stroke

1. CT SCAN , MRI IN STROCKE
• DR. SAAD ALYOUSEF
QATAR RED CRESCENT- AL HEMAILA CENTRE
• SYRIAN BOARD /DIGNOSTIC RADIOLOGY

2. Stroke - Definition and Statistics
• ƒAcute, vascular injury to CNS
• <24 hrs = TIA
• >24 hrs = stroke (CVA)
• ƒAffects 600,000 people/ yr
• (that is 1 stroke per minute!)
• ƒIs #3 cause of mortality in adults
• Is #1 cause of disability

3. Types of Stroke
• ƒHemorrhagic (20%)
• ƒusually hypertensive hemorrhage
• ƒIschemic (80%)
• ƒ Thrombotic (40%)
• ƒintracerebral atherosclerosis
• ƒ Embolic (60%)
• ƒCardiac embolus (thrombus, tumor, septic embolus)
• ƒartery-to-artery (mainly carotid thrombus)
• ƒParadoxical embolus (thrombus, fat, air)

4. Risk Factors for Stroke
• ƒAtherosclerosis risk factors
• ƒFamily history of CVA, TIA, or MI
• ƒHypertension
• ƒSmoking
• ƒDiabetes
• ƒHypercholesterolemia
• ƒPrevious CVA, TIA, or MI
• ƒAtrial fibrillation

5. Differential Diagnosis
• ƒMany CNS diseases can mimic ischemic
• stroke
• ƒHemorrhage
• ƒMass lesion (tumor, abscess, AVM)
• ƒSeizure (Todd’s paralysis)
• ƒHemiplegic migraine
• ƒMS flare
• ƒVenous infarct

6. • Goals of Imaging in Acute Stroke
• 1. Rule in or out other disease processes
• 2. Define location, extent and age of infarct

7. Cerebrovascular Anatomy

8. Imaging Modalities in Acute Stroke
• ƒCT without contrast
• ƒConventional MRI
• ƒDiffusion-Weighted and Perfusion MRI
• ƒMRA

9. CT Imaging in Acute Stroke
• ƒInitial test of choice
• ƒBest modality for
detecting hemorrhage
• ƒIdentifies mass lesions
(tumor, abscess, AVM)
Fast and readily available
Crucial for stroke triage
(rule in/out other diseases)

10. CT Imaging in Acute Stroke
• HOWEVER,
CT is poor at detecting
acute infarcts
• Only 40% sensitivity <24 h
• Film Findings :
• Normal Initial Head CT
• 2 hours post stroke
Patient #1 1-2 hrs post stroke

11. CT SCAN 8 hours later

15. • Therefore, other imaging
modalities are used to detect
strokes < 6 hours!

16. Imaging Modalities in Acute Stroke
• CT without contrast
• Conventional MRI
• Diffusion-Weighted and Perfusion MRI
• MRA

18. CT SCAN EARLY SIGN
• Hypo attenuating brain tissue
• Obscuration of lentiform nucleus
• Dense MCA sign
• Insular ribbon sign
• Loss of sulcal effacement

19. Hypo attenuating brain tissue
• MCA infarction: on CT an
area of hypo attenuation
appearing within six
hours is highly specific
for irreversible ischemic
brain damage

20. Obscuration lentiform nucleus
Axial unenhanced CT image
shows hypo attenuation and
obscuration of the left
lentiform nucleus (arrows),
which, because of acute
ischemia in the lenticulostriate
distribution, appears
abnormal in comparison with
the right lentiform nucleus.

21. Obscuration lentiform nucleus
Axial unenhanced CT images show obscuration of the right lentiform nucleus (arrow in b). This feature is less
visible with the routine brain imaging window used for a (window width, 80 HU; center, 35 HU)
than with the narrower window used for b (window width, 10 HU; center, 28 HU).

22. Insular ribbon Sign
Axial unenhanced CT image, shows
hypo attenuation and obscuration of the
posterior part of the right lentiform
nucleus (white arrow) and a loss of gray
matter–white matter definition in the
lateral margins of the right insula (black
arrows).The latter feature is known as
the insular ribbon sign.

23. Insular ribbon Sign

24. Conventional MR Imaging in Acute
Stroke
• Conventional MRI can detect acute infarcts
slightly earlier than CT
• Additional techniques are still needed for
early stroke detection

25. Conventional MR Imaging in Stroke
? Absent R. MCA Flow Void
(suggestive of MCA occlusion)

26. Diffusion Weighted MRI Imaging
(DWI)
Osmotic pump failure is 1st event in ischemia
Fluid shift extracellular>intracellular
Water in cells now can’t diffuse!
diffusion coefficient (ADC)
restriction of diffusion (DWI)
Detects change within 30 minutes
of onset of stroke

27. Timing of stroke detection
• Imaging Modality Time of post-stroke imaging
2H 8H 30H
• CT without contrast _ + +
• Conventional MRI _ ND +
• DWI MRI + ND +
• MRA + ND +
+ = evidence of acute stroke; - = no evidence of acute stroke; ND = not determined

28. DIFFERENTIAL DIAGNOSIS
Stroke on NECT
• Tumor
• Old Blood clot
– EDH
– SDH
• Abscess
• Brain Edema
• Trauma

29. Tumor
• Mets from CA breast

30. Chronic Hemorrhage
• CT axial- left chronic frontoparietal
subdural hematoma, hypo intense
area.
• Subacute hemorrhage

31. Abcess
• NECT
• CECT

32. Brain Edema

33. Traumatic Contusion

34. CTA
• Insular ribbon sign in
right insular cortex
• CTA disclose
thrombus in rt. MCA

35. CT Perfusion (CTP)
• With CT and MR imaging we can get a good
impression of the area that is infracted.
• but we cannot preclude a large ischemic penumbra
(tissue at risk).
With perfusion studies we monitor the first pass of
an iodinated contrast agent bolus through the
cerebral vasculature.
Perfusion will tell us which area is at risk.
Approximately 26% of patients will require a
perfusion study to come to the proper diagnosis.

36. MRI
• On PD/T2WI and FLAIR infarction is seen as high SI.
• These sequences detect 80% of infarctions before
24 hours.
• They may be negative up to 2-4 hours post-ictus!
• MR Hperintensity = CT Hypodensity

37. • T2WI and FLAIR
demonstrating
hyperintensity in
the territory of the
middle cerebral
artery.
• Notice the
involvement of the
lentiform nucleus
and insular cortex.

38. Diffusion Weighted Imaging (DWI)
• DWI is the most sensitive sequence for stroke
imaging.
• Also called Stroke sequence

39. DWI in posterior, anterior and middle cerebral
infarction
Diffusion Weighted Imaging (DWI)

40. Diffusion Weighted Imaging (DWI)
• very subtle hypodensity and swelling in the left frontal
region with effacement of sulci compared with the
contralateral side.
• DWI shows marked superiority in detecting infarct

41. Hemorrhagic Stroke
• Intra-axial haemorrhage
– intracerebral haemorrhage
– basal ganglia haemorrhage
– lobar haemorrhage
– pontine haemorrhage
– cerebellar haemorrhage
• Intraventricular haemorrhage (IVH)
• extra-axial haemorrhage
– extradural haemorrhage (EDH)
– subdural haemorrhage (SDH)
– subarachnoid haemorrhage (SAH)

42. Intracerebral Hemorrhage
• Large intracerebral
hemorrhage with midline shift

43. ICH with Intraventricular Extension

44. Basal Ganglia Hemorrhage with IC
extension

45. Subarachnoid Hemorrhage

46. THANX