Electroneuroography (ENoG/ENOG) in Bell's palsy measures compound muscle action potential amplitude compared to the normal side. An ENoG showing >90% degeneration within 2 weeks is significant because:

• A It indicates Wallerian degeneration and predicts poor prognosis; surgical decompression may be considered ✓
• B It confirms complete recovery will occur within 2 months
• C It confirms an acoustic neuroma as the underlying cause
• D It mandates immediate high-dose IV corticosteroids as the primary intervention

Explanation

ENoG >90% degeneration on the affected side within 2 weeks of onset indicates extensive Wallerian degeneration of the facial nerve and predicts a poor prognosis for recovery. This finding, combined with the absence of voluntary motor unit potentials on EMG, is used in selected centres as the threshold for considering surgical decompression of the facial nerve (transmastoid or middle fossa approach). Steroids given early in Bell's palsy may reduce degeneration but are less impactful once >90% degeneration occurs.

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.