Hi Susan,

This is a very interesting question -- A foundational question in clinical aphasiology in some ways....but, unfortunately, one that has little empirical support. 

So often we read and are taught about the first six months post onset and the extent of recovery -- or the recovery trajectory -- and how the greatest change occurs at that time.  This is often linked to the concept of "spontaneous recovery" and that is where some real difficulties arise. With colleagues we have conducted some work looking at the idea of the optimal recovery window and how spontaneous recovery is employed with this. The work is not completed but I can share some aspects with you.

First, however, let me give a direct answer to your question about the "optimal recovery window".  The best data set that I know of is the work of Bruce Porch when developing and using the Porch Index of Communicative Ability (PICA) to study processing deficits in individuals with aphasia.  The PICA is an amazing tool with psychometric characteristics unrivaled by any other test of aphasia (and most other assessment tools).  The reliability and validity indices are extremely strong most likely due to the rigid administration requirements, the very powerful and sensitive multi-dimensional scoring system, and the use of ten common objects throughout each subtest of the battery.  Also, the training requirements are quite rigorous.  This results in a powerful tool that can stand up to careful analysis.  Based upon the testing of 357 Individuals with aphasia, Dr. Porch has described the recovery trajectory in aphasia and found that there was a decelerating recovery curve from onset to six months post-onset with the greatest change being one month post-onset and then the deceleration after one month....So the optimal based on this large data set would not be 3-6 months but 1-3 months.  Also, these are group data and there is certainly individual variation...recovery appears to continue in many cases when extending out past 12 months post-onset but not at a similar rate (i.e. deceleration).

This is not surprising since the first six weeks or so also deals with the damaged brain undergoing various physiological changes for protection and reaction to damage (increased catacholomines, endema, H2O infusion....even ...diaschisis ...if you believe in it)....

Two other issues.  First, we need to remember the difference between "physiological recovery" and "functional recovery".  IF we look at physiological and de-contextualized processing changes in the brain, then recovery is a decelerating curve that tends to flatten out around 4-6 months and then may even plateau after 6-12 months.  If we look at "functional recovery" where we look not only at the brain of the individual with aphasia but the social dyad within which the IWA operates, then recovery is almost unlimited.....the kinds of collaborative and individual strategies that are developed (look at the work of Ray Wilkinson, Suszanne Beeke, Nina Simmons-Mackie and lots of others dealing with more social aspects of aphasia) show continued possibilities for recovery long-term....albeit due to the social actions more than the brain recovery.

Regarding spontaneous recovery, our work suggests that after extensively reviewing the available literature in aphasia on spontaneous recovery:

•28/30 textbooks discussed Spontaneous recovery

•12 articles over the past 20 years in ASHA archival journals discussed Spontaneous Recovery

•9/30 or 30% of textbooks suggested that concept was not well understood

•30/42 or 72% of these publications cited earlier work.

However,

Only 4/42 or 9% cited work suggesting origins of the concept of Spontaneous Recovery.

•Four references were mentioned

–Animal motor studies in 1930s (Kannard)

–Homeostasis and edema (Cannon, 1922)

–Diaschiasis (von monakow)

–Luria (1963)

None of these studies actually provide verification of Spontaneous Recovery. 

Although this work and the data collection is on-going, so far the following appears to be the case:

* Although the concept of Spontaneous Recovery has been prominently presented in the aphasia textbooks over the past 40 years, the fact that the concept is not well understood has been less prominently displayed.

•There is very little discussion about the actual origins of the concept of Spontaneous Recovery.  Several citations are used but they focus on animal studies or speculate are the mechanism for SR and not its verification.

Dear Susan,

I don't know any large scale epidemiological study, but I linked two studies:

- fMRI evolution in the first year after stroke in one aphasic patient

- prediction of aphasia severity with data collected during the first week after stroke

Hope this will help.

http://www.ncbi.nlm.nih.gov/pubmed/15297629

http://www.ncbi.nlm.nih.gov/pubmed/23117494

Current concepts of neuroplasticity indicate that brain plastic change remains possible even well after the optimal time window of 3-9 months after stroke.  fMRI studies support the concept, especially in the case of motor rehabilitation with some evidence for cognitive rehabilitation.  

Many thanks to each of you for your thoughtful responses.  Jack, I agree with you regarding differentiating between spontaneous and functional recovery.  I think you hit the nail on the head with regard to why clinicians (like myself) often object to this idea of a "recovery window," but studies looking at physiological brain changes seem to confirm the concept.  I wish you good luck in your study and thank you for this very useful information.  Emmanuelle, thank you for the links.  Keh-chung, thanks for your response. I'm interested in differences between motor and cognitive recovery post-stroke as well.

Many thanks, Davide, for the kindness of your response.  The case report is much appreciated.  Thanks again for your valuable help.

http://mobile.journals.lww.com/co-neurology/_layouts/15/oaks.journals.mobile/articleviewer.aspx?year=2014&issue=12000&article=00003

Check this collection of studies. I think it may help you