Stroke & TIA Overview

1) Overview of Stroke Classifications, and New definition of TIA

Stroke: Ischemic (~70%) vs Hemorrhagic (~30%)
Ischemic Stroke - Thrombotic (Large vessel vs Small vessel) vs Embolic (Arterial, i.e. Carotid Stenosis, vs Cardiac, i.e. A-fib) vs Hypoperfusion (Watershed infarct from hypotension, i.e. cardiac arrest).
Hemorrhagic Stroke - Intraparenchymal bleed vs Subarachnoid bleed.
TIA - traditionally has been defined as neurological deficits from cerebral ischemia that resolve within 24 hours; however, new definition (2009 AHA/ASA Guidelines) define TIA as brief episode of neurologic dysfunction from focal temporary cerebrial ischemia that is not associated with cerebral infarction (as seen on imaging), whereas CVA is ischemia that involves infarction of CNS tissue. In other words, the main thing that distinguishes TIA from Ischemic stroke is the lack of infarction on neuroimaging, REGARDLESS OF THE DURATION OF SYMPTOMS. Even if a pt's neuro symptoms resolve in 1 hr, for example, but he has evidence of infarction on MRI, that patient has had a stroke, not a TIA.

2) Review Risk Assessment for TIAs: ABCD2 score - has been reasonably well validated and predicts risk of recurrent ischemic CVA within 2 days.

A - Age > 60 - 1 pt
B - BP > 140 or diastolic > 90 - 1 pt
C - Clinical: Unilateral weakness - 2 pts, Isolated speech deficit - 1 pt, Other - 0 pts
D - Duration: > 60 min - 2 pts, 10-59 min - 1 pt, < 10 min - 0 pts
D - Diabetes - 1 pt

Score of 3 or more --> should hospitalize for further workup (2009 AHA/ASA Guidelines). Score of 0-2 = 1% risk of ischemic CVA in 2 days --> reasonable to do outpt workup, if can be sure you can get pt MRI and f/u in the next 2 days. Score of 4-5 = 4% risk, 6-7 = 8% risk of recurrent ischemic CVA within 2 days.

3) Review basic management of ischemic stroke

Workup: Noncontrast head CT to r/o bleed, then MRI which is much more sensitive for early ischemic CVA. Also need imaging of head and neck vessels, with MRA or CTA vs ultrasound, and consider cardioembolic source - obtain TTE and EKG/tele monitoring to eval for a-fib.
Antiplatelet therapy - see below
Thrombolysis - consider if pt within 4.5 hour window (recently expanded from 3 hour window due to ECASS III - NEJM 2008) and persistent severe neuro deficits, but large list of contraindications
?Anticoagulation - simple rule is that you should really never acutely anticoagulate with IV heparin or Lovenox (even for cardioembolic from A-fib). Reduction in recurrent ischemic CVA is balanced by increase in hemorrhagic transformation. If cardioembolic CVA from A-fib, reasonable to start Coumadin prior to discharge (without bridge).
Blood pressure control - permissive HTN is ok - do not treat HTN unless severe (>220/120) due to risk of hypoperfusion.
Other risk factor management: Smoking cessation, statins, diabetes control
If >70% carotid stenosis --> carotid endarterectomy (preferred over carotid stenting).
tobacco cessation (smoking doubles your stroke risk, quitting decreases your risk)
marijuana has been associated with strokes in younger persons without other risk factors

Basics of MRI in stroke assessment:
T1 sagittal: look at basic brain structures: gyri, corpus collosum, ventricles, brainstem.
T2 axial: CSF is bright. Can see acute strokes- they look bright but T2 flair is better
T2 flair: same as T2 but the bright csf is suppressed so you can see the tissue abnormalities better.
DWI: shows you areas of restricted diffusion- ie stroke- as bright. Confirm with ADC
ADC: should be dark where the DWI is bright if it is a stroke
PWI: difference between PWI and DWI gives you the penumbra (area at risk i.e. ischemic but reversible)

4) Overview of efficacy of antithrombotic/antiplatelet agents for reducing risk of recurrent ischemic CVA

ASA - RRR of 22% vs placebo (BMJ Metanalysis 2002)
Clopidogrel - Compared to ASA, reduces risk of MI/CVA/Vascular death vs ASA (5.3% vs 5.8%, CAPRIE - Lancet 1996)
Aggrenox - Compared to ASA, reduces risk of MI/CVA/Vascular death vs ASA (13% vs 16%, ESPIRIT - Lancet 2006)
ASA + Clopidogrel - Compared to ASA, no reduction in vascular events, but increases risk of major bleeding (MATCH - Lancet 2004)
Coumadin - vs ASA, no reduction in CVA, but increased bleeding (NEJM 2001)

Basically, ASA, Clopidogrel, and Aggrenox are all first-line options, with Clopidogrel and Aggrenox having a slight edge in efficacy, but significantly more costly. Do not use combination of ASA + Clopidogrel for CVAs, and do not use Coumadin (except for cardioembolic CVA from a-fib).

(Katharine Cheung MD, 7/13/10)

(Chanu Rhee MD, 8/24/10)