- Email: [email protected]
Epidemiology of cerebral palsy
Symposium: special needs
Epidemiology of cerebral palsy
loss of motor function. A child with spina bifida is not included among CP cases unless his/her brain has suffered at birth, a very unlikely coincidental event. Progressive motor disorders, spinal, nerve or muscular diseases and also brain metabolic disorders fall outside the scope of CP, although the special needs of these children may be very similar. A decision tree has been developed to promote the consistent implementation of these criteria.1
Christine Cans Javier De-la-Cruz
Public health perspective
Marie-Ange Mermet
CP is the most prevalent severe disability in childhood after severe intellectual impairment. In school age children it is twice as common as Down syndrome and it accounts for 60% of severe motor disabilities.3 Other motor disabilities are neuromuscular diseases, spinal cord disorders and some rare tissue and skeletal diseases (dermatomyositis, arthrogryposis). Although used as an umbrella term for different diseases, some of them infrequent, CP itself is not usually considered to be a rare disease due to its overall prevalence, around 2 per 1000 live births. It can be estimated that 650 000 families in Europe (EU 25) either have a child with CP or support an adult with CP. Many persons with CP have associated impairments such as intellectual impairment, sensorial impairment or epilepsy. Most children with CP require some specific help during their schooling period. As adults, half of them will face difficulties in getting a job and living independently. Among the elderly population with CP, more than one-third will be institutionalized for permanent medical assistance. An increase in life-expectancy for children with CP has been shown over the last decades. Nevertheless, their 20-year survival rate is lower than that for the general population.
Abstract Definition of cerebral palsy (CP) has become more precise in recent years and, even if CP remains an umbrella term, a simple classification system for CP types has been proposed. CP is the commonest motor impairment in childhood. New validated motor scales for gross and fine motor functions describe a third of children with CP as severely impaired. Children with CP may also have associated impairments, other than motor, that deserve particular attention and support at school and work, and which are responsible for lower survival rates. The prevalence of CP, 2 per 1000 children, has remained remarkably stable over the last 30 years, particularly for term children who represent half of all children with CP. However, recently, a consistent downward trend has been seen in moderately and very low birth weight children. Prevention measures still seems difficult to define since CP is the result of multifactorial events. Decreasing multiple births and specific health actions during early infancy may have an impact. Followup programmes have been implemented to assess how the consequences of CP are best reduced.
Keywords cerebral palsy; classification; disability; epidemiology; impairment; motor function; prevalence
Classification of cerebral palsy To obtain a complete clinical pattern of CP (based on phenotypical expression), children can be described according to observed neurological signs, current loss of motor function and associated impairments.
Definition Cerebral palsy (CP) is the commonest motor impairment in childhood. It affects 1 in 500 children, and is responsible for permanent limitation of activity and participation. The prevailing definitions of CP have common elements: CP is a group of permanent, but not unchanging, disorders of movement and/or posture and of motor function due to a nonprogressive interference, lesion or abnormality of the developing/immature brain.1 Recently, the changing concepts of impairment and limitation of activity were taken into consideration, and it was also highlighted that children with CP often show accompanying impairments.2 It is worth pointing out conditions that are not CP. For example, a child with dyspraxia may face activity limitation and a learning disability but he/she does not show neurological signs or
Classification based on neurological signs Spasticity is one of the main neurological signs in the clinical description of a case of CP. To discriminate subgroups of CP with spasticity, classification systems often used to refer to the localization of the motor function loss, with terms such as diplegia, double hemiplegia, quadriplegia, tetraplegia and hemiplegia. However, it has been shown, and recently confirmed, that the distinction between these terms is not sufficiently reliable.4 A European network of population-based surveys and CP registers adopted a simple classification of CP types to ensure data comparability between centres. This research collaboration reached a consensus between professionals with different background and skills for the very simple classification of CP subtypes into four main groups: unilateral spastic, bilateral spastic, dyskinetic and ataxic. To promote this standardized way of classifying CP types, SCPE (Surveillance of Cerebral Palsy in Europe) developed a classification tree1 and a reference and training manual in CD format including video sequences of the different clinical patterns of neurological signs and motor function impairments.5 Table 1 shows very similar proportions of CP subtypes when
Christine Cans MD PhD is Senior Epidemiologist at RHEOP-SCPE ThEMAS, Grenoble University Hospital, France. Javier De-la-Cruz MD is Clinical Epidemiologist at CIBERESP, Hosp Univ 12 de Octubre, Madrid, Spain. Marie-Ange Mermet MSc is a member of the ThEMAS Team, UJF Faculté de Médecine de Grenoble, Grenoble, France.
