Are white matter lesions directly associated with cognitive impairment in patients with lacunar infarcts?

Forty-four patients (mean age 66, SD 8 years) with either clinical evidence of a focal lacunar syndrome (n=36) or with disorders of memory or gait (n=8) in the presence of a lacunar infarct on CT were studied for cognitive functioning and for the presence of white matter lesions on MRI. MR images were assessed by a neurologist and a neuro-radiologist blinded to the clinical data. Thirty-six patients had one or more lacunar infarets on CT or MRI (in the thalamus in 5, in the caudate nucleus in 3 and in the internal capsule or corona radiata in the remaining patients). Twelve patients had multiple infarcts. Severe lesions of the white matter were found in 13 patients, mild to moderate lesions in 20 patients. Scores on Digit Span, Digit Symbol and delayed recall of the 15-Words test were significantly lower in the group with severe lesions, whilst there was a trend in the same direction for the Cognitive part of the Cambridge Examination of Mental Disorders in the Elderly, the Trailmaking B, Stroop colour interference test and the delayed visual reproduction of the Wechsler Memory Scale. These findings suggest that diffuse lesions of the white matter are an independent factor in the pathogenesis of intellectual dysfunction, also in patients with lacunar infarcts, but a truly independent analysis is difficult because the most severe involvement of the white matter tended to be associated with the largest number of lacunar infarcts.