Neuropsychological performance one week after carotid endarterectomy reflects intra-operative ischemia

Fourteen patients with severe bilateral carotid artery stenosis underwent carotid endarterectomy. Intra-operative ischemia was monitored by somatosensory evoked potentials (SSEP) bilaterally. Neuropsychological evaluations were completed within two days before operation and 4-9 days after operation. Complete loss of N1-P1 or P1-N2 components of the SSEP (seen in 4 patients) was associated with a worsening of neuropsychological abilities (p less than .01). Two of these patients subsequently had strokes (7 and 35 days after operation). No other patients in the series have had strokes. Patients whose N1-P1 or P1-N2 amplitudes decreased by 50% or more performed worse after operation than patients with less severe reductions in these amplitudes (p less than .02). Time since first ischemic symptoms, age, education, clamp time, pre-operative stroke, and interval from surgery to assessment were not statistically related to changes in neuropsychological abilities. Patients with ischemic events in the week prior to surgery tended to improve in neuropsychological abilities 4-9 days after operation (p less than .05). Recentness of ischemic episode, however, was not related to intra-operative SSEP change. Results suggest the potential utility of intra-operative SSEP monitoring and early post-operative neuropsychological assessments both for clinical and research purposes.