The Hidden Side of Posterior Circulation Strokes: Diagnostic Efficacy of POST-NIHSS

The National Institutes of Health Stroke Scale (NIHSS) has been widely accepted for quantifying stroke severity; however, its anterior circulation bias renders it inadequate for posterior circulation strokes (PCSs). The Posterior NIHSS (POST-NIHSS) was designed to allow comprehensive evaluation of PCS severity.

To compare the diagnostic and severity-determining capacity of POST-NIHSS with that of NIHSS in PCSs and to propose a structured severity grading model for POST-NIHSS.

This cross-sectional study included 243 PCS patients admitted between January 2023 and March 2025 at a tertiary care center in India. Demographics, vascular risk factors, and clinical variables were collected. Stroke severity was measured using NIHSS and POST-NIHSS at admission. Functional outcome was assessed using modified Rankin Scale (mRS) at the end of 90 days since admission. Univariate and multivariate logistic regression analyses were performed to identify significant determinants of severity.

Among 243 PCS patients (mean age 59.4 ± 11.2 years, 68% male), hypertension and diabetes were the predominant risk factors. On multivariate regression, previous cerebrovascular accident/transient ischemic attack (OR 1.97, 95% CI 1.01-3.82, P = 0.044) and alcohol use (protective, OR 0.38, 95% CI 0.18-0.79, P = 0.008) showed significant associations. NIHSS ≥ 3.5 correlated with higher severity (OR 7.09, 95% CI 3.52-14.26, P < 0.001), while POST-NIHSS ≥ 7.5 demonstrated the strongest independent association (OR 14.92, 95% CI 7.14-31.14, P < 0.001). ROC analysis showed superior discrimination for POST-NIHSS (AUC 0.82) compared to NIHSS (AUC 0.71). Based on distribution and ROC thresholds, a three-tier severity grading for POST-NIHSS was proposed: mild (<7), moderate (7-13), and severe (>13).

POST-NIHSS effectively stratifies stroke severity in posterior circulation strokes and outperforms conventional NIHSS in diagnostic precision. Incorporation of posterior domain-specific parameters enables refined clinical assessment and better interobserver consistency.