Motor Conduction Findings in Fisher Syndrome

OBJECTIVE: To report detailed motor conduction findings on Fisher syndrome (FS). METHODS: We retrospectively reviewed motor conduction findings of 55 patients with pure FS and compared them with those obtained from 83 age- and sex-matched healthy volunteers. RESULTS: In the FS group, distal and F-wave latencies of the median, ulnar, peroneal and tibial nerves were all significantly prolonged; motor conduction velocities were slowed in the median, ulnar and peroneal nerves. Conversely, an abnormally low compound muscle action potential amplitude was found only in the median and tibial nerves. Among the four parameters, distal and F-wave latencies were more frequently encountered abnormalities. None of our patients had abnormal temporal dispersion in any motor nerve. Focal involvement of the ulnar nerve across the elbow segment was observed in 6 patients (11%). Of the 55 FS patients, 31 (56%) had abnormal motor conduction results in at least one nerve. Abnormal motor conduction results were noted in 43 and 61% of patients when the tests were performed in the first week and 1 week after onset of FS, respectively (p=0.238). CONCLUSION: Our results confirmed that mild motor conduction abnormalities were noted in pure FS, with a pattern similar to those observed in Guillain-Barré syndrome.