Ischemic Lesions as seen on CT/MRI

1. Ischemic Lesions as seen on CT/MRI Ryan Hakimi, DO, MS Associate Professor Director, Critical Care Neurology Emmaculate Fields, APRN-CNP Clinical Instructor Department of Neurology The University of Oklahoma Health Sciences Center

2. DISCLOSURES • FINANCIAL DISCLOSURE • Nothing to disclose • UNLABELED/UNAPPROVED USES DISCLOSURE • Nothing to disclose • Some of the slides have been adapted from teaching materials used at the University of Oklahoma Health Sciences Center

3. LEARNING OBJECTIVES Upon completion of this course, participants will be able to: • Describe the significance of neuroimaging in the management of patients presenting with ischemic stroke • Identify the various neuroimaging tools available to clinicians to aid in the management of patients with ischemic stroke • Distinguish the common neuroimaging findings in patients with ischemic stroke that help identify the underlying etiology

4. Ischemic lesions • Ischemic strokes occur more so than hemorrhagic strokes • Ischemic strokes approximately 80- 85% of all strokes • Cerebrovascular disease- 20% • Lacunar disease-20% • Embolism-20% • Cryptogenic-30%

5. Neuroimaging in acute stroke CT MRI MRI if CT contraindicated such as with pregnancy DWI identifies ischemic lesions within minutes, distinguish recent (within 2 weeks) infracts from chronic infarcts. MRA detects vascular abnormalities that led to the stroke (stenosis/occlussion, aneurysm, vascular malformation) DWI and MRA are well-established techniques, perfusion MRI is still largely investigational but promising. • Non contrast CTH usually the first study done widely given it is quickly accessible, cheap and fast. • Accurately demonstrates intracranial hemorrhage • Demonstrates the extent of infarction with limitations of posterior circulation • Contrast enhancement can provide CT angiographic and perfusion information • CTA/MRA to identify vascular lesion responsible for diagnosis

6. CTA VS MRA CTA MRA MR angiography (MRA) of the head does not require contrast administration as it uses time-of-flight imaging that eliminates the risk of a serious allergic reaction and contrast induced nephropathy. In addition, radiation exposure is avoided. The sensitivity and specificity of 1.5 Tesla MRA is lower the than that of modern multi-slice CTA studies • CT angiography (CTA) is performed by combining the intravenous administration of iodinated contrast material and CT scanning to evaluate vascular related conditions, such as aneurysms or stenoses. • Disadvantages of CTA include radiation exposure and contrast administration with subsequent risk of contrast induced nephropathy and serious allergic reaction.

7. Digital Subtraction Cerebral Angiography (DSA) • Most invasive neuroimaging technique utilized in the assessment of patients with ICH. • It involves placing a femoral sheath introducer in either right or left common femoral artery followed by the introduction and advancement of a catheter in to the artery of interest under direct fluoroscopy. Contrast is then injected through the catheter and images are obtained using time-controlled X-rays. The images are subtracted from a ‘pre-contrast image,’ hence the term ‘digital subtraction angiography’. • Complications such as stroke, vessel dissection, vessel perforation, contrast allergic reaction, contrast induced nephropathy, groin hematoma etc. as well as exposure to radiation.

8. A B Day 1 Acute infarction Day 3 Subacute infarction NONCONTRAST CT BRAIN: ISCHEMIC STROKE (= CEREBRAL INFARCTION) • In 1st few hours to day, CT usually normal (though may show blurring of gray-white junction & sulcal effacement as seen on next slide) • By day 2, CT shows dark area with mass effect (compression of surrounding structures)

9. Normal gray-white junction (distinct ribbon of cortical gray matter) Large, acute MCA-territory infarction with: 1) blurring of gray-white junction & 2) sulcal effacement Normal sulcus NONCONTRAST CT SCAN:ACUTE CEREBRAL INFARCTION (4 HOURS) R L R Description L Description

