LAUSR

Objective The aim of the study is to evaluate the diagnostic value of triple stimulation technique (TST) and cortical excitability studies as markers of upper motor neuron degeneration in ALS patients and to compare the extent of electrophysiological changes in abductor pollicis brevis (APB) and abductor digiti minimi (ADM) muscles. Methods Fifteen patients with ALS and 15 healthy controls (HCs) were included in the study. Motor evoked potential (MEP) responses, contralateral and ipsilateral silent periods (ISP) and paired-stimulation tests were recorded from both hypothenar and thenar muscles simultaneously. Paired-stimulation studies were performed with interstimulus intervals (ISI) of 2 and 3 ms for short-interval intracortical inhibition (SICI) and 10 and 12 ms for intracortical facilitation. TST responses were recorded from APB and ADM muscles. Results ISP duration was significantly shorter in the ALS group both for ADM and APB muscles (31.1 and 27.6 ms in ALS; 43.3, 39.3 ms in HCs respectively). SICI with 2 ms was reduced from thenar and hypothenar muscles in ALS patients when compared with HCs. MEP amplitudes were lower in ALS patients. TST test/control values in ADM and APB muscles were lower in ALS patients (86.4 and 73.7 in ALS; 100.8 and 107.8 in HCs respectively). Although TSTtest/control values had a tendency to be higher in the ADM, the results of the TMS studies were not significantly different between ADM and APB muscles in ALS patients. Conclusion These findings may be indicators of increased cortical excitability together with the upper motor neuron degeneration in ALS patients.