ABSTRACT
Transcranial magnetic stimulation [TMS] is a technique that can activate cortical motor areas and the corticospinal tract without causing discomfort to the patients. To evaluate the parameters of motor evoked potentials [MEP] induced by TMS in motor neuron disease [MND] and their relations to the severity of the disease. Twenty five subjects with motor neuron disease [MND] who had been diagnosed as MND using the standard clinical and electrophysiological studies [nerve conduction studies, 5MG and the somatosensory evoked potential studies] had been subjected to TMS and the MEP parameters [threshold, central motor conduction time [CMCT,], amplitude percentage quotient, phases and duration of the MEPs] were determined. Ten matched healthy persons were selected as control. Functional evaluation and disease severity assessment had been scored using the amyotrophic lateral sclerosis [ALS] Functional Rating Scale [ALSFRS] and the ALS Severity Score [ALSSS] respectively and compared to the control group. There was a statistical significant difference of all the studied parameters between patients and the control group. The mean central conduction time [CMCT] was correlated with the severity of the disease, while the amplitude changes were evident in late stages especially when associated with bulbar manifestations whereas there was no correlation between MEP parameters and the functional rating scale. From these findings it would be recommended to use the TMS to predict the severity of MND