Transcranial and direct cortical stimulation for motor evoked potential monitoring in intracerebral aneurysm surgery

To analyse the parallel use of transcranial electrical stimulation (TES) and direct cortical stimulation (DCS) for eliciting muscle motor evoked potentials (MMEPs) in intracranial aneurysm surgery; to correlate permanent or transient TES- and/or DCS-MMEP changes with surgical maneuvers and clinical motor outcome. TES and DCS were intraoperatively performed in 108 patients (51.5 ± 14.7 years); MMEPs were obtained in muscles belonging to the vascular territory of interest. Monopolar, anodal stimulation was achieved with a train of five stimuli consisting of an individual pulse width of 0.5 ms, an interstimulus interval of 4 ms, a train repetition rate of 0.5–2 Hz, and maximum stimulation intensities up to 200 mA (TES) versus 25 mA (DCS). In 95/108 (88%) patients, no changes in MMEPs occurred and none of these patients suffered a permanent severe motor deficit. In 14/108 (12%) patients, we observed nine (64%) temporary changes, four (29%) permanent deteriorations and one (7%) permanent MMEP loss. Out of 14 MMEP changes, nine (64%) occurred with TES, compared to 13 (93%) with DCS (Fishers’ p = 0.165). Parallel changes in TES- and DCS-MMEPs occurred in 8/14 patients (57%), in which case a permanent loss was always followed by a permanent severe motor deficit. Sixty-seven percent of all permanent changes occurred with DCS-MMEPs, compared to 33% with TES-MMEPs ( p = 0.567, NS). In aneurysm surgery, provided that close-to-motor-threshold stimulation and the most focal stimulating electrode montage are used, TES- and DCS-MMEPs do not differ in their capacity to detect an impending lesion of the motor cortex or its efferent pathways. TES stimulation can cause significant muscular contraction during surgery, potentially disrupting the operating surgeon. DCS maintains the singular advantage of stimulating a very focal and superficial motor cortex stimulation that does not result in patient movement. Analyser l’utilisation simultanée de la stimulation électrique transcrânienne (SET) et corticale directe (SCD) pour l’obtention de potentiels évoqués moteurs (PEM). Ont été étudiées en particulier les modifications des PEM obtenues par SET ou SCD et leur corrélation avec les manipulations chirurgicales et le pronostic clinique des fonctions motrices. Cent huit patients (âge : 51,5 ± 14,7 ans) ont bénéficié d’un monitorage peropératoire utilisant la SET ou la SCD avec enregistrement des PEM correspondant au territoire vasculaire en question. La stimulation a été appliquée a