To validate POST NIHSS as a reliable tool for assessing stroke severity and predicting functional outcomes in PCS within an Indian cohort, and to compare its effectiveness against the NIHSS in this specific population.

NIHSS is a standard tool for assessing stroke severity, but it has limitations in accurately predicting the severity of posterior circulation strokes (PCS), as it does not account for posterior circulation-specific symptoms. POST NIHSS was developed to address this gap. Its application and validity in Indian population has not been studied, warranting this investigation.

This is a single center, cross-sectional observational study. Data on demographics (age, sex), comorbidities (diabetes, hypertension, old stroke), and lifestyle factors (alcohol, smoking, tobacco use) were collected. Stroke severity was assessed using both NIHSS and POST NIHSS at admission and functional outcomes were evaluated at 3 months telephonically using the modified Rankin Scale (mRS).

The study included 101 patients with 71 males and 30 females with a mean age of 57 years. Mean NIHSS and POST NIHSS was 4.6 and 8.3 respectively. Around 77 had good functional outcome at 90 days (mRS <2). Of all comorbidities, patients have old CVA (n=22) had a higher chance of poor functional outcome (p= 0.07). The ROC curve comparison between NIHSS and POST NIHSS shows that NIHSS has an Area Under the Curve (AUC) of 0.77 while POST NIHSS has an AUC of 0.81.

Both NIHSS and POST NIHSS are moderate predictors of functional outcomes, but POST NIHSS slightly outperforms NIHSS in this dataset, with a higher AUC (0.81 vs. 0.77) thus making it more valid and accurate tool than NIHSS for predicting the severity and functional outcomes of PCS. It highlights the importance of incorporating posterior circulation-specific symptoms in stroke severity assessment and calls for broader validation of POST NIHSS in diverse populations.