Single photon emission computed tomography, magnetic resonance imaging hyperintensity, and cognitive impairments in...

The relationship between subcortical hyperintensity (SH) on magnetic 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 dementia (VaD), paying particular attention to frontal lobe function to determine whether the presence of SH on MRI was associated with frontal hypoperfusion on SPECT, which in turn would be associated with impairments of executive-attention function.

Patients with vascular dementia (n = 26) were 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 interest 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 cognitive, MRI, and SPECT indices.

SH volume on MRI was significantly associated with frontal lobe perfusion, but not with global cortical perfusion as measured by SPECT. Frontal lobe perfusion did not consistently correlate with performance on measures of executive-attention function, although both total and frontal perfusion ratios were significantly associated with other cognitive functions.

These results suggest that a functional "disconnection" between the frontal lobes and subcortical structures does not fully account for the magnitude of global cognitive impairment in VaD. Cortical perfusion as measured by SPECT appears to be associated with cognitive performance, but not specifically executive-attention dysfunction. Additional studies are needed to further examine the relationship between subcortical and cortical function in VaD.