| COMMENTARIES |
Intracranial Atherosclerosis: An Underdiagnosed Disease?
Mikael Mazighi and Pierre Amarenco, Service de Neurologie et Centre d'Accueil et de Traitement de l'Attaque Cérébrale, Unité INSERM 698: Recherche Clinique en Athérothrombose, Groupe Hospitalier Bichat Claude Bernard, 46, rue Henri Huchard, 75877 Paris Cedex 18, Tel: (+44) 01 40 25 87 25, Fax: (+44) 01 40 25 71 98
Intracranial atherosclerosis is considered to be a severe but rare condition, occurring more frequently in Asian, Afro-American, or Hispanic populations [1]. Overall, intracranial atherosclerosis is considered to account for 5% to 10% of ischemic strokes [1] and is associated with a high risk of recurrent ischemic events as high as 22% per year [2,3]. The severity of intracranial atherosclerosis warrants an accurate diagnostic work-up and a correct knowledge of the natural history of the disease. Among the available imaging modalities, x-ray angiography,
Today, because of the dramatic decline in post-mortem studies, large autopsy studies are rare. For this reason, extensive and thoroughly studied autopsy material is unique. A systematic analysis of intra- and extracranial arteries, the aortic arch, and the heart in 339 consecutive autopsies of fatal stroke patients was conducted in
In multivariate analyses, diabetes and male sex were significantly associated with intracranial atherosclerosis. Based on these findings, intracranial atherosclerosis may be highly represented in Caucasian populations with diffuse atherosclerosis. The independent association between either male sex or diabetes and intracranial atherosclerosis favors this hypothesis. It is worth noting that diabetes appeared to be positively related to the degree of stenosis, a relationship not described previously. Obviously, these findings can only be applied to fatal strokes because autopsy studies are not representative of the whole spectrum of strokes. Patients who died were more likely to have had the most severe strokes, accounting for the high prevalence of cardioembolic strokes and low prevalence of lacunar strokes observed in this study. These results need to be confirmed using modern imaging of the arterial wall of intracranial arteries in series of patients with nonfatal stroke.
These data bring new insights compared with early pathological studies, which supported the rarity of intracranial atherosclerosis. Some decades earlier, in a necropsy series of 200 stroke patients, Fisher [6] failed to identify a single MCA thrombosis. Whereas, 15 years later, in a necropsy study of a predominantly Afro-American population performed in 142 patients with recent BI, Moossy [7] identified the presence of intracranial thrombi in 55%. The ethnic disparity, between the studied populations, was considered to be the main explanatory factor for the increase in intracranial lesion incidence; and atherosclerosis as the cause for intracranial lesions was even debated. Beyond the abundant literature on intracranial lesions in Asian, Afro-American, and Hispanic populations, some groups have argued that the increased prevalence of intracranial atherosclerosis was not related to ethnicity but to a higher prevalence of vascular risk factors [1].
Intracranial atherosclerosis may be underdiagnosed and responsible for a higher proportion of ischemic strokes than is currently accepted, particularly if stenosis > 30% to 75% are identified. In large registries, such patients are probably classified as having had a stroke of unknown cause. New arterial wall imaging techniques should be used to reevaluate the frequency and role of intracranial artery plaques in living patients with stroke. The use of accurate arterial wall imaging of intracranial arteries with, for example, high resolution MRI, should prompt a reappraisal of the frequency of intracranial atherosclerosis in nonfatal strokes patients. These findings emphasize the importance of identifying intracranial atherosclerosis in ischemic stroke patients and may impact on the management of intracranial lesions.
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