Looks like a good thread to tack onto. Latest blog entry on Eide Neurolearning, references a study on dysgraphia using fMRI.

http://eideneurolearningblog.blogspot.com/2012/09/fmri-of-dysgraphia-lack-of-automaticity.html

Really illustrates that dysgraphia has a bigger impact as a lot processing is chewed up in the writing, which can reduce available processing for the actual content. I've sometimes wondered if maybe there isn't so much an underlying problem as there is a brain that just can't "mind" its own darn business.