Background and Purpose--Infratentorial abnormalities may cause cognitive deficits, but current research criteria for vascular dementia (VaD) do not consider them. Our purposes were to determine the prevalence of infratentorial abnormalities in VaD, their relation with supratentorial abnormalities, and whether they are relevant to cognition.

Methods--We examined 182 patients (120 men, mean age=73 years, SD=8) with probable VaD at inclusion into a multicenter clinical trial. MRI scans were evaluated for infratentorial vascular abnormalities, midbrain atrophy, cerebellar atrophy, basilar artery diameter and tortuosity, and supratentorial abnormalities. Cognitive testing included the mini-mental state examination (MMSE) and the vascular dementia assessment scale (VaDAS-cog).

Results--One hundred forty-one (77.5%) patients had infratentorial abnormalities: 119 (65.4%) had focal infratentorial vascular lesions, 65 (35.7%) had diffuse pontine vascular abnormalities hyperintense on T2-weighted images, 20 (11.0%) had midbrain atrophy, and 16 (8.8%) had cerebellar atrophy. Significant correlations were found between number of infratentorial vascular lesions and basilar artery diameter (r_s=0.26; P<0.0001), infratentorial and basal ganglia (including thalamus) vascular abnormalities (r_s=0.30; P<0.0001), as well as between midbrain atrophy and global supratentorial atrophy (r_s=0.27; P<0.0001). Infratentorial vascular abnormalities and cerebellar atrophy were not significantly associated with cognitive impairment. Patients with midbrain atrophy performed worse on cognitive tests than those without midbrain atrophy. After correction for sex, age, education, supratentorial abnormalities, and center, midbrain atrophy remained significantly associated with lower MMSE scores (P<0.05).

Conclusions--Infratentorial abnormalities often occur in patients with VaD, but only midbrain atrophy was found to be relevant to cognition.