A Beginner's Guide to Brain CT in Acute Stroke

Transcription

1 A Beginner's Guide to Brain CT in Acute Stroke Poster No.: C-2524 Congress: ECR 2012 Type: Educational Exhibit Authors: M. E. A. Noeman; Güstrow/DE Keywords: Ischemia / Infarction, Embolism / Thrombosis, Thrombolysis, CTAngiography, CT, Neuroradiology brain DOI: /ecr2012/C-2524 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. Page 1 of 34

2 Learning objectives The purpose of this exhibit is: 1- To have a systematic approach in evaluating brain CT. 2- To recognize and describe the early signs of acute ischemic stroke. 3- To exclude lesions that mimic acute ischemic stroke. Background Even in the era of diffusion and perfusion-weighted MRI, cranial computed tomography (CCT) remains the first-line diagnostic test - after physical examination- for the emergency evaluation of early ischemic stroke having the advantages of being available in most hospitals, available 24 hours a day, 7 days a week, performed fast, easily performed in severely ill patients who are dependent on support and monitoring devices and above all CCT is sensitive for detection of intracranial hemorrhage. Stroke is considered the third most common cause of death and one of the leading causes of adult disability in North America, Europe, and Asia. Thrombolytic therapy with recombinant tissue plasminogen activator (rt-pa) is the treatment of choice for ischemic stroke provided that there is no contraindication to this treatment. However, the benefit of intravenous thrombolysis decreases steadily over time from symptom onset, so that the time window for intervention can be as narrow as 3 hours (19). "Time is brain", therefore having frontline radiologists to be proficient in interpreting the emergency CCT scan improves the efficiency of the whole pathway of care and is potentially life saving. Stroke can be defined as a rapid loss of brain function(s) due to disturbance in the blood supply to the brain. There are two major types of stroke: Page 2 of 34

3 a) ischemic (lack of blood flow) caused by blockage (thrombosis, arterial embolism) (nearly 80%). b) or a hemorrhage (leakage of blood) (20%). The goal of CT imaging in a patient with acute stroke is (4): 1- to exclude lesions that mimic stroke like intracranial hemorrhage, subdural hematoma, cerebritis etc.. 2- to define the extension of the ischemic brain tissues. 3- to identify the presence of stenosis or occlusion of major extra and intracranial arteries. The key principle behind successful interpretation when dealing with ischemic stroke is knowing "where" to look and "what" to look for (5). Imaging findings OR Procedure details Systematic approach to interpretation: (8) 1- Check the scout image. May see a fracture or gross abnormality. 2- A quick 'first pass' is recommend, noting gross pathology, followed by a more detailed analysis of the images. 3- Use the mnemonic 'ABBCS' to remember important structures. 4- Finally, extend search pattern to include orbits, sinuses, oropharynx, ears, craniocervical junction, face, vault and scalp. The "ABBCS System": A: Asymmetry: comparing one side with another. B: Blood:acute hemorrhage --> hyperdense compared to brain (Figure 1). Page 3 of 34

4 Fig. 1: Axial non-enhanced CT scan of the brain shows acute intracranial hemorrhage "hyperdense" (red arrows) in the right frontal lobe with perifocal edema "hypodense"(blue arrows). References: M. E. A. Noeman; Radiology Department, Akademishes Lehrkrankenhaus der Universitäts Rostock, Güstrow, GERMANY B: Brain: * Abnormal density: - Hyperdensity: acute blood, tumour, bone, contrast media. Page 4 of 34

5 - Hypodensity: edema/infarct, air and tumour (Figure 2). Fig. 2: A- Axial non-enhanced brain CT demonstrates finger-like focal edema in the left parietal lobe with compression of the left lateral ventricle and displacement of the interhemispheric fissure towards the right side. B- After administration of contrast media, it revealed a solitary intra-axial supratentorial focal lesion with ringenhancement "blue arrows" which turned to be brain metastases. References: M. E. A. Noeman; Radiology Department, Akademishes Lehrkrankenhaus der Universitäts Rostock, Güstrow, GERMANY * Displacement: - Midline shift (Figure 3). - Midline structures (falx cerebri, pituitary & pineal glands). - Asymmetry of CSF spaces. - Effacement of the basal cisterns and tonsillar herniation. * Grey/white matter differentiation (see later in early signs of infarction). Page 5 of 34

