The Natural History and Reperfusion Therapy Outcomes of Acute Ischemic Stroke due to Isolated M2 Occlusions

Abstract

Objective: Currently, the standard treatment modality for patients with acute ischemic stroke (AIS) presenting with isolated M2 occlusions is not specific. We therefore assessed the difference in treatment outcomes for patients with isolated M2 occlusions.

Methods: We retrospectively analyzed consecutive patients with AIS presenting with isolated M2 occlusions from October 1, 2018, to June 30, 2020. Patients were divided into 3 groups based on the treatments they received: no reperfusion therapy (NRT), intravenous thrombolysis treatment (IVT), and endovascular intervention (EVT), which comprised IVT in conjunction with EVT or EVT alone. The primary outcomes were improvements in modified Rankin Scale (mRS) scores at 90 days and National Institutes of Health Stroke Scale (NIHSS) scores at 24 hours after treatment compared with the baseline. The secondary efficacy outcome comprised a good outcome rate defined as a 90 - day mRS score ≤ 2, final infarct volume (FIV), 90-day mortality rate, and successful recanalization rate, which was defined as a modified thrombolysis in cerebral infarction score ≥ 2b. Safety outcomes included symptomatic intracerebral hemorrhage and procedure-related complications.

Results: Seventy patients were enrolled and divided into 3 groups: the NRT group (n = 25), IVT group (n = 27), and EVT group (n = 18). Twenty-four-hour posttreatment NIHSS scores were substantially decreased by EVT compared with NRT (adjusted β -4.01, 95% confidence interval [CI] -6.60 to -1.43; P = 0.003) or IVT (adjusted β, -3.61 [95% CI, -6.45 to -0.77]; P = 0.013). Compared with the outcomes observed after NRT, patients who received EVT were more likely to achieve lower 90-day mRS scores (adjusted β, -1.42 [95% CI, -2.66 to -0.63]; P = 0.007), higher good outcome rates (adjusted odds ratio, 8.73 [95% CI, 1.43-53.24]; P = 0.019), and smaller FIVs (adjusted β, -29.66 [95% CI, -59.73 to 0.42]; P = 0.048). The recanalization rate of EVT was high (88.89%), and procedure-related complications were rare (5.56%).

Conclusions: For acute, isolated M2 occlusions, EVT could dramatically and rapidly improve neurological deficits with high safety and effectiveness. These changes were observed at 24 hours after treatment and were maintained over the long term.

Figure 1

Distribution of mRS scores at 90 days in the three groups. Notes: proportion of mRS scores at 90 days in patients in the NRT, IVT, and EVT groups. NRT: no reperfusion therapy; IVT: intravenous thrombolysis treatment; EVT: endovascular intervention; mRS: modified Rankin Scale. A 90-day mRS score of 0-1 was defined as an excellent outcome, an mRS score of 0-2 was defined as a good outcome, an mRS score of 3-5 was defined as a bad outcome, and an mRS score of 6 referred to death.

Figure 2

Comparison of NIHSS scores among the three groups. Notes: box and whisker plots comparing median NIHSS scores at admission and 24 hours after treatment in the no reperfusion therapy (NRT), intravenous thrombolysis treatment (IVT), and endovascular intervention (EVT) groups. The horizontal line in the middle of each box represents the median, and the upper and lower boundaries of the box represent the 75th percentile and 25th percentile, respectively. The whiskers above and below the box indicate the 90th and 10th percentiles, respectively.