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Developing Tools to Detect Cognitive Impairment from Silent Strokes

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For release: Monday, November 06, 2006

Scientists from the National Institute of Neurological Disorders and Stroke (NINDS) and the Canadian Stroke Network recently wrapped up a workshop – the first of its kind – aimed at harmonizing clinical and research tools for assessing vascular cognitive impairment (VCI), a common disability linked to stroke.

A term that’s just beginning to catch on in the medical community, VCI refers to a loss of higher mental function that occurs when blood vessels in the brain malfunction, for example, because of hypertension or a clot.  It affects about 2 million Americans.

The VCI workshop was intended to help physicians and researchers come to an agreement about what the clinical manifestations of VCI are, with the ultimate goal of developing standard diagnostic criteria for the disorder. “There are no well-defined diagnostic criteria for VCI…And you need to diagnose a condition before you start trying treatments,” says Gabrielle Leblanc, Ph.D., a workshop co-chair and program director in the NINDS Division of Extramural Research.

Vladimir Hachinski, M.D., D.Sc., of the University of Western Ontario in Canada, and Costantino Iadecola, M.D., of Weill Cornell Medical College in New York also served as co-chairs of the workshop, which is summarized in the September 21, 2006 issue of Stroke.*

The spectrum of cerebrovascular disease that can cause VCI includes full-blown strokes, and transient ischemic attacks (TIAs), which involve a brief loss of blood flow to the brain.  VCI is easiest to detect when it occurs after a stroke or TIA, since people with those conditions usually seek emergency medical treatment, says Dr. Leblanc.

Other individuals, however, have “silent vascular disease that doesn’t appear as a clinically obvious stroke, but rather causes gradual impairment over time,” she explains.  This type of VCI is hardest to diagnose, because its effects are often subtle.

Most neurologists agree that VCI’s hallmark is a loss of the brain’s executive, or planning, function – which is needed for activities from tying your shoes to managing your finances.  In theory, that helps distinguish it from Alzheimer’s disease – whose hallmark is memory loss – but in practice making the distinction is often difficult.

To flesh out those criteria, the workshop divided into eight groups focused on distinct areas of clinical practice and research:  Clinical/Epidemiology, Neuropsychology, Clinical Trials, Neuroimaging, Neuropathology, Experimental Models, Biomarkers, and Genetics. 

The Clinical/Epidemiology group recommended a set of data – such as personal and family medical history – to be collected from patients who are enrolled in studies or seeing a doctor for the first time.

The task of the Neuropsychology and the Clinical Trials groups was to develop tests for uncovering the unique loss of executive function in VCI.  Three different protocols of varying length and complexity were developed, in which patients are asked to complete various tasks, such as taking one minute to name as many words as they can that begin with the letter “F”.  One protocol – based on the Montreal Cognitive Assessment (available at http://www.mocatest.org/) – is designed to be completed in 5 minutes, and should be useful for gathering fast data in large clinical trials or providing quick consults over the phone.

The Neuroimaging and Neuropathology groups focused on ways to detect anatomical changes in the brain that accompany VCI.  The Neuroimaging group recommended standardized procedures for collecting and quantifying data from MRI and CT scans.  Among other things, the Neuropathology group recommended changing current autopsy practices so that both halves of the brain can be examined for signs of cerebral blood clots and hemorrhaging.  (Current practice dictates that one hemisphere is prepped for anatomical studies, while the other is frozen for molecular studies.)

The Experimental Models, Biomarkers, and Genetics groups were focused on basic research in VCI.  The Experimental Models group identified laboratory animal models that have been developed to mimic certain features of VCI via genetic, surgical, or dietary manipulations.  The Biomarkers and Genetics groups discussed the importance of identifying proteins in blood and cerebrospinal fluid whose levels might rise or fall during the course of VCI – and genes that, when mutated, might create a predisposition toward VCI.

The workshop, Dr. Leblanc emphasizes, isn’t the last word on VCI diagnosis; it’s just the opening dialogue.  The next step, she says, is “for people in clinical settings to try these tests and determine which ones are actually helpful in diagnosing the disease.”

*Hachinski V et al.  “National Institute of Neurological Disorders and Stroke-Canadian Stroke Network Vascular Cognitive Impairment Harmonization Standards.”  Stroke, September 21, 2006, Vol. 37, pp. 2220-2241.

-By Daniel Stimson, Ph.D.


Date Last Modified: Wednesday, January 31, 2007