Fax +41 61 306 12 34 E-Mail karger@karger.ch www.karger.com Laboratory Investigation Stereotact Funct Neurosurg 221 DOI: 10.1159/000XXXXXX Bilateral Anterior Thalamic Nucleus Lesions Are Not Protective against Seizures in Chronic Pilocarpine Epileptic Rats Clement Hamani a, b Flavio I.S. Ewerton c Flávia Marcolin de Almeida a Saulo M. Bonilha a Luciene Covolan a Clarissa Fantin Cavarsan a Gerson Ballester c Luiz E. Mello a Andres M. Lozano b a Departamento de Fisiologia, Escola Paulista de Medicina, Universidade Federal de São Paulo, São Paulo, Brazil; b Division of Neurosurgery, University of Toronto, Toronto, Ont., Canada, and c Lim 45, Faculdade de Medicina, Universidade de São Paulo, São Paulo, Brazil Introduction The anterior nucleus of the thalamus (AN) is an effec- tive target for seizure modulation in animal models of epilepsy and humans [1–11]. In a recent publication, we have shown that bilateral AN lesions or high-frequency stimulation were protective against the development of pilocarpine-induced generalized seizures and status epi- lepticus (SE) [4]. Our study however was conducted dur- ing the acute phase of the model, with thalamotomies done prior to pilocarpine administration. To more close- ly mimic the human condition, the so-called chronic models are certainly more informative. As an example, animals that recover from pilocarpine-induced SE often develop spontaneous recurrent seizures and a pathologic substrate that corresponds to some extent to the one ob- served in patients with temporal lobe epilepsy [12, 13] . To assess whether AN thalamotomies are also protec- tive during the chronic phase of the pilocarpine model, we compare the frequency of spontaneous seizures in an- imals treated with AN radiofrequency (RF) lesions or sham surgery 2 weeks after pilocarpine-induced SE. Key Words Thalamus  Deep brain stimulation  Thalamotomy  Epilepsy  Surgery  Anterior nucleus Abstract Aims: To investigate whether anterior thalamic nucleus (AN) lesions are protective against spontaneous recurrent sei- zures in the chronic phase of the pilocarpine model of epi- lepsy. Methods: Two groups of rats were treated with bilat- eral AN radiofrequency thalamotomies or sham surgery 2 weeks after pilocarpine-induced status epilepticus. After the lesions, animals were videotaped from the 2nd to the 8th week after status epilepticus (total 180 h). Results: During the 6 weeks of observation, no differences in the frequency of spontaneous seizures were found between animals that had bilateral AN lesions (n = 26; 3.1 8 0.6 seizures per animal) and controls (n = 25; 3.0 8 0.6 seizures per animal; p = 0.8). Conclusions: We conclude that AN thalamotomies were not effective in reducing the frequency of seizures during the chronic phase of the pilocarpine model of epilepsy. Copyright © 2009 S. Karger AG, Basel Published online: $$$ Clement Hamani Division of Neurosurgery, University of Toronto 399 Bathurst Street WW 4-447, Toronto, ON, M5T 2S8 (Canada) Tel. +1 416 603 6200, Fax +1 416 603 5298 E-Mail c.hamani@sympatico.ca © 2009 S. Karger AG, Basel 1011–6125/09/0000–0000$26.00/0 Accessible online at: www.karger.com/sfn SFN221.indd 1 SFN221.indd 1 03.02.2009 10:23:57 03.02.2009 10:23:57