Case Presentation

1. Neuroimaging of Stroke Andrew Perron, MDAssistant ProfessorDepartment of Emergency MedicineUniversity of VirginiaCharlottesville, VA

2. Case Presentation • Community ED • No Neurologist • Radiologist…65 minutes away • No teleradiology • CT scanner

3. Case Presentation • 58 year old female • 2 hours 15 minutes of dysarthria, right sided weakness • “Mildly obtunded” per EMS • Code Stroke called (gets you and CT scan tech ready)

4. Case Presentation • Dysarthric, weak RUE/RLE, NIHSS = 18 • Toes up-going bilaterally • Family relates a few weeks of left arm tingling and clumsiness • Off to CT…returns with the films on the bed • Nurse asks if you are going to read the CT, since only 15 minutes left before the 3 hour mark (Radiologist still 45 minutes away)

5. Head CT

6. Dense MCA Insular Ribbon Sign ECASS Criteria Visible vessel Stroke Mimic Diffusion/Perfusion NINDS Criteria

7. Cranial CT Scanning • First line imaging study in suspected stroke patients • Exquisite sensitivity for the detection of blood • Ubiquitous in hospitals • Fundamental branch point in the work up of a suspected stroke patient

8. 3 Possible CT Findings • Stroke Mimic • Non-stroke mass lesion (Abscess, Tumor) • Intracerebral Hemorrhage • Subarachnoid Hemorrhage • Normal CT • Cerebral Infarction

9. Stroke Mimics • Tumor • Blood clot • EDH • SDH • SAH • IPH • Abscess

10. Stroke Mimics • Blood clot EDH SDH

11. Stroke Mimics • Subarachnoid Hemorrhage

12. Stroke Mimics • Subarachnoid Hemorrhage

13. Stroke Mimics • Intraparenchymal Hemorrhage/IVH

14. CT scan fundamentals • Even 3rd and 4th generation scanners will not demonstrate acute ischemic stroke in the first few hours • “Normal CT Scan” is the most common CT finding in the patient with acute stroke

15. CT scan fundamentals • Gray matter is more susceptible to ischemia than white matter • More metabolically active • Loss of gray-white differentiation is the earliest CT change • Due to edema in the gray matter

16. Grey-White Differentiation

17. CT scan fundamentals • Subtle edema can be seen in < 1 hour • By 6 hours, 3/4 of patients with MCA strokes will show edema in the insular cortex • “Insular Ribbon Sign” • After12-24 hours, additional edema is recruited into the area • Lesion will become conspicuous on CT

18. Cerebral Infarction • Hyperdense Artery Sign • Insular Ribbon Sign • Loss of Cortical Gray-White Differentiation • Mass Effect

19. Hyperdense Artery Sign • Typically MCA, PCA, or ACA • Indicates a major vessel occlusion with thrombus formation • False positives can occur • Unilateral calcification • ICA or MCA proximal trunk occlusions more serious than occlusions of MCA branches, PCA, or ACA

20. Hyperdense Artery Sign

21. Hyperdense Artery Sign • Whether the at risk territory will undergo ischemic necrosis is a matter of collateral blood supply • Therefore, this is NOT an infarct sign • Indicates the volume of at risk tissue • If collateral supply fails • Recanalization not achieved

22. Insular Ribbon Sign • Area of extreme gray-white differentiation in the MCA artery territory • Located between the sylvian fissure and the basal ganglia • Supplied by perforators off of the MCA

23. Insular Ribbon Sign • Loss of the insular stripe is one of the earliest indications of MCA stroke • Normal stripe = Thin white line (gray matter) adjacent to darker gray line (subcortical white matter) • Ischemia effects metabolically active gray-matter • Causes intracellular edema

24. Insular Ribbon Sign

25. Insular Ribbon Sign • With ischemia • Insular stripe is lost • Homogeneous appearance is noted • NOT an exclusion criterion for thrombolytic therapy • Should prompt re-confirmation of stroke ictus reported by patient/family

26. Loss of Cortical Gray-White Differentiation • Similar process as loss of insular stripe • Loss of cortical gray-white indicates edema in metabolically active gray-matter • ECASS studies have suggested withholding t-PA from patients with > 1/3 of the MCA territory effected by de-differentiation • Increased risk for hemorrhagic conversion

27. Loss of Cortical Gray-White Differentiation

28. Loss of Cortical Gray-White Differentiation • No similar rules for anterior/posterior circulation • Interobserver consistency for defining 1/3 of MCA territory de-differentiation is low • Use as an exclusion criterion is controversial

29. Mass Effect • Brain swelling is extremely subtle in the first hours after arterial occlusion • Sulcal effacement • CSF space compression • Ventricular shift • Swelling often not visible for the first 6 hours

30. Mass Effect

31. Mass Effect • In ECASS, 21% of initial CT scans demonstrated focal brain swelling • Associated with a poorer outcome • Use as an Exclusion Criterion is controversial

32. Summary for t-PA: Inclusion • No evidence of : • Hemorrhage • EDH/SDH • IPH • SAH • Non-stroke etiology • Tumor • Abscess • Trauma

33. Summary for t-PA: Relative Contraindications • Controversial • Evidence of a large MCA territory infarction • Gray-white de-differentiation > 1/3 of territory • Sulcal effacement/mass effect > 1/3 of territory

34. Future Trends • MRI/MRA • MR diffusion/perfusion/spectroscopy • Transcranial doppler • PET (Positron Emission) /SPECT (Single Photon Emission)

35. Returning to our case…Diagnosis?

36. Our Case • Acute L MCA stroke (Loss of insular ribbon, gray-white differentiation) No Blood…done? Gray/white Insular ribbon Gray/White

37. Our Case • Right frontal tumor with edema Tumor Edema

38. Our Case • Thrombolysis witheld due to tumor • Patient transferred to neurosurgical center • Craniotomy yields diagnosis of astrocytoma

39. Questions?