Atherosclerosis of the intracranial carotid arteries in Nigerians: A pilot autopsy study

Abstract

Background: Evidence suggests that intracranial cerebral atherosclerosis (ICCA) occurs rarely in Caucasians, but more frequently in Asians, African-Americans, and Hispanics. Pathological studies verifying this claim are few in Africans. Objective: This prospective study aimed at grading the extent, severity, and frequency of atherosclerosis of the circle of Willis in Nigerians, using the American Heart Association (AHA) classification.Methods: This study is part of a descriptive, cross-sectional survey carried out on bodies referred for post-mortem to the Department of Morbid Pathology in the University College Hospital, Ibadan, Oyo State, Nigeria. The circle of Willis of 44 consecutive patients ≥20 years of age were examined for atherosclerosis using the AHA classification.Results: Twenty (45.5%) of the 44 patients studied had atherosclerotic lesions in their intracranial cerebral vessels. The internal carotid arteries (ICAs) (10.1%) were the most frequently affected, followed by the basilar artery (BA) and the middle cerebral arteries (MCAs) (8.5% each). Fifteen (75%) of the 20 patients who had atherosclerotic lesions had at least one risk factor for atherosclerosis. Age, waist circumference, and abdominal wall thickness were strong risk factors for ICCA. A total of 188 (30.5%) atherosclerotic lesions were found in the 616 histological sections of blood vessels examined in the 44 patients. Ninety-six (51.1%) of the lesions were mild, 53 (28.2%) were moderate, and 39 (20.7%) were severe. Severe atherosclerotic lesions were most frequently observed in the Lt ICA (20.5%) and Rt MCA (15.4%). Using the AHA classification, type I lesions were found in 6.4%, type II 17.6%, type III 27.1%, type IV 10.1%, type V 18.1%, type VI 11.7%, type VII and IX 0.5%, and type VIII lesions were found in 8.0% patients.Conclusions: The frequency of ICCA in our study was 45.5%, and this is worrisome for a population in a low-resource setting such as Nigeria, as the risk of stroke and recurrence in patients with symptomatic ICCA is high. Our findings are at variance with the other studies on ethnic or racial distribution of cerebral atherosclerosis, in which Chinese, Japanese, Hispanics, and African-Americans have higher rates of ICCA, and Caucasians have higher rates of extracranial carotid artery atherosclerosis (ECCA).