Intraoperative dual monitoring during carotid endarterectomy using motor evoked potentials and near-infrared spectroscopy.

ABSTRACT

BACKGROUND: Carotid endarterectomy (CEA) is a useful procedure to prevent subsequent ischemic stroke in patients with severe stenosis of internal carotid artery. However, lowering of morbidity is still essential to keep its clinical significance. This study aimed to evaluate the validity of dual monitoring using transcranial motor evoked potential (MEP) and near-infrared spectroscopy (NIRS) during CEA. METHODS: Transcranial MEP and NIRS monitoring were conducted in 20 consecutive CEAs. MEP was recorded in the contralateral extremities. Regional cerebral saturation of oxygen (rSO(2)) was continuously measured in the ipsilateral forehead. The changes of MEP amplitudes and rSO(2) during cross-clamping of carotid artery were compared in each case. RESULTS: The amplitudes of MEP significantly decreased when rSO(2) reduced to more than 20% during carotid clamping. There was a significant correlation between the changes of MEP amplitude and rSO(2) during carotid clamping in a quadratic manner (P < .001, r = 0.821). However, NIRS could not detect critical cerebral ischemia in 1 patient with cerebral infarction in the ipsilateral frontal lobe. On the other hand, MEP could not identify it in 1 patient with severe motor deficit. No perioperative complication occurred. CONCLUSIONS: These findings strongly suggest that both MEP and NIRS can detect critical cerebral ischemia during CEA in most patients. Dual MEP and NIRS monitoring may further increase the sensitivity to identify it, being valuable to prevent perioperative complications due to cerebral ischemia during CEA.