Limitations
- Clinical and radiological grading systems
- All have relatively poor sensitivity & specificity
- Grading inaccurate if there is acute hydrocephalus, post-ictal state or drugs affecting conscious level
- Half of patients with poor grades on admission have good outcomes
- Clinical grades are better at predicting outcomes, radiological grades are better at predicting vasospasm
Radiological
Modified fisher scale:
- Thin SAH is classified a < I mm in depth.
- Thick SAH is classified as > I mm in depth
- Original study did not include a specified measurement or criteria to define thick vs thin haemorrhage.
- Any intraventricualr haemorrhage, no matter how small, is counted.
- Has better vasospasm prediction ability than original fisher scale.
Grade | SAH | Intraventricular haemorrhage | Risk of clinical spasm |
0 | No | No | 0% |
1 | Localized or diffuse thin SAH | No | 24% |
2 | No or localized or diffuse thin SAH | Yes | 33% |
3 | Localized or diffuse thick SAH | No | 33% |
4 | Localized or diffuse thick SAH | Yes | 40% |
- Fisher scale not as good as Modified Fisher scale (2006) in predicting vasospasm:
- In 1355 patients with SAH (in placebo arm of RCT for tirilazad), of whom 33% developed vasospasm.
- Early angiographic vasospasm, history of hypertension, neurological grade, and elevated admission mean arterial pressure were identified as risk factors for symptomatic vasospasm.
- After adjusting for these variables, the modified Fisher scale remained a significant predictor of symptomatic vasospasm (adjusted OR 1.28, p = 0.01) while the original Fisher scale was not (adjusted OR 1.1, p = 0.488).
Fisher scale: highest risk of grade 3 not grade 4 see under risk factor below for percentage
Grade | SAH | IVH/ICH | Risk of clinical spasm |
1 | No | No | 21% |
2 | <1mm vertical thick diffuse | No | 25% |
3 | >1mm vertical thick localized or diffuse | No | 37% |
4 | Diffuse or no SAH | Yes | 31% |
- The Fisher Scale (1980) was proposed to predict cerebral vasospasm after aneurysmal SAH and prospectively validated in 47 patients:
- Limitations of this original scale include:
(i) Poor resolution compared to current CT scans,
(ii) Blood thickness measurements used were actual measurements on printed CT scan images and had no relationship to the real clot thickness,
(iii) No SAH and SAH < 1 mm in true thickness (Grades 1 and 2) are both uncommon,
(iv) It does not account for patients with thick SAH with ICH/IVH or those with ICH/IVH alone.
Clinical
WFNS grade (1988)
- Developed by WFNS committee on a universal SAH grading scale
- Considered data from the International Cooperative Aneurysm Study that assessed the prognostic importance of headache, stiff neck, and major focal neurological deficits.
- Uses
- GCS (objective) -> better inter observer agreement
- Presence or absence of a focal neurological deficit is used to distinguish between grades 2 and 3.
- Biggest determinant of mortality is conscious state, whilst the predictor of morbidity is the presence of hemiparesis or aphasia.
- In a series of approximately 3500 patients with SAH who were graded prospectively and assessed for outcome on the GOS 3 months after aneurysmal clipping (favourable outcome was good recovery or moderate disability [GOS 4-5] and an unfavourable outcome was severe disability, a vegetative state, or death [GOS 1-3]) admission WFNS was shown to be predictive of outcome (p < 0.0001).
