Predicting seizure control: Cortical excitability and antiepileptic medication
Article first published online: 20 JUL 2009
Copyright © 2010 American Neurological Association
Annals of Neurology
Volume 67, Issue 1, pages 64–73, January 2010
How to Cite
Badawy, R. A. B., Macdonell, R. A. L., Berkovic, S. F., Newton, M. R. and Jackson, G. D. (2010), Predicting seizure control: Cortical excitability and antiepileptic medication. Ann Neurol., 67: 64–73. doi: 10.1002/ana.21806
- Issue published online: 23 FEB 2010
- Article first published online: 20 JUL 2009
- Accepted manuscript online: 20 JUL 2009 12:00AM EST
- Manuscript Accepted: 10 JUL 2009
- Manuscript Revised: 29 JUN 2009
- Manuscript Received: 13 FEB 2009
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.
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.
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.
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. ANN NEUROL 2010;67:64–73