Introduction: Mechanical thrombectomy (MT) efficacy in medium vessel occlusion (MeVO) stroke, particularly in patients with low Alberta Stroke Program Early Computed Tomography Score (ASPECTS), remains less explored.

Methods: This retrospective study analyzed data from 443 AIS patients treated with MT for MeVO and low ASPECTS (4-7) at 37 centers across North America, Asia, and Europe, from September 2017 to July 2021. Patients were categorized into ASPECTS of 4-5 and 6-7.

Results: Of 443 patients, 51 (12%) had ASPECTS of 4-5, and 392 (88%) had scores of 6-7. The median age was 65 years (IQR: 46-79), with a balanced sex distribution between the groups. The most common site of initial occlusion was M2 branch in both groups (92% in ASPECTS 4-5 and 85% in ASPECTS 6-7) (p = 0.68). The ASPECTS 4-5 group had lower TICI 2c-3 achievement (31% vs. 55%, p = 0.002) and poorer functional outcomes (mRS 0-1 at 90 days: 12% vs. 29%, p = 0.03) compared to the ASPECTS 6-7 group. Intracranial hemorrhagic complications were higher in the ASPECTS 4-5 group (69% vs. 47%, p = 0.007). Multivariable analysis revealed ASPECTS 6-7 to be associated with higher odds of TICI 2c-3 (OR: 2.5; CI: 1.28 to 4.89, p = 0.007) and lower odds of intracranial hemorrhagic complications (OR: 0.4; CI: 0.19 to 0.81, p = 0.012).

Conclusion: MT may be associated with improved outcomes in patients with moderate-to-low ASPECTS (6-7), though the lack of a control group limits definitive conclusions about its effectiveness. In patients with very low ASPECTS (4-5), higher rates of hemorrhagic complications and poorer outcomes were observed, but this does not necessarily preclude the use of MT. These findings highlight the need for further research and careful patient selection.