The Spring issue of Pediatric Physical Therapy reports that functional electrical stimulation (FES) for 8 weeks to the dorsiflexors and quadriceps in a small group of children with cerebral palsy had no long term treatment effects. 

Reference:  van der Linden, Marietta L. PhD; Hazlewood, M Elizabeth MCSP; Hillman, Susan J. MSc, CEng; Robb, James E. MD, FRCS. (2008)  Functional Electrical Stimulation to the Dorsiflexors and Quadriceps in Children with Cerebral Palsy.  Pediatric Physical Therapy. 20(1):23-29.

Check out the electronic book Teaching Motor Skills to Children with Cerebral Palsy at www.YourTherapySource.com/cpmotorskills