Changes in the F wave during recovery from peripheral facial paralysis

Abstract

We studied normal F wave parameters and F wave changes in patients with longstanding facial paralysis. Controls were 11 healthy volunteers studied to estimate normal F wave parameters. Subjects were 8 patients with Hunt's syndrome and 12 with Bell's palsy available for F wave detection among outpatients at our department between April 1999 and March 2000. They had ENoG of 0% within 2 weeks of paralytic onset. The test was repeated 68 times. DIAGNOSTIC INTERVENTION: Results of 68 tests were classified into 5 groups based on the course after paralysis developed and their F wave parameters were compared with controls. F wave parameters were minimal latency, maximum latency, mean latency, and frequency of F wave development. Stimulation was repeated 20 times in a test. No significant difference was noted in minimal latency in each group compared to controls. Maximum and mean latency were prolonged significantly in each group compared to controls. The frequency of F wave development was significantly reduced in groups in which examinations were done in less than 6 months and for 6 months to 1 year. Nerve fibers with fast conduction were considered to have recovered with on 6 months. This suggested that nerve conduction velocity in facial paralysis patients does not recover the same as normal conduction velocity. The maximum and mean latency in each of the postpalsy group was significantly longer than that in the normal control group. We therefore concluded that regenerated nerve fibers include some with a conduction velocity significantly slower than normal. The frequency in groups A and B was significantly lower than that in controls, but after 1 year or more had elapsed after the onset of palsy, the frequency was approximately the same as that in controls.