What to expect on post mechanical thrombectomy CT - a guide to correct diagnosis.

What to expect on post mechanical thrombectomy CT - a guide to correct diagnosis. Poster No.: C-2257 Congress: ECR 2017 Type: Educational Exhibit Authors: T. Buende Tchokouako, H. Nejadhamzeeigilani, A. Bailey, W. Waldmeyer, T. Patankar, T. Goddard; Leeds/UK Keywords: CNS, Cardiovascular system, Emergency, CT, Catheter arteriography, Recanalisation, Thrombolysis, Contrast agentintravenous, Acute, Hemodynamics / Flow dynamics, Hemorrhage DOI: 10.1594/ecr2017/C-2257 Any information contained in this pdf file is automatically generated from digital material submitted to EPOS by third parties in the form of scientific presentations. References to any names, marks, products, or services of third parties or hypertext links to thirdparty sites or information are provided solely as a convenience to you and do not in any way constitute or imply ECR's endorsement, sponsorship or recommendation of the third party, information, product or service. ECR is not responsible for the content of these pages and does not make any representations regarding the content or accuracy of material in this file. As per copyright regulations, any unauthorised use of the material or parts thereof as well as commercial reproduction or multiple distribution by any traditional or electronically based reproduction/publication method ist strictly prohibited. You agree to defend, indemnify, and hold ECR harmless from and against any and all claims, damages, costs, and expenses, including attorneys' fees, arising from or related to your use of these pages. Please note: Links to movies, ppt slideshows and any other multimedia files are not available in the pdf version of presentations. www.myesr.org Page 1 of 44

Learning objectives We provide a pictorial review of a 2 year cohort of patients from a tertiary centre who underwent mechanical thrombectomy in order to: demonstrate normal radiological features post-thrombectomy; highlight the CT characteristics of post-thrombectomy complications and discuss approaches to differentiate between normal evolutional changes and complications. Background Acute ischaemic stroke is characterised by the sudden loss of blood circulation to an area of the brain, resulting in a corresponding loss of neurologic function. It is a devastating disease and is the leading cause of chronic disability and the second leading cause of dementia in the western world. It also has very high direct and indirect financial costs. Early recanalization is one of the most important factors to reduce tissue at risk and reverse neurologic deficits. Computer Tomography Angiogram (CTA) holds a key role in the management of patients with acute ischaemic stroke. In particular, in those with hyperattenuated vessel on noncontrast CT as this is a marker of a proximally located thrombus that may not respond to standard IV lysis. The role of the CTA is to demonstrate the site of vessel occlusion, determine the extent of the clot. In addition, CTA scoring systems such as the clot burden score and collateral score are useful tools to predict the clinical outcome after recanalization. Thrombolysis with intravenous recombinant tissue plasminogen activator (tpa) has been demonstrated to be an effective treatment for acute ischemic stroke especially in patient with distal occlusion and smaller clot extent. However, there is a substantial risk of cerebral hemorrhage when thrombolytic agents are used in the setting of cerebral ischemia. In selected patients (Fig. 1 on page 3) with acute ischaemic stroke caused by large vessel occlusion and/or increased clot length, mechanical thrombectomy ( Fig. 2 on page 3) is now considered the gold standard treatment to achieve rapid and complete reperfusion. Page 2 of 44

Since the publication of the NICE guidelines on mechanical thrombectomy for treating acute ischaemic stroke in February 2016, we anticipate an increase in the frequency of such procedures. As per national guidelines a 24 hours post intervention CT head is performed as routine practice. Images for this section: Fig. 1: Eligibility criteria for thrombectomy. Leeds General infirmary - Leeds/UK Page 3 of 44

Fig. 2: Thrombectomy performed on a 65 year old male with left MCA occlusion. Leeds General infirmary - Leeds/UK Page 4 of 44

