A patient develops complete unilateral lower motor neuron facial palsy (House-Brackmann Grade VI) after a parotid surgery. Electrophysiological testing performed on day 3 shows complete electrical excitability of the facial nerve distal to the lesion. What does this finding indicate about the prognosis and nerve injury type?
- A Axonotmesis with good prognosis; wallerian degeneration has not yet occurred
- B Neuropraxia; recovery expected within days to weeks without wallerian degeneration ✓
- C Neurotmesis; immediate surgical exploration is indicated
- D Wallerian degeneration is complete; prognosis is poor
Explanation
In neuropraxia (Seddon classification), there is a focal conduction block without axonal disruption or wallerian degeneration. The nerve distal to the injury remains electrically excitable because the axons are intact — only their myelin (or local membrane function) is impaired. Electrical excitability testing on day 3 still showing normal response distal to the lesion indicates no axonal degeneration, consistent with neuropraxia. In axonotmesis/neurotmesis, by day 3–5 wallerian degeneration begins distally and excitability is progressively lost. Neuropraxia has an excellent prognosis with full recovery in days to weeks.
Reference: Dhingra Diseases of Ear, Nose and Throat, 7th ed.
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Written and medically reviewed by the StethoPrep medical team.