Aneurysmal Subarachnoid Hemorrhage Grading in Animal Models - Animal Models of Acute Neurological Injuries: Injury and Mechanistic Assessments - page 305

much the same way clinicians have graded the disease so that they
may evaluate the effi cacy of their own treatments.
Clinicians have developed both clinical and radiographic scales
for categorizing the severity of aneurysmal subarachnoid hemor-
rhage. The most recognized scales based on neurological exam are
the Hunt and Hess Grading system, followed by the World
Federation of Neurological Surgeons (WFNS) Grading of SAH.
These scales have been shown to be predictive of outcome and cor-
relate with vasospasm ( 8, 9 ). These types of clinical scales were
designed to predict mortality and outcome in humans undergoing
standard of care surgical and medical therapies for aneurysmal
SAH. Similar clinical grading scales for animals are not truly appli-
cable in a controlled experimental environment where one is seek-
ing to fi nd differences between treatment groups and untreated
controls.
Radiographic scales, such as the Fisher Scale, Modifi ed Fisher
Scale, and Classen Score, are based on CT scans that describe and
quantify the amount of blood in the basal cisterns and ventricles
following aneurysmal SAH. With variable degrees of accuracy,
these scales are predictive of vasospasm and outcome, and provide
and effective means categorizing the severity of the SAH ( 10 ).
Quantifying hemorrhage volume in SAH not only confi rms the
diagnosis of SAH (or the successful creation of experimental SAH),
but is also a strong predictor of outcome and incidence of vasos-
pasm, making it an ideal marker. The utilization of an experimental
SAH grading scale based on hemorrhage volume was fi rst pub-
lished in 2008 ( 11 ). The scale evaluates the amount of subarach-
noid blood in the basilar cisterns with digital photography of the
brain following its removal from the cranium. Prior to the publica-
tion of this scale, previous studies simply confi rmed the absence or
presence of SAH based on nondescriptive visual inspections. Other
groups confi rmed the successful induction of SAH by monitoring
the spikes in ICP that typically follow endovascular puncture.
Others have attempted to include or exclude animals from study
based on the severity of monitored cerebral blood fl ow reductions
following SAH, but no formal methods or criteria are published.
These indirect methods make the assumption of successful SAH,
and cannot exclude the possibility subdural or epidural hemor-
rhages as the cause for the readings. Prunell et al. described a
method of quantifying the SAH blood volume using spectroscopy
( 5 ). This method was useful for his analysis of the differences
between experimental models of SAH, but is impractical for the
purposes of original experimentation, as the process requires the
collection and homogenization of the brain samples for use in
spectroscopy, precluding their use in other tests. Therefore, to
date, there is only one published SAH grading scale for use in ani-
mal models. This scale is described below.