Correspondence Address:
Okechukwu S Ogah
Department of Medicine, University College Hospital, PMB 5116, Ibadan, Oyo State
Nigeria

Full Text

Intracranial atherosclerosis of the major vessels (intracranial internal carotid artery, middle cerebral artery, vertebral artery, and basilar artery) is the most common pathologic mechanism of ischemic stroke all over the world. [1]

Intracranial atherosclerotic disease (ICAD) is defined as atherosclerosis of the large vessels at the base of the brain. ICAD is commoner in South Asians, Far East Asians, Hispanics, and African Americans, compared to Whites. [1] It accounts for 30-50% and 8-10% of the ischemic strokes in Asians and Caucasians of North America, respectively. [2]

It is now known that 20-45% of non-Caucasians with large artery disease have combined intracranial and extracranial lesions. [2]

In terms of epidemiology, the prevalence of ICAD is 20-54% in adult South Asians, 7% in East Asians, 1-24% in US Whites, 6-22% in US Blacks, and 11% in Hispanics in the USA. [1],[2],[3],[4] ICAD also occurs in 33-50% of Chinese, 26.4-56.3% of Koreans, 47.9% of Singaporeans, and 47% of Thai people. [1]

It is suggested that polymorphic expression of stroke suppressor genes may explain the racial variability to ICAD. [5],[6]

Data from the Warfarin versus Aspirin in Symptomatic Intracranial Disease (WASID) study showed that Blacks with ICAD were more likely to have hypertension, diabetes mellitus, high low-density lipoprotein (LDL), and elevated total cholesterol. [7] Studies have also shown that compared to extracranial atherosclerosis, ICAD is not associated with typical risk factors for coronary artery disease (CAD) or peripheral artery disease, such as male gender and hypercholesterolemia. [8],[9] Metabolic syndrome, but not the individual components, is also associated with ICAD. [10],[11],[12]

In this issue of NJC, Oladapo et al., [13] in a pilot autopsy study at Ibadan, have ignited interest on ICAD in Nigerians. The last attempt to define this condition in Nigerians in the same hospital was about four decades ago by William et al. [14],[15] In the latter study, it was found that 13% of subjects had ICAD, which was commoner in those with cardiovascular (CV) risk factors such as hypertension and diabetes mellitus.

Therefore, the present study is timely, especially because of the fact that stroke and stroke-related complications have become a major cause of morbidity and mortality in the country. [16],[17],[18],[19],[20],[21] The authors documented a prevalence of 45% as against 13% reported by Williams in the late 60s or 70s. Their subjects had various degrees of ICAD (51.1% mild, 28.2% moderate, and 20.7% severe lesions). Over 70% had at least one risk factor for atherosclerosis such as age, increased waist circumference, and abdominal wall thickness.

The high rate of ICAD reported in this pilot study is worrisome, but may also explain the rising burden of stroke in the country.

As this is a pilot study, a larger and more detailed study, preferably a multicenter one, is needed to confirm this finding.

References