Hi, I am sorry but I am bit confused with the term you are using Dystonic. If I am not mistaken, Wikipedia reference-linkdystonia goes more with getting stucked with one posture as children with athetoid. however your child as he looks, goes more with dynamic spasticity. he seems to have moderate spasticity at rest as sitting with support, which increases to severe with movement. I would lebell this child moderate spastic diplegic, lowerlimb involved> upper limb, left side involved > right side. I would describe therapy plan of one session how we can progress during the session.

take him in supine on wedge. start from shld take one L in TIP i.e depression, abd, ext rot at shoulder, elbow straight and wrist and fingers open, taking shld as key point of controll. try to get this position gradually as child allows you. after moments when you feel arm is relaxed, mobilize the shld more in ext rotation. now keep that arm at side and do the same with R shld. now bring the two legs apart and in ext rotation with knees straight as much as possible. mobilize hips in external rot. now fix the legs at knees by sitting over the knees, make the child to do trunk rot at pelvis by picking any big object with L hand from same side and dropping on R side of body. do the same on R side. after this u will feel decreased spasticity in legs.

progress from here to long sitting, by pulling child to sit. make the child to to side lying on L side using R shld as KPC and help him to come up to sitting taking wt on L arm. come behind the child supporting his back from your body and keep his legs straight using your legs coming over his knees. now bring one arm in abd at 90 degrees keeping elbow straight and palms open. sup him from shld and wrist and make the child to hit small balls with open hands in different directions to get big and rapid movts at shoulder. this will also help to dev weight shifting at pelvis thus reducing spasticity in legs. repeat the same with other arm. now bring tilting/ balance board on L side. make child to transfer on balance board and take him in supine. come behind the child at his head side. bring both arms in abd at 90 degrees keeping elbows straight as much as possible. now move balance board side to side slowly to shift body weight to one side and wait till child comes in middle to keep his body straight. from here bring him again in long sitting as you did before in lying on floor. adapt the same long sitting position by sitting behind the child on balance board and engage him in play with both hands. keep moving board side to side with your body weight to make the child to adjust with weight shifting and balancing himself. from here you can take child in cross sitting on board and come in front to play with him keeping the board moving side to side.