6 Fig. 3: Axial non-enhanced brain CT demonstrates extensive intracranial bleeding (red arrows) after brain contusion. Notice the total compression of the left lateral ventricle (yellow arrows) and the displacement of the midline towards the right side (blue arrows). Page 6 of 34

7 References: M. E. A. Noeman; Radiology Department, Akademishes Lehrkrankenhaus der Universitäts Rostock, Güstrow, GERMANY C: CSF spaces: Cisterns, sulci and ventricles. * Sizes of the ventricles and sulci, in proportion to each other and the brain parenchyma. * Normal cisterns (quadrigeminal plate, suprasellar and the mid brain region) and fissures (interhemispheric and Sylvian). * Pathology may be primary, within a ventricle, or may result from secondary compression from adjacent brain pathology. * Diffuse brain swelling can result in ventricular compression and reduced conspicuity of the normal sulcal/gyral pattern. S: Skull and scalp: Assess the scalp for soft tissue injury. * Useful in patients where a full history is absent. * Help to localise coup and contracoup injuries. * Assess the bony vault underlying a soft tissue injury for evidence of a fracture (Figure 4). * Assess the bony vault for shape, symmetry and mineralisation. * Adjust windowing to optimise bony detail. Page 7 of 34

8 Fig. 4: Axial non-enhanced brain CT with (bone window) demonstrates longitudinal fracture of the right petrous bone (red arrow). Notice the hypodene material (blue arrow)(most probably blood) in the middle ear. References: M. E. A. Noeman; Radiology Department, Akademishes Lehrkrankenhaus der Universitäts Rostock, Güstrow, GERMANY Main arterial blood supply of the brain: (Figure 5) Anterior cerebral artery (ACA): Supplies the medial part of the frontal and the parietal lobe and the anterior portion of the corpus callosum, basal ganglia and internal capsule. Middle cerebral artery (MCA): Page 8 of 34

9 Supplies the lateral surface of the hemisphere, except for the medial part of the frontal and the parietal lobe (ACA), and the inferior part of the temporal lobe (PCA). Posterior cerebral artery (PCA): Supplies parts of the midbrain, subthalamic nucleus, basal nucleus, thalamus, mesial inferior temporal lobe, and occipital and occipitoparietal cortices. Also supplies inferomedial part of the temporal lobe, occipital pole, visual cortex, and splenium of the corpus callosum. Besides, it is an important sources of collateral circulation for the middle cerebral artery (MCA) territory (18). Page 9 of 34

10 Fig. 5: Cerebral Arterial Territory: ACA: Anterior cerebral Artery, MCA: Middle cerebral Artery, PCA: Posterior cerebral Artery. References: M. E. A. Noeman; Radiology Department, Akademishes Lehrkrankenhaus der Universitäts Rostock, Güstrow, GERMANY Page 10 of 34

11 Early Signs of Stroke 1- Hypodensity of the brain tissue: Hypodensity = irreversible ischemic brain damage * Appearance: - It appears as area(s) of hypoattenuation compared to nearby normal brain tissues (Figure 6, 7). * Value: - It is highly specific for irreversible ischemic brain damage when detected within first 6 hours. - Patients who present with symptoms of stroke and who demonstrate hypodensity on CT within first six hours were proven to have larger infarct volumes, more severe symptoms, less favorable clinical courses and they even have a higher risk of hemorrhage. - The presence of hypoattenuation affecting more than one-third of the MCA territory is a contraindication for revascularization because it has been demonstrated that hemorrhagic complications are associated with larger established infarcted lesions before treatment (1). * Explanation: - The reason we see hypodensity on CT is that an ischemia cytotoxic edema develops as a result of failure of the ion-pumps. - These fail due to an inadequate supply of ATP. Page 11 of 34

