Notes of MRI talks at ISC 2011 by Michael Lev and by Greg Albers

These two talks demonstrate patients for whom intervention is NOT likely to help.

* BASIS (reference here: http://www.ajnr.org/cgi/reprint/29/6/1111 )

Lev

1.  Contrary to hypothesis, mismatch IS NOT discriminatory regarding clinical outcome after recanalization.  Most all M1 occlusions with small admission DWI have mismatch, but not all respond to therapy.  The independent outcome predictors, are, NIHSS <= 10 and BASIS* negative have good outcomes, NIHSS > 10 and BASIS + have poor outcomes  and those with one or other are intermediate.

2.  What you need to know, basically, is the amount of core infarct less than 70 cc.  If so, recanalization can be of benefit. You can measure this best, through DWI although CT can be used (see notes below).

3. The other thing you need to know is that a corresponding perfusion deficit exists.  These 2 criteria by MRI are specific but not sensitive for core.

4.  Idea of time is brain uses clock that starts with imaging of a DWI lesion less than 70 cc, not onset of symptoms. 

5.  Yoo Aj et al. Stroke 2010.  DWI and MTT volumes predicts outcome > mismatch.  DWI > 72 ml and NIHSS > 20 are associated with a poor outcome.  MTT < 47 mL and NIHSS < 8 have good outcome.  Combining gives prognosis over 70 %, much better than NIHSS alone (43 %) or imaging alone (54 %).

6.  Protocol is to do noncontrast head CT, then a CTA, then a DWI and only do CT perfusion if patient is not able to get a MRI.  Also notes current focus on radiation.

7.  Uses above characteristics to assess wake up strokes.

8.  Good collaterals is highly specific for small DWI

9.  THRESHOLDED CBF IS LESS VARIABLE THAN CBV AND IS MORE SENSITIVE FOR SALVAGEABLE BRAIN (CBV MORE SPECIFIC).  CT CBF NOT CBV IS "NEXT BEST THING" IF DWI IS NOT AVAILABLE TO DETERMINE SIZE OF CORE.  However there are issues with CT including luxury perfusion, standardization, post-processing and others.

ALBERS TALK

Discusses DEFUSE trial and adds that he criticizes Lev's talk because there is ANOTHER group of patients who do badly with recanalization and that is those with very large perfusion deficit even with a tiny DWI deficit who have a "malignant pattern" of infarct who will do much worse if treated.  A discussion ensued and Wade Smith mentioned a case with a "so-called malignant pattern" who was observed deteriorating, was promptly treated, and got better, therefore felt clinical part was important.  Again mismatch was overrated and not key.

Albers also spoke of converging evidence that > 5.5 or 6 seconds for contrast to reach brain was a threshold of very sick brain.  He also mentioned a case where one branch was not recanalized, but the branch that was recanalized reperfused dead tissue. 

Wade Smith talk

Many points not mentioned. Of interest he thinks IMS 3 is going to really open up intervention therapies.