Transcranial magnetic stimulation in Alzheimer disease: motor cortex excitability and cognitive severity

To study the possible changes of cortical excitability in the Alzheimer dis ease (AD) by transcranial magnetic stimulation (TMS) and to evaluate their eventual correlation with its stage twenty-one AD patients and 18 normal co ntrols underwent TMS. Motor threshold, amplitudes of motor evoked potential s (MEPs), central motor conduction time (CMCT) and silent period (SP) were considered. The motor threshold in AD patients was lower than in normal sub jects with a significant correlation between the stage of cognitive severit y. The amplitude of MEPs was increased and the SP duration was reduced in A D patients. No significant differences were obtained for CMCT. These findin gs could suggest a correlation between increased motor cortical excitabilit y and cognitive severity. Moreover, the increased cortical excitability cou ld represent a key to understand the mechanism of AD and may have implicati on for novel treatment strategies. (C) 2001 Elsevier Science Ireland Ltd. A ll rights reserved.