Cognitive functioning in patients with carotid artery occlusion; a systematic review

Introduction: Patients with complete occlusion of the internal carotid artery (CAO) are vulnerable to cerebral hypoperfusion. Since cerebral hypoperfusion is associated with accelerated cognitive decline, patients with CAO may have an increased risk of cognitive impairment. We aimed to assess the prevalence and profile of cognitive impairment in patients with CAO and to explore the relation between hemodynamic impairment and cognitive functioning. Methods: We systematically searched Medline and EMBASE for studies including patients with symptomatic or asymptomatic CAO subjected to cognitive testing that were published between 1980 and 2017. We did not include patients with carotid stenosis. We obtained data on type of study, patient characteristics, cerebral imaging and neuropsychological testing. In addition, we extracted data on potential causes of systemic hemodynamic impairment and the presence and stage of cerebral hemodynamic impairment. We assessed methodological quality of included studies with the Newcastle-Ottawa Scale. Results: We found eight studies comprising 244 patients (mean age 61 years, 76% male, 93% symptomatic CAO). The proportion of patients with cognitive impairment ranged from 54 to 71% in four studies; in the other four studies patients with CAO performed worse on cognitive testing than controls, but results were not quantified. Impairment was reported in all cognitive domains. We found no data on the association between systemic hemodynamic impairment and cognitive functioning. Studies that assessed whether cerebral hemodynamic impairment was associated with cognitive functioning showed conflicting results. Conclusion: In patients with CAO, cognitive impairment is present in about half to two-thirds of patients and is not restricted to specific cognitive domains. The effect of systemic and cerebral hemodynamic impairment on cognitive functioning in patients with CAO deserves further study.