Abstracts

Rationale: Mesial temporal lobe epilepsy (MTLE) is the most frequent type of epilepsy encountered in epilepsy surgery centers, and surgery has the greatest proven impact on the patient s quality of life. Given parahippocampal multidirectional connectivity, its role as hippocampal output gate and potential epileptogenic role, we suggest selective resection of the parahippocampus has the same surgical results in terms of seizure control as selective amygdalohippocampectomy. However, better neuropsychological outcomes might be expected since the anatomical structure involved in semantic memory is spared. Methods: Experimental, longitudinal, prospective study comparing selective amygdalohippocampectomy through a trans-T3 resection approach to a trans-T3 resection approach plus parahippocampectomy, (subiculum as upper limit). Presurgical evaluation was conducted according to standardized protocol, including patients with MTLE and hippocampal sclerosis. Patients were randomly selected to one or the other surgical procedure after signing an informed consent. Patients were followed up for 12 months, and evaluated using the Engel outcome scale and standard neuropsychological tests. Results: We performed 20 procedures, 10 selective amygdalohippocampectomies and 10 selective parahippocampectomies. There was no statistical difference in seizure control at 12 months follow up, in the parahipocampectomy group 9 patients are Engel 1 and one patient IVa. Neuropsychological outcomes in semantic memory were statistically significant superior in patients subjected to parahippocampectomy. Conclusions: Parahippocampectomy allows deafferentation of the principal afferent pathways of the hippocampus ensuring desynchronization. Hiperexcitability in patients with MTLE is reduced by disconnection of the glutaminergic circuitry. Parahippocampectomy seems to provide the same outcome in terms of seizure reduction as conventional procedures, with lesser negative impact on neuropsychological parameters. It remains to be seen if seizure control is maintained in the long term.