Findings and procedure details Between June 2014 and June 2016, 50 patients (mean age, 64 ± 17 years) underwent mechanical thrombectomy at our centre. Of the 50 patients, 39 presented with MCA occlusion, 4 with a combination of a MCA and ICA occlusions and 7 with basilar artery occlusion. 30 patients (60% of the total) received intravenous thrombolysis prior to the thrombectomy (Fig. 3 on page 23 ). We reviewed all post-operative CT imaging in order to determine the accuracy of reporting with regards to reported complications as oppose to normal changes. Ischaemic changes The momentary loss of cerebral blood flow causes ischaemia in the affected vessel territory which will maturate after recanalization (Fig. 4 on page 24, Fig. 5 on page 25, Fig. 6 on page 26). Basal ganglionic infarction before thrombectomy is associated with a worse prognosis and higher rates of haemorrhage after intervention. However, caudate head and anterior lentiform nucleus infarctions are commonly identified post mechanical thrombectomy and seem to have little clinical impact ( Fig. 7 on page 27, Fig. 8 on page 28). Page 5 of 44

Fig. 4: 60 year old male, admitted with right hemiparesis and expressive dysphasia, NIHSS 20. NECT (a,b,c) performed on admission shows hyperdense left MCA (red arrow) indicating acute thrombus. A CTA (d,e,f) demonstrated attenuated blood flow within the left MCA (white arrow). 24 hours post thrombectomy CT (g,h,i) shows left insular low attenuation consistent with ischaemia/infarction (yellow arrow). The prior left MCA thrombus has been removed in the interim and this vessel is no longer hyperdense (green arrow). References: Leeds General infirmary - Leeds/UK Page 6 of 44

Fig. 5: 37 year old admitted with left hemiparesis, NIHHS 15. NECT (a,b,c,d) performed on admission shows an hyperdense right MCA (black arrow). A repeat NECT (e,f,g,h) performed 48 hours post thrombectomy shows a subacute infarction affecting the right MCA territory with low attenuation within the right caudate (red arrow), lentiform (yellow arrow) and insular regions which also extends into the right corona radiata. References: Leeds General infirmary - Leeds/UK Page 7 of 44

Fig. 6: 55 year old lady admitted with left hemiparesis, NIHSS 33. NECT (a,b,c,d) on admission shows hyperdense right MCA (black arrow). CTA (e,f,g,h) confirms acute thrombus in the right MCA (red arrow) along with an occlusion of the left internal carotid artery (yellow arrows). Post thrombectomy CT (I,j,k,l) shows infarction in the right insular region (white arrow) and right corpus striatum (green arrow). References: Leeds General infirmary - Leeds/UK Page 8 of 44

Fig. 7: 71 year old male, admitted with right hemiparesis, NIHSS 23. A NECT (a,b,c) performed on admission shows a dense left MCA (white arrow). CTA (d,e,f) confirms occlusion of the left MCA (red arrow). Post thrombectomy NECT (g,h,i) shows reduced attenuation in the left corpus striatum (green arrow) and left posterior temporal lobe (black arrow) in keeping with evolving infarction. References: Leeds General infirmary - Leeds/UK Page 9 of 44

Fig. 8: 62 year old male admitted with right hemiparesis and expressive dysphasia, NIHSS 21. NECT (a,b,c,d) performed on admission demonstrated increased attenuation of the left middle cerebral artery (white arrow) indicative of vessel thrombosis. CTA (e,f,g,h)confirms occlusion of the proximal left middle cerebral artery (red arrow). 24 hours post thrombectomy NECT (i,j,k,l) shows ischaemic changes in the left corpus striatum infarction (yellow arrow). References: Leeds General infirmary - Leeds/UK Haemorrhagic transformation ( Fig. 9 on page 29, Fig. 10 on page 30, Fig. 11 on page 31, Fig. 12 on page 32, Fig. 13 on page 33) Haemorrhagic transformation of acute ischaemic stroke is a complex and multifactorial phenomenon. After the onset of ischaemia, there is disruption of the blood-brain barrier, and cerebral autoregulation. Additional thrombolytic on board may predispose to extravasation when the ischaemic tissue is eventually reperfused. There is trend toward increased haemorrhage rate as the time between stroke and vessel recanalization increases. Mechanical thrombectomy is associated with higher haemorrhage rates, perhaps as a result of combination of mechanical manipulation of the blood vessel and increased reperfusion rate. Page 10 of 44

