Overall executive function skills are important in a high proportion of patients with TIA or minor stroke.
SAN ANTONIO—As many as 40% of patients who have had a transient ischemic attack (TIA) or a minor ischemic stroke have impaired executive function skills, according to findings that were presented at the 2010 International Stroke Conference.
Michael Harnadek, PhD, a neuropsychologist at the London Health Sciences Center–University Hospital in Ontario, Canada, and colleagues examined data from 140 patients with TIA (n = 63) or minor stroke (n = 77) who were referred to a TIA clinic. The mean age of the sample was 67, and 61% were women. TIA was defined as the presence of neurologic symptoms that were resolved within one hour of onset, and minor ischemic stroke was defined as having symptoms that persisted longer than one hour but fewer than 24 hours. All evaluations were conducted within one week of symptom onset.
All patients were originally enrolled in the Improving Prevention of Stroke (IMPRES) study and Promoting Adherence to Regimen of risk factor modification by Trained Nonmedical personnel (volunteers) Evaluated again Regular practice Study (PARTNERS), which were aimed at improving secondary stroke prevention through monitoring and counseling for vascular risk factors. Participants who had a history of major stroke, drug or alcohol abuse, dementia, or aphasia were excluded from the analysis.
Measuring Executive Dysfunction
Dr. Harnadek’s group used four tests—the Trail Making Test (Parts A and B), Cognistat Judgment subtest, and Clock Drawing test—to measure executive function skills, including speeded visual search, cognitive flexibility, verbal reasoning, problem solving, visuo-constructional skills, and higher-order cognitive abilities. “In addition, we included a general measure of cognitive ability—the Mini-Mental State Examination (MMSE)—because it is frequently used by clinicians to evaluate mental functioning in these patients,” said Dr. Harnadek.
The percentage of cognitive impairment was calculated separately for all tests, and the frequency of impairment was compared with normal, expected rates in a healthy population. Age-adjusted T scores were used on the Trail Making tests.
Dr. Harnadek and colleagues found no significant group differences in test performances regarding the type of stroke that patients had. Furthermore, “No significant differences were seen in the proportion of impairment across tests,” he said.
About 5% of patients were impaired according to their scores on the MMSE, 13.1% were impaired per the Cognistat Judgment subtest, and 15.3% were impaired per the Clock Drawing test. In addition, 31.2% were impaired according to the Trail Making Test (Part A), and 39.6% were impaired per the Trail Making Test (Part B).
“The majority of patients were impaired on at least one test of executive function, though the proportion was not statistically significant,” Dr. Harnadek commented. Of the 57.2% of the sample who scored as impaired on one or more tests, 27.9% were impaired on one test, and 29.3% were impaired on two or more tests. Nearly 43% of patients were not considered impaired on any of the tests.
“The frequency of impairment on the executive functioning tests was greater than the expected rate in the healthy population,” said Dr. Harnadek. “However, the frequency of impairment on the MMSE was not different from the community base rate of 5%.”
For the patients who had a TIA, their symptoms generally went away within 24 hours, he noted. Among patients with minor stroke, physical or sensory symptoms persisted but they did not cause serious disability.
How Effective Is the MMSE After Stroke?
Initially designed as a tool to help identify patients with Alzheimer’s dementia, the MMSE is not a sensitive tool for assessing cognitive changes in patients with minor stroke or TIA, according to Dr. Harnadek. “Cognitive impairment, common in patients who have experienced TIA, can be missed if physicians rely on measures designed to test for Alzheimer’s dementia. Therefore, measures that test executive functioning are needed as well.
“What we learned from our research was that impaired executive functioning skills are quite common in individuals following TIAs and minor ischemic strokes,” Dr. Harnadek said. “Based on our results, as many as 40% of individuals showed impairment. Furthermore, because impaired executive functioning skills are common, clinicians need to consider the cognitive functioning of their patients when they are evaluating them following a TIA or minor ischemic stroke. The neurologic symptoms … may have resolved, but cognitive difficulties may still be present.
“However, the clinician’s choice of measures to evaluate the mental functioning of their patients is important,” he concluded. “Using measures designed to assess dementia such as the MMSE proved to be insensitive in detecting the difficulties in cognitive functioning in this patient population. Instead, clinicians need to rely on and use measures of executive function skills.”