10. Subacute infarction is dark (hypodense) with mass effect (note: this is cytotoxic edema, occurring 2-5 days after ischemia & affecting both gray and white matter) Normal lateral ventricle Compressed lateral ventricle NONCONTRAST CT SCAN: SUBACUTE CEREBRAL INFARCTION (4 DAYS) R L R Description L Description

11. ACA MCA AChA PCA Middle cerebral artery Anterior cerebral artery Posterior cerebral artery Anterior choroidal artery CT SCAN OF THE BRAIN ARTERIAL TERRITORIES

12. Thalamus MRA axial view Occipital lobe • VF deficit (contra) • Hemisensory loss (contra, F/A/L) Subacute infarction in proximal PCA territory involving both thalamus and occipital lobe; note that a distal PCA occlusion spares the thalamus CT SCAN OF THE BRAIN INFARCTION ARTERIAL PATTERN 4 D E S C R I P T I O N

13. ACA-MCA watershed PCA-MCA watershed • Neurobehavior deficits • VF deficits &/or visual hallucinations (Motor deficits are minimal to nonexistent in watershed strokes) Infarctions in watershed territories (arrows); in this case, L > R (with concurrent left LMCA infarction outlined with broken line) due to hypotension in patient with LICA occlusion and RICA stenosis (“watershed” and “borderzone” are equivalent terms) CT SCAN OF THE BRAININFARCTION ARTERIAL PATTERN 5Click on box to make description appear and disappear D E S C R I P T I O N

14. FLAIR DWI ADC ACUTE CORTICAL INFARCTION: MIDDLE CEREBRAL ARTERY (MCA) BRANCHTERRITORY INFARCTION • The lesion is a recent infarction (< a few weeks) since it is seen on both DWI and ADC New MCA branch infarct

15. MRI sequences T1 sequence T2 sequence Gliosis from old infarcts

16. MRI sequences-cont’d. Gliosis from old infarcts DW1 New infarct ADC New infarct Flair

17. ACUTE SUBCORTICAL INFARCTION ANTERIOR CHOROIDAL ARTERY (AChA) TERRITORY INFARCTION • The lesion is a recent infarction (< a few weeks) since it is seen on both DWI and ADC AChA Territory FLAIR DWI ADC New AChA infarct

18. MRA axial view MRI DWI R AChA Territory • Common: • hemiparesis (contra, F/A/L) • hemisensory loss (contra, F/A/L) • Less common • hemianopsia • aphasia (L) • neglect (R) • other lacunar syndromes P Infarction in anterior choroidal artery (AChA) territory in subcortical white matter, in this case, posterior limb internal capsule; the AChA is a very small artery not usually seen on MRA or even catheter angiography that originates from the distal ICA or, less commonly, the proximal MCA; because it is small and comes off the ICA at a right angle, AChA-territory infarctions are usually due to small-artery disease, though complete AChA-territory infarctions may be due to embolism. ANTERIOR CHOROIDAL ARTERY (AChA)TERRITORY INFARCTION:ANATOMY & CLINICAL SYNDROME

19. MRI DWI MRA coronal view ACUTE BRAINSTEM INFARCTIONPOSTERIOR INFERIOR CEREBELLAR ARTERY (PICA) TERRITORY INFARCTION • Crossed pin sensory loss (ipsi face, contra body) • Vertigo, nausea • Dysphagia, hoarseness • Horner syndrome (ipsi) • Hemi-ataxia (ipsi) Acute infarction in PICA territory involving lateral medulla; PICA occlusions are nearly always due to embolism, vertebral artery atherothromboembolism more often than cardioembolism; called lateral medullary syndrome or Wallenburg syndrome

20. References • Greer, D. M. (2007). Acute Ischemic Stroke : An Evidence-based Approach. Hoboken, N.J.: Wiley-Liss • Ramani, N. V., & Gan, R. N. (2008). The Stroke Clinician's Handbook : A Practical Guide to the Care of Stroke Patients. New Jersey: World Scientific Publishing Company. • Silverman, I. E., & Rymer, M. M. (2009). Ischemic Stroke : An Atlas of Investigation and Treatment. Oxford: Clinical Publishing.

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