Cerebral regions preserved by successful endovascular recanalization of acute M1 segment occlusions: A voxel based analysis

Objective: To identify cerebral regions preserved by successful recanalization of the middle cerebral artery M1 segment and their association with early clinical outcome. Methods: 47 patients who underwent endovascular treatment for acute unilateral M1 segment occlusion were included. Successful recanalization was defined by a modified thrombolysis in cerebral infarction score of 2b/3. Final infarct volumes were segmented on follow-up MRI/CT, 2-7 days post-symptom onset. The differences in topography of infarct lesions associated with successful vs unsuccessful recanalization were assessed using voxel-based analysis. Favourable outcome was defined by a modified Rankin Scale score ≤2 at discharge, and disability/death by score >2. Results: Successful recanalization of M1 segment occlusion was achieved in 26/47 (55%) patients, which was associated with higher rate of favourable outcome (54% vs 9%, p = 0.002) and smaller final infarct volumes (34.3 ± 43.7 vs 98.1 ± 47.7 ml, p < 0.001). In voxel-based analysis, patients with successful recanalization had a lower rate of infarction in precentral gyrus and posterior insular ribbon compared with those without recanalization. Favourable outcome was achieved in 16 (34%) patients, who were younger (62.2 ± 13.9 vs 70.9 ± 13.9, p = 0.048), had higher rate of successful recanalization (88% vs 39%, p = 0.002) and had smaller infarct volumes (25.2 ± 23.6 vs 82.2 ± 57.1 ml, p < 0.001) compared with those with disability/death. In voxel-based analysis, infarction of the insula, precentral gyrus, middle centrum semiovale and corona radiata were associated with disability/death. Conclusion: Successful endovascular recanalization of acute M1 segment occlusion tends to preserve posterior insular ribbon and precentral gyrus from infarction; and infarction of these regions was associated with higher rates of disability/death. Advances in knowledge: The knowledge of the topographic location of potentially salvageable cerebral tissue can provide additional information for treatment triage and selection of patients with acute stroke for endovascular treatment based on the "areas at risk" rather than the "volume at risk". Also, such knowledge can help with preferential recanalization, where the neurointerventionalist may choose to preferentially recanalize certain branches supplying salvageable and eloquent cerebral regions in favour of timely reperfusion treatment.