1. Neuroimaging of Stroke Andrew Perron, MD Assistant Professor Department of Emergency Medicine University of Virginia Charlottesville, VA 54 1 54

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 Normal CT Cerebral Infarction
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?