WFNS Subarachnoid Haemorrhage Grade Interpreter
WFNS Subarachnoid Haemorrhage Grade Interpreter
Grade aneurysmal subarachnoid haemorrhage I to V from the Glasgow Coma Scale and the presence of a motor deficit. It exists because Hunt and Hess asks for a judgement; it has a gap of its own, at GCS 15 with a focal deficit.
WFNS grade
GCS plus motor deficit to grade I to VGlasgow Coma Scale 11 (E3 V3 M5) on arrival, no aphasia and no limb weakness
The grades
- a major focal deficit
- aphasia, hemiparesis or hemiplegia. A cranial nerve palsy is not one — a direct divergence from Hunt and Hess, where a cranial nerve palsy is explicitly allowed within grade II. And the deficit only matters at a GCS of 13 to 15: at 12 or below the grade is set by the GCS alone, on the reasoning that a patient who cannot follow commands cannot reliably be examined for one
- the undefined cell
- a GCS of 15 WITH a major focal motor deficit has no grade. The published scale puts a deficit into grade III only alongside a GCS of 13 or 14, and reproductions differ on what to do with an alert hemiparetic patient. This page reports it as undefined rather than guessing
- discrimination
- in a 415-patient cohort across three Hanoi hospitals, 32 per cent had a poor 90-day outcome, and the area under the ROC curve was 0.837 (95% CI 0.793–0.881) for the WFNS grade against 0.836 (0.791–0.881) for Hunt and Hess. The two performed identically; the WFNS advantage is reproducibility between raters, not discrimination. The 2023 AHA/ASA guideline recommends either at Class 1, Level B-NR, and prefers neither
- it inherits the GCS’s problems
- including the biggest one. An intubated or sedated patient has no valid Glasgow Coma Scale total, because a component recorded as Not Testable cannot be summed — and most poor-grade patients are intubated within minutes. The Glasgow Coma Scale is copyright of the University of Glasgow and is free to use for clinical care and research, with attribution
Worked example
Glasgow Coma Scale 11 (E3 V3 M5) on arrival, no aphasia and no limb weakness
A GCS of 11 falls in the 7 to 12 range, so the grade is IV, conventionally poor-grade subarachnoid haemorrhage
The absence of a motor deficit changes nothing: below a GCS of 13 the deficit is not scored
Raise the GCS to 13 and the grade becomes II — two grades on two points of GCS, because the scale has no grade III without a deficit. Add a hemiparesis at GCS 13 and it becomes III
Drop the GCS to 6 and the grade becomes V. The whole scale turns on two GCS boundaries, 6/7 and 12/13, and on one yes-or-no question that only applies above 12
The same patient on the Hunt and Hess scale is graded on words rather than a number — drowsy and confused is grade III there, not grade IV. The two are not interchangeable, so a grade should always be recorded with the scale it came from
The five grades
| Grade | Glasgow Coma Scale | Major focal motor deficit |
|---|---|---|
| I | 15 | Absent |
| II | 13 to 14 | Absent |
| III | 13 to 14 | Present |
| IV | 7 to 12 | Present or absent |
| V | 3 to 6 | Present or absent |
| Undefined | 15 | Present |
Where the two recommended scales disagree
| Patient | WFNS | Hunt and Hess |
|---|---|---|
| Alert, isolated third nerve palsy | Grade I — a cranial nerve palsy is not a motor deficit | Grade II — a cranial nerve palsy is explicitly allowed |
| Alert, hemiparesis | Undefined | Grade III |
| GCS 14, no deficit | Grade II | Grade III |
| GCS 14, hemiparesis | Grade III | Grade III or IV |
| GCS 11, no deficit | Grade IV | Grade III or IV |
| GCS 5, extending | Grade V | Grade V |
A number instead of an adjective, and the cell it forgot
The World Federation of Neurological Surgeons published this grade as a two-page committee report in 1988, with an explicit purpose: to get one subarachnoid haemorrhage severity scale used everywhere, so that series from different units could be compared. The design follows from the diagnosis of what was wrong with the alternative. Hunt and Hess asks whether a patient is “drowsy” and whether a deficit is “mild”, and experienced clinicians disagree about both; the WFNS grade replaces those adjectives with a Glasgow Coma Scale total and one yes-or-no question about a major focal motor deficit.
