Version May 2024
INTRODUCTION — Nontraumatic subarachnoid hemorrhage (SAH) is most commonly caused by ruptured saccular aneurysms. SAH is often a devastating event with substantial mortality and high morbidity among survivors. The appropriate therapy for SAH depends in part upon the severity of hemorrhage. Level of consciousness on admission, patient age, and the amount of blood on initial head computed tomography (CT) scan are the most important prognostic factors for SAH at presentation [1].
Several grading systems are used in practice to standardize the clinical classification of patients with SAH based upon the initial neurologic examination and the appearance of blood on the initial head CT. This topic will provide an overview of the more commonly used clinical and radiologic grading scales for SAH. Other aspects of aneurysmal SAH are discussed separately.
●(See "Aneurysmal subarachnoid hemorrhage: Epidemiology, risk factors, and pathogenesis".)
●(See "Aneurysmal subarachnoid hemorrhage: Clinical manifestations and diagnosis".)
●(See "Aneurysmal subarachnoid hemorrhage: Treatment and prognosis".)
INDIVIDUAL GRADING SCALES — An ideal SAH grading scale would provide the following capabilities [2-4]:
●Guide management decisions that are influenced by the severity of SAH
●Provide prognosis for clinicians, patients, and family members
●Assist practitioners in their ability to compare individual patients and groups of similar patients regarding studies that examine the impact of new treatments
●Enable practitioners to detect and quantify changes in disease severity while following an individual patient
While a number of SAH grading scales have been proposed, none meets all of these requirements or is universally accepted [4,5]. Results for an individual patient may vary depending on the interval between symptom onset and assessment of the patient. Furthermore, there is a paucity of validation studies, and no prospective controlled comparison studies have been performed.
Glasgow Coma Scale — The Glasgow Coma Scale (GCS) (table 1) was devised in the early 1970s [6]. The GCS is not a true SAH grading scale, but is rather a standardized method for evaluating the level of consciousness in a number of neurologic conditions including SAH. The GCS assigns points based on three parameters of neurologic function:
●Eye opening (spontaneous = 4, response to verbal command = 3, response to pain = 2, no eye opening = 1)
●Best verbal response (oriented = 5, confused = 4, inappropriate words = 3, incomprehensible sounds = 2, no verbal response = 1)
●Best motor response (obeys commands = 6, localizing response to pain = 5, withdrawal response to pain = 4, flexion to pain = 3, extension to pain = 2, no motor response = 1)
In a prospective series of 765 patients with SAH, a higher GCS correlated with better outcome after aneurysm surgery [7]. However, a significant difference in outcome was observed only between patients with GCS scores of 15 and 14, while no significant differences were found between the remaining adjacent GCS scores.
The interobserver variability of the GCS for patients with SAH is moderate (kappa 0.46) [8].
The GCS has been incorporated into several additional SAH grading systems. (See 'World Federation of Neurological Surgeons grading scale' below and 'Ogilvy and Carter grading system' below.)
It should be recognized that sedating medications and intubation can confound interpretation of the clinical SAH scales, particularly the GCS and those that incorporate it, since such interventions will reduce the level of consciousness and impair verbal responses.
Hunt and Hess grading system — The grading system proposed by Hunt and Hess in 1968 (table 2) [9] is one of the most widely used [10]. The scale was intended as an index of surgical risk. The initial clinical grade correlates with the severity of hemorrhage.
●Grade 1: Asymptomatic or mild headache and slight nuchal rigidity
●Grade 2: Moderate to severe headache, stiff neck, no neurologic deficit except cranial nerve palsy
●Grade 3: Drowsy or confused, mild focal neurologic deficit
●Grade 4: Stupor, moderate or severe hemiparesis
●Grade 5: Deep coma, decerebrate posturing
The grade is advanced one level for the presence of serious systemic disease (eg, hypertension, diabetes, severe arteriosclerosis, chronic pulmonary disease) or vasospasm on angiography.
A subsequent modification proposed by Hunt and Kosnik added a grade 0 for unruptured aneurysms and a grade 1a for a fixed neurologic deficit without other signs of SAH [11].
Although the Hunt and Hess scale is easy to administer, the classifications are arbitrary, some of the terms are vague (eg, drowsy, stupor, and deep coma) and some patients may present with initial features that defy placement within a single grade [4]. As an example, a rare presentation of SAH may include severe headache (ie, grade 2), normal level of consciousness, and severe hemiparesis (ie, grade 4). In such cases, the clinician must subjectively decide which of the presenting features is most important for determining the grade.
A systematic review of SAH grading scales found conflicting data regarding the utility of the Hunt and Hess scale for prognosis [4].
Furthermore, it is unclear if there are significant differences in outcome for adjacent Hunt and Hess grades.
