A protocol for precise comparisons of small vessel disease lesions between ex vivo magnetic resonance imaging and histopathology

Rationale
Neuroimaging and clinical studies have defined human sporadic cerebral small vessel disease but the pathophysiology remains relatively poorly understood. To develop effective therapies and preventative strategies, we must better understand the heterogeneity and development of small vessel disease at a cellular level.

Hypothesis
Small vessel disease lesions as seen on neuroimaging have specific neuropathological correlates.

Methods and design
Standard histological samples are taken from strategic areas of the brain typically affected by small vessel disease, in cases with a range of disease from mild to severe and controls. Tissue is formalin fixed, scanned using 7-tesla magnetic resonance imaging and processed for histology. Histological slides are digitalized then registered with the corresponding magnetic resonance image. Small vessel disease burden is assessed and lesions are precisely identified on the ex vivo imaging and microscopy independently then compared. The tissue can be interrogated using multiple magnetic resonance sequences and histological methods targeting the gliovascular unit.

Study outcomes
The primary outcome is identifying and defining the cellular characteristics of small vessel disease lesions compared to imaging. Secondary outcomes are related to obtaining information about abnormalities of protein expression in the gliovascular unit, defining groups of small vessel disease severity in our cohorts for future analysis and developing a reliable, reproducible protocol for accurate radiological–histological lesion comparison, which can be applied to other neurological diseases in the future.

Discussion
Comprehensive, precise pathological–radiological–clinical correlations in small vessel disease will provide greater insight into associations and pathophysiology underlying magnetic resonance imaging findings in normal- and abnormal-appearing tissue, ex vivo and in vivo.