Neuroimaging in patients with sickle cell anemia: capacity building in Africa

Analysis of structural effects of sickle cell disease on brain vasculature of mice using three-dimensional quantitative phase imaging

Significance

Although the molecular origins of sickle cell disease (SCD) have been extensively studied, the effects of SCD on the vasculature-which can influence blood clotting mechanisms, pain crises, and strokes-are not well understood. Improving this understanding can yield insight into the mechanisms and wide-ranging effects of this devastating disease.

Aim

We aim to demonstrate the ability of a label-free 3D quantitative phase imaging technology, called quantitative oblique back-illumination microscopy (qOBM), to provide insight into the effects of SCD on brain vasculature.

Approach

Using qOBM, we quantitatively analyze the vasculature of freshly excised, but otherwise unaltered, whole mouse brains. We use Townes sickle transgenic mice, which closely recapitulate the pathophysiology of human SCD, and sickle cell trait mice as controls. Two developmental time points are studied: 6-week-old mice and 20-week-old mice. Quantitative structural and biophysical parameters of the vessels (including the refractive index (RI), which is linearly proportional to dry mass) are extracted from the high-resolution images and analyzed.

Results

qOBM reveals structural differences in the brain blood vessel thickness (thinner for SCD in particular brain regions) and the RI of the vessel wall (higher and containing a larger variation throughout the brain for SCD). These changes were only significant in 20-week-old mice. Further, vessel breakages are observed in SCD mice at both time points. The vessel wall RI distribution near these breaks, up to 350    μ m away from the breaking point, shows an erratic behavior characterized by wide RI variations. Vessel diameter, tortuosity, texture within the vessel, and structural fractal patterns are found to not be statistically different. As with vessel breaks, we also observe blood vessel blockages only in mice brains with SCD.

Conclusions

qOBM provides insight into the biophysical and structural composition of brain blood vessels in mice with SCD. Data suggest that the RI may be an indirect indicator of vessel rigidity, vessel strength, and/or tensions, which change with SCD. Future ex vivo and in vivo studies with qOBM could improve our understanding of SCD.

A Massive Extradural Hematoma in Sickle Cell Disease and the Importance of Rapid Neuroimaging

Sickle cell disease (SCD) is an inherited hemoglobinopathy leading to several serious organ complications and early death. It is mostly found in equatorial countries like Tanzania. Extradural hematoma (EDH) is a rare, but serious complication to SCD and may have debilitating consequences. Hitherto, there is no report of EDH in SCD where neuroimaging has been available before, during, and after such an event. Here, we describe a young female SCD patient who developed EDH that required surgical evacuation. She had made full recovery after three months. Neuroimaging performed two years prior to this event was unremarkable except for multiple small cerebral infarcts. On admission, neuroimaging revealed a subgaleal hematoma, possibly indicating disruption of the skull cortex due to increased hematopoiesis. Three months after evacuation of the hematoma, neuroimaging showed evidence of brain atrophy and the previously reported cerebral infarcts and multifocal bone infarction, but no vasculopathy. Possibly, disruption of the skull cortex with subsequent bleeding caused the EDH. As the differential diagnoses of neurological complications in SCD are many and some complications are reversible, neuroimaging should be performed without delay.