NEUROPSYCHOLOGICAL CORRELATES OF WHITE-MATTER LESIONS IN HEALTHY ELDERLY SUBJECTS - A THRESHOLD EFFECT

The clinical significance of white-matter lesions (WMLs) detected by computed tomography and magnetic resonance imaging in healthy elderly subjects has been controversial, with some studies reporting associated deficits in cognition and others failing to document cognitive disturbance. In our sample of 100 healthy elderly individuals, almost half (n = 46) had no WMLs, approximately one fourth had minimal (less-than-or-equal-to 1 cm2; n = 27) or moderate (> 1 cm2 but less-than-or-equal-to 10 cm2; n = 21) WML areas, and six subjects had large WML areas (> 10 cm2). Substantial disturbances in basic attention and selected frontal lobe skills were detected in the six subjects with the large WML areas. These findings suggest that a "threshold" of WML area must be present before cognitive deficits are observed. Surprisingly, no significant relationships between duration of hypertension or cholesterol levels and WMLs were detected, suggesting that factors other than vascular disturbances are involved in the origin of at least some WMLs.