A patient with complete Bell's palsy undergoes electroneurography (ENoG) at 12 days and shows 92% degeneration. No voluntary motor unit potentials are seen on needle EMG. According to guidelines, what is the significance of this finding regarding surgical decompression?

• A 92% degeneration indicates neurapraxia — complete recovery guaranteed without surgery
• B 90-95% degeneration on ENoG within 14 days in complete paralysis is the threshold for considering surgical decompression of the facial nerve ✓
• C Surgical decompression is contraindicated once degeneration exceeds 90% as the nerve cannot regenerate
• D ENoG findings alone are sufficient to mandate surgery regardless of EMG findings

Explanation

ENoG >90-95% degeneration within 14 days of onset in a patient with COMPLETE facial paralysis (no voluntary motor units on needle EMG) is the accepted electrophysiological threshold for considering surgical decompression of the facial nerve (transmastoid + middle fossa approach to the meatal foramen where compression is maximal). The rationale is that >90% axon loss within the critical 2-week window predicts poor spontaneous recovery (<50% achieve complete recovery). This remains controversial — the AAO-HNS recommends informed patient discussion. The window closes at ~14 days because wallerian degeneration makes ENoG unreliable after this point.

Reference: Dhingra Diseases of Ear, Nose and Throat, 7th ed.

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Written and medically reviewed by the StethoPrep medical team.