Author: Dr Alex Dimancea

Emergency University Hospital Bucharest, Romania

Twitter: @DimanceaAlex

Performing mechanical thrombectomy (MT) in acute ischaemic stroke (AIS) is progressively expanding and becoming more streamlined by the introduction of newer devices and indications.1 Patient history as well as initial CT/MRI scan can provide a clue of the thrombus composition and thus potentially allow for a more adequate initial MT strategy. In previous randomised control trials, using first-line catheter aspiration (CA) versus first-line stent-retriever (SR) demonstrated similar recanalisation rates and favorable outcomes.2,3 However, a more nuanced MT approach may potentially provide better outcomes. Along with occlusion location, presumed thrombus composition and stroke etiology, occlusion appearance on the initial angiogram may be the last decisional factor influencing initial MT strategy.

Four different angiographic patterns have been described on the initial angiogram, at the interface between the proximal end of occluding thrombi and the patent arterial segment4,5 (Fig. 1, upper panel):

  1. Cut-off appearance: abrupt interruption of contrast, without generating any specific shape.
  2. Tapered appearance: gradual luminal narrowing, forming an acute angle over the superior/inferior vessel wall.
  3. Meniscus appearance: abrupt interruption of contrast delineating a concavity towards the proximal lumen.

3.1 Claw-sign appearance6: variation of the meniscus occlusion, in which the protrusion length of the contrast on each side of the thrombus convexity was more than half of the parent vessel diameter (Fig. 1, lower panel).

  1. Tram-track appearance: a partially occlusive lesion, with visible distal contrast filling the lumen and several pieces of thrombotic material serially positioned. The extended linear contrast can be observed on one or both arterial walls.

Alternatively, Consoli et al. classified acute occlusions as either regular (corresponding to cut-off occlusions, as per description) and irregular (encompassing all other patterns).7

Although there is no published study concomitantly comparing all described occlusion patterns and their association with efficiency of MT method, several features emerge:

  • The cut-off and tapered occlusion types were considered as fully occlusive, the meniscus and tram-track appearances might rather suggest a sub-occlusive4
  • The cut-off pattern seemed the most refractory to MT, requiring one supplementary passage on average (2.7 vs. 1.7 for tapered and vs. 1.9 for meniscus/tram-track occlusions, p 0.01). Furthermore, the cut-off or regular pattern was also more responsive to first-line CA (100% vs. 33.3%, p 0.001).7
  • In contrast, successful recanalisation was more frequently achieved after first-line SR for irregular occlusions (73.9% vs. 38.4%, p 0.036).7
  • The tapered pattern was associated with intracranial stenosis (54.8% vs. 18%) and re-occlusion, truncal type occlusion and use of rescue therapy such as permanent stenting.5
  • A meniscus/tram-track pattern in the posterior circulation8,9 as well as the ‘claw-sign’ positive occlusions6 were associated with a higher rate of recanalisation (89.3% vs. 63.6%, p 0.004 and an OR of 12.50 95% CI 1.50-103.00, p 0.019, respectively), as well as a higher first pass effect in the former (even higher for first-line CA than SR).

In conclusion, as MT will be performed more extensively owing to expanded indications, the experience regarding different angiographic patterns and their relative ‘responsiveness’ to MT techniques will increase. This knowledge, along with patient history and emergent cerebral imaging, may determine a tailored MT approach for intracranial large vessel occlusions.

Fig 1: Upper panel, from left to right: Cut-off, tapered, meniscus and tram-track occlusion patterns. Reproduced with permission from Pr. Ashfaq Shuaib, Department of Medicine (Neurology), University of Alberta, Edmonton, AB, Canada; Lower panel: ‘Claw-sign’ positive occlusion pattern with contrast protrusion length on each side estimated at more than half of the parent vessel diameter. Reproduced with permission from Dr. Yuki Yamamoto, Department of Clinical Neuroscience, Institute of Biomedical Sciences, Tokushima University, Tokushima, Japan.


  1. Jovin TG, Li C, Wu L, et al. Trial of Thrombectomy 6 to 24 Hours after Stroke Due to Basilar-Artery Occlusion. N Engl J Med. 2022;387(15):1373-1384. doi:10.1056/NEJMoa2207576
  2. Lapergue B, Blanc R, Gory B, et al. Effect of Endovascular Contact Aspiration vs Stent Retriever on Revascularization in Patients With Acute Ischemic Stroke and Large Vessel Occlusion: The ASTER Randomized Clinical Trial. JAMA. 2017;318(5):443-452. doi:10.1001/jama.2017.9644
  3. Turk AS, Siddiqui A, Fifi JT, et al. Aspiration thrombectomy versus stent retriever thrombectomy as first-line approach for large vessel occlusion (COMPASS): a multicentre, randomised, open label, blinded outcome, non-inferiority trial. Lancet. 2019;393(10175):998-1008. doi:10.1016/S0140-6736(19)30297-1
  4. Mönch S, Boeckh-Behrens T, Berndt M, et al. Angiographic Baseline Proximal Thrombus Appearance of M1/M2 Occlusions in Mechanical Thrombectomy. Clin Neuroradiol. 2021;31(1):189-196. doi:10.1007/s00062-019-00863-4
  5. Garcia-Bermejo P, Patro SN, Ahmed AZ, et al. Baseline occlusion angiographic appearance on mechanical thrombectomy suggests underlying etiology and outcome. Front Neurol. 2019;10(MAY):1-7. doi:10.3389/fneur.2019.00499
  6. Yamamoto Y, Yamamoto N, Kanematsu Y, et al. The Claw Sign: An angiographic Predictor of Recanalization After Mechanical Thrombectomy for Cerebral Large Vessel Occlusion. J Stroke Cerebrovasc Dis. 2019;28(6):1555-1560. doi:10.1016/j.jstrokecerebrovasdis.2019.03.007
  7. Consoli A, Rosi A, Coskun O, et al. Thrombectomy for M1-middle cerebral artery occlusion: Angiographic aspect of the arterial occlusion and recanalization: A preliminary observation. Stroke. 2018;49(5):1286-1289. doi:10.1161/STROKEAHA.117.018987
  8. Baik SH, Jung C, Kim BM, Han K, Kim DJ. Clot meniscus sign: An angiographic clue for choosing between stent retriever and contact aspiration in acute basilar artery occlusion. Am J Neuroradiol. 2021;42(4):732-737. doi:10.3174/AJNR.A6988
  9. Baik SH, Kim JW, Kim BM, Kim DJ. Significance of angiographic clot meniscus sign in mechanical thrombectomy of basilar artery stroke. J Neurointerv Surg. 2020;12(5):477-482. doi:10.1136/neurintsurg-2019-015321

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