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Ischemic stroke
Original research
A population-based incidence of M2 strokes indicates potential expansion of large vessel occlusions amenable to endovascular therapy
  1. Ansaar T Rai1,
  2. Jennifer R Domico1,
  3. Chelsea Buseman2,
  4. Abdul R Tarabishy3,
  5. Daniel Fulks4,
  6. Noelle Lucke-Wold1,
  7. SoHyun Boo1,
  8. Jeffrey S Carpenter1
  1. 1 Department of Interventional Neuroradiology, West Virginia University Hospital, Morgantown, West Virginia, USA
  2. 2 Department of Enterprise Analytics, West Virginia University Hospital, Morgantown, West Virginia, USA
  3. 3 Department of Neuroradiology, West Virginia University, Morgantown, West Virginia, USA
  4. 4 Department of Medicine, The University of Tennessee Graduate School of Medicine, Knoxville, Tennessee, USA
  1. Correspondence to Dr Ansaar T Rai, Department of Interventional Neuroradiology, West Virginia University, Morgantown, West Virginia 26508, USA; ansaar.rai{at}gmail.com

Abstract

Background M2 occlusions may result in poor outcomes and potentially benefit from endovascular therapy. Data on the rate of M2 strokes is lacking.

Methodology Patients with acute ischemic stroke discharged over a period of 3 years from a tertiary level hospital in the ‘stroke belt’ were evaluated for M2 occlusions on baseline vascular imaging. Regional and national incidence was calculated from discharge and multicounty data.

Results There were 2739 ICD-9 based AIS discharges. M2 occlusions in 116 (4%, 95% CI 3.5% to 5%) patients constituted the second most common occlusion site. The median National Institute of Health Stroke Scale (NIHSS) score was 12 (IQR 5–18). Good outcomes were observed in 43% (95% CI 34% to 53%), poor outcomes in 57% (95% CI 47% to 66%), and death occurred in 27% (95% CI 19% to 37%) of patients. Receiver operating characteristics curves showed the NIHSS to be predictive of outcomes (area under the curve 0.829, 95% CI 0.745 to 0.913, p<0.0001). An NIHSS score ≥9 was the optimal cut-off point for predicting poor outcomes (sensitivity 85.7%, specificity 67.4%). 71 (61%) patients had an NIHSS score ≥9 and 45 (39%) an NIHSS score <9. The rate of good-outcome was 22.6% for NIHSS score ≥9 versus 78.4% for NIHSSscore <9 (OR=0.08, 95% CI 0.03 to 0.21, p<0.0001). Mortality was 42% for NIHSS score ≥9 versus 2.7% for NIHSS score <9 (OR=26, 95% CI 3.3 to 202, p<0.0001). Infarct volume was 57 (±55.7) cm3 for NIHSS score ≥9 versus 30 (±34)cm3 for NIHSS score <9 (p=0.003). IV recombinant tissue plasminogen activator (rtPA) administered in 28 (24%) patients did not affect outcomes. The rate of M2 occlusions was 7 (95% CI 5 to 9)/100 000 people/year (3%, 95% CI 2% to 4%), giving an incidence of 21 176 (95% CI 15 282 to 29 247)/year. Combined with M1, internal carotid artery terminus and basilar artery, this yields a ‘large vessel occlusion (LVO)+M2’ rate of 31 (95% CI 26 to 35)/100 000 people/year and a national incidence of 99 227 (95% CI 84 004 to 112 005) LVO+M2 strokes/year.

Conclusion M2 occlusions can present with serious neurological deficits and cause significant morbidity and mortality. Patients with M2 occlusions and higher baseline deficits (NIHSS score ≥9) may benefit from endovascular therapy, thus potentially expanding the category of acute ischemic strokes amenable to intervention.

  • stroke
  • thrombectomy
  • incidence
  • M2

This is an Open Access article distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited and the use is non-commercial. See: http://creativecommons.org/licenses/by-nc/4.0/

https://doi.org/10.1136/neurintsurg-2017-013371

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    Footnotes

    • Contributors ATR: study design, data analysis, manuscript preparation. JRD, CB, ART, DF, SB: data collection. JSC: manuscript preparation.

    • Competing interests None declared.

    • Ethics approval Institutional Review Board.

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

    • Data sharing statement There are no additional supplemental data.