Hi
For patients after stroke, there is the Trunk Impairment Scale (TIS) which can be used as an outcome tool and a guide for therapy since the development of the scale was based on the neurorehabilitation (clinical) literature and the opinion of experts in the field. I have attached the pdf (2004) of the article.
The TIS consists of 17 tasks ranging from sitting on the edge of the bed, sitting on the edge with a more narrow base of support, and various selective movements of the trunk (lateral flexion and rotation), initiated from the shoulder girdle and pelvic girdle.
A better performance on the TIS early after stroke has been shown as an important prognostic factor for ADL (Activities of Daily Living) outcome at six months after stroke (see attached 2007 pdf).
Of course trunk stability and selective movements are only the first step in a recovery process. Hopefully the TIS can be a first guide in this journey.
Good luck!
Geert