Kevin O’Connor, MD

Alemseged F, Rocco A, Arba F, Schwabova JP, Wu T, Cavicchia L, Ng F, Ng JL, Zhao H, Williams C, et al. Posterior National Institutes of Health Stroke Scale Improves Prognostic Accuracy in Posterior Circulation Stroke. Stroke. 2021.

The NIH Stroke Scale (NIHSS) is an indispensable part of acute stroke evaluations, but its components focus more on anterior circulation deficits than posterior circulation deficits. Alemseged et al. developed the POST-NIHSS to augment the NIHSS with additional posterior circulation deficits based on retrospective analysis of 202 patients with clinical and radiographic evidence of posterior circulation stroke and NIHSS score <10 who did not undergo mechanical thrombectomy from the Basilar Artery Treatment and Management registry. They then validated their POST-NIHSS with 65 prospectively recruited patients.

Clinical features of posterior circulation strokes may include gait/truncal ataxia, diplopia, ptosis, nystagmus, internuclear ophthalmoplegia, vertical gaze impairment, Horner syndrome, palatal palsy, tongue deviation, and abnormal cough. The retrospective analysis identified gait/truncal ataxia (OR, 3.14 [95% CI, 1.24–7.92], P=0.02), dysphagia (OR, 5.22 [95% CI, 1.63–16.7], P=0.005), and abnormal cough (OR, 8.17 [95% CI, 1.49–44.8], P=0.02) as significantly associated with poor outcome. To the standard NIHSS, the POST-NIHSS adds 3 points for gait/truncal ataxia when assessing item 7 and a new item 12 to assess for abnormal cough (5 points) and dysphagia (4 points). In a ROC analysis for age-adjusted poor outcome, POST-NIHSS performed better than NIHSS (POST-NIHSS AUC, 0.80 [95% CI, 0.73–0.87] versus NIHSS AUC, 0.73 [95% CI, 0.64–0.83]). In a subgroup sensitivity analysis of 156 of the 202 patients with NIHSS 0-5 (77%), POST-NIHSS remained associated with age-adjusted poor outcome (OR, 1.40 [95% CI, 1.14–1.70], P=0.01) while NIHSS was not (OR, 1.12 [95% CI, 0.82–1.56], P=0.46).

In the validation cohort (n=65), POST-NIHSS again performed better than NIHSS in ROC analysis for age-adjusted for poor outcome (POST-NIHSS AUC, 0.82 [95% CI, 0.69–0.94] versus NIHSS AUC, 0.73 [95% CI, 0.58–0.87]). In sensitivity analysis of the subgroup of NIHSS 0-5 patients, POST-NIHSS remained associated with age-adjusted poor outcome (OR, 1.41 [95% CI, 1.11–1.78], P=0.005) compared to NIHSS (OR, 1.33 [95% CI, 0.88–2.03], P=0.18). In the prospective analysis, a speech therapist performed the dysphagia assessment of the POST-NIHSS within 48 hours of presentation (Figure 3).

Figure 3. Posterior National Institutes of Health Stroke Scale (NIHSS) item 12: bulbar signs.
Figure 3. Posterior National Institutes of Health Stroke Scale (NIHSS) item 12: bulbar signs.

Posterior circulation strokes are potentially devastating injuries, and better screening tools for associated deficits may reduce morbidity and mortality by identifying candidates for chemical thrombolysis or endovascular therapy that may be underappreciated using the NIHSS. The POST-NIHSS provides a potential tool for identifying disabling posterior circulation strokes, but additional prospective study is needed to further validate it and determine inter-rater reliability.