Victor J. Del Brutto, MD

Nagel S, Bouslama M, Krause LU, Küpper C, Messer M, Petersen M, et al. Mechanical Thrombectomy in Patients With Milder Strokes and Large Vessel Occlusions: A Multicenter Matched Analysis. Stroke. 2018

Over half of acute ischemic strokes in the U.S. present with mild deficits as defined by an initial NIHSS score of 5 or less. Despite having deficits perceived as “minor”, around 30% of these patients will not achieve a good functional outcome at follow-up. Large vessel occlusion (LVO) is found in 10 to 20% of patients with minor strokes. Presence of LVO has been associated with early neurological deterioration, as well as decreased likelihood of good recovery. Minor symptoms in the setting of a major occluded vessel pictures good collateral flow maintaining tissue perfusion. On the other hand, frequent early clinical deterioration and worse functional outcomes expose the potential failure of aforementioned collaterals and infarct expansion.

Mechanical thrombectomy  (MT) is the current standard of care for selected patients with LVO and initial NIHSS score ≥6; however, the benefit of MT in patients with milder symptoms remains uncertain. Recanalization is an appealing solution to prevent clinical deterioration and improve long-term functional outcome in these patients. Nonetheless, the treatment effect might not provide a significant benefit and could add potential risk for complications related to the procedure, such as hemorrhagic conversion, emboli to new vascular territories, failure of collaterals due to transient hypotension related to anesthesia, etc.

In the present study, Nagel and colleagues addressed the dilemma about the optimal management of LVO in minor strokes. The authors present a large multicenter retrospective analysis of acute ischemic strokes with LVO and initial NIHSS ≤5. Functional outcomes at day 90 were compared between patients who received immediate mechanical thrombectomy (IMT, n=80) and those who received best medical management including IV-tPA and rescue MT in case of neurological deterioration (BMM-MT, n=220). A good functional outcome defined as mRS of 0-2 at day 90 was achieved in 85% of patients in the IMT group versus 70% of patients in the BMM-MT group (adjusted OR 3.1 [95% CI, 1.4–6.9]). No significant difference was found in the proportion of patients who achieved an excellent functional outcome (mRS 0-1) among groups. In addition, the rate of mortality and symptomatic intracranial hemorrhages (sICH) was low in both groups, with a non-significant trend of higher sICH in patients treated with IMT (5% versus 1.4%, p=0.08). A separate analysis of matched controls by age, NIHSS and site of vessel occlusion showed similar results.

Regarding the study of patients with minor strokes and LVO, two topics might require further consideration and discussion. First, patients with low NIHSS strokes should be differentiated between disabling and non-disabling deficits. This might be of relevance when considering long-term functional outcomes. A different point of view would argue that in the setting of an LVO, the potential large volume of tissue at risk is more important that the nature of the initial deficits. Second, an mRS of 2 might not be contemplated as good enough functional outcome in patients presenting with minor deficits. However, similar to above, if we consider an underlying LVO compromising large areas of brain tissue, an mRS of 2 or better could be considered a reasonable good outcome in this population.

In summary, the data presented suggest a relevant clinical benefit of acute mechanical thrombectomy in patients with minor deficits, as well as a relative safety of this treatment approach. The retrospective nature of the study design precludes definitive conclusions. Moreover, the lack of randomization and the fact that treatment decisions were made by physician discretion raise the possibility of sample bias. The authors accurately emphasize the need for prospective, randomized controlled trials to establish the ideal management for LVO patients presenting with low clinical severity.