Cognitive test performance and brain pathology

Cognitive impairment, assessed using paper-and-pencil tests, occurs with multiple syndromes, including heart failure; however, relationships between test performance and brain injury are unclear.

To determine the extent of brain injury assessed by magnetic resonance T2 relaxometry procedures in a mixed sample with cognitive impairment as measured by the Mini-Mental State Examination, Trailmaking Test parts A (TMT-A) and B (TMT-B), and the Watson Clock-Drawing Test (CDT).

A comparative design was used with a convenience sample of 66 participants (age 48.2 +/- 8.4 years, 41 males, 52 right-handed). Normal and abnormal performances on cognitive tests were compared using T2 relaxation values across the brain (p < .005). Fifty-four of the participants were healthy, and 12 had heart failure (New York Heart Association classes II-III, left ventricular ejection fraction <0.40).

All participants scored normally on the Mini-Mental State Examination; thus, this test was excluded from further analysis. Abnormal cognitive scores were found in 14-20% of the participants, with significant brain injury appearing in participants with abnormal test scores. Injured structures included frontal, temporal, parietal, insular, and cingulate cortices; corpus callosum; and caudate. The CDT results showed the greatest extent of structural injury. The TMT-A test demonstrated relationships to specific injury sites, whereas the TMT-B showed relationships only to isolated areas of damage.

The findings suggest that paper-and-pencil cognitive tests relate to injury in brain structures, with CDT values relating to the greatest extent of injury. Specific damage sites may correlate with unique tests, such as TMT-A. Specialized tests should be developed that would indicate neural injury in specific areas.