●Some studies evaluating Hunt and Hess grades found significant differences in outcome for some adjacent grades and not others [8,12]
●A study of 230 patients with SAH found a significant difference in outcome for compressed but not adjacent Hunt and Hess grades; patients with grades 1 to 3 had better outcomes compared with those with grades 4 and 5 [13]
●Another study of 405 patients with SAH found no significant difference for the risk of poor outcome or death between patients with Hunt and Hess grades 0 to 2 [2]. Furthermore, the risk was significantly different only when comparing patients with Hunt and Hess grade 3 to those with grade 0.
The interobserver variability for the Hunt and Hess scale is moderate (kappa 0.41 to 0.48) [8,14,15].
World Federation of Neurological Surgeons grading scale — The grading system of the World Federation of Neurological Surgeons (WFNS) (table 3) was proposed in 1988 [16]. It is based on the GCS score (see 'Glasgow Coma Scale' above) and the presence of motor deficits.
●Grade 1: GCS score 15, no motor deficit
●Grade 2: GCS score 13 to 14, no motor deficit
●Grade 3: GCS score 13 to 14, with motor deficit
●Grade 4: GCS score 7 to 12, with or without motor deficit
●Grade 5: GCS score 3 to 6, with or without motor deficit
Unlike the Hunt and Hess scale, the WFNS scale uses objective terminology to assign grades [4]. However, it may be more complex to administer than the Hunt and Hess scale because it requires assessment of both motor function and GCS. One study of 50 patients with SAH found that the interobserver variability for the WFNS scale was moderate (kappa of 0.6) [15].
A systematic review of SAH grading scales found conflicting data regarding the prognostic power of the WFNS grades [4]; two studies showed a stepwise increase in the likelihood of poor outcome with increasing WFNS grade [8,17], while others did not find consistent significant differences in outcome between adjacent WFNS grades [7,12,18]. In a study assessing a series of 185 patients with SAH, the Hunt and Hess score correlated more strongly with outcome at six months than the GCS or World Federation of Neurological Surgeons Scale (WFNS) [19]. However, individual grades for all three scales demonstrated suboptimal sensitivity, specificity, and predictive value. In addition, nearly half of the patients with poor scale grades on admission had a good outcome.
The WFNS in conjunction with the Japan Neurosurgical Society proposed a modification to the scale such that the presence of motor deficit as outlined above is excluded. In two studies, this modified scale appeared to have better discriminatory value compared with the original WFNS scale, but broader validation studies are required [20-22].
Fisher scale — The Fisher scale (table 4) was devised in 1980 as an index of vasospasm risk (but not clinical outcome) based upon the hemorrhage pattern seen on initial head CT scan [23].
●Group 1: No blood detected
●Group 2: Diffuse deposition or thin layer with all vertical layers of blood (in interhemispheric fissure, insular cistern, or ambient cistern) less than 1 mm thick
●Group 3: Localized clots and/or vertical layers of blood 1 mm or more in thickness
●Group 4: Intracerebral or intraventricular clots with diffuse or no subarachnoid blood
The Fisher scale was validated in a small prospective series of 41 patients with SAH [24]. The interobserver variability for the Fisher scale indicates excellent agreement between observers (kappa 0.90) [2].
The Fisher scale has also been incorporated into other SAH grading systems. (See 'The VASOGRADE' below and 'Ogilvy and Carter grading system' below.)
Modified Fisher scale — Like the Fisher scale, the modified Fisher scale (also known as the Claassen grading system) proposed in 2001 is an index of the risk of delayed cerebral ischemia due to vasospasm after SAH (table 5) [25,26]. It does not address clinical outcome. Unlike the Fisher scale, the modified Fisher scale takes into account the separate and additive risk of SAH and intraventricular hemorrhage (IVH).
Ten cisterns or fissures are evaluated for blood with the modified Fisher scale. These include the frontal interhemispheric fissure, the quadrigeminal cistern, the bilateral suprasellar and ambient cisterns, and the bilateral basal sylvian and lateral sylvian fissures. The scale is graded as follows:
●Grade 0: No SAH or IVH
●Grade 1: Minimal SAH and no IVH
●Grade 2: Minimal SAH with bilateral IVH
●Grade 3: Thick SAH (completely filling one or more cistern or fissure) without bilateral IVH
●Grade 4: Thick SAH (completely filling one or more cistern or fissure) with bilateral IVH
The modified Fisher scale was derived from analysis of data from 276 patients with SAH who had a head computed tomography (CT) scan within 72 hours of onset [25]. The best predictors of delayed cerebral ischemia due to vasospasm were thick SAH completely filling any cistern or fissure (odds ratio [OR] 2.3, 95% CI 1.5-9.5) and bilateral IVH (OR 4.1, 95% CI 1.7-9.8).
Interrater reliability has been reported to be suboptimal [27]. While the modified Fisher scale has been validated in retrospectively, prospective validation is awaited [28,29].
