The clinical outcomes of mechanical thrombectomy for proximal M1 occlusion involving lenticulostriate perforators: Is it worse than distal M1 occlusion? Retrospective observational study

Although the success rate of recanalization in acute intracranial artery occlusion is high, there is a poor rate of improvement in functional clinical outcome. The purpose of this study was to assess the functional outcome of mechanical thrombectomy for proximal M1 occlusion involving lenticulostriate arteries (LSAs) compared with distal M1 occlusion-sparing the LSAs. A retrospective analysis was conducted in patients with middle cerebral artery (MCA) M1 occlusions who had a successful recanalization subsequent to mechanical thrombectomy. The recanalization results were estimated using the thrombolysis in cerebral infarction grade assessed by digital subtraction angiography. To confirm the ischemic change resulting from the lenticulostriate artery occlusion, we reviewed the neuroimaging findings from magnetic resonance imaging 1 day after mechanical thrombectomy. The functional outcomes were then evaluated using the modified Rankin scale at 90 days. In total, 28 patients with MCA M1 occlusion had successful recanalization outcomes with thrombolysis in cerebral infarction grades IIa, IIb, and III. Among the 28 patients, 17 had proximal M1 occlusions and 11 had distal M1 occlusions. Demographic factors, including initial National Institutes of Health Stroke Scale score, time from symptom to recanalization, and recanalization rate did not differ considerably between patients with proximal and distal M1 occlusions. Regarding infarctions in the basal ganglia, internal capsule, and corona radiata, there were statistically significant differences between the proximal and distal M1 occlusions. However, there were no significant differences in good functional outcome (modified Rankin scale ≤2) observed between the groups at 90 days after mechanical thrombectomy. Although proximal M1 occlusion had more frequent infarctions associated with the LSA territories, these were not related to poor functional outcomes. Both proximal and distal M1 occlusion demonstrated comparably good outcomes.