Carotid Disease and Cognitive Dysfunction

The introduction of cerebral angiography in the 1930s by Moniz, followed by detailed postmortem studies of the cervical portion of the carotid artery in the 1950s by Miller Fisher, drew attention to the extracranial carotid artery's being more important than the middle cerebral artery in ischemic stroke (1). The description of the diagnostic features of carotid disease soon followed, and this led to strategies for preventing or eliminating carotid lesions. From the earliest writings, clinical investigators have debated a possible connection between severe carotid disease and impaired cognition. Few dispute the relationship between cognitive decline and large areas of infarction of cortex supplied by the carotid artery. The unsettled component is the causal relationship between mild cognitive decline and asymptomatic disease in the carotid artery that supplies the dominant hemisphere (the left carotid in 98% of right-handed individuals). In the presence of intellectual changes, should an otherwise-asymptomatic person be called a symptomatic patient? Management could depend on the answer, and we will return to that subject at the end of this editorial.

In this issue, Johnston and colleagues (2) report on cognition at baseline and subsequent cognitive decline in 4006 patients in the Cardiovascular Health Study who were free of symptomatic vascular disease. The major finding was the prevalence of impaired cognition in patients with high-grade stenosis of the left internal carotid artery but not the right internal carotid. Twelve of 32 patients (34%) with 75% or more stenosis of the left internal carotid artery had significant baseline cognitive impairment compared with only 107 of 1497 (7%) with 0% stenosis. Cognition subsequently declined in 14 of 28 (50%) patients with severe left-sided stenosis compared with 264 of 1401 (19%) without stenosis. The relationship between stenosis and impaired cognition was absent when stenosis occurred in …