Cortical excitability in drug-naive patients with partial epilepsy: a cross-sectional study.
OBJECTIVE
To use paired-pulse transcranial magnetic stimulation (TMS) to investigate cortical excitability in drug-naive patients with partial epilepsy.


METHODS
Twenty-one drug-naive patients with partial epilepsy and 15 control subjects were studied. The relaxed threshold to TMS, the central silent period, and the intracortical inhibition/facilitation were measured. Statistics implied cluster analysis methods. Also assessed were the patient interictal EEG epileptiform abnormalities (EAs) on a semiquantitative basis. Then the TMS was contrasted to the clinical and EEG findings, using chi2 or Fisher exact tests.


RESULTS
One-third of the patients made up a "pathologic" cluster with a disrupted intracortical inhibition (p < 0.01). Two-thirds had a normal inhibition. Interictal EAs predominated in the pathologic cluster, for frequency (p < 0.04), duration (p < 0.04), and focality (p < 0.02).


CONCLUSIONS
Intracortical inhibition, which was impaired in one-third of the patients, reflects gamma-aminobutyric acid (GABA) activity within cortical area 4. Defective GABA inhibition is a typical pathogenic factor in partial epilepsy. Transcranial magnetic stimulation proved able to detect it. The weaker cortical inhibition had a direct relation to the severity of interictal epileptiform abnormalities.
Varrasi
C
C
Department of Medical Sciences, Section of Neurology, Università del Piemonte Orientale A. Avogadro, Novara, Italy.
Civardi
C
C
Boccagni
C
C
Cecchin
M
M
Vicentini
R
R
Monaco
F
F
Cantello
R
R
D000293:Adolescent; D000328:Adult; D002540:Cerebral Cortex / Q000503:physiopathology*; D003430:Cross-Sectional Studies; D004569:Electroencephalography; D004828:Epilepsies, Partial / Q000503:physiopathology*; D005260:Female; D006801:Humans; D008280:Magnetics; D008297:Male; D008875:Middle Aged; D005680:gamma-Aminobutyric Acid / Q000502:physiology
D005680:gamma-Aminobutyric Acid