MR-angiography allows defining severity grades of cerebral vasospasm in an experimental double blood injection subarachnoid hemorrhage model in rats

Abstract

ObjectiveMagnetic resonance (MR) imaging has been used for the detection of cerebral vasospasm (VSP) related infarction in experimental subarachnoid hemorrhage (eSAH) in rats. Conventional angiography is generally used to visualize VSP, which is an invasive technique with a possible increase in morbidity and mortality. In this study we evaluated the validity of MR-angiography (MRA) in detecting VSP and its feasibility to define VSP severity grades after eSAH in rats.MethodsSAH was induced using the double-hemorrhage model in 12 rats. In two rats, saline solution was injected instead of blood (sham group). MR was performed on day 1, 2 and on day 5. T1-, T2-, T2*-weighted and time-of-flight MR sequences were applied, which were analyzed by two blinded neuroradiologists. Vessel narrowing of 25–50% was defined as mild, 50–75% as moderate and >75% as severe VSP.ResultsWe performed a total of 34 MRAs in 14 rats. In 14 rats, MRA was performed on day 2 and day 5. In six rats MRA was additionally performed on day1 before the blood injection. A good visualization of cerebral vessels was possible in all cases. No VSP was seen in the sham group neither on day 2 nor on day 5. We found vasospasm on day 2 in 7 of the 14 rats (50%) whereas all 7 rats had mild and one rat had additionally moderate and severe vasospasm in one vessel, respectively. On day 5 we found vasospasm in 8 of the 14 rats (60%) whereas 4 rats had severe vasospasm, 1 rat had moderate vasospasm and 3 rats demonstrated mild vasospasm. In 4 of the 14 rats (30%) an ischemic lesion was detected on day 5. Three of these rats had severe vasospasm and one rat had mild vasospasm. Severe vasospasm on day 5 was statistically significant correlated with the occurrence of ischemic lesions (Fisher’s Exact test, OR 19.5, p = 0.03).ConclusionsMRA is a noninvasive diagnostic tool, which allows a good visualization of the cerebral vasculature and provides reproducible results concerning the detection of VSP and the differentiation into three severity grades in rats. Future studies are needed to directly compare MRA with conventional angiography.

The impact of transcranial direct current stimulation on cerebral vasospasm in a rat model of subarachnoid hemorrhage

“…Previous studies were able to demonstrate that this specific model facilitates the reliable induction of severe SAH with a high incidence of vasospasm, making it specifically suitable for the evaluation of this phenomenon. 17,18,31 In the present study, we found an overall high incidence of cerebral vasospasm on day 2 (65%) as well as on day 5 (86%), which again reflects the aforementioned benefits of this experimental SAH-model. Considering vasospasm severity, expectedly, severe vasospasm was seen more often on day 5 (49%) compared to day 2 (21%).…”

“…SAH was induced using the modified double hemorrhage model, as first described by Güresir et al and recently utilized by our study group. 17 , 18 This model includes the injection of 0.25 ml autologous arterial blood into the cerebellomedullary cistern on two consecutive days. In the sham-group, the same volume of saline solution was injected instead of blood.…”

“…In a previous publication, we have already defined the reference values for the assessment of vasospasm based on MR-angiography (MRA) in rats. 18 Examples of normal and spastic vessels are shown in Figure 2 .…”

The ESAS-score: A histological severity grading system of subarachnoid hemorrhage using the modified double hemorrhage model in rats

“…The double blood injection model allows the induction of a severe eSAH, that can be reliably scored using the ESAS-score. Additionally, the double blood injection eSAH-model is associated with a calculable mortality rate [4,12,18,20]. These findings might contribute to more reliable planning of future experimental studies of severe SAH with the possibility to reduce the number of animals included.…”

“…During the procedure, the body temperature was maintained between 36.5 and 37.5˚C by a heating blanket, controlled by a rectal temperature probe (Homeothermic Monitor, Harvard Apparatus, Hugo Sachs Elektronik, Germany). eSAH was induced in 135 Sprague Dawley male rats using the modified double hemorrhage model, as recently described by our study group and first described by Güresir et al [18,20]. This model consists of the injection of 0.25 ml autologous arterial blood in the subarachnoid space on two consecutive days.…”