Which nerve conductions findings have prognostic significance in Bell palsy (idiopathic facial paralysis) (IFP)?

Updated: Jun 14, 2019
  • Author: Danette C Taylor, DO, MS, FACN; Chief Editor: Selim R Benbadis, MD  more...
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Comparison to the contralateral side helps to demonstrate the extent of nerve injury and has prognostic implications. Nerve conduction responses are abnormal if a difference of 50% in amplitude between the paralyzed and normal side is detected; a difference of 90% between the 2 sides suggests a poorer prognosis.

May et al demonstrated that prognosis may be favorable if the motor amplitude of the affected side is greater than 25% of that of the normal side. An incomplete recovery was observed in patients whose results demonstrated less than 25% amplitude on the paralyzed side. [41] Blink reflexes can be used to measure conduction across the involved segment, but they are commonly absent in Bell palsy.

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