Adults and older adolescents with confirmed or strongly suspected aneurysmal subarachnoid haemorrhage at first ED, neurology, neurosurgical or ICU assessment to communicate clinical severity and support prognostication.

The Hunt & Hess scale was introduced in 1968 by neurosurgeons at Ohio State University, based on several hundred patients with ruptured intracranial aneurysms undergoing surgical repair. Five grades (I–V) were defined using headache and meningeal features, level of consciousness, focal neurological deficit and serious comorbid disease, and correlated with operative mortality risk.
Higher Hunt & Hess grades are consistently associated with poorer survival and functional outcome after aneurysmal subarachnoid haemorrhage. Good-grade patients (grades I–III) generally have substantially better outcomes than poor-grade patients (grades IV–V), and this good- versus poor-grade grouping is widely used in outcome and treatment studies.
The scale remains in routine use alongside the World Federation of Neurological Societies (WFNS) grade and CT-based scores (e.g. Fisher or modified Fisher) when assessing aneurysmal subarachnoid haemorrhage severity. It is primarily a prognostic and communication tool rather than a stand-alone treatment decision rule.
Limitations include interobserver variability in grading and the impact of sedation, intubation, intoxication and metabolic disturbance on level of consciousness. Historical mortality estimates by grade pre-date modern endovascular techniques and neurocritical care, so contemporary outcomes are generally better than those reported in the original surgical series.

The primary source or current guidance provides the model definition, source population and supporting evidence.

Hunt & Hess Classification of Subarachnoid Haemorrhage