The Glasgow Coma Score (GCS) was developed in the early 1970s as a mechanism to assess level of consciousness after a head injury using a three axes system of eyes, verbal, and motor response (Table 2) (12). Throughout the years, the GCS scale has been used and modified to help assess everything from acute care by the emergency medical technicians in the setting of trauma to long-term assessment of the neurologically impaired patient in an ICU setting.

Naturally, the utility of the GCS scale has been examined for outcome assessment in the SAH patient. Gotoh et al. (13) completed a prospective study that showed a very high correlation between good GCS and good functional outcomes using the Glasgow Outcome Scale (GOS) in SAH patients. Not surprisingly, no clearly defined breakpoints existed between their groups of patients and they tended to fall along a continuum from good to bad outcomes. This fact is most likely by-product of small range (five) of potential outcomes using the GOS.

Charles Drake in 1988 identified the shortcomings of the grading scales in coming usage at that time and helped to develop a grading scale labeled the World Federation of Neurologic Surgeons (WFNS) scale for SAH that utilized the ubiquitous GCS in combination with identification of a focal deficit (14). First, it was noted that initial level of consciousness described by the GCS was predictive of death and disability while the presence or the absence of hemiplegia and aphasia added to the predictive value of the GCS alone as the addition of these deficits made rehabilitation difficult. Condensing the GCS into a five subdivisions and adding an axis that accounted for the identification of a focal deficit provide the scoring for the WFNS scale (Table 3).

The WFNS scale has been studied for predictive power with some interesting results. It would appear, not surprisingly, that a continuum exists toward worse outcome with increasing WFNS score, however, clear distinctions between individual scores has not been proven (10, 15). These breakpoints are important for prognostication in order to show for example that a grade of WFNS 2 predicts a significant different outcome from WFNS grades of 1 and 3 (11). The WFNS is a very top heavy scale where the majority of patients based on GCS will theoretically fall in the grades 0–3 while grades 4 and 5 encompass a GCS range of 3–12. Looking at WFNS 4 as an example a GCS 12 without a focal deficit would seem to be quite different from a GCS 7 with hemiplegia which both have the same WFNS score.

Rosen et al. (15) reviewed the cases of 3,500 patients with SAH who were prospectively graded and assessed for outcome. Three months after SAH the GOS was scored and likelihood ratio of a poor outcome for each individual score was: WFNS grade 1  =  0.36, WFNS grade 2  =  0.61, WFNS grade 3  =  1.78, WFNS grade 4  =  2.47, and WFNS grade 5  =  5.22 (15).

Two thirds of patients fell into the WFNS grade 1 or 2 while the remaining one third was about equally split between the other three grades. With a large proportion of patients falling into the best grades, drawing conclusions becomes difficult based on the relatively small number of poor grade SAH included.

The Fisher grading scale (Table 4) relating to SAH was developed not for outcome assessment but rather to determine risk for the development of cerebral vasospasm (16). The Fisher grading scale was developed at time (circa 1980) when the resolution on CT scanners was much less than those in common use today. Other important variables that were not addressed when the Fisher scale was developed also include density of blood clot and clot location which are known to play a role in the clinical course of SAH (17).

Additional studies have attempted to utilize the Fisher grading scale as a standalone mechanism to predict outcome with some success (18). The issue becomes that the majority of patients fall into a Fisher grade 3 as most SAH patients do not present with either absent blood (grade I) or clot that is less than 1 mm in thickness (grade II). More recently, outcome prediction based on the Fisher scale has been bolstered with the addition of patient age, aneurysm size, and aneurysm location. These adaptations to the Fisher scale have predicted patient outcomes with some reliability but they have as of yet been included in day-to-day management of the SAH patient (17).

Higher resolution CT images and MRI sequences (19) play an important role in the management of the SAH patient that was not present when the Fisher scale was developed, however, their utility in prediction of clinical outcomes remains in question and requires additional study as stand-alone techniques.

With the explosion of new MRI techniques, the future prediction models based on imaging studies alone will likely include the use of diffusion tensor imaging, perfusion sequences and likely MR spectroscopy. It does, however, remain to be seen if an imaging modality without consideration of clinical picture will provide additional predictive information.

The Massachusetts General Hospital (MGH) aneurysm grade (Table 5) (17) is assigned based on retrospective review of 409 patients who had their aneurysms surgically treated with the patient’s clinical outcome as the primary goal of the study. Using a combination of five clinical and radiographic admission factors, a score was assigned to each patient with an intracranial aneurysm. The combination of clinical and radiographic findings attempt to paint a more complete picture of the SAH patient that was missing from the earlier studies that have included either one or the other.