Single photon emission computed tomography, magnetic resonance imaging hyperintensity, and cognitive impairments in patients with vascular dementia

Background. The relationship between subcortical hyperintensity (SH) on mag netic resonance imaging (MRI), cortical perfusion on single photon emission computed tomography (SPECT), and cognitive function is not well understood . The authors examined these relationships in individuals with vascular dem entia (VaD), paying particular attention to frontal lobe function to determ ine whether the presence of SH on MRI was associated with frontal hypoperfu sion on SPECT, which in turn would be associated with impairments of execut ive-attention function. Methods. Patients with vascular dementia (n = 26) w ere assessed on neurocognitive tests and brain MRI and SPECT. SH volume was quantified from the axial T2-weighted fluid attenuated inversion recovery MRI. Total counts of activation across voxels for 12 cortical regions of in terest were determined from SPECT. Perfusion ratios of both total cortical and frontal activation relative to cerebellum activation were derived, and regression analyses were performed to determine the relationships between c ognitive, MRI, and SPECT indices. Results. SH volume on MRI was significant ly associated with frontal lobe perfusion. but not with global cortical per fusion as measured by SPECT. Frontal lobe perfusion did not consistently co rrelate with performance on measures of executive-attention function, altho ugh both total and frontal perfusion ratios were significantly associated w ith other cognitive functions. Conclusions. These results suggest that a fu nctional "disconnection" between the frontal lobes and subcortical structur es does not fully account for the magnitude of global cognitive impairment in VaD. Cortical perfusion as measured by SPECT appears to be associated wi th cognitive performance, but not specifically executive-attention dysfunct ion. Additional studies are needed to further examine the relationship betw een subcortical and cortical function in VaD.