The document outlines key aspects of acute stroke diagnosis using imaging techniques, emphasizing the importance of a multimodal CT protocol which includes NCCT, CT angiography, and perfusion CT. It discusses the Alberta Stroke Program Early CT Score (ASPECTS) for assessing infarct volume and highlights critical signs indicating malignancy in MCA infarctions. Additionally, it compares the efficacy of MRI in detecting strokes, especially in differentiating between ischemic penumbra and core infarcts.

1. Presenter: Dr. Vipul Phogat
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2. 20% cases- wrongly diagnosed clinically!!!!!!!!!
To decide treatment
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3. Acute stroke
• Hyperacute stroke: 0-6hrs
• Acute stroke: 6-48hrs
3

4. Acute stroke CT protocol
• A multimodal protocol including
1. NCCT brain
2. CT angio neck + brain vessels ( not MR angio- motion artefacts)
3. Perfusion CT
• All can be done within 15 mins with helical acquisition with separate contrast
boluses.

5. NCCT
Initial vs late parenchymal signs
Initial hours (0-3)
Lost GM-WM differentiation
After 24 hours
Well delineated hypodensity with
cortical sulcal effacement

6. NCCT
Other Initial signs
Hyperdense MCA sign Dense artery sign
Hyperdense MCA
Normal MCA
Hyperdense basilar artery
Infarct
Dot sign
M2
M2
M3

7. NCCT
Other signs
Insular ribbon sign
Hypodense Rt insula
Disappearing BG sign
Hypodense
Rt BG Normal
Lt BG
Calcified emboli
Old infarcts
Calcified
emboli
Calcified
emboli

8. ASPECT score
Alberta Stroke Program Early Computed Tomography Score
• Can be applied to both CT
and MR
• A 10 point score. 1 point
subtracted for each region
affected.
• MCA cortex= 6 points
• Subcortical structures= 3
points
• Insular ribbon= 1 point
• Score <7= >1/3rd MCA
territory involvement

9. pc-ASPECTS
• MIDBRAIN- 2 POINT OCCIPITAL LOBES- 1 POINT EACH
• PONS- 2 POINT CEREBELLUM- 1 POINT EACH
• THALAMI- 1 POINT EACH

10. NCCT
Malignant MCA infarct
• More than 1/3rd MCA territory involved i.e ASPECT score <7
• C/F: Rapid deterioration of consciousness, headache, vomiting,
• Pathology: Severe cerebral swelling,
• Importance: increased risk of-
‣ Hemorrhagic transformation on thrombolysis
‣ Transtentorial herniation
‣ Brainstem compression
From BMJ

11. CT Angiography

12. CT Angiography
Neck + Brain vessels
• From aortic arch to vertex
• To assess - Location of thrombus- Large vessel occlusion?
- Length of thrombus
- Collateral blood flow

13. CT Angiography
Coronal CTA shows right MCA occlusion.
Note poor opacification of right M3, M4 branches
compared with normal left side .
Axial CTA showing Right M1 occlusion with
collateral flow in delayed phase

14. Left CCA stenosis Right proximal ICA stenosis

15. Perfusion CT

16. Perfusion CT
• To see extent of infarcted core and ishcemic
penumbra
• Faster and correlates well with DWI and pMR (but inferior)
• Less reliable for- estimating final infarct volume
- Predicting those who will not benefit from intra-arterial therapy
• Parameters seen:
1. CBV: Volume of blood flowing in a given volume of brain (ml/100mg)
2. CBF: Rate of blood flowing in a given volume of brain (ml/100mg/min)
3. MTT: Avg. time taken by blood to flow through a given brain volume (sec)

17. pCT
Normal
CBV
CBF
CBV
MTT
Normal perfusion parameters
are:
• Gray matter
◦ CBF: 60 mL/100 g/min
◦ CBV: 4 mL/100 g
◦ MTT: 4 s
• White matter
◦ CBF: 25 mL/100 g/min
◦ CBV: 2 mL/100 g
◦ MTT: 4.8 s

18. pCT
Stroke
CBF CBV TTP
MTT
CBF 10-25ml/100mg/min-
Ichemia (Blue)
CBF <10ml/100mg/min-
infarction (purple-black)

19. pCT
Ischemic penumbra
• CBV/CBF mismatch
CBV CBF
CBV/MTT mismatch
CBV MTT

20. pCT
Acute crossed cerebellar diaschisis
CBF TPP
TPP

21. MR in stroke
• Time consuming, so expediated rapid stroke protocol:
‣ Fast FLAIR
‣ T2
‣ DWI
‣ pMR
• Superior to CT in detecting small vessel and brainstem stroke.
• Better delineation of ischemic penumbra in cases of CT/CTA and clinical
mismatch

22. MRI
DWI-ADC
• Positive in ~95% hyperacute infarcts
• Diffusion restriction and ADC fall
• Within minutes
• Due to cytotoxic edema
• DTI: even more sensitive, especially for
pontine and medullary lesions.
• DWI negative strokes: lacunar strokes,
brainstem lesions, rapid recanalisation,
transient/fluctuating hypoperfusion.

23. MRI
FLAIR
‣ 0-4 hrs- 30% to 50% cases show
hyperintensity and cortical swelling.
‣ >7hr- nearly all strokes positive
‣ T2: Positive after 12-24 hours.
‣ Intra-arterial hyperintensity = slow/retrograde
flow, an early sign.

24. MRI
FLAIR-DWI mismatch
• DWI+ and FLAIR-
• Occurs in early stroke
• A quick indicator of
viable ischemic
penumbra
• Eligibility for
thrombolysis

25. MRI
T2-GRE
• Blooming thrombus sign
• Succeptibility vessel sign

26. MRI
T1-C+
• Intravascular
enhancement due to
slow flow in patent non-
thrombosed vessels
• No parenchymal
enhancement in acute
stroke

27. Perfusion MRI
• DWI reflects the densely ischemic
core
• pMR shows the ischemic
penumbra also
• DWI-PWI mismatch: Ratio >2.6
provides 90% sensitivity and 83%
specificity

28. Stroke mimics
False hyperdense vessel sign on CT
In a case of HSV encephalitis, due to
relative hypodensity of surrounding
parenchyma

29. Stroke mimics
False hyperdense vessel sign on CT
Calcified Right MCA. Attenuation values close to bone

30. Stroke mimics
False hyperdense vessel sign on CT
Diffuse hyperdense vessels due to raised hematocrit in a case of polycythemia vera

31. Stroke mimics
DWI
Case of Rt sided weakness with left
cortical and thalamic DWI restriction
(non-vascular pattern) with sparing of
WM, in a case of status epilepticus
DWI restriction in Hypoglcemia in a neonate

35. Primary CNS lymphoma.
Left frontal periventricular lesion showing
prominent diffusion restriction,
presenting with hyperintensity on DWI (a),
low ADC value (b) and
mild hyperintensity on T2WI (c), all typical
features of this type of hypercellular tumour.
T1WI post gadolinium (d) shows
homogeneous and intense contrast
enhancement