Prevalence of CP

Epidemiological data on the prevalence of cerebral palsy using a consensus classification for CP was presented by the Surveillance of Cerebral Palsy in Europe (SCPE) network. This data has been collected over a 30-year period (1964-1994) from 14 different registries, located in six different European countries. The prevalence of CP-related impairments and known risk factors, extracted from a literature review, and compiled by the SCPE, was also presented.

The SCPE reports that the current prevalence of CP is similar in all six countries in the registry (2.12 to 2.45 per 1000 live births) as is the increasing trend in time from well below 2 per 1000 (1.7) live births in the 70’s to well above 2 per 1000 live births (2.4) in the 90’s. The SCPE reports that the proportion of low-birthweight infants among all children with CP is rising: 32% of all cases in 1966 and 50% in 1989. In addition, they report that there is a strong association between socioeconomic status and the occurrence of CP as a whole and in the subgroups of diplegia and hemiplegia. In the UK, the prevalence of CP is 3.33 per 1000 live births in the poorest quintile compared with 2.08 in the most affluent quintile as measured by the Carstairs area deprivation index. The higher prevalence of CP in the poorer quintile holds true for normal weight (>2500 grams) infants as well as the low birthweight infants. Male infants form a small majority of those diagnosed with CP (58%).

CP-related Impairments

Epidemiological data on the prevalence of cerebral palsy using a consensus classification for CP was presented by the Surveillance of Cerebral Palsy in Europe (SCPE) network. This data has been collected over a 30-year period (1964-1994) from 14 different registries, located in six different European countries. The prevalence of CP-related impairments and known risk factors, extracted from a literature review, and compiled by the SCPE, was also presented.

1. Motor Impairments – Some form of motor impairment is present in 100% of CP cases. It is estimated that 72 to 91% of those with CP have the spastic syndrome of which they may either have hemiplegia (21-40%), diplegia (13-25%) or tetraplegia (20-43%). The motor impairments of CP, especially the spastic types, may lead to other impairments of the musculoskeletal system. For example, among hemiplegic children and adolescents, 75% have hip luxations, 73% contractures and 72% scoliosis.

2. Cognitive Impairments –It is estimated that between 23 to 44% of those with CP have cognitive difficulties including mental retardation and behavioral problems such as hyperactivity. The prevalence of cognitive impairments varies with type of CP and especially increases when epilepsy is present.

3. Sensory Impairments – Sensory impairments are most common among those with hemiplegia. Nine out of 10 hemiplegic children have significant bilateral sensory deficits. Stereognosis and proprioception are the chief modalities affected bilaterally. The extent of the sensory loss does not mirror the severity of the motor deficit. Speech impairment is common (42-81%) and is strongly associated with the type and severity of motor impairment: dyskinetic the most (95%), tetraplegic (85%), and diplegic the least (20%). The most common impairment is dysarthria, but aphasia also occurs. Finally, ophthalmic abnormalities are present in 62% of CP children. Seventy-one percent of children with CP are reported to have low visual acuity. Because ophthalmological examination cannot explain the low visual acuity of the vast majority, there is a high probability of cerebral visual disturbance.

4. Endocrine Impairments – A majority of CP children have gastrointestinal as well as feeding problems. Sucking and swallowing in the first 12 months of life are common: 57 and 38% respectively. Eighty percent have been fed non-orally on at least one occasion. Significant silent aspiration is found in 68.2% of those with severe spastic CP. Linear growth in diplegic and hemiplegic children is often significantly reduced. More than half of CP children have problems with their weight, either under or over-weight. Almost a quarter of CP children have stunted growth. Finally, bone-mineral density in children and adolescents with spastic CP greatly varies, but averages 1 standard deviation below the age-matched normal averages.

5. Urogenital Impairments – Almost 25% of CP children and adolescents have primary urinary incontinence. Tetraplegia and low intellectual capacity are the most important determinants.

Risk Factors

Most studies investigating causes of CP conclude that there are many pathways to the development of CP and many may be multifactorial. Risk factors for CP can be categorized as prenatally, perinatally or postnatally acquired. The most well known prenatal risk factor is chorioamnionitis. In full-term infants the relative risk of chorioamnionitis for CP is 4.7 (CI 1.3 -16.2) and in preterm infants it is 1.9 (1.4 -2.5). The relative risk of CP increases approximately 4-fold in very low-birthweight infants with a neonatal history of sepsis. Intrapartum initiation of the CP etiological pathway is likely in only 9% of the cases. Reported perinatal risk factors for CP are: neonatal convulsions, birth asphyxia, instrument-assisted delivery, neonatal jaundice, antepartum hemorrhage and neonatal infection. Finally, multiple gestation is a significant risk factor for CP. The prevalence of CP is 2.3 per 1000 single births, 12.6 in twins and 44.8 in triplets. Among infants weighing 2500 g or more, there is a significantly higher risk in multiple than single births, but among those weighing less than 2500 grams there is no such difference in risk.

Commentary

Detailed epidemiological information on the trends and demographics of CP such as outlined in this paper are only possible through the use of large population-based registries. Registers are useful not only to clinicians by providing information about subgroups of CP and possible avenues of inquiry regarding etiology, but also to policy makers for information regarding disease burden and possible environmental interventions. In addition, registries are useful to parents and caregivers of CP children and adults because they can provide accurate information regarding the natural history of many CP sub-groups which allows for health care and life planning. Northern England has had a cerebral palsy registry for over 40 years. Elsewhere in Europe, there are at least 13 different CP registers in 7 countries which allow for collaborative research within a network of European investigators.

Unfortunately, the US does not have a nationwide CP registry. Many researchers and policy-makers must rely on the incidence and prevalence data obtained from small independent registries around the country. The CDC Metropolitan Atlanta Congenital Disabilities and Development Surveillance Program is the only source for CP trend data in the US.

© UCP Research & Educational Foundation, July 2006