To determine the effects of MRI white matter hyperintensities (WMH) on cognitive functioning, we used neuropsychologic tests and MRI to study 150 elderly volunteers free of neuropsychiatric or general disease. There were 76 (50.3%) individuals without and 74 (49.7%) with WMH. The latter subset was older (61.3 +/- 6.6 years versus 58.5 +/- 5.8 years, p = 0.005), had a higher mean arterial blood pressure (103.7 +/- 11.4 mm Hg versus 99.9 +/- 10.3 mm Hg, p = 0.03), and a larger ventricular-to-intracranial-cavity ratio (6.3 +/- 5.6% versus 4.7 +/- 1.6%, p = 0.02). Individuals with WMH performed worse than their counterparts without such abnormalities on all tests administered. After adjusting for the group differences in age, arterial blood pressure, and ventricular size, we noted statistically significant results on form B of the Trail Making Test (121.8 +/- 37.8 msec versus 100.3 +/- 47.9 msec, p = 0.04), a complex reaction time task (680.8 +/- 104.9 msec versus 607.1 +/- 93.9 msec, p = 0.001), and the assembly procedure of the Purdue Peg-board Test (27.5 +/- 5.8 versus 30.6 +/- 5.9, p = 0.02). Partial correlations did not reveal any relationship between test scores and the semiautomatically assessed total area of WMH. Our data suggest that the presence of WMH exerts a subtle effect on neuropsychologic performance of normal elderly individuals, which becomes particularly evident on tasks measuring the speed of more complex mental processing.
Schmidt et al. (1993) studied this question.