Fig. 9: 63 year old male admitted with left hemiparesis. NECT on admission (a,b,c) demonstrated hyperdense right MCA (red arrow). CTA (d,e,f) shows opacification of the right MCA (black arrow) with poor contrast enhancement distally reflecting right MCA thrombus. 24 hours post thrombectomy NECT (g,h,i) shows extensive right hemispheric loss of grey-white differentiation consistent with a large MCA territory Infarction and haemorrhagic transformation. A NECT performed 3 days post thrombectomy (j,k,l) shows maturation of the haemorrhagic transformation. Patient died. References: Leeds General infirmary - Leeds/UK Page 11 of 44

Fig. 10: 51 year old male admitted with right hemiparesis, NIHSS 17. NECT (a,b,c,) acquired on admission demonstrated a left basal ganglionic established infarction (yellow arrow). CTA (d,e) imaging demonstrated a filling defect within the left MCA. The perfusion scan (l,m) shows increase in mean transit time in the MCA territory with a small central core in the basal ganglia (white arrow) suggesting a large area of mismatch perfusion deficit. 24 hours post thrombectomy NECT (I,j,k) shows low density in the left internal capsule and insula region associated with haemorrhagic transformation of the left lentiform nucleus (black arrow). References: Leeds General infirmary - Leeds/UK Page 12 of 44

Fig. 11: 20 year old, admitted with left hemiparesis, NIHSS 17. NECT (a,b,c) on admission shows a hyperdense right MCA. 24 post thrombectomy NECT (d,e,f) shows evolution of the right MCA territory infarct with significant oedematous change with resultant midline shift to the left and early contralateral hydrocephalus. 5 days post thrombectomy NECT (g,h,i) shows decompressive craniectomy on the right associated with changes of acute infarction in the right cerebral hemisphere in the distribution of the right middle cerebral artery with further changes of acute infarction in the right anterior cerebral artery territory and in the ganglionic region on this side. References: Leeds General infirmary - Leeds/UK Page 13 of 44

Fig. 12: 62 year old female admitted with low GCS. NECT (a,b,c,d) on admission did not show any abnormality of the basilar artery. 3-D rotational angiogram imaging (e)demonstrated tight focal stenosis at the basilar termination and left posterior cerebral artery. 24 hours post thrombectomy NECT (f,g,h,i) shows a large parenchymal haematoma in the left cerebral hemisphere (green arrow) with associated subarachnoid (red arrow) and interventricular haemorrhage (yellow arrow). References: Leeds General infirmary - Leeds/UK Page 14 of 44

Fig. 13: 88 year old female, admitted with left hemiparesis, NIHSS 25 NCET (a,b,c,d) acquired on admission shows hyperdense left MCA. CTA imaging (e,f,g,h) shows occlusion of the right ICA to origin (red arrows) and thrombus is seen extending into the proximal right MCA(yellow arrows). 24 hours post thrombectomy NECT (I,j,k,l) shows right-sided MCA territory infarction, with new high attenuation foci seen within this region in keeping with haemorrhage. 2 weeks post thrombectomy NECT (m,n,o,p) shows on-going maturation of right MCA territory infarction. References: Leeds General infirmary - Leeds/UK Haemorrhage/contrast stained areas ( Fig. 14 on page 34, Fig. 15 on page 35, Fig. 16 on page 36, Fig. 17 on page 37) These lesions are commonly seen after intra-arterial thrombolysis. These have been considered a risk factor for haemorrhagic transformation and symptomatic haemorrhage. However, their significance after mechanical thrombectomy alone remains uncertain. They can have similar appearances to haemorrhagic strokes/transformations and may even co-exist and may be frequently misinterpreted by less experienced radiologists. Page 15 of 44

Fig. 14: 48 year old male, admitted with right hemiparesis, NIHSS 22. NECT (a,b,c) performed on admission shows a hyperdense left MCA (red arrow). Post thrombectomy NECT (d,e,f) demonstrated diffuse gyriform contrast extravasation within the left frontal lobe (yellow arrow) and marked left-sided brain swelling and oedema with approximately 12 mm of rightward midline shift (black arrow). The patient died. References: Leeds General infirmary - Leeds/UK Page 16 of 44

