The National Institutes of Health Stroke Scale (NIHSS), an instrument designed to quantify neurologic severity and identify patients eligible for reperfusion therapy for acute ischemic stroke (AIS), underestimated the severity of infratentorial vs supratentorial lesions in patients with thrombolysis-eligible AIS, according to study results published in Neurology.
Data from patients randomly assigned to a low- and high-dose alteplase group in the ongoing Enhanced Control of Hypertension and Thrombolysis Stroke Study (ENCHANTED) trial were included in this analysis (N=2902). The investigators evaluated the association between characteristics of supratentorial and infratentorial AIS at baseline with poor functional outcome, which represented the primary outcome, as defined by a score of 3 to 6 on the modified Rankin Scale. Symptomatic intracranial hemorrhage (ICH) comprised the primary safety outcome.
The optimal NIHSS predictor cutpoint was identified with area under the curve (AUC) receiver operating characteristics.
A total of 2613 patients included in the analysis had supratentorial AIS, and 289 had infratentorial AIS. Patients with infratentorial AIS had significantly lower NIHSS scores compared with patients with supratentorial AIS (median, 7 vs 9, respectively; P <.001).
Cut points for poor functional outcome according to the NIHSS scores were 10 (AUC 76, sensitivity 65%, specificity 73%) for supratentorial AIS and 6 (AUC 69, sensitivity 72%, specificity 56%) for infratentorial AIS.
Although functional outcome was not significantly different than symptomatic ICH by any definition, any ICH was found to be lower after infratentorial AIS vs supratentorial AIS (8.3% vs 19.1%, respectively; P <.001).
Limitations of the study included the lack of a control group and the retrospective nature of the analysis.
“Because thrombolysis treatment has low effect on stroke outcome in patients with infratentorial AIS when baseline NIHSS score is more than 6,” the researchers concluded, “additional treatment such as endovascular treatment should be considered to improve stroke outcome.”
Yoshimura S, Lindley RI, Carcel C, et al; for the ENCHANTED Investigators. NIHSS cut-point for predicting outcome in supra- vs infratentorial acute ischemic stroke. Neurology. 2018;91(18):e1695-e1701.