Cerebral Palsy Definition Cerebral palsy (CP) is a clinical entity characterized by a three-part definition: a disorder of movement and posture (1) caused by a nonprogressive injury (2) to the immature brain (3). The distinctive characteristic of these syndromes is the change in muscle tone and posture, both at rest and with voluntary activity. The definition of CP implies that the underlying pathologic process in the brain does not progress, and occurred during early development of the brain. The first year or two of life is included in most definitions, although it is unclear what the upper age limit is of a postneonatal brain insult. The definition of CP is being reviewed at present. The diagnosis is made in children who are demonstrating delayed motor development, and is confirmed with MRI. Where indicated, other metabolic, biochemical, or genetic testing might be necessary. There is a subset of children for whom no imaging abnormality is seen. Epidemiology Cerebral palsy is one of the most common disabling conditions affecting children. The reported incidence varies but is approximately 1-2.3 per 1000 live births.203 The Collaborative Perinatal Project measured a prevalence rate of 5.2 per 1000 live births at 1 year of age, but reported resolution in up to half of these children by 7 years of age. Discrepancies in the rate are due to difficulties in diagnosis for a variety of reasons. Diagnosis is not made at any specific age, and can 'resolve' in up to 50% of children diagnosed prior to 2 years of age, or the brain insult might not occur until later in childhood. Various terms are also used, including neonatal encephalopathy, birth asphyxia, periventricular leukomalacia (PVL), hypoxic brain injury, stroke, traumatic brain injury, and shaken infant syndrome. There is also a wide variation in normal attainment of motor milestones, making early diagnosis less reliable. There were hopes that recent improvements in neonatal care would decrease the incidence of CP, but the prevalence in full-term infants has remained relatively constant. Despite improved neonatal outcomes in general, the increased survival of premature low birth weight (