Cerebral perfusion heterogeneity and complexity in patients with acute subarachnoid haemorrhage

Background The pathophysiological mechanisms of impaired perfusion during acute subarachnoid haemorrhage (SAH) are incompletely understood. Cerebral perfusion at the micro vascular level can be assessed by single photon emission computed tomography (SPECT). We used a SPECT approach with (99)mTc-ECD to measure the cerebral perfusion heterogeneity and complexity in patients with acute aneurysmal SAH or perimesencephalic non-aneurysmal SAH (PNSAH). Methods The perfusion SPECT data of 61 patients with aneurysmal SAH, 18 patients with PNSAH, and 20 healthy control subjects were analysed by dividing the brain into 384 regions of interest. The magnitude of spatial perfusion heterogeneity was assessed by calculating the relative dispersion (RD=coefficient of variation). The fractal dimension (FD) was used to describe the overall complexity of global cerebral perfusion. Results Patients with aneurysmal SAH (RD= 11.30 +/- 2.17, P < 0.001) and PNSAH (10.38 +/- 2.27, P= 0.023) had a higher perfusion heterogeneity than control subjects (8.69 +/- 0.80). Patients with aneurysmal SAH tended to have a higher perfusion heterogeneity than patients with PNSAH (P=0.061). Also the overall complexity of cerebral perfusion was decreased in aneurysmal SAH (FD = 1.11 +/- 0.06, P < 0.001) and PNSAH (1.11 +/- 0.06, P=0.004) as compared with control subjects (1.17 +/- 0.06). Acute SAH causes increased regional cerebral perfusion heterogeneity and decreased overall complexity of global cerebral perfusion. Conclusion Non-invasive assessment of cerebral perfusion characteristics is feasible with SPECT and fractal analysis in patients with acute SAH and may help evaluating micro vascular function in SAH.