Grade | GCS score | Major focal deficit (aphasia, hemiparesis or hemiplegia) | Unfavoruable (GOS 1-3) at 3 months |
0 | Not bleeding aneurysm | ||
1 | 15 | - | 13% |
2 | 13-14 | - | 24% |
3 | 13-14 | + | 48% |
4 | 7-12 | +/- | 55% |
5 | 3-6 | +/- | 66% |
- Limitations
- How to grade patients with GCS 15 and focal neurological deficit
- Cut off points in the WFNS scale are based on consensus, not on formal analysis
Modified WFNS
Grade | GCS grade |
0 | Unruptured |
1 | 15 |
2 | 14 |
3 | 13 (poor grade) |
4 | 7-12 |
5 | 3-6 |
Modified Hunt and Hess
Grade | Headache/stupor/coma | Neuro deficit | Others | Survival |
0 | Nil | No | unruptured aneurysm | |
1a | Nil | Yes | No meningeal reaction | |
1 | Mild H/A | No | slight meningismus | 70% |
2 | Moderate to severe | No (CN palsy can be present) | Meningismus present | 60% |
3 | Lethargy confusion | Mild focal (CN palsy is not considered) | 50% | |
4 | Stupor | Moderate to severe hemiparesis | Early decerebrate rigidity | 20% |
5 | Deep coma | Decerebrate rigidity, moribund appearance | 10% |
- Intended to guide timing of aneurysm clipping based on grades of surgical risk
- Grade 1 and 2 operate ASAP to reduce rebleed risk
- >= grade 3 wait till recover to grade 2 before surgery
- However, have life threatening haematoma or multiple bleeds —> just operate
- Add a point for comorbidity or radiological spasms
- Presence of hemiparesis and aphasia had no effect on mortality but signs of meningeal irritation has
- Majority die of rebleed
- Mortality
- Admission Grade 1 or 2: 20% mortality
- If treatment (during old times were all surgery): 14% mortality
- Severe vasospasm on CTA/DSA
- Major cause of death in grade 1 or 2 is rebleed
- Signs of meningeal irritation increase surgical risk
Original hunt and Hess (1968)
Grade | Clinical condition | Survival |
1 | Asymptomatic or minimal headache and slight neck stiffness | 70% survival |
2 | Moderate to severe headache; neck stiffness; no neurologic deficit except cranial nerve palsy | 60% survival |
3 | Mild focal neurologic deficit, lethargy, or confusion | 50% survival |
4 | Stuporous; moderate to severe hemiparesis; possibly early decerebrate rigidity and vegetative disturbances | 20% survival |
5 | Deep coma; decerebrate rigidity; moribund appearance | 10% survival |
- Aimed to retrospectively create an index of surgical risk and to aid neurosurgeons in deciding on the appropriate time after SAH at which the neurosurgeon should operate.
- Surgical risk was felt to be best estimated by the
- Intensity of meningeal inflammatory reaction,
- Severity of neurological deficit/level of arousal (indicating arterial spasm, ischemia, and brain edema and thus greater vulnerability to manipulation),
- Presence of associated disease.
- Their practice at that time was to take
- Grade I and II to surgery as soon as a diagnosis could be made (ideally < 24 h admission),
- Graded III-V treated conservatively until they improved to Grade I or II (except in the case of multiple rebleeds or life-threatening ICH).
- After retrospective review of 275 cases, they concluded that
- Aneurysm clipping can be accomplished with an extremely low mortality rate in the absence of
- Severe meningeal reaction,
- Neurological deficit, or
- Serious associated disease
- Preop Grade I 1.4% versus Grade II 22% versus Grade III-IV approx. 40%
- In 1974, Hunt and Kosnik proposed a modification of their SAH scale by
- Adding a zero grade for unruptured aneurysms
- 1a grade for a fixed neurological deficit in the absence of other signs of SAH.
- Although the Hunt and Hess scale is easy to administer, the classifications are arbitrary, some of the terms are vague (e.g. drowsy, stupor, and deep coma) and some patients may present with initial features that defy placement within a single grade.
- Cons
- In one study which compared Hunt and Hess Scale with GCS, and WFNS Scale in a series of 185 patients with aneurysmal SAH showed that it had the strongest predictive power for GOS at 6 months, though half of poor-grade patients achieved good recoveries suggesting that current admission grading scales are not accurate enough to be the sole basis for treatment decisions.
- They also found that scores on the day of operation were of more prognostic value than values observed immediately after hospitalization.
- Furthermore other studies have struggled to find outcome differences between the individual grades, but did when lower grades were merged suggesting the possibility of an oversplitting error weakening the prognostic power of the scale.
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