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In the stereo-electro-encephalography (SEEG) methodology developed by Talairach and Bancaud in Sainte-Anne Hospital in Paris, France, the objective of placing depth electrode recordings in presurgical evaluation is to study the spatial and temporal organization of a seizure. This defines for each patient the cortical onset zone, the propagation pattern of the seizure, and the possible involvement of eloquent areas of the cortex. This methodology requires a meticulous stereotactic surgical technique. We report here the SEEG methodology, surgical technique, and morbidity.

In patients with severe drug-resistant partial epilepsy, undergoing Stereo-EEG investigations, spatial definition of the "epileptogenic area" is mainly based on spontaneous seizures recordings, but also on seizures induced by intracerebral electrical stimulation (ES). Only "trains" ES (TES, 50 pps) are currently used with this aim; "shocks" ES (SES, 1 pps) are principally applied to localize motor pathways. We have shown, during a prospective study concerning 10 temporal lobe epileptic patients, that SES could frequently induce seizures, especially when stimulation is applied in the anterior part of the Ammon's horn. Even if its efficacy seems lower than by TES, this kind of stimulation, in the majority of the cases, does reproduce isolated ictal subjective symptomatology, allowing the visualization of the progressive organisation of ictal electrical discharges, and avoids "unexpected" ("false positive"?) clinical responses.

Controlled hypotension with nitroglycerin has been used n 30 neurosurgical procedures for aneurysms clipping, artero-veinous malformations, cerebral vascularised tumours and in some cases in the course of serial carotido-cerebral angiography. Farmacodynamic aspects of this drug and its effects on intracranial pressure are compared with sodium nitroprusside. Controlled hypotension was induced with prepared solution of nitroglycerin via an infusion pump in order to achieve a mean arterial blood pressure from 70 to 40 torr. All patients during hypotension were monitored by continuous blood pressure, pulse rate and intracranial pressure records. First results of our clinical evaluation indicate that this drug produce a rapid fall in blood pressure without harmful effect and does not significantly modify intracranial pressure. Its potential benefit in spasm of intracranial arteries associated with subarachnoid bleeding is investigated.