Assessment of Vasospasm and Delayed Cerebral Ischemia after Subarachnoid Hemorrhage: Current concepts and Value of CT Perfusion and CT Angiography Poster No.: C-2563 Congress: ECR 2012 Type: Educational Exhibit Authors: L. Feyen, T. Niederstadt, V. Hesselmann, A. Kemmling ; 1 1 2 2 2 2 Münster/DE, Muenster/DE Keywords: Neuroradiology brain, CT, CT-Angiography, CT-Quantitative, Diagnostic procedure, Computer Applications-General, Ischemia / Infarction DOI: 10.1594/ecr2012/C-2563 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 15
Learning objectives The aim of the study is to present an overview of the currently used radiologic methods in the evaluation of delayed cerebral ischemia and vasospasm with a special focus on CTP and CTA. Background Vasospasm related delayed cerebral ischemia (DCI) constitutes the main cause for death and morbidity for patients surviving the initial event of subarachnoid hemorrhage (SAH). DCI is defined as the delayed development (typically 4-12 days post-sah) of a focal neurological deficit, and/or cerebral infarction that is unrelated to aneurysm treatment and other causes of neurological deficits (Vergouwen, Vermeulen et al. 2010). The clinical evaluation of new neurological deficits due to DCI is often challenging due to the poor neurological condition of many SAH patients. The early diagnosis of DCI is of high importance, because early treatment seems to maximise the chances of averting ischaemia. Intensified therapy consists of haemodynamic augmentation as the mainstay of medical treatment as well as transluminal balloon angioplasty and super-selective intra-arterial infusion of vasodilators (Rabinstein, Lanzino et al. 2010). Imaging findings OR Procedure details 1.Doppler Ultrasound In 2004, a consensus statement by the Therapeutics and Technology Assessment Subcommittee of the American Academy of Neurology concluded, that transcranial doppler reliably predicts the absence or presence of angiographic vasospasm of the middle cerebral artery, but not other cerebral vessels. The following criteria for vasospasm diagnosis were advocated for identifying vasospasm: flow velocities <120 or >200 cm/s, a rapid rise in flow velocities, or a higher Lindegaard ratio (velocity of MCA/ velocity of ICA) (Sloan, Alexandrov et al. 2004). 2. Value of CTA and CTP in the evaluation of vasospasm: comparison to gold standard digital subtraction angiography Page 2 of 15
Compared to DSA, CTA constitutes the method with highest specificity for vasospasm (0.9) whereas a prolongation of the CTP derived mean transit time (MTT) over 6.4 seconds constitutes the single value with the highest sensitivity (0.95). The combination of both methods achieves a positive predictive value of 89.9% and a negative predictive value of 93.6% (Wintermark, Ko et al. 2006). However, some patients suffer from DCI despite inconspicious DSA. 3. Value of CTP in the evaluation of acute DCI A relative difference of MTT between both hemispheres over 1.1 seconds is the most sensitive marker for DCI (sensitivity 0.8, specificity 0.6). A prolongation of MTT over 5.9 seconds has the highest predictive value (sensitivity 0.7, specificity 0.8) of all single, absolute values (Dankbaar, de Rooij et al. 2009). 4. Value of early CTP for risk stratification and selection for intensified therapy Patients that develop DCI in the course of SAH related hospitalization exhibit altered cerebral perfusion values at admission with a threshold for CBF of 24-25 ml/100 g/min (sensitivity 0.5, specificity 0.9) and for MTT of 5.5 s (sensitivity 0.6, specificity 0.7). CBF is lower and MTT higher in DCI patients compared to no-dci patients up to 3 days before, during, and after DCI, with the largest difference between the groups at the time of DCI, while CBV remains relatively constant in both groups. Furthermore, MTT asymmetry develops in DCI patients at the time of DCI and decreases after DCI (Dankbaar, de Rooij et al. 2011). 5. Value of baseline NECT for risk stratification and selection for intensified therapy Early NECT scans offer valuable information to estimate the risk of delayed vasospasm; the presence of not only cisternal but also intraventricular blood increases the risk of vasospasm. This is incorporated in the modified Fisher scale. Minimum or thin SAH, with the exclusion of intraventricular hemorrhage is classified as modified Fisher grade 1, minimum or thin SAH with IVH in both lateral ventricles is classified as modified Fisher grade 2, thick SAH with the exclusion of IVH is defined as modified Fisher grade 3 and thick SAH with IVH in both lateral ventricles is defined as modified Fisher grade 4 (Kramer, Hehir et al. 2008). Hijdra et al. have proposed a more accurate grading scale, that is used less often, because the amount of blood in 10 basal cisterns/fissures and in 4 ventricles is graded separately (Hijdra, Brouwers et al. 1990). Images for this section: Page 3 of 15
