Background The Penumbra system is effective for recanalization of the primary arterial occlusion (PAO) in acute stroke. However, clinical outcomes are not as promising. The authors hypothesized that the formation of procedural distal emboli (PDE) during mechanical thrombectomy may lead to poorer patient outcomes.

Design/methods A retrospective review of patients with acute ischemic stroke treated with the Penumbra system was undertaken. Patients' outcome was evaluated by comparing discharge National Institute of Health stroke scale and modified Rankin score (mRS) of patients with and without PDE.

Results Out of 20 patients reviewed, recanalization of PAO was 100%. Six patients (30%) were confirmed to have PDE, of which two died (33.3%) and one (16.7%) had mRS of 2 or less. Of the 14 patients without PDE, three died (21.4%) and six (42.9%) had mRS of 2 or less. In the patient group who survived, mean National Institute of Health stroke scale decrease was only 2.3 in patients with PDE versus a decrease of 10.6 in patients without PDE.

Conclusions In spite of PAO recanalization, distal emboli formed subsequent to Penumbra thrombectomy may contribute to poorer clinical outcome in acute stroke patients.