Dynamic CT Perfusion imaging in subarachnoid hemorrhage related vasospasm

Abstract

Vasospasm (VSP) and changes in cerebral blood flow (CBF) are complications of subarachnoid hemorrhage (SAH) that can lead to delayed ischemic deficits (DID). In many institutions, nimodipine is the standard treatment used to prevent DIDs subsequent to SAH. However, there are discrepancies regarding the ability of nimodipine to improve outcome in all SAH patients. As new therapies become available for the treatment of DIDs associated with SAH, it will be necessary to develop a method to assess the need for, and the response to, therapy. In response to this need, we attempt to demonstrate the feasibility of using a functional computed tomography (CT) imaging protocol to quantify the effects of nimodipine on VSP and CBF in a rabbit model of SAH. SAH was induced by injecting autologous blood into the cistern magna in New Zealand White rabbits randomized to two groups: nimodipine (n=14) or control (n=12). Subcutaneous nimodipine (2.5 mg/kg) was given one hour after SAH, and every 24 hours after this for the duration of the study. CT Perfusion (CTP) and CT angiography (CTA) were used to measure CBF and basilar artery (BA) diameter at baseline, 10, 30, and 60 minutes after SAH, and on day 3,5,7,9, and 16. Neurological assessments were performed by a blinded observer on each day of scanning. There was no difference in the incidence or severity of VSP between the control and nimodipine groups (p > 0.05). When VSP >15%, nimodipine significantly increased CBF in the brainstem, cerebellum, parieto-occipital cerebrum, and subcortical regions (p < 0.05) (See figure 1). Nimodipine had no effect on CBF when all degrees of VSP were included in the analysis. The degree of neurological deficit was less in the nimodipine group compared to the control group (p < 0.05). We demonstrated that CTP and CTA imaging can quantify arterial VSP and CBF changes in a rabbit SAH model and that these techniques may be useful for evaluating the potential of new therapies for SAH compared to, or in the presence of, nimodipine. Specifically, we showed that nimodipine improves neurological outcome and increases CBF in the presence of moderate or severe VSP.