The VASOGRADE — The VASOGRADE grading scale was developed to predict the risk of delayed cerebral ischemia following SAH [30]. It is based on the WFNS scale and modified Fisher scale (mFS) at time of admission. The scale is divided into three categories:
●Green – WFNS 1 or 2 and mFS 1 or 2
●Yellow – WFNS 1 to 3 and mFS 3 or 4
●Red – WFNS 4 or 5 and any mFS
Compared with patients classified as "green," patients classified as "red" had a higher risk for delayed cerebral ischemia (OR 3.19; 95% CI 2.07-4.50) [30]. Patients classified as "yellow" had a similar risk as those classified as "green" (OR 1.31; 95% CI 0.77-2.23).
Ogilvy and Carter grading system — A SAH classification system to predict outcome for surgical management of SAH due to ruptured aneurysm was proposed by Ogilvy and Carter (table 6) in 1998. It stratifies patients based upon age, Hunt and Hess grade (clinical condition), Fisher grade (SAH volume and vasospasm risk), and aneurysm size [2]. (See 'Hunt and Hess grading system' above and 'Fisher scale' above.)
One point is given for each of the following variables:
●Age greater than 50
●Hunt and Hess grade 4 to 5 (in coma)
●Fisher grade score 3 to 4
●Aneurysm size >10 mm
●An additional point is added for a giant posterior circulation aneurysm (≥25 mm)
The total score ranges from 0 to 5, corresponding to grades 0 to 5.
The Ogilvy and Carter scale mitigates the potential subjectivity inherent in the Hunt and Hess system by compressing it into two grades (coma or no coma). Similarly, it compresses the Fisher scale into two grades. Nonetheless, it is more complex to administer than the Hunt and Hess scale, and requires knowledge of aneurysm size.
In a prospective evaluation of this system in 72 patients with SAH, the authors reported good to excellent outcomes in greater than 78 percent of patients with grades 0 to 2 [2]. In comparison, good outcomes were seen in 67 percent of grade 3 and 25 percent of grade 4 patients. Of note, there was no statistical difference in outcomes between grades 0 and 1. However, patients with grades 2, 3, and 4 had statistically worse outcomes compared with those in the adjacent lower grade. Only surgically treated patients were included in the study, and none with grade 5 had surgery.
The interobserver variability for the Ogilvy and Carter scale is very good, reflecting substantial observer agreement (kappa 0.69) [2].
SOCIETY GUIDELINE LINKS — Links to society and government-sponsored guidelines from selected countries and regions around the world are provided separately. (See "Society guideline links: Stroke in adults".)
SUMMARY
●Grading scale selection – Several subarachnoid hemorrhage (SAH) grading scales are available, but the selection of any grading scale is based on individual or institutional preference. No scale is optimal to help direct management, detect clinical changes over time, and guide prognosis. In addition, there are few validation studies of these scales and no prospective controlled comparison studies. (See 'Individual grading scales' above.)
●Glasgow Coma Scale – The Glasgow Coma Scale (GCS) (table 1) is a standardized scale for evaluating the level of consciousness. It is widely known and has utility for predicting outcome after SAH. Sedating medications and intubation can confound interpretation of the GCS. It has moderate interobserver variability. (See 'Glasgow Coma Scale' above.)
●Hunt and Hess grading scale – The Hunt and Hess grading scale (table 2) assesses severity of SAH. It is widely used and is easy to administer, but the terminology is subjective and atypical presentations of SAH may be difficult to classify. The interobserver variability is moderate. (See 'Hunt and Hess grading system' above.)
●World Federation of Neurological Surgeons grading scale – The World Federation of Neurological Surgeons (WFNS) grading scale (table 3) assesses severity of SAH. It uses the GCS score and objective terminology to assign grades. Interobserver variability for the WFNS scale is fair. (See 'World Federation of Neurological Surgeons grading scale' above.)
●Fisher and modified Fisher scales – The Fisher scale (table 4) is an index of vasospasm risk (but not clinical outcome) based upon the hemorrhage pattern seen on initial head computed tomography (CT) scan. It has been validated prospectively, and interobserver variability is excellent. (See 'Fisher scale' above.)
The modified Fisher scale (table 5) is an index of the risk of delayed cerebral ischemia due to vasospasm after SAH. Unlike the Fisher scale, the modified Fisher scale takes into account the separate and additive risk of SAH and intraventricular hemorrhage (IVH). (See 'Modified Fisher scale' above.)
●VASOGRADE scale – The VASOGRADE is a three-category grading scale using the WFNS and modified Fisher scales to predict the risk of delayed cerebral ischemia following SAH. (See 'The VASOGRADE' above.)
●Ogilvy and Carter scale – The Ogilvy and Carter scale (table 6) system was developed to predict outcome for surgical management of SAH due to ruptured aneurysm. It incorporates patient age, Hunt and Hess, Fisher grade, and aneurysm size. It is more complex to administer than Hunt and Hess. Interobserver variability for the Ogilvy and Carter scale is very good. (See 'Ogilvy and Carter grading system' above.)
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