Fig. 15: 49 year old male, woke up with right hemiparesis, NIHSS 23. NECT (a,b,c) performed on admission shows hyperdense left MCA (blue arrow). CTA (d,e) demonstrated an abrupt contrast cut off at the left MCA in keeping with left MCA occlusion (red arrow). The left MCA occlusion was confirmed by 3-D rotational angiogram imaging (m). Post thrombectomy NECT (f,g,h) shows an area of high attenuation within the left temporal lobe consistent with contrast extravasation (green arrow). 24 post thrombectomy NECT (I,j,k) shows maturation of the left anterior and middle cerebral artery territory infarction and resolution of the contrast extravasation. References: Leeds General infirmary - Leeds/UK Page 17 of 44

Fig. 16: 74 year old female, admitted with right hemiparesis, NIHSS 20. NECT (a,b,c,) acquired on admission shows a long segment of hyperdense MCA (red arrow) and early ischaemic changes in the left basal ganglia (blue arrow). CTA (d,e,f) confirms the presence of clot in the left MCA (black arrow) and the absence of blood flow throughout the entire left MCA territory. Post thrombectomy NECT (g,h,i) shows a high density material demonstrated mainly in the left frontal lobe, left basal ganglia and within the medial aspect of the left temporal lobe (green arrow)in keeping with contrast extravasation. A NECT (k,l,m) performed 24 hours post thrombectomy shows reduced intensity of the contrast extravasation (yellow arrow). References: Leeds General infirmary - Leeds/UK Page 18 of 44

Fig. 17: 23 year old female admitted with low GCS. NECT(a,b,c) performed on admission shows a hyperdense basilar artery (blue arrow). CTA (d,e,f) confirms basilar artery thrombosis (yellow arrow). 24 hours NECT (e,f,g) shows an ill-defined area of hyperdensity in the central and right-side of the pons (black arrow) consistent with contrast extravasation. A subsequent NECT performed a week after thrombectomy (j,k,l) shows resolution of the contrast extravasation and ischaemic changes in the pons (green arrow). References: Leeds General infirmary - Leeds/UK Subarachnoid haemorrhage ( Fig. 18 on page 38, Fig. 19 on page 39) Subarachnoid haemorrhage after mechanical thrombectomy usually occurs in complicated cases. It does not appear to be associated with an impaired clinical outcome or an elevated risk for consecutive haemorrhage. Page 19 of 44

Fig. 18: 60 year old male admitted with low Glasgow coma scale (GCS). NECT(a,b,c,d) performed on admission shows a hyperdense intraluminal thrombus (yellow arrow) within the basilar artery consistent with acute basilar artery thrombosis. CTA (e,f,g,h) demonstrated the presence of a soft thrombus in the basilar artery (green arrow) which was confirmed on 3-D rotational angiogram imaging (m,n). 24 hours post thrombectomy NECT (I,j,k,l) shows a small focus of acute subarachnoid haemorrhage in the interpeduncular cistern (red arrow) and infarction in the left occipital lobe (white arrow). References: Leeds General infirmary - Leeds/UK Page 20 of 44

Fig. 19: 84 year old female admitted with right hemiparesis, NIHSS 20. Non-enhanced CT (NECT) performed on admission (a,b,c) shows increased attenuation of the left MCA (green arrow) consistent with acute MCA occlusion. CTA (d,e,f) demonstrates proximal left internal carotid artery (red arrow) and left proximal MCA (purple arrow) occlusions. 24 hours post thrombectomy NECT (g,h,i) demonstrates a subtle high density in the posterior aspect of left sylvian fissure in keeping subdural haematoma (yellow arrow). In addition, there is an infarction within the medial lenticular nucleus on the left (blue arrow). References: Leeds General infirmary - Leeds/UK Failed thrombectomy ( Fig. 20 on page 40, Fig. 21 on page 41). Page 21 of 44

In some cases, recanalization is not achievable and the procedure has to be abandoned. Fig. 20: 85 year old male, presented with left hemiparesis, NIHSS 29. A NECT (a,b,c) performed on admission shows increased attenuation in branches of right MCA (white arrow) with slight low attenuation of right insula (yellow arrow) suggestive of early right MCA infarction with proximal vessel thrombosis. Angiography pre thrombectomy shows occlusion of the right MCA (d). Final angiography post thrombectomy (e,f) shows a stent deployed in the distal right ICA (black arrow) and TICI grade 1 perfusion into several proximal MCA branches. 24 hours post thrombectomy NECT (g,h,i) shows evolution of right the MCA infarct with loss of grey-white matter differentiation and hypoattenuation affecting the majority of right MCA territory (blue arrow). The stent is demonstrated in the proximal right ICA and MCA (green arrow). References: Leeds General infirmary - Leeds/UK Page 22 of 44

