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

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].

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 > 2]. External validation of the mHH was performed using data from a prospectively maintained aSAH registry.

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 < 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.

The mHH achieved a favorable diagnostic performance profile using retrospective data and may aid in the prognostication of high-severity patients with aSAH.