The structure is not symmetric, and that is worth looking at. A GCS of 15 with no deficit is grade I; 13 to 14 with no deficit is grade II; 13 to 14 with a deficit is grade III; 7 to 12 is grade IV and 3 to 6 is grade V, in both cases regardless of any deficit. So the motor-deficit question does exactly one piece of work in the whole scale — separating grade II from grade III — and below a GCS of 13 it is not scored at all, on the reasonable ground that a patient who cannot follow commands cannot reliably be examined for aphasia or a hemiparesis. It also means the scale jumps: a two-point change in GCS from 11 to 13 moves a patient from grade IV to grade II, because there is no grade III without a deficit. And there is a cell it forgot. A fully alert patient with aphasia or a hemiparesis has no grade, because a motor deficit only enters the published scale alongside a GCS of 13 or 14. Reproductions handle this differently, some assigning grade II and some grade III, and this page reports it as undefined rather than picking one, because an invented grade is indistinguishable from a published one once it is written in the notes.
On performance the two recommended scales are hard to separate. In a 415-patient cohort across three Hanoi hospitals, where 32 per cent had a poor 90-day outcome, the area under the ROC curve was 0.837 for the WFNS grade and 0.836 for Hunt and Hess. The 2023 AHA/ASA guideline recommends either, at Class 1 and Level B-NR, “to determine initial clinical severity and predict outcome”, and expresses no preference. The WFNS advantage is reproducibility, not discrimination; its cost is that it inherits every problem the Glasgow Coma Scale has, including the one that bites hardest here — an intubated or sedated patient has no valid GCS total, and most poor-grade patients are intubated within minutes of arrival. Grade from the pre-intubation assessment, and record that that is what you did. A grade is not a diagnosis and a cohort risk is not this patient’s probability: a stratum in which 72 per cent died tells you about that cohort, not which 72 per cent. This page reports what a stratum predicted in a study. It recommends no action. Every threshold here comes from a named cohort, and cohorts differ in case mix, era and treatment; where your unit’s protocol differs, it takes precedence.
Frequently asked questions
What are the WFNS subarachnoid haemorrhage grades?
Grade I is a Glasgow Coma Scale of 15 with no major focal motor deficit; II is GCS 13 to 14 with no deficit; III is GCS 13 to 14 with a deficit; IV is GCS 7 to 12 with or without a deficit; V is GCS 3 to 6 with or without a deficit. A major focal deficit means aphasia, hemiparesis or hemiplegia.
Is a cranial nerve palsy a motor deficit for the WFNS grade?
No. The deficit the scale asks about is aphasia, hemiparesis or hemiplegia. This is a real divergence from Hunt and Hess, where a cranial nerve palsy is explicitly allowed within grade II: an alert patient with an isolated third nerve palsy is WFNS grade I and Hunt and Hess grade II.
What grade is an alert patient with a hemiparesis?
The published scale does not define that cell. A motor deficit only enters the WFNS grid alongside a Glasgow Coma Scale of 13 or 14, so a GCS of 15 with a deficit has no grade, and reproductions differ on whether to call it II or III. Hunt and Hess covers the case as grade III.
WFNS or Hunt and Hess?
The 2023 AHA/ASA guideline recommends either at Class 1, Level B-NR, and prefers neither; in a 415-patient cohort they discriminated 90-day outcome identically (area under the ROC curve 0.837 against 0.836). WFNS agrees better between raters because it substitutes a number for a judgement. They are not convertible.
How do I grade an intubated patient on the WFNS scale?
With difficulty, and this is the scale’s practical weak point. An intubated patient has no verbal score, so there is no valid Glasgow Coma Scale total to feed in — the published GCS guidance is to record the component as Not Testable and not to report a sum. Grade from the pre-intubation assessment where one exists, and document that.
Related calculators
References
- Hoh BL, Ko NU, Amin-Hanjani S, et al. 2023 guideline for the management of patients with aneurysmal subarachnoid hemorrhage. Stroke. 2023;54(7):e314–e370.
- Subarachnoid haemorrhage grading systems. Life in the Fast Lane, litfl.com (accessed 7 October 2026), citing the Report of World Federation of Neurological Surgeons Committee on a Universal Subarachnoid Hemorrhage Grading Scale, J Neurosurg 1988;68(6):985–986.
- Nguyen TA, Mai TD, Vu LD, et al. Validation of the accuracy of the modified World Federation of Neurosurgical Societies subarachnoid hemorrhage grading scale for predicting the outcomes of patients with aneurysmal subarachnoid hemorrhage. PLoS ONE. 2023;18(8):e0289267.
- Grading of subarachnoid haemorrhage severity. Deranged Physiology, neurological intensive care chapter 172, derangedphysiology.com (accessed 7 October 2026).
Not medical advice. For healthcare professionals and education. Reference intervals vary by laboratory and assay — always use your own laboratory's. Never base a dose or a treatment decision on this page alone. Full disclaimer at calcengines.com/disclaimer/