Perihematomal changes in glucose metabolism and cell counts in the rat collagenase model for intracerebral hemorrhage

While the perihematomal region of a spontaneous intracerebral hemorrhage (ICH) provides a potential therapeutic target, the pathophysiological processes in that region remain unclear. To evaluate the nature, extent and localization of perihematomal changes, we investigated glucose uptake, water diffusion, and cell counts in the acute phase of collagenase-induced ICH. Sprague-Dawley rats were intrastriatally injected with collagenase or saline (control group). 2-deoxy-2-[¹⁸F]fluoro-D-glucose ([¹⁸F]FDG) PET, T2-weighted and diffusion-weighted MRI were performed at baseline (n = 30) and day 1 (n = 28), 3 (n = 14) and 7 (n = 14) after injection. Astrocytes, microglia and neurons in the piriform cortex were quantified using immunohistochemistry on brain slices obtained at day 2 (n = 14) or 8 (n = 14) after injection. Decreased [¹⁸F]FDG uptake and increased ADC values were seen in the perihematomal region, and were most pronounced on day 1 and 3 in the piriform cortex and basal ganglia. Significantly less neurons and more glia were found ipsilateral compared to contralateral at day 2 and 8 (p < 0.05), with no significant difference between timepoints. The unchanged glial and neuronal numbers are in contrast to the [¹⁸F]FDG uptake that partially recovered over time, suggesting that the absolute numbers of cells do not correlate directly to the perihematomal changes in glucose metabolism following ICH.