Predicting seizure control: cortical excitability and antiepileptic medication.
OBJECTIVE
Approximately 30% of patients with newly diagnosed epilepsy do not respond to antiepileptic drugs (AEDs), but this is not predictable. We used transcranial magnetic stimulation to determine the effect of AEDs on cortical excitability in patients with epilepsy and correlated this with a successful response to treatment.


METHODS
Ninety-nine drug-naïve patients with newly diagnosed epilepsy (55 idiopathic generalized epilepsy, 44 focal epilepsy) were evaluated. Motor threshold and cortical excitability on recovery curve analysis were measured before and 4 to 16 weeks after starting medication. After 1 year of treatment, 43 of 55 idiopathic generalized epilepsy and 26 of 44 focal epilepsy patients were seizure free.


RESULTS
A decrease in cortical excitability occurred in the seizure-free group as indicated by an increase in motor threshold (p < 0.05) and intracortical inhibition on recovery curve analysis, maximum at the 250-millisecond interstimulus interval (p < 0.01) compared with pretreatment values. These changes were not present in the group with ongoing seizures.


CONCLUSIONS
Seizure freedom is marked by a reduction in transcranial magnetic stimulation measures of cortical excitability, evident shortly after beginning therapy. This virtual normalization of cortical excitability occurred regardless of the seizure characteristics or AED used. Failure to show this response to AED treatment may be valuable as an early predictor of pharmacoresistance in individual patients.
Badawy
Radwa A B
RA
Department of Neurology, Austin Health, Heidelberg, Australia.
Macdonell
Richard A L
RA
Berkovic
Samuel F
SF
Newton
Mark R
MR
Jackson
Graeme D
GD
D000293:Adolescent; D000328:Adult; D000368:Aged; D000927:Anticonvulsants / Q000627:therapeutic use*; D001921:Brain / Q000187:drug effects* / Q000503:physiopathology*; D015331:Cohort Studies; D004828:Epilepsies, Partial / Q000175:diagnosis / Q000188:drug therapy / Q000503:physiopathology; D004829:Epilepsy, Generalized / Q000175:diagnosis / Q000188:drug therapy / Q000503:physiopathology; D019054:Evoked Potentials, Motor / Q000187:drug effects; D005260:Female; D005500:Follow-Up Studies; D007839:Functional Laterality; D006801:Humans; D008297:Male; D008875:Middle Aged; D012640:Seizures / Q000175:diagnosis / Q000188:drug therapy* / Q000503:physiopathology*; D013997:Time Factors; D050781:Transcranial Magnetic Stimulation / Q000379:methods; D016896:Treatment Outcome; D055815:Young Adult
D000927:Anticonvulsants