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The Corpus Callosum and Epileptic Seizures: Experimental Results in Cats
Author(s) -
Yamashiro Katsumi,
Tomiyama Ndoki,
Ishida Akihiko,
Terada Yukitoshi,
Kinjo Toshihiko,
Yoshii Yoshihiko,
Mukawa Jiro
Publication year - 1998
Publication title -
epilepsia
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.687
H-Index - 191
eISSN - 1528-1167
pISSN - 0013-9580
DOI - 10.1111/j.1528-1157.1998.tb01957.x
Subject(s) - corpus callosum , thalamus , gyrus , neuroscience , spike and wave , epilepsy , medicine , cortex (anatomy) , anatomy , psychology
Purpose : Corpus callosotomy (CC) has recently been recognized as an effective treatment for patients with intractable generalized seizures. Experimental studies also reported the same seizure‐suppressive effects. We investigated the effects of sectioning the corpus callosum in models of epilepsy in cats. Methods : Acute and subacute models of epilepsy were made by the topical application of estrogen and cobalt powder, respectively, at the left anterior sigmoid gyrus (ASG). The electrocorticogram (ECoG) and steady potentials (SPs) were recorded from both sides of the anterior sigmoid gyrus and the ventrolateral (VL) nucleus of the thalamus. The spindle‐like afterdischarges were elicited by direct stimulation of the cortex or VL nucleus of thalamus. The “surface negative (SN) wave” produced by pyramidal tract stimulation and recorded at the cortical surface has been identified as a reflection of postsynaptic potentials generated through recurrent inhibitory pathways (Humphrey et al. 1968). SN waves were analyzed for the assessment of the cortical inhibitory mechanisms before and after sectioning the corpus callosum. Results : Topical application of estrogen to the left ASG (acute model) induced spike‐waves on both sides of the ASG and VL. The SP showed a negative shift on the same side as the estrogen application: however, no change in the SP was seen on the contralateral side. In this (acute) model, a remarkable reduction or disappearance of spike‐waves on the side contralateral to estrogen application, was seen just after the sectioning of the corpus callosum. The spindle‐like afterdischarges were also difficult to induce on the same side as estrogen application after callosal sectioning. Cobalt powder also induced spike‐waves after topical application to the left ASG (subacute model). The spindle‐like afterdischarges showed a reduction after the callosal sectioning. The SN waves gradually diminished in amplitude after topical application of cobalt powder on the same side of the ASG as the application. In the contralateral ASG, the SN waves showed a slight reduction in amplitude. These phenomena were presumably due to depression of recurrent postsynaptic inhibition caused by the topical application of the epileptogenic agents. After callosal section, the SN waves recovered in amplitude on both sides. Conclusions : These data suggest that the corpus callosum is maintaining epileptiform activity during the advanced stages of epilepsy. They also suggest that sectioning of the corpus callosum suppress epileptic activity because of recovery of cortical inhibitory mechanisms as represented by the amplitude of the SN wave.