INTERICTAL INHIBITORY MECHANISMS IN PATIENTS WITH CRYPTOGENIC MOTOR CORTEX EPILEPSY - A STUDY OF THE SILENT PERIOD FOLLOWING TRANSCRANIAL MAGNETIC STIMULATION
M. Cincotta et al., INTERICTAL INHIBITORY MECHANISMS IN PATIENTS WITH CRYPTOGENIC MOTOR CORTEX EPILEPSY - A STUDY OF THE SILENT PERIOD FOLLOWING TRANSCRANIAL MAGNETIC STIMULATION, Electroencephalography and clinical neurophysiology, 107(1), 1998, pp. 1-7
The silent period (SP) following transcranial magnetic stimulation (TM
S) of the motor cortex is mainly due to cortical inhibitory mechanisms
. The aim of the present study was to investigate these inhibitory phe
nomena in primary motor cortex epilepsy. We studied the TMS-induced SP
in both the first dorsal interosseous (FDI) muscles in 8 patients who
suffered from cryptogenic partial epilepsy with seizures starting wit
h clonic movements of the right upper limb. All patients were on chron
ic medication with antiepileptic drugs. Therefore, besides contrasting
the results with 16 age-matched normal controls, we also studied 10 p
atients receiving similar antiepileptic treatments who suffered from c
ryptogenic partial epilepsy with seizures characterised by the absence
of clonic manifestations. The duration of the SP was bilaterally incr
eased in the patients with clonic seizures when compared with the two
other groups of subjects. The SP was longer in the left FDI muscle (co
ntralateral to the side of the clonic manifestation in all the patient
s). Our findings likely indicate enhanced interictal inhibitory mechan
isms in patients with partial epilepsy involving the primary motor cor
tex. The resulting inhibitory effect could be greater in the intact he
misphere rather than in the affected one, in which the hyperexcitabili
ty of the epileptic focus had to be counterbalanced. (C) 1998 Elsevier
Science Ireland Ltd. All rights reserved.