (e.g., aminoglycosides, cisplatin)
  • Labyrinthitis (viral or bacterial infection)
  • Cerebrovascular Accident (CVA) affecting AICA/PICA
  • Multiple Sclerosis (demyelinating plaques)
  • Perilymphatic fistula (history of trauma/barotrauma)
  • Acoustic neuroma (vestibular schwannoma)

⭐ Gadolinium-enhanced MRI of the brain and internal auditory canals is mandatory in unilateral SSNHL to rule out retrocochlear pathology, especially vestibular schwannoma (acoustic neuroma).

Treatment & Prognosis - Sounding the Alarm for Recovery

SSNHL is an otologic emergency; prompt action is key!

• Other Treatments:
  • Antivirals, Vasodilators: Generally not recommended due to limited/controversial evidence.
• Prognostic Factors (Recovery Influencers):
  • Key: Time to treatment (↓ delay = ↑ recovery).
  • Severity of initial hearing loss.
  • Age (↑ age = ↓ prognosis).
  • Presence of vertigo (associated with poorer prognosis).
  • Audiogram pattern (e.g., upsloping favorable).

⭐ The most crucial prognostic factor for recovery in SSNHL is the time to initiation of steroid therapy, ideally within 72 hours to 2 weeks of onset.

High‑Yield Points - ⚡ Biggest Takeaways

• SSNHL: ≥30 dB SNHL over ≤72 hours in ≥3 consecutive audiometric frequencies.
• Mostly idiopathic; MRI Brain with Gadolinium essential to rule out acoustic neuroma (retrocochlear pathology).
• Treat promptly with high-dose oral corticosteroids (e.g., Prednisolone 1mg/kg/day). Intratympanic steroids are an alternative.
• Spontaneous recovery occurs in 30-65% of cases, often within the first two weeks.
• Poorer prognostic factors: severe loss, associated vertigo, older age, and delayed treatment.
• Pure Tone Audiometry (PTA) confirms diagnosis. Urgent ENT referral is critical.