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Original research
Incomplete mechanical recanalization of middle cerebral artery occlusions facilitates endogenous recanalization within 5 h
  1. Yince Loh1,
  2. Zhongsong Shi2,
  3. David Liebeskind3,
  4. Reza Jahan4,
  5. Nestor Gonzalez4,
  6. Paul M Vespa5,
  7. Sidney Starkman3,
  8. Jeffrey L Saver3,
  9. Satoshi Tateshima4,
  10. Fernando Vinuela4,
  11. Gary Duckwiler4
  1. 1Department of Medicine, Madigan Army Medical Center, Tacoma, Washington, USA
  2. 2Department of Neurosurgery, The First Affiliated Hospital of Sun Yat-sen University, Guangzhou, China
  3. 3Department of Neurology, UCLA, Los Angeles, California, USA
  4. 4Division of Interventional Neuroradiology, UCLA Medical Center, Los Angeles, California, USA
  5. 5Department of Neurosurgery, UCLA, Los Angeles, California, USA
  1. Correspondence to Dr Yince Loh, Medicine, Madigan Army Medical Center, 9040A Fitzsimmons Drive, Tacoma, WA 98431, USA; yincer{at}


Background and purpose Successful revascularization can often improve functional outcome after large intracranial arterial occlusions. However, incomplete or unsuccessful recanalization is often the end result after attempted mechanical thrombectomy. A study was undertaken to determine whether partial recanalization of proximal isolated middle cerebral artery (MCA) occlusions facilitates endogenous thrombolysis and spontaneous recanalization.

Methods We retrospectively analyzed consecutive patients with acute ischemic stroke undergoing mechanical thrombectomy using the Merci Retriever System for occlusions involving any portion of the M1 segment of the MCA. Only those patients with a residual obstruction of the proximal MCA segments were included. The rates of facilitated endogenous recanalization (FER5) by imaging within the 5 h following intervention were compared in patients with partial proximal recanalization and those in whom recanalization was unsuccessful.

Results Forty-two patients were included in the analysis. Twenty-six patients had good recanalization of the proximal aspect of the target lesion with an arterial occlusive lesion score of 2 or 3 but a residual partial or total occlusion of the MCA, while 16 patients failed to recanalize any portion of the target occlusion. Twelve patients (46%) in the first group and only one (5.9%) in the second group had facilitated endogenous recanalization on interval imaging 5 h after intervention (OR 12.9, 95% CI 1.5 to 112.2). Nine patients with proximal recanalization had good clinical outcomes at discharge (mRS ≤2) compared with none without recanalization (p=0.01), but FER did not have a relationship with clinical outcome.

Conclusions Despite initially incomplete proximal mechanical thrombectomy, nearly half of all patients with residual M1 occlusions will undergo further endogenous recanalization within the subsequent 5 h.

  • Acute stroke
  • thrombectomy
  • middle cerebral artery
  • recanalization
  • thrombolysis
  • aneurysm
  • arteriovenous malformation
  • stenosis
  • stroke
  • spinal cord
  • atherosclerosis
  • stent
  • subarachnoid
  • angioplasty
  • flow diverter
  • artery
  • vein
  • vasculitis
  • complication
  • catheter
  • balloon
  • malformation
  • intervention
  • embolic
  • coil
  • brain
  • angiography

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  • Competing interests All authors are or have been employees of the University of California, which holds several patents on retriever devices for stroke. GD is a Scientific Advisor for and shareholder in Concentric Medical. DL is a consultant for Concentric Medical. SS has received grant funding for clinical trials from Concentric Medical and Genentech. JLS is a scientific consultant for CoAxia, Concentric Medical, Talecris, Ferrer, AGA Medical, BrainsGate, PhotoThera and Cygnis; has received lecture honoraria from Ferrer and Boehringer Ingelheim; received support for clinical trials from Concentric Medical; and is a site investigator in multicenter trials sponsored by AGA Medical and the NIH for which the UC Regents received payments based on the number of subjects enrolled. The views expressed in this article are those of the authors and do not reflect the official policy or position of the Department of the Army, the Department of Defense or the US Government.

  • Ethics approval Ethics approval was provided by the local IRB.

  • Provenance and peer review Not commissioned; externally peer reviewed.