BACKGROUND This study proposes a modification to the traditional Hunt and Hess (tHH) grading scale for prognostication in aneurysmal subarachnoid hemorrhage (aSAH), which differentiates the most severe‐grade patients based on the presence or absence of brainstem dysfunction [determined by Glasgow Coma Scale (GCS) scores 3‐5]. METHODS Weighted aSAH hospitalizations were retrospectively identified in the National Inpatient Sample from 2015 to 2019 and were stratified by tHH and modified HH (mHH) grades. mHH grade 5 was defined as tHH grade 5 with GCS score 3–5, while mHH grade 4 comprised tHH grade 5 with GCS score 6–8 and tHH grade 4. HH grades 1–3 do not differ between the traditional and modified scales. Measures of diagnostic performance were compared for the primary study end point [poor outcome as determined by the previously validated NIS‐SAH Outcome Measure (NIS‐SOM), shown to have high concordance with modified Rankin Scale scores &gt; 2]. External validation of the mHH was performed using data from a prospectively maintained aSAH registry. RESULTS Among 6130 aSAH hospitalizations, 2245 (36%) were tHH grade 5. Seven hundred and eighty‐five (35%) of these had a GCS 3–5 and were designated as mHH grade 5. Poor outcomes were identified in 78% and 77% of grade 4 tHH and mHH, respectively, and in 83% and 95% of grade 5 tHH and mHH, respectively. In comparison with the tHH, the mHH achieved superior discrimination [c‐statistic 0.793 (95% CI 0.768, 0.818) versus 0.780 (95% CI 0.750, 0.807); DeLong p &lt; 0.001] for poor outcome, as well as improved specificity (0.929 versus 0.304) and positive predictive value (PPV) (0.949 versus 0.827). External registry validation of the mHH demonstrated excellent discrimination [c‐statistic 0.835 (95% CI 0.801, 0.870)], with a specificity of 0.950 and PPV of 0.905. CONCLUSION The mHH achieved a favorable diagnostic performance profile using retrospective data and may aid in the prognostication of high‐severity patients with aSAH.

Prognostication Following Aneurysmal Subarachnoid Hemorrhage: The Modified Hunt and Hess Grading Scale