A magnetic resonance imaging grading system for subarachnoid hemorrhage severity in a rat model

Abstract

Background: The endovascular perforation model of subarachnoid hemorrhage (SAH) has a large variation in outcomes. This may reflect differences in the SAH size.

New method: Magnetic resonance imaging (MRI) was performed 24h after endovascular perforation in adult male (n=58) and female (n=58) rats. Rats were divided into five grades according to MRI characteristics: grade 0: no SAH or intraventricular hemorrhage (IVH); grade 1: minimal or thin SAH without IVH; grade 2: minimal or thin SAH with IVH; grade 3: thick SAH without IVH; grade 4: thick SAH with IVH. We investigated whether MRI grading scale reflected severity of SAH (determined post mortem) and neurological score.

Results: There was a strong correlation between MRI grading scale and current SAH grading scale (P<0.01) and neurological score (P<0.01) in male rats. In female rats, there was also a strong correlation between MRI grading scale and SAH grading scale (P<0.01) but not with neurological score (P=0.24).

Comparison with existing methods: The current grading system is based on the amount of SAH and needs animal euthanasia to evaluate SAH severity. There is no useful grading system to classify severity of SAH without decapitating animals.

Conclusions: We demonstrated a correlation between the MRI grading scale and the current SAH grading scale in an endovascular perforation rat model. The MRI grading scale allows evaluation of SAH severity without euthanizing animals.

Keywords: Endovascular perforation; Magnetic resonance imaging; Rat; Subarachnoid hemorrhage.