SYMPTOMATIC AND ASYMPTOMATIC HIGH-GRADE UNILATERAL INTERNAL CAROTID-ARTERY STENOSIS - SCALP TOPOGRAPHY OF EVENT-RELATED POTENTIALS (P300) AND PSYCHOMETRIC TESTING

Unilateral internal carotid artery (ICA) stenosis may be accompanied b y widespread atherosclerosis of extra- and intracranial vessels leadin g to subtle cognitive disorders. We applied multichannel recording of P300 in 28 patients (68.3 +/- 8.1 years; 15 asymptomatic, 13 with a hi story of transient ischemic attack (TIA)) and compared them with an ag e- and sex-matched control group. All underwent a visual ''odd-ball pa radigm'' as well as a psychometric test, the Cognitive Performance Tes t (CPT), testing mainly visual attention and memory. The potentials we re derived from 16 electrodes according to the 10/20 system against li nked mastoids. The latencies and amplitudes of N250 and P300 were meas ured and their amplitudes additionally mapped. Furthermore, the early sensory exogenous potentials, P1 and N1, within the P300 potentials as well as conventional pattern reversal visual evoked potentials (PVEPs ) were evaluated. (1) Both the early exogenous potentials and the conv entional PVEPs showed no significant differences among all groups. (2) There were no significant differences between asymptomatic patients a nd those with a TIA history in all parameters of the P300 complex so t hat one total patient group was constructed and compared to the contro ls. (3) Patients' P300 amplitudes showed significant reductions over h emispheres ipsilateral (P less than or equal to 0.014) and contralater al (P less than or equal to 0.044) to the stenosis. (4) The N250 ampli tudes were reduced only in the central leads (P less than or equal to 0.05). (5) The latencies of N250 potentials were significantly prolong ed at many electrodes, not only ipsi-(P less than or equal to 0.0007) but also contralateral (P less than or equal to 0.022) to the stenosis . (6) The patients' P300 latencies showed significant lengthening only at occipital sites (P less than or equal to 0.05) compared to control s. (7) In all measured parameters, within the patient group, the diffe rences between hemispheres ipsilateral versus contralateral to the ICA stenoses did not reach statistical significance. (8) The CPT values d etected slight cognitive disorders for both patient groups and they co rrelated significantly with the latencies in many leads. (9) The highe st test sensitivity to classify patients versus controls (z score > 2) was reached in P300 maps of TIA patients (77%). An altered P300 indic ates electrophysiologically, and CPT behaviorally, subclinical cogniti ve deficits even in asymptomatic patients with unilateral tight ICA st enoses. Interestingly, no differences between asymptomatic and TLA pat ients with a high-grade unilateral ICA stenosis could be found.