Lenticulostriate infarctions after successful mechanical thrombectomy in middle cerebral artery occlusion

BACKGROUND: In stroke due to middle cerebral artery (MCA) occlusion, collaterals may sustain tissue in the peripheral MCA territory, extending the time window for recanalizing therapies. However, MCA occlusions often block some or all of the 'lenticulostriate' (LS) arteries originating from the M1 segment, eliminating blood flow to dependent territories in the striatum, which have no collateral supply. This study examines whether mechanical thrombectomy (MTE) can avert imminent striatal infarction in patients with acute MCA occlusion. METHODS: 279 patients with isolated MCA occlusion subjected to MTE were included. Actual LS occlusions and infarctions were assigned to predefined 'LS occlusion' and 'LS infarct' patterns derived from known LS vascular anatomy. The predictive performance of LS occlusion patterns regarding ensuing infarction in striatal subterritories was assessed by standard statistical measures. RESULTS: LS occlusion patterns predicted infarction in associated striatal subterritories with a positive predictive value (PPV) of 91% and a negative predictive value of 81%. In 15 of the 22 patients who did not develop the predicted striatal infarctions, reassessment of angiographies revealed LS vascular supply variants that explained these 'false positive' LS occlusion patterns, raising the PPV to 96%. Symptom onset to recanalization times were relatively short, but this alone could not account for the false positive LS occlusion patterns in the remaining seven of these patients. CONCLUSIONS: With currently achievable symptom onset to recanalization times, striatal infarctions are determined by MCA occlusion sites and individual vascular anatomy, and cannot normally be averted by MTE, but there are exceptions. Further study of such exceptional cases may yield important insights into the determinants of infarct growth in the hyperacute phase of infarct evolution.