Fig. 21: 89 year old female, admitted with right hemiparesis and expressive dysphasia, NIHSS 15. A NECT (a,b,c,d) on admission shows an hyperdense left MCA(red arrow). CTA (e) and 3-D rotational angiogram imaging (f,g) show distal left MCA obstruction (black arrows). During the thrombectomy, the capture clot retrieval stent got stuck into the distal left MCA and could not be retrieved. The procedure was abandoned. 48 hours post thrombectomy NECT shows a high density materiel in the left temporal lobe consistent with intraparenchymal haemorrhage (yellow arrow). In addition, the capture clot retrieval stent in still visible in the left MCA (green arrow). References: Leeds General infirmary - Leeds/UK Images for this section: Page 23 of 44

Fig. 3: Patient demographics. Leeds General infirmary - Leeds/UK Page 24 of 44

Fig. 20: 85 year old male, presented with left hemiparesis, NIHSS 29. A NECT (a,b,c) performed on admission shows increased attenuation in branches of right MCA (white arrow) with slight low attenuation of right insula (yellow arrow) suggestive of early right MCA infarction with proximal vessel thrombosis. Angiography pre thrombectomy shows occlusion of the right MCA (d). Final angiography post thrombectomy (e,f) shows a stent deployed in the distal right ICA (black arrow) and TICI grade 1 perfusion into several proximal MCA branches. 24 hours post thrombectomy NECT (g,h,i) shows evolution of right the MCA infarct with loss of grey-white matter differentiation and hypoattenuation affecting the majority of right MCA territory (blue arrow). The stent is demonstrated in the proximal right ICA and MCA (green arrow). Leeds General infirmary - Leeds/UK Page 41 of 44

Conclusion Mechanical thrombectomy changes the clinical and radiological course of acute stroke due to large vessel occlusion. Familiarisation with the post intervention CT changes and complications, particularly distinguishing contrast extravasation from haemorrhage is crucial in patient management. Personal information References 1. Parilla G, Garcia-villalba et al. Haemorrhage/Contrast Staining Areas after Mechanical Intra-Arterial Thrombectomy in Acute Ischemic Stroke: imaging Findings and Clinical Significance. AJNR 2012; 33: 1791-1796 2. Rosenthal E. S, Schwamm L. H. et al. Role of Recanalization in Acute Stroke Outcome: Rationale for a CT Angiogram-Based "Benefit of Recanalization" Model. AJNR 2008; 29: 1471-75 3. Warwick Pexman H, Philip A et al. Use of the Alberta Stroke Program Early CT Score (ASPECTS) for assessing CT Scans in Patients with Acute Stroke. AJNR 2001; 22:1534-1542 4. Tan I. Y. L, Demchuk A. M et al. CT Angiography Clot Burden Score and Collateral Score Correlation with Clinical and Radiologic Outcomes in Acute Middle Cerebral Artery Infarct. AJNR 2009; 30:525-31 5. John R. Sims, Guy Rordorf et al. Arterial Occlusion Revealed by CT Angiography Predicts NIH Stroke Score and Acute Outcomes after IB tpa Treatment. AJNR 2005; 26:246-251 6. Bruce C V Campell, Geoffrey A Donnan et al. Endovascular thrombectomy for stroke: current best practice and future goals. Vascular Neurology 2016; 1:e000004. Page 43 of 44

7. Eric S. Sussman and E. Sander Connolly, Jr. Haemorrhagic Transformation: A review of the Rate of Haemorrhage in the Major Clinical Trials of Acute Ischaemic Stroke. Front Neurol. 2013; 4:69 8. Nikoubashman O, Reich A et al. Postinterventional subarachnoid haemorrhage after endovascular stroke treatment with stent retrievers. Neuroradiology 2014 Dec; 56(12): 1087-96 9. Yince Loh, Towfighi A et al. Basal ganglionic infarction before mechanical thrombectomy predicts poor outcome. Stroke 2009; 40:3315-3320. Page 44 of 44