Abstracts

To investigate whether or not the electrocortical and behavioural responses elicited by electrical stimulation of the centromedian thalamic nucleus in patients with Lennox-Gastaut Syndrome can be reproduced by ITP stimulation in MDD patients. In these patients, electrodes were implanted in ITP and Nucleus Reticularis Thalami (Re) as a part of a therapeutic neuromodulation procedure. Both structures were bilaterally stimulated by 20-30 s trains, where individual pulses had 1.0 ms duration, 3 Hz frequency and increasing intensities in steps of 0.5 mAmps each. In addition, clinical symptoms were systematically recorded and changes in responsiveness were assessed by response to flash presentation of patient under a simple response task. Bilateral, intense (10.0-12.0 mAmps), 3 Hz stimulation of either ITP or Re produced generalized responses of spike-wave complexes. However, while Re responses were accompanied by only delayed reaction time, ITP responses were accompanied by all symptoms described for spontaneous typical absence attack. That is, motionless stare, fixed sight, small eye blinking and total irresponsiveness to environment stimuli and verbal command. EEG and symptoms of genuine generalized seizures can be reproduced by ITP stimulation in humans with non-epileptic cortices. (Supported by Unit of Stereotactic and Functional Neurosurgery, General Hospital of México, (SSA) and Unit of Medical Research in Neurophysiology, National Institute of Social Securitiy (IMSS), México City, México)