To the Editor.—
In their article "Carotid Artery Disease, Carotid Endarterectomy, and Behavior" (Archives 1980;37:743-748), Kelly et al imply that carotid endarterectomy has a beneficial effect on "mentation" and "intellectual function." The erroneous conclusions of their report rest on the statistical ruse of a "controlled" study and reflect an apparent misunderstanding of the relationship between cerebrovascular disease and such nonfocal brain disorders as memory loss. Any alleged improvement in intellectual function in a group of already neurologically normal patients must be viewed with skepticism and certainly cannot be ascribed to improved cerebral perfusion after bilateral, or especially unilateral, carotid endarterectomy. It is well known that carotid artery stenosis does not predictably influence cerebral blood flow until the luminal diameter is reduced to 2 mm or less. An unknown number of patients in this study had ulcerated plaques with nonhemodynamic stenosis and no attempt was made to measure regional cerebral blood