Cognitive impairment in asymptomatic cerebral arterial stenosis: a P300 study

BACKGROUND: Cerebral arterial stenosis (CAS), in the absence of a structural lesion, can result in cognitive impairment that represents an ongoing contention among studies. Accordingly, we investigated cognitive functions in asymptomatic patients with CAS, using P300 which is a neurophysiological tool. We also compared cognition in intracranial stenosis (ICS) and extracranial stenosis (ECS). METHODS: Asymptomatic patients with CAS (≥ 70%) in the absence of structural brain lesions were categorized into ICS and ECS groups of 15 patients each, in addition to 15 normal controls. MRI, MRA, CT angiography, P300 analysis, Mini-Mental State examination (MMSE), Wisconsin Card Sorting Test (WCST), and Wechsler Memory Scale Test-Revised (WMST) were performed to all patients. RESULTS: Impairment on all cognitive scales ranged from 70 up to 100% among CAS group. Prolonged p300 latency and reaction time correlated with worse performance on WMST (p = 0.02), while lower amplitude and decreased accuracy correlated with more errors on WCST (p = 0.01). ICS scores on WCTS were lower than those of ECS group (p = 0.001), while ECS had a longer reaction time (p = 0.02) and lower scores on MMS and WMST than those of ICS group (p = 0.03). CONCLUSION: Patients with asymptomatic CAS had a high prevalence of cognitive dysfunction which places them at risk of higher morbidity. ICS group showed impairment on executive functions, while the ECS group showed predilection to memory and information processing dysfunction.