Steal physiology is spatially associated with cortical thinning.

BACKGROUND: The physiological impact of severely impaired cerebral autoregulatory vascular reactivity on cortical integrity is unknown. The purpose of this study is to determine the relationship between severe impairment of autoregulatory flow control associated with steal phenomenon and its impact on cortical thickness.
METHODS: 250 blood oxygen level dependent (BOLD) MRI cerebrovascular reactivity (CVR) studies were reviewed in order to identify subjects with severe unilateral exhausted cerebrovascular reserve demonstrating steal physiology but with normal appearing cortex on fluid attenuated inversion recovery imaging. 17 patients meeting the inclusion criteria were identified. A reconstructed inflated cortical surface map was created for every subject using Freesurfer software (http://surfer.nmr.mgh.harvard.edu/). The region of interest (ROI) reflecting the steal physiology was determined by overlaying the subject's CVR map on to the cortical surface map. This ROI was compared with the corresponding area in the healthy hemisphere which provided control cortical thickness measurement in each subject.
RESULTS: The hemisphere with steal physiology showed an 8% thinner cortex (2.23+/-0.28 mm) than the corresponding healthy hemisphere (2.42+/-0.23 mm) (p=0.0005).
CONCLUSIONS: Our findings indicate that a spatial correspondence exists between impairment of autoregulatory capacity with steal physiology and cortical thinning.