Factors related to the initial stroke severity of posterior circulation ischemic stroke.

Background: Posterior circulation (PC) stroke, which was previously less well known than anterior circulation (AC) stroke, has become more identified due to the development of imaging equipment. Recently, the initial stroke severity assessed by the NIH Stroke Scale (NIHSS) was reported as a useful measure for predicting the outcome of PC as well as AC stroke. The aim of our study was to investigate the factors related to the stroke severity of PC ischemic stroke as assessed by the baseline NIHSS and the predictors of progressive neurological deficit and 3-month outcome.

Methods: All patients with first-time PC stroke (onset ≤ 7 days), admitted for a 5-year period and given a complete evaluation including brain MRI and angiographic studies, were enrolled. Patients were divided into two groups by the baseline NIHSS: moderate-to-severe stroke (MTSS, NIHSS > 5) and mild stroke (MS, NIHSS ≤ 5). Baseline characteristics, symptoms and progression, etiological subtypes, lesion characteristics from imaging, and patient 3-month outcome assessed by the modified Rankin Scale (mRS) were compared between the two groups.

Results: Among 604 enrolled patients with PC ischemic stroke, 143 belonged to the MTSS group and 461 to the MS group. In logistic regression analysis, MTSS was independently associated with white blood cell count (odds ratio, OR = 1.00, p = 0.001), high sensitivity C-reactive protein level (OR = 1.23, p = 0.004), dysarthria (OR = 2.59, p = 0.013), weakness (OR = 6.43, p < 0.001), dysphagia (OR = 5.77, p < 0.001) and decreased consciousness (OR = 10.54, p < 0.001). The independent predictors associated with progressive neurological deficit were MTSS (OR = 3.82, p = 0.001), the distal territory classified by lesion location (OR = 0.09, p = 0.004) and dysphagia (OR = 2.38, p = 0.010). The independent predictors associated with a 3-month mRS of 3-6 were MTSS (OR = 7.69, p < 0.001), diplopia (OR = 0.26, p = 0.023), visual field defect (OR = 4.87, p = 0.014), dysphagia (OR = 3.15, p < 0.001) and progressive neurological deficit (OR = 4.27, p < 0.001).

Conclusions: The initial severity categorization of PC ischemic stroke by the NIHSS has provided several distinctions and could help with the prediction of neurological deficit progression and 3-month clinical outcome.