22s Neurophysiol Clin (1990) 20, S, 22s-24s © Elsevier, Paris

Communications orales Oral communications

SESSION 8

Monitorage EEG et potentiels 6voqu4s (2) EEG and EP monitoring (2)

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ROLE OF SEP MONITORING IN SELECTION OF PATIENTS REQUIRING TE~IPORARY SBUNTING IN CAROTID SURGERY E.Fava*, A.Ducati% E.Bortolani#, S.Miani#. Inst. of Neurosurgery~ University of Milano (*) and Ancona (~), Inst. of General and Cardiovascular Surgery (#), University of Milano, Italy.

One hundred and fifty patients undergoing internal carotid endarterectomy under general anesthesia during the last three years in the Institute of General and Cardiovascular Surgery (University of Milano, Italy) were subjected to brain monitoring with two neurophyslologlcal tecnhiques. Both eight-channels electroencephalogram (EGG) and median nerve somatosensory evoked potentials (MN-SEPs) have been recorded during the entire surgical act in all patients. The aim of intraoperative neurophysiological brain monitoring was to identify the patients requiring a temporary shunt, in order to avoid cerebral ischemic lesions due to hypoperfuaion. However~ intraluminal shunt can be a technical hindrance for the surgeon and carries its own morbidity. The persistence of MN-SEP N20 on the involved hemisphere was chosen as an index of sufficient perfusion, significant EEG changes notwithstanding. A shunt was used in patients showing suppression of N20 (approximately 5~, as opposed to a previous 15g selected on EgG changes). No patient with preservation of N20 had postoperative ischemic deficits. Two patients had Intraoperative strokes~ producing a sudden loss of N20~ probably due to distal embollzation. In one of them, no significant E~ changes were observed. We conclude that MN-SEP monitoring should be used in parallel with EgG recording in carotid surgery, allowing a more limited use of shunt and a quite good neurological outcome.

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MONITORING OF THE MOTOR PATHWAY DURING SURGERY

F. Tabaraud*, J.M. Boulesteix*, D. Moulies **, A. Lansade *, G. Terrier **, J. Hugon * • Service Neurologie • * Service de Chirurgie P~diatrique C.H.R.U, de LIMOGES FRANCE

Paraplegia due to irreversible lesions of the spina I cord is one of the major complications followiag scoliosls surgery. Several monitoring methods were proposed but none is fully satisfactory. Since 1986 we have carried out motor pathway assessment during scollosls surgery, using electric cortical stimulation and lower limbs muscle recordings (Tibialis anterior muscle). 21 patients with idiopathic scollosis were included in this study. Recordings in anesthetized patients with hypothermia were performed before and after the spinal derotation during the surgical procedure. Control recordings were made after magnetic cortical stimulation in awake patients before and after surgery. Reproductlble responses were obtained in 17 patients under anesthesia. In ii patients no difference of the latencie of the muscle response was detected before and after the correction of the spine angle. In 6 patients the measure of the latency increased from 0.8 ms to 5.2 ms. We found a good relation between slowing of the motor conduction and the magnitude of the spine correction. No neurological complications were seen after surgery. Anesthesia produces a slowing of the central motor conduction linked to drug effects, hypothermia, and decreased blood pressure. In conclusion, our study demonstrates that motor pathway assessment in anesthetized patients can be used at different times during the surgical procedure. Cortical stimulation represents a feasible method to detect very early an abnormal central motor conduction.