Mirror movements in amyotrophic loteral sclerosis

Introduction: Patients with Amyotrophic Lateral Sclerosis (ALS) were tested for the presence of mirror movements and ipsilateral motor evoked potentials (MEP) following transcranial magnetic stimulation (TMS). Methods: 26 patients between 34 und 75 years of age were enrolled in the study. According to the El Escorial criteria, 5 patients had definite ALS, 4 probable ALS, 7 possible ALS and 10 patients suspected ALS. Patients were clinically investigated with particular reference to mirror movements. Thereafter, TMS was applied and bilateral MEPs were recorded from the abductor pollicis brevis muscle. Results: 30% of the patients showed clinical mirror movements which were observed in early stages as well as in later ones. Ipsilateral MEPs were recorded in 46% of patients. Dicussion: The results show that clinical mirror movements are relatively common in ALS representing an unspecific sign of pyramidal tract involvement. Recording of ipsilateral MEPs which can be regarded as a preclinical sign of corticospinal involvement increases the yield. The sensitivity of the method is in the same range as that of other technically more difficult TMS techniques such as double or triple pulse stimulation.