12 Fig. 6: A- Axial non-enhanced brain CT shows a large area of hypoattenuation in the territory of the right MCA (red arrows), after 24 hours of onset of clinical symptoms. BSame patient after 48 hours. Notice the well-demarcation of the Infarction. References: M. E. A. Noeman; Radiology Department, Akademishes Lehrkrankenhaus der Universitäts Rostock, Güstrow, GERMANY Page 12 of 34

13 Fig. 7: Axial non-enhanced CT scans show: A) Hypodensity in the middle 1/3 of the territory of the left MCA (parietal lobe). B) Hypodensity in the posterior 1/3 of the territory of the right MCA (temporal lobe). C) Hypodensity in the territory of the right ACA (frontal lobe). D) Hypodensity in the territory of the left PCA (occipital lobe). References: M. E. A. Noeman; Radiology Department, Akademishes Lehrkrankenhaus der Universitäts Rostock, Güstrow, GERMANY 2- The insular ribbon sign: Page 13 of 34

14 * Anatomy: - The insula or island of Reil is an "island" of cortex that lies at the base of the sylvian fissure, overlying the extreme capsule and claustrum. - The insular ribbon refers to the island of Reil, extreme capsule, and claustrum. * Appearance: - It is the loss of graywhite interface definition, reflects cytotoxic edema and relates to specificity of arterial anatomy. * Explanation: - The insular ribbon is supplied exclusively by the insular segment of the middle cerebral artery (MCA) and its claustral branches. - With interruption of MCA flow, the insular ribbon becomes the region most distal from the anterior and posterior cerebral collateral circulations (17,20). Fig. 17: Insular ribbon sign on the left in axial non contrast CT images, obtained in a 58-year-old man (a) 3 and (b) 26 hours after the onset of symptoms. References: G. Krumina; MR, CT and US centre, Medical Academy of Latvia, Riga, LATVIA 3- Disappearing basal ganglia sign: Page 14 of 34

15 * Anatomy (Figure 8): - The basal ganglia include the caudate nucleus, amygdala, claustrum, internal capsule, external capsule, extreme capsule, and lentiform nucleus. - The lentiform nucleus comprises the globus pallidus and putamen. - The caudate nucleus, globus pallidus, and putamen are collectively referred to as the corpora striatum. Page 15 of 34

16 Fig. 8: Anatomy of the basal ganglia References: M. E. A. Noeman; Radiology Department, Akademishes Lehrkrankenhaus der Universitäts Rostock, Güstrow, GERMANY * Appearance: Page 16 of 34

17 - It appears as a loss of the normal delineation of the basal ganglia, with the affected basal ganglia exhibiting abnormal morphologic features (Figure 9). - This is best appreciated when a comparison is made between the affected basal ganglia and the contralateral side of the brain. * Explanation: - Normally, the lentiform nucleus and caudate nucleus are slightly hyperattenuated when compared with the surrounding white matter. When present, a vascular insult will usually manifest at CT as areas of hypoattenuation (Figure 10). - Is caused by MCA occlusion proximally to lenticulostriate arteries. Involvement of the lenticulostriate territory indicates that a proximal M1 occlusion must have been present (7,12). * DD considerations: - Include arterial dissection, trauma, vasculitis, and hemolytic uremic syndrome (7,12). Page 17 of 34

18 Fig. 9: Axial non-enhanced brain CT demonstrates the disappearance of the lateral border of the left basal ganglia in acute stroke patient. References: M. E. A. Noeman; Radiology Department, Akademishes Lehrkrankenhaus der Universitäts Rostock, Güstrow, GERMANY Page 18 of 34

