F-wave and Nerve Conduction Studies in 91 Patients with Amyotrophic Lateral Sclerosis

Objective To investigate the features of F-wave and nerve conduction in patients with amy-otrophic lateral sclerosis (ALS). Methods Standard sensory and motor nerve conduction were performed in median nerve.ulnar nerve and tibial nerve in 91 patients with ALS. F-wave was studied in median nerve. Parameters studies included sensory conduction velocity and amplitude, distal motor latency (DML) and compound muscle action potential (CMAP) amplitude, F-wave velocity and frequency. The relations of muscle strength with DML, CMAP amplitude and F-wave frequency were also analyzed in median nerve. Results Delayed DML of median nerve, ulnar nerve and tibial nerve were found in 16. 6%, 13. 9% ,7. 2% patients respectively, and the decreased CMAP amplitudes were found in 50. 0%,44. 7%,28. 6% patients respectively; Decreased F-wave velocity was found in 6.6% patients, decreased F-wave frequency was found in 60% patients. Only 3 cases had abnormal sensory conduction. The abnormality of DML, CMAP amplitude and frequency of median nerve were more severe in weaker muscles. Conclusions Delayed DML and decreased amplitude of CMAP are found in ALS patients. The amplitude of CMAP is a sensitive parameter related to the severe of ALS. F-wave velocity is relatively normal while F-wave frequency significantly decreases in ALS. The abnormal of DML, CMAP amplitude and F-wave frequency are correlated with muscle strength.