According to this study in Neurorehabilitation and Neural Repair, tai ji quan improves balance and strength in people who have suffered a stroke.
When compared with the controls, the Tai Chi group showed greater COG excursion amplitude in leaning forward, backward, and toward the affected and nonaffected sides (P < .05), as well as faster reaction time in moving the COG toward the nonaffected side (P = .014) in the end-program and follow-up assessments. The Tai Chi group also demonstrated better reliance on vestibular integration for balance control at end-program (P = .038).
Here's a short summary from the New York Times in plain English.
Traditional Chinese Medicine gets good results treating stroke victims. One particularly successful form of therapy is scalp acupuncture.