Sound waves aim to calm uncontrollable movements in kids with cerebral palsy

Copied word for word from the study's registry entry, so the wording is the study team's rather than ours.

Inclusion Criteria: * The treating physician has chosen GPi-DBS or pallidotomy for the treatment of the secondary dystonia caused by cerebral palsy in this patient * Patient and/or legal representative, if the patient is underaged or not capable to give consent himself, have chosen pallidotomy as treatment * The consent to participate in the trial of the underaged patient, if he is capable to understand the study requirements, is required * Age at enrolment 8-22 years * Diagnosis of secondary dystonia due to cerebral palsy caused by perinatal hypoxic injury * Anti-dystonic pharmacotherapy insufficient * Stable anti-dystonic medication over the last 30 days * Globus pallidus internus (pars posterior) and thalamus (motor part) intact on MRI (not older than 2 years - if possible) * No fixed severe skeletal deformations with loss of function, which need immediate orthopaedic surgical intervention * Sufficient compliance of the patient or the legal representative if the patient is underaged or not capable to give consent himself to take part in the study * Informed consent to take part in the study from patient and/or legal representative if the patient is underaged or not capable to give consent himself * Patient and/or legal representative if the patient is underaged or not capable to give consent himself, understands the study requirements and the treatment procedures and provides written informed consent before any study-specific tests or procedures are performed Exclusion Criteria: * Patients with known primary (e.g. DYT1) or idiopathic dystonia * Severe axial hypotonia with total loss of head control (e.g. absence of control at "upper thoracic level" in the SATCo score) (medication effect excluded) * Fixed hemi-dystonia * Severe spasticity in knee- and elbow-flexors and -extensors (Modified Ashworth Scale \>3) * Fixed severe skeletal contractions with loss of function which require immediate orthopaedic surgical intervention * Patients with other severe concurrent neurological disease (e. g. brain tumor, neurodegenerative diseases, trauma etc.) * Condition likely to require use of MRI in the future * Any intracranial abnormality or medical condition that would contraindicate DBS surgery * Any findings in neuropsychological screening assessments that would contraindicate DBS surgery * Any current drug and / or alcohol abuse * Any history of frequent grand-mal seizures without response to anticonvulsive treatment * Any other active implanted device (e.g. Cochlear implant, pacemaker), whether turned on or off, would be allowed provided that they do not interfere with functioning of the device. * The presence of DBS leads due the risks of these ferromagnetic devices in the MRI environment. * A history of neurostimulation intolerance in any area of the body. * Currently on any anticoagulant medications that cannot be discontinued during perioperative period. * Any significant medical condition that is likely to interfere with study procedures or likely to confound evaluation of study endpoints, including any terminal illness with survival \<24 months. * Participation in another drug, device, or biologics trial concurrently or within the preceding 30 days; any other trial participation should be approved by the Principal Investigator. * A female that is breastfeeding or of childbearing potential with a positive urine pregnancy test or - if a person is sexually active - not using sufficient contraception with a Pearl Index of less than 1% including all forms of hormonal contraception ("antibaby-pill", hormonal plaster, NuvaRing®, Implanon®, hormonal depot injections, contraceptive coil), the tubal ligature (female sterilization). Alternatively, the female of child bearing potential is sexually abstinent. * Subjects who have contraindications to anesthesia, in the judgment of the attending anesthesiologist * Subjects who are unwilling or unable to undergo general anesthesia * Presence of a condition or abnormality that in the opinion of the Investigator would compromise the safety of the subject or the quality of the data. * Minimum head circumference \< 49cm * Skull Density Ratio (SDR) \<0.40.