Nerve conduction studies in 205 patients with amyotrophic lateral sclerosis

Objective To investigate the F-wave and nerve conduction in patients with amyotrophic lateral sclerosis (ALS) and explore the correlation between these parameters and muscle strength, disease duration and onset site.Methods The data of outpatients and inpatients diagnosed with ALS were collected in Peking Union Medical College Hospital from January 1997 to May 2008.Standard sensory and motor nerve conduction study of the median nerve, ulnar nerve and tibial nerve was performed in 205 patients with ALS.F-wave velocity and frequency was measured in median nerve.Parameters for analyses included sensory conduction velocity and amplitude, distal motor latency (DML), and compound muscle action potential (CMAP) amplitude.Correlation between muscle strength and DML, CMAP amplitude or F-wave frequency were also explored.Results Delayed DML of the median nerve, ulnar nerve and tibial nerve were found in 24.9% (48/193), 15.3% (25/163), 21.2% (7/33) of patients respectively.Decreased CMAP amplitudes were found in 57.0% (110/193), 49.7% (81/163), 39.4% (13/33) of patients respectively.Decreased F-wave frequency of the median nerve was found in 68.9% (122/177) of patients.The abnormality of DML,CMAP amplitude and F-wave frequency of median nerve were increased in weaker muscles.Decreased median nerve CMAP amplitude (81.5% (53/65)) and F-wave abnormality (decreased persistence 70.9%(44/62), absent responses 45.1% (28/62)) in spinal onset groups were significantly higher than those in bulbar onset groups (CMAP 32.4% (11/34); F-wave: decreased persistence 38.2% (13/34), absent responses 14.7% (5/34); x2 = 23.629, 9.753, 9.029,all P <0.01).Compared with the bulbar onset group,the abnormality of DML in spinal onset group was higher, but not reach statistical significance.Logistic regression revealed a strong direct association between decreased CMAP amplitudes and upperextremity muscles strength, disease duration and onset symptom.Abnormality of F-wave frequency was associated with upper-extremity muscles strength and onset symptom.Conclusions Delayed DML and decreased amplitude of CMAP are found in ALS patients.CMAP amplitude is a sensitive parameter related to the severity of ALS.F-wave velocity is relatively normal while F-wave frequency of the median nerve is correlated with muscle strength.Decreasing CMAP amplitude and F-wave frequency are correlated strongly with muscle weakening,disease duration and symptom onset over limbs. Key words: Amyotrophic lateral sclerosis; Nerve conduction