An abnormality of facial nerve conduction velocity distribution (FNCVD) in Bell's palsy patients

We studied bilateral facial nerve conduction velocity distribution (FNCVD) of 8 Bell's palsy patients in their paretic and recovered state and unilateral FNCVD of 13 normal control using collision method. Dual supramaximal stimuli were adapted to marginalis mandibulae branch of facial nerve and compound muscle action potential (CMAP) was recorded from the surface of mentalis muscles. Peak of FNCVD in normal control was present at 22-23 m/sec. In Bell's palsy patients, there was no significant change in FNCVD either at paretic or recovery state. Peak of involved side FNCVD of Bell's palsy patient was almost normal but its amplitude was low. However, in healthy side of Bell's palsy patient, peak of FNCVD was present at 18-19 m/sec. This finding shows that facial nerve diameter distribution in the healthy side of Bell's palsy patient has smaller peak than that of normal control.