Mechanical thrombectomy in stroke patients with acute occlusion of the M1- compared to the M2-segment: Safety, efficacy, and clinical outcome

Abstract

Purpose
 
Endovascular treatment (ET) in occlusions of the M1- and proximal M2-segment of the middle cerebral artery (MCA) is an established procedure. In contrast, ET in distal M2-occlusions has not been sufficiently evaluated yet. The purpose of this study was to assess relevant parameters for clinical outcome, efficacy and safety of patients undergoing ET in M1-, proximal M2- and distal M2-occlusions.

Methods

One-hundred-seventy-four patients undergoing ET in acute ischemic stroke with an occlusion of the M1- or M2-segment of the MCA were enrolled prospectively. Non-parametric analysis of variance in three months mRS, TICI scale and complication rates were performed with Kruskal-Wallis-test between M1-, proximal and distal M2-occlusions. Subsequent pairwise group comparisons were calculated using Mann-Whitney-U-tests. Binary logistic regression (BLR) models were calculated for each occlusion site. 

Results
 
There were no significant group differences in three-months mRS, mTICI scale or complication rates between M1- and M2-occlusions nor between proximal and distal M2-occlusions. BLR in patients with M1-occlusions showed a substantial explanation of variance (NR2=0.35). NIHSS (p=0.009) and Maas Score as parameter for collateralization (p=0.01) appeared as significant contributing parameters. BLR in M2-occlusions showed a high explanation of variance (NR2=0.50) of mRS but no significant factors.
 
Conclusions
 
Clinical outcome and procedural safety of patients with M2-occlusions undergoing ET are comparable to those of patients with M1-occlusions. Clinical outcome of patients with M1-occlusions undergoing ET is primarily influenced by the initial neurological deficit and the collateralization of the occlusions. By contrast, clinical outcome in patients with M2-occlusions undergoing ET is more multifactorial.

Direct myosin-2 inhibition improves brain functions after ischemic stroke

“…MT has become the safe and standard clinical intervention for the treatment of acute ischemic stroke (AIS) 15 of which the occlusion of the M1 segment 16 of the MCA is the most common target 17 . However, if the thrombus is located in the distal M2-branches or beyond, the revascularization maneuvers are difficult which is associated with the relatively uncommon risk of haemorrhagic transformation due to arterial perforation or dissection 17,18 .…”