New ways of imaging Stroke/TIA Dr Suzanne O’Leary Neuroradiology SpR Frenchay Hospital

Cerebrovascular disease TIA- warning, deal with it now! Stroke- salvage as much as possible

TIA A transient episode of neurological dysfunction caused by focal brain, spinal cord, or retinal ischemia, without acute infarction Definition and evaluation of transient ischemic attack: a scientific statement for healthcare professionals from the American Heart Association/American Stroke Association Stroke Council; Council on Cardiovascular Surgery and Anesthesia; Council on Cardiovascular Radiology and Intervention; Council on Cardiovascular Nursing; and the Interdisciplinary Council on Peripheral Vascular Disease. The American Academy of Neurology affirms the value of this statement as an educational tool for neurologists. Stroke. 2009;40(6):

TIA 50% of TIA patients have new small ischaemic lesions on DWI Risk of major stroke in the following 3 /12 First week highest risk.

TIA imaging MRI Brain +DWI Contrast enhanced MRA neck vessels+ COW.

CTP in TIA Increased MTT, but not greater than 145% Increased CBV Reduced CBF

Treatment options TIA- risk factors- statins, antihypertensives, anti-platlet endarterectomy/carotid stenting

Stroke CT CTA aortic arch- vertex CT perfusion

CT Non contrast CT head Exclude a contraindication to IV thrombolysis Early changes of infarct

CTA CTA- arch to Vertex Carotid stenosis Dissections Occluded vessel ? suitable for IA thrombectomy

CT perfusion Capillary level blood flow mls IV contrast with a power injector. Rate 7mls/sec Saline chaser 20-40mls High concentration contrast g/dL iodine

CT perfusion- Image acquistion Few seconds after injection 80 kv,150 mas 64 slice MDCT- 4cm slab Parallel and superior to the orbital roof- ACA, MCA, PCA. One image per second for 40 seconds.

CT perfusion “Core” “Ischaemic Penumbra”

CT Perfusion Cerebral blood flow-CBF Cerebral blood volume-CBV Mean Transit time-MTT

Cerebral blood volume CBV- total volume of blood in a given unit volume of the brain. Blood in the tissue as well as vessels Units - milliliters of blood per 100g of brain tissue Gray matter-4ml/100gm White matter- 2ml/100gm “Core”- CBV decreased as no autoregulation. “Ischaemic penumbra”- CBV increases to auotreg compensate for the reduced flow

Cerebral blood flow-CBF Volume of blood moving through a given unit volume of brain per unit time. mL of blood per 100g of brain tissue per minute, mL/100g/min Decreases in the “ischaemic penumbra”- Gray matter- 60 mL/100gm/min White matter- 25 mL/100gm/min

CBF CBF <10-15ml/100g/min for 2-20 mins- irreversible damage-core. CBF < 20ml/100g/min- neurological deficit which may be reversible. Margin of brain tissue maintained by collaterals at 10-20ml/100g/min- ischaemic penumbra, not neurologically functional but not irreversibly damaged- hours. Treatment directed here.

Mean Transit Time- MTT Average of the transit time of blood through a given brain region Seconds Gray matter- 4 White matter- 4 Extended in the ischaemic penumbra. MTT=CBV/CBF

Time to Peak- TTP TTP extended in the core and the ischaemic penumbra. Affected by stenosis

Mismatch Core- CBV lesion volume Ischaemic penumbra- MTT or CBF lesion volume Mismatch -difference between the two.

Summary CBFCBVMTT Autoregulation N++ Ischaemia -+++ Irreversibl e damage ----/+

Penumbra- CBF down CBV up MTT up Penumbra- CBF down CBV up MTT up

CTP- False positive Severe extracranial carotid stenosis/occlusion Delayed intracranial flow due to AF or low ejection fraction

65 yrs. L hemiparesis. NIHSS- 17

CBF CBV MTT

IA thrombectomy

CTP post treatment

Clinical outcome Fully independent. Self discharged that night, bored in hospital!

42 yrs old. Marfans. On warfarin. Previous CVA.

CTA

CTP

IA thrombectomy

CT post treatment

Clinical outcome Fully independent Back at work.

69yrs. L Hemi paresis. NIHSS 23

CTA

CBF CBV MTT

Post IV thrombolysis

MRI- DWI Alterations in the motion of water molecules- Brownian motion. 30 mins of onset of stroke Rare cases of false negative

MRI+DWI b1000 images ADC map Restricted diffusion -not irreversible

DWI-Stroke Hyperintensity on DWI- cytotoxic oedema

ADC map Low signal on the ADC map. Tells true restricted diffusion rather than T2 shine through(subacute/chronic infarction)

Restricted diffusion Abscess- bacterial, some fungal Epidermoid, lymphoma, medulloblastoma Acute demyelination Acute encephalitis Haemorrhage- oxyhaem, extracellular haem DAI CJD

Syndrome with reversible deficit but may have restricted diffusion Global ischaemia Hypoglycaemia Hemiplegic migraine Seizures TIA

ADC reversibility TIA in which the imaging is performed within 4 hours Reduced ADC in the ischaemic penumbra indicates hypoperfused tissue. This may revert after thrombolytic therapy.

Reversibility

Summary Hyper acute stroke- CT, CTA TIA- medical emergency- MR+ DWI+CEMRA,(CTA)