19 Fig. 10: Axial non-enhanced brain CT demonstrates well-demarcated infarction of the right basal ganglia (red arrows) in acute stroke patient. References: M. E. A. Noeman; Radiology Department, Akademishes Lehrkrankenhaus der Universitäts Rostock, Güstrow, GERMANY 4- Loss of grey/white differentiation: * Appearance: Page 19 of 34

20 - Appears as loss of the normal distinction between the grey matter and the white matter (Figure 11). * Explanation: - White matter is of slightly reduced attenuation compared to grey matter due to increased fatty myelin content. - In an early infarct, oedema leads to loss of this differentiation. Fig. 11: A) Axial non-enhanced brain CT of acute stroke patient demonstrating loss of grey/white matter differentiation in the posterior 1/3 of the territory of the right MCA (red arrows) as an early sign of infarction compared to normal brain tissues on the normal left side (blue arrow). Note the old posterior infarction on the left side (green arrows). B) Axial non-enhanced brain CT demonstrates loss of grey/white matter differentiation in the territory of right MCA (blue arrows). References: M. E. A. Noeman; Radiology Department, Akademishes Lehrkrankenhaus der Universitäts Rostock, Güstrow, GERMANY 5- Hyperdense artery sign: The hyperdense artery sign represents stasis of flow due to arterial thrombus, most frequently seen in MCA. a) Hyperdense middle cerebral artery sign (HMCAS)(Figure 12, 13): * Incidence: Page 20 of 34

21 - It has been reported that HAS in MCA is present in 75% of the infarctions in the first 90 minutes and in 15% from hour 12 to hour 24 (9). * Value: - The presence or absence of (HMCAS) on NCCT can predict also the thrombus volume. - Thrombus volumes are significantly larger in patients with HMCAS than in those without HMCAS in ICA and M1 occlusions. - An association between a hyperattenuating MCA sign and the location of infarction has also been found. Patients with a proximal hyperattenuating MCA sign developed cortical and larger deep MCA infarctions more often(10). * DD: - False positive sign have been documented in patients with calcified atherosclerosis or high hematocrit levels (10). Fig. 12: a) Axial non-enhanced brain CT image shows hyperattenuation in the proximal (M1) segment of the left MCA "hyperdense MCA-Sign"(red arrow). b) reformatted images from CT-angiography of the same patient show the apparent absence of the same vessel segment(red arrows) compared to the normal vessel right MCA (blue arrows). References: M. E. A. Noeman; Radiology Department, Akademishes Lehrkrankenhaus der Universitäts Rostock, Güstrow, GERMANY Page 21 of 34

22 Fig. 13: A) Axial non-enhanced brain CT demonstrates "hyperdense MCA sign" of the left MCA. B) 3D-Reconstruction image of the intracranial circulation demonstrates the occlusion of the left MCA confirming the diagnosis. References: M. E. A. Noeman; Radiology Department, Akademishes Lehrkrankenhaus der Universitäts Rostock, Güstrow, GERMANY b) Hyperdense dot sign (Figure 14, 15): It is a variant of the hyperdense vessel sign and is relatively recent added symptom on non contrast CT in the setting of suspected acute stroke. * Definition: - It is a punctate focus of hyperattenuation located in the sylvian fissure and is seen on a noncontrast CT (2). - To be properly applied, the MCA dot sign should have a higher attenuation than any other visible vessel. * Explanation: - It represents a thromboembolus within a segmental branch of the MCA located within the sylvian fissure (M2 or M3 segment). - The sign appears when this highattenuation structure is viewed in cross section, since the occluded vessel courses in a plane perpendicular to the transverse plane of imaging (14). * Value: Page 22 of 34

23 - MCA dot sign is important for the thrombolytic therapy selection and prognosis. Patients with MCA dot sign are good candidates for thrombolysis, as it reflects more distal vessel occlusion and therefore suggests a smaller territory at risk (15). * DD: - Calcification associated with intracranial atherosclerosis, however, these smaller-caliber intracranial vessels are less likely to be affected by atherosclerosis than larger intracranial vessels (13). Fig. 14: Axial non-enhanced brain CT demonstrates: a) Hyperdense dot sign in the right sylvian fissure. b) Same patient after 8 hours with demarcated infarct in the territory of the right MCA. References: M. E. A. Noeman; Radiology Department, Akademishes Lehrkrankenhaus der Universitäts Rostock, Güstrow, GERMANY Page 23 of 34

