 The ITB Therapy treatment arm will receive a combination of ITB Therapy and physiotherapy. During the run-in phase, a test with intrathecal baclofen will be performed to evaluate the response of the patient. Patients fulfilling the test success criterium will be implanted with a Medtronic SynchroMedII infusion system. Following implant, patients will enter into the 6 month active trial, which includes a 6 week titration phase, during which time oral antispastic medications must be gradually reduced with complete discontinuation by the end of the titration period. 