MRI white matter hyperintensities and neuropsychological performance in a clinical sample.

Objective: White-matter hyperintensities (WMH) are commonly observed on MRI of non-demented patients. Findings are mixed regarding their association with neuropsychological test performance. The purpose of this study is to investigate the association of white-matter hyperintensities on routine clinical MRI and neuropsychological test performance in non-demented outpatients.

Method: Two groups were selected based on MRI results: (1) normal (n = 62, M_age = 50.21, M_edu = 14.89) and (2) WMH without other MRI abnormality (n = 56, M_age = 55.43, M_edu = 14.04). Neuropsychological tests assessed five cognitive domains for which index scores were calculated and categorized in the following clinical ranges: well below average, below average, low average, average, and above average.

Results: Likelihood ratios comparing base rates for the WMH and normal groups across these clinical ranges revealed significant base rate differences only for attention/processing speed (Lχ2 = 16.47, df = 4, p < .01), with more WMH patients in the below average range and fewer above average. Odds ratios were calculated using two z-score cutoffs: -1.67 and -1.00. While patients with WMH were significantly more likely to have an index z-score ≤ -1.00 on attention/processing speed tests (OR = 3.62, 95% CI: 1.08-12.19) and an executive function test of reasoning (OR = 4.63, 95% CI: 1.18-18.19), there was no difference in the likelihood the groups would have a z-score ≤ -1.67 in any cognitive domain.

Conclusions: Taken together, these findings indicate that among referred outpatients without dementia, WMH on routine clinical MRI are associated with relatively mild decreased attention and processing speed.