24 Fig. 15: Axial non-enhanced brain CT demonstrates "hyperdense dot sign" typically in the left sylvian fissure as an early sign of acute stroke. References: M. E. A. Noeman; Radiology Department, Akademishes Lehrkrankenhaus der Universitäts Rostock, Güstrow, GERMANY c) Hyperdense posterior artery sign (HPCA): Page 24 of 34

25 * Definition: - It is a hyperdensity seen within the ambient cistern, medial to the tentorium cerebelli (Figure 16). - Is typically visualized in 1 or 2 adjacent slices and can extend into the quadrigeminal cistern. - Is a marker of acute ischemia in the posterior cerebral artery (PCA) territory. * Incidence: - This sign is detected with good interobserver reliability in more than one third of all patients with PCA ischemia (6). * Value: - The sign is often associated with thalamic infarction, large PCA territory ischemia, more severe neurological symptomatology, and a higher risk of hemorrhagic transformation. - Therefore, it may not only be helpful in the early diagnosis of PCA infarction but might also act as a prognostic marker in acute PCA territory ischemic stroke (6). Fig. 16: Axial non contrast CT images, obtained in a 64-year-old female 7 hours after the onset of symptoms: hyperdense posterior artery sign a, black arrow ), corresponding large PCA territory ischemia (b). References: G. Krumina; MR, CT and US centre, Medical Academy of Latvia, Riga, LATVIA Page 25 of 34

26 Images for this section: Fig. 5: Cerebral Arterial Territory: ACA: Anterior cerebral Artery, MCA: Middle cerebral Artery, PCA: Posterior cerebral Artery. Page 26 of 34

27 Fig. 6: A- Axial non-enhanced brain CT shows a large area of hypoattenuation in the territory of the right MCA (red arrows), after 24 hours of onset of clinical symptoms. BSame patient after 48 hours. Notice the well-demarcation of the Infarction. Page 27 of 34

28 Fig. 8: Anatomy of the basal ganglia Page 28 of 34

29 Fig. 12: a) Axial non-enhanced brain CT image shows hyperattenuation in the proximal (M1) segment of the left MCA "hyperdense MCA-Sign"(red arrow). b) reformatted images from CT-angiography of the same patient show the apparent absence of the same vessel segment(red arrows) compared to the normal vessel right MCA (blue arrows). Page 29 of 34

30 Fig. 13: A) Axial non-enhanced brain CT demonstrates "hyperdense MCA sign" of the left MCA. B) 3D-Reconstruction image of the intracranial circulation demonstrates the occlusion of the left MCA confirming the diagnosis. Page 30 of 34

31 Conclusion Stroke is usually encountered by young radiologists, with ischemic stroke accounting for nearly 80% of cases. Thrombolytic therapy with recombinant tissue plasminogen activator (rt-pa) is the treatment of choice for ischaemic stroke presenting within 3 hours of clinical onset, provided that there is no contraindication to this treatment, including exclusion of intracranial haemorrhage by CT. Thus, recognition of early features is vitally important as it minimises morbidity and mortality. CT of the brain remains the modality of choice and the gold standard for initial assessment of acute stroke in most institutions being rapid, reliable, readily-available tool and can distinguish between stroke and its clinical mimics - potentially reducing the risk of postthrombolysis complications. Personal Information Mohammed Noeman Radiology Resident Department of Diagnostic and Interventional Radiology KMG Klinikum Güstrow Academic Teaching Hospital of the University of Rostock Güstrow - Germany dr_noman99@hotmail.com Images for this section: Page 31 of 34

