Mechanical Thrombectomy in Stroke

Abstract

Background: The introduction of neurological stroke units and of thrombolysis with the intravenous (IV) administration of recombinant tissue-type plasminogen activator (tPA) have markedly improved the treatment of stroke. Five randomized trials of catheter-based interventional treatment of stroke with special stents were published in 2015.

Methods: Recently published randomized trials of mechanical thrombectomy are selectively reviewed.

Results: These trials documented the clinical efficacy of mechanical thrombectomy (MT) in the treatment of occlusion of a major cerebral artery in the distribution of the internal carotid artery (evidence level 1a, recommendation grade A). Roughly 4-10% of all stroke patients could benefit from such an intervention. In the trials, 85% of the patients were first treated with IV-tPA. A recanalization of the occluded vessel was achieved by MT in 59-88% of patients. The percentage of patients with no deficit or only a mild deficit was 33-71% among those who received the intervention, compared to 19-40% in the control groups. The trial data indicate that MT is effective for elderly patients as well (age over 80). Thrombectomy did not increase the rate of secondary, symptomatic intracranial hemorrhage.

Conclusion: MT can only be used to treat the occlusion of major cerebral arteries. In appropriate patients, it expands the spectrum of treatment options for stroke. Long-term data are not yet available.

Figure 1

If there is a proximal thromboembolic occlusion of the middle cerebral artery (a), the stent retriever is run past the intra-arterial thrombus in a microcatheter (b). When the microcatheter is retracted, the stent retriever is pushed out and released inside the thrombus. After a few minutes, the stent expands into the thrombus so that the mesh of the stent hooks into the thrombus (c). The expanded stent, together with the whole thrombus, is then removed into a larger catheter (d).

Figure 2

Relationship between clinical/functional outcome (rate of mRS score 0 to 2 after 90 days) and recanalization rate (TICI IIb/III rate) in thrombectomy arm of the five 2015 randomized trials on thrombectomy. mRS: Modified Rankin Scale; TICI: Thrombolysis in cerebral infarction

Figure 3

The Alberta Stroke Program Early Computed Tomography Score (ASPECTS) describes the spatial extent of ischemic lesions in the cortical and subcortical areas supplied by the middle cerebral artery (MCA). It can take values between 10 and 0. Ten is the normal score for intact brain parenchyma supplied by the MCA, while 0 corresponds to diffuse ischemia throughout the area supplied by the middle cerebral artery (MCA). Cd: Caudate nucleus; L: Lentiform nucleus; IC: Internal capsule; In: Insular cortex; M1: anterior cortex supplied by MCA; M2: Lateral insular cortex; M3: Posterior cortex supplied by MCA; M4, M5, M6: Anterior, lateral, and posterior MCA territories, directly above (rostrally) M1, M2, and M3 respectively and therefore also rostral to the basal ganglia. (M1 in the context of ASPECTS does not correspond to the horizontal, proximal segment M1 of the middle cerebral artery. The fact that the names are identical are coincidental.)