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Changes in cortical excitability differentiate generalized and focal epilepsy
Author(s) -
Badawy Radwa A. B.,
Curatolo Josie M.,
Newton Mark,
Berkovic Samuel F.,
Macdonell Richard A. L.
Publication year - 2007
Publication title -
annals of neurology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 4.764
H-Index - 296
eISSN - 1531-8249
pISSN - 0364-5134
DOI - 10.1002/ana.21087
Subject(s) - epilepsy , ictal , motor cortex , neuroscience , transcranial magnetic stimulation , idiopathic generalized epilepsy , silent period , inhibitory postsynaptic potential , psychology , generalized epilepsy , cortex (anatomy) , excitatory postsynaptic potential , medicine , stimulation
Objective Different pathophysiological mechanisms related to the balance of cortical excitatory and inhibitory influences may underlie focal and generalized epilepsies. We used transcranial magnetic stimulation to search for interictal excitability differences between patients with idiopathic generalized epilepsy (IGE) and focal epilepsy. Methods Sixty‐two drug‐naive patients with newly diagnosed epilepsy (35 IGE, 27 focal epilepsy) were studied. In the latter group, the seizure focus was not located in the motor cortex. Motor threshold at rest, cortical silent period threshold, recovery curve analysis using paired‐pulse stimulation at a number of interstimulus intervals), and cortical silent period were determined. Results were compared with those of 29 control subjects. Results Hyperexcitability was noted in the recovery curves at a number of interstimulus intervals in both hemispheres in patients with IGE and in the hemisphere ipsilateral to the seizure focus in those with focal epilepsy compared with control subjects and the contralateral hemisphere in focal epilepsy. Motor threshold and cortical silent period threshold were higher in the ipsilateral hemisphere in focal epilepsy compared with the contralateral hemisphere. No other intragroup or intergroup differences were found in the other measures. Interpretation The disturbance of cortical excitatory/inhibitory function was found to be bilateral in IGE, whereas in focal epilepsy it spread beyond the epileptic focus but remained lateralized. This finding confirms that there are differences in cortical pathophysiology comparing the two major types of epilepsy. Ann Neurol 2007