32 Fig. 18: Diagnostic and Interventional Department KMG Klinikum Güstrow Page 32 of 34

33 References (1) Acute stroke: usefulness of early CT findings before thrombolytic therapy by R von Kummer et al. Radiology 1997, Vol 205, , (2) Barber PA, Demchuk AM, Hudon ME, Pexman JH, Hill MD, Buchan AM. Hyperdense sylvian fissure MCA "dot" sign: a CT marker of acute ischemia. Stroke 2001;32: (3) Bogousslavsky J, Kaste M, Skyhoj Olsen T, et al. Risk factors and stroke prevention: European Stroke Initiative (EUSI). Cerebrovasc Dis 2000; 10:12-21 (4) Brain Ischemia - Imaging in Acute Stroke, by Majda Thurnher Department of Radiology, Medical University of Vienna (online) (5) Brain CT in Clinical Practice: Usiakimi Igbaseimokumo, Springer e-isbn (6) Brandt T, Steinke W, Thie A, Pessin MS, Caplan L. Posterior cerebral artery territory infarcts: clinical features, infarct topography, causes and outcome. Cerebrovasc Dis. 2000;10: (7) Dahnert W. Radiology review manual. Philadelphia, Pa: Lippincott Williams & Wilkins, 2000; 197. (8) Interpretation of Emergency Head CT, A Practical Handbook, Erskine J. Holmes, MRCS (9) G. Krumina; CT or MRI in the acute ischemic stroke? Poster No.: A-273, ECR 2010 (10) Kharitonova T, Thorén M, Ahmed N, Wardlaw J M, von Kummer R, Thomassen L, Wahlgren N. Disappearing hyperdense middle cerebral artery sign in ischaemic stroke patients treated with intravenous thrombolysis: clinical course and prognostic significance. J Neurol Neurosurg Psychiatry 2009;80: (11) Latchaw R, Alberts M, Lev M, Connors J, Harbaugh R, Higashida R, Hobson R, Kidwell C, Koroshetz W, Mathews V, Villablanca P, Warach S, Walters B. Page 33 of 34

34 Recommendations for Imaging of Acute Ischemic Stroke. A Scientific Statement From the American Heart Association. Stroke. 2009;40:3646 (12) Osborn A, Tong K. Handbook of neuroradiology: brain and skull. St Louis, Mo: Mosby, 1996; 52-53, (13) Rauch RA, Bazan C 3rd, Larsson EM, Jinkins JR. Hyperdense middle cerebral arteries identified on CT as a false sign of vascular occlusion. AJNR Am J Neuroradiol 1993;14: (14) Rutgers DR, van der Grond J, Jansen GH, Somford DM, Mali WP. Radiologicpathologic correlation of the hyperdense middle cerebral artery sign: a case report. Acta Radiol 2001;42: (15) Somford DM, Nederkoorn PJ, Rutgers DR, Kappelle LJ, Mali WP, van der Grond J. Proximal and distal hyperattenuating middle cerebral artery signs at CT: different prognostic implications. Radiology 2002;223: (16) State-of-the-Art Imaging of Acute Stroke by Ashok Srinivasan et al RadioGraphics 2006;26:S75-S95 (17) Tanriover N, Rhoton AL, Kawashima M, Ulm AJ, Yasda A. Microsurgical anatomy of the insula and the sylvian fissure. J Neurosurg May;100(5): (18) The vascular territories of the carotid and vertebrobasilar systems. Diagrams based on CT studies of infarcts. by Savoiardo M. Ital J Neurol Sci Aug;7(4): (19) Tissue plasminogen activator for acute ischemic stroke. The National Institute of Neurological Disorders and Stroke rt-pa Stroke Study Group. N Engl J Med 1995; 333: (20) Truwit CL, Barkovich AJ, Gean-Marton A, Hibri N, Norman D. Loss of the insular ribbon: another early CT sign of acute middle cerebral artery infarction. Radiology, 1990 Sep;176(3):801-6 Page 34 of 34