Myotonic dystrophy: Pathological and electrophysiological study on 8 patients

Objective:To identify the relationship between pathological features and electrophysiological changes in patients with myotonic dystrophy（DM）.Methods:Eight subjects diagnosed as myotonic dystrophy in PLA General Hospital were studied about their muscle pathological findings,routine electromyography（EMG） and nerve conductive velocity（NCV） changes retrospectively.Results:Classical myopathic changes of DM were found in these muscle biopsies.With ATPase staining,there was no consistent abnormality of fiber type distribution,with 4 specimen having type I predominance and 4 having type II predominance.EMG was abnormal in all patients showed potentials of myotonia and myogenic damage.Compared with the cases with type II predominance,the rates of insert spontaneous potentials extension,the degree of motor unit potentials（MUP） duration shortening,and the percentage of polyphasic potentials were higher in the cases with type I predominance(83.3% vs 16.7%: χ²=14.9610,P= 0.000,Fisher’s exact=0.000;36.8% vs 19.3%: t=2.7253,P=0.0102;and 24.4% vs 11.0%: t=3.1901,（P=0.0030）.)Conclusion:In patients with DM the severity of the myoelectrophysiological changes were related to the pathological features,especially to the predominant fibre type.