The effect of valproate on silent period and corticomotor excitability

dc.contributor.author	Kazis, DA	en
dc.contributor.author	Kimiskidis, VK	en
dc.contributor.author	Papagiannopoulos, S	en
dc.contributor.author	Sotirakoglou, K	en
dc.contributor.author	Divanoglou, D	en
dc.contributor.author	Vlaikidis, N	en
dc.contributor.author	Mills, KR	en
dc.contributor.author	Kazis, A	en
dc.date.accessioned	2014-06-06T06:47:15Z
dc.date.available	2014-06-06T06:47:15Z
dc.date.issued	2006	en
dc.identifier.issn	12949361	en
dc.identifier.uri	http://62.217.125.90/xmlui/handle/123456789/3490
dc.relation.uri	http://www.scopus.com/inward/record.url?eid=2-s2.0-33745758760&partnerID=40&md5=463331d95fb04f9395d7308fceb5ce93	en
dc.subject	Corticomotor threshold	en
dc.subject	Silent period	en
dc.subject	Transcranial magnetic stimulation	en
dc.subject	Valproate	en
dc.subject.other	valproic acid	en
dc.subject.other	adolescent	en
dc.subject.other	adult	en
dc.subject.other	article	en
dc.subject.other	clinical article	en
dc.subject.other	controlled study	en
dc.subject.other	evoked muscle response	en
dc.subject.other	female	en
dc.subject.other	generalized epilepsy	en
dc.subject.other	human	en
dc.subject.other	idiopathic disease	en
dc.subject.other	nerve excitability	en
dc.subject.other	priority journal	en
dc.subject.other	stimulus response	en
dc.subject.other	transcranial magnetic stimulation	en
dc.subject.other	Adolescent	en
dc.subject.other	Adult	en
dc.subject.other	Anticonvulsants	en
dc.subject.other	Dose-Response Relationship, Drug	en
dc.subject.other	Epilepsy, Generalized	en
dc.subject.other	Evoked Potentials, Motor	en
dc.subject.other	Female	en
dc.subject.other	Follow-Up Studies	en
dc.subject.other	Humans	en
dc.subject.other	Male	en
dc.subject.other	Motor Cortex	en
dc.subject.other	Transcranial Magnetic Stimulation	en
dc.subject.other	Valproic Acid	en
dc.title	The effect of valproate on silent period and corticomotor excitability	en
heal.type	journalArticle	en
heal.publicationDate	2006	en
heal.abstract	Objective. To investigate, by transcranial magnetic stimulation, the effects of valproate on silent period and corticomotor excitability. Methods: thirty patients with generalized epilepsy were studied at baseline, and re-examined 4 (S1) and 25 (S2) weeks after the administration of valproate (mean dose: 1040 ± 284 mg). Transcranial magnetic stimulation was performed with a figure of eight coil (recording, first dorsal interosseous). Threshold was measured at 1% steps. Silent period was measured using a recently described protocol. Briefly, silent periods were elicited at 5% increments from 0 to 100% maximum stimulus intensity. At each stimulus intensity, 4 silent periods were obtained and the average value of silent period duration was used to construct a stimulus/response curve of stimulus intensity versus silent period. The resulting curves were then fitted to a Boltzman function and were statistically compared. The motor-evoked potential recruitment curve was constructed under active conditions and analyzed in a similar way. Results. Valproate increased threshold from 36.5 ± 5.99% at baseline to 41.02 ± 7.84% at S1 (p < 0.0001, paired t-test). The maximum value of the silent period curve decreased from 257.5 ± 3.9 ms at baseline to 230.3 ± 3.9 ms at S1 (p < 0.0001, F-test and AIC) while the other best-fit values (V50, slope, threshold) were not significantly affected. Regarding the motor-evoked potential recruitment curve, the maximum value decreased significantly post-drug (from 0.449 ± 0.007 to 0.392 ± 0.009, p < 0.01, F-test and AIC test), whereas the rest of the best-fit values remained unaffected. Conclusion. In patients with idiopathic generalized epilepsy, valproate increases threshold and reduces the maximum values of the silent period curve and the motor-evoked potential recruitment curve. These findings probably reflect valproate's effects on voltage-dependent Na+ channels, as well as an activation of GABAA receptors.	en
heal.journalName	Epileptic Disorders	en
dc.identifier.issue	2	en
dc.identifier.volume	8	en
dc.identifier.spage	136	en
dc.identifier.epage	142	en