A patient undergoes mastoid surgery and sustains an iatrogenic facial nerve injury. Post-operatively, the nerve monitor shows a 100% degeneration on Electroneuronography (ENoG) on day 10. According to the House-Brackmann scale, the clinical finding that MOST urgently indicates surgical facial nerve decompression is:
- A House-Brackmann Grade III with >90% degeneration on ENoG
- B House-Brackmann Grade V–VI with >90% degeneration on ENoG within 14 days of complete palsy onset ✓
- C Any grade of palsy persisting beyond 3 months
- D House-Brackmann Grade II with 50% degeneration
Correct answer: B. House-Brackmann Grade V–VI with >90% degeneration on ENoG within 14 days of complete palsy onset
Explanation
ENoG (electroneuronography) measures the compound motor action potential amplitude of the facial nerve. Degeneration >90% on ENoG occurring within 14 days after onset of complete (HB Grade V–VI) facial palsy indicates massive wallerian degeneration and is an indication for urgent surgical decompression to prevent irreversible axonal loss. This threshold (>90% ENoG + complete palsy + within 14 days) is the criterion for decompression in Bell's palsy and traumatic palsy. Grade III or partial palsy with high degeneration does not meet this threshold.
Reference: Dhingra Diseases of Ear, Nose and Throat, 7th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.