Fig. 2: CBF is reduced in patients with vasospasm as an indicator for endovascular therapy. Page 4 of 15
Fig. 3: regional CBV is mainly preserved. Page 5 of 15
Fig. 4: Vasospasm: Significantly abnormal brain perfusion in the distribution of the right MCA branches is seen primarily on MTT maps. Note the difference between both hemispheres of over 1.1 seconds in the MTT maps as the most accurate sign of acute DCI. Page 6 of 15
Fig. 5: Vasospasm: absolute perfusion values in the indicated regions of interest. Significantly abnormal brain perfusion in the distribution of the right MCA branches is seen primarily on MTT maps. Note the difference between both hemispheres of over 1.1 seconds in the MTT maps as the most accurate sign of acute DCI. CBF is reduced as an indicator for endovascular therapy while regional CBV is mainly preserved. Page 7 of 15
Fig. 6: Gold standard DSA confirms severe vasospasm of the horizontal segment of the middle cerebral artery. Page 8 of 15
Fig. 7: CTP Study after intraarterial treatment. Note the higher cerebral blood flow in the treated hemisphere. Page 9 of 15
Fig. 8: CTP Study after intraarterial treatment.regional CBV is slightly elevated. Page 10 of 15
Fig. 9: CTP Study after intraarterial treatment. After intraarterial administration of 2 mg Nimodipin in the right internal carotid artery a normalization of the MTT differences between both hemispheres and absolute values below 6.4 sec are documented. Page 11 of 15
Fig. 10: Absolute perfusion values in the indicated regions of interest after treatment. 2 mg Nimodipin was administered in the right internal carotid artery and a normalization of the MTT differences between both hemispheres and absolute values below 6.4 sec were documented. Note the higher cerebral blood flow in the treated hemisphere. Page 12 of 15
Fig. 11: A normal diameter of the horizontal branch of the horizontal segment of the middle cerebral artery indicates the cessation of the severe vasospasm after intraarterial therapy. Page 13 of 15
Conclusion The value of CTP and CTA in the risk stratification and selection of patients for intensified therapy is subject of ongoing research. CTP derived MTT is the most sensitive parameter in the evaluation of SAH related DCI that occurs even without angiographic evidence for vasospasm in CTA and DSA. The broad application of CT based methods in the evaluation of DCI and vasospasms in patients with SAH is increasingly feasible due to drastically lowered radiation doses achievable with latest available CTP protocols and modern CT scanners. Personal Information Ludger Feyen Department of Clinical Radiology University of Münster, Münster, Germany feyen@uni-muenster.de References Dankbaar, J. W., N. K. de Rooij, et al. (2011). "Changes in cerebral perfusion around the time of delayed cerebral ischemia in subarachnoid hemorrhage patients." Cerebrovascular diseases (Basel, Switzerland) 32(2): 133-140. Dankbaar, J. W., N. K. de Rooij, et al. (2009). "Diagnosing delayed cerebral ischemia with different CT modalities in patients with subarachnoid hemorrhage with clinical deterioration." Stroke; a journal of cerebral circulation 40(11): 3493-3498. Hijdra, A., P. J. Brouwers, et al. (1990). "Grading the amount of blood on computed tomograms after subarachnoid hemorrhage." Stroke 21(8): 1156-1161. Kramer, A. H., M. Hehir, et al. (2008). "A comparison of 3 radiographic scales for the prediction of delayed ischemia and prognosis following subarachnoid hemorrhage." J Neurosurg 109(2): 199-207. Page 14 of 15
Rabinstein, A. A., G. Lanzino, et al. (2010). "Multidisciplinary management and emerging therapeutic strategies in aneurysmal subarachnoid haemorrhage." Lancet neurology 9(5): 504-519. Sloan, M. A., A. V. Alexandrov, et al. (2004). "Assessment: transcranial Doppler ultrasonography: report of the Therapeutics and Technology Assessment Subcommittee of the American Academy of Neurology." Neurology 62(9): 1468-1481. Vergouwen, M. D., M. Vermeulen, et al. (2010). "Definition of delayed cerebral ischemia after aneurysmal subarachnoid hemorrhage as an outcome event in clinical trials and observational studies: proposal of a multidisciplinary research group." Stroke 41(10): 2391-2395. Wintermark, M., N. U. Ko, et al. (2006). "Vasospasm after subarachnoid hemorrhage: utility of perfusion CT and CT angiography on diagnosis and management." AJNR American journal of neuroradiology 27(1): 26-34. Page 15 of 15