PAEDIATRICS AND CHILD HEALTH 18:9
393
© 2008 Elsevier Ltd. All rights reserved.
Symposium: special needs
Distribution of cerebral palsy types in different countries (postneonatal cases included)
Europe6 Western Australia7 Quebec8 Atlanta, USA9 South-east Australia4
Number
Bilateral spastic (%)
Unilateral spastic (%)
Dyskinetic (%)
Ataxic (%)
Other (%)
6174 1599 217 815 323
50 44 54 56 56
30 39 31 23 30
7 8 1
6 8 6 21 3
7 1 8
2
9
Table 1
applying this classification system to data from Europe, North America and Australia.
should be considered when giving information to parents about their child’s prognosis. It has been shown, for example, that severe intellectual impairment has a strong influence on walking ability in children with unilateral spastic CP type.16
Classification based on motor function Until recently, severity of motor impairment was commonly assessed by describing walking ability. Data comparison was hindered by different underlying definitions of ‘walking ability’, which could mean walking a few meters only, walking outdoors or just being able to walk without actually walking in everyday life. The assessment of motor function has improved significantly with specific motor scales for gross and fine motor functions. The Gross Motor Function Measurement Scale (GMFMS, 88 or 66 items) was developed for clinical use, reduced to a five-point scale for epidemiological purposes (the Gross Motor Function Classification System [GMFCS]),10 and extended and revised in 2007. More recently, similar scales for fine motor abilities have been developed: the Manual Ability Classification System (MACS) and the Bimanual Fine Motor Function (BFMF) scales. GMFCS and MACS are both validated in depth and available online.11,12 BFMF offers the advantages that it takes account of asymmetry and allows data to be extracted from medical records. BFMF validation is pending.13 The use of these scales has greatly increased comparability of results between centres. Table 2 shows that the proportion of more severely impaired children on either scale (level IV/V) is around 25–35% of all CP cases. The dyskinetic group shows the highest variability between studies, suggesting residual difficulties in classifying mixed forms.
Early determinants of cerebral palsy The risk of developing CP for children born preterm is 10–50 times higher than for term children. A third of children with CP are born very preterm or with a very low birth weight (VLBW), whilst half of children with CP are born at term. The risk of developing CP is also higher for children born with a congenital anomaly or growth deviation, and for children admitted, for whatever reason, to a neonatal intensive care unit (NICU). At least 15% of children with CP have a congenital anomaly (brain or nonbrain). Growth retardation in singleton children (born at 32–42 weeks’ gestation) increases the risk of developing CP 4–6 times, and macrosomy 2–3 times. This is particularly relevant because growth deviation is not infrequent in the general population (6%), i.e. 3% have a low birth weight and 3% an excessive birth weight. Some authors are trying to identify babies who might later develop CP from their early movement pattern. There is a consensus about the usefulness of follow-up programmes for newborns admitted to NICUs to ensure early diagnosis. However, and despite promising results, further studies are needed to establish the benefit of intensive early therapy on longer term abilities.
Frequency and trends over time
Associated impairments in cerebral palsy cases The importance of impairments other than motor, commonly observed in children with CP, has recently been highlighted. For epidemiological and quality of care purposes, a severity measurement of each associated impairment should distinguish between, for example, a child with CP and strabismus and a child with total blindness, or between a child with CP and severe mental retardation (IQ less than 50 following WHO classification cut-off point) and a child with CP and mild mental retardation (IQ 50–69). Hearing impairment is rarely associated with CP, whilst other types of impairment are frequent. Severe intellectual impairment occurs in one-third of children with CP, blindness or nearblindness in 1 in every 10, and epilepsy in up to one-third. The proportion of children with CP without any severe associated impairment varies from one-third to one-half, depending on CP type and birth weight. The impact of these and of other associated impairments (speech, communication and feeding impairments)
PAEDIATRICS AND CHILD HEALTH 18:9
CP prevalence is around 2 per 1000 live births in both developed and developing countries (even if for very different reasons). For term children CP prevalence is 1 per 1000 live births. For moderately preterm children (32–36 weeks’ gestation) estimates are 6–10 times higher and for very preterm children (less than 32 weeks’gestation) prevalence is 10 times higher than in moderately preterm children (Figure 1). CP rates for live births show a lower prevalence for babies of birth weight less than 1000 g than for those with a birth weight of 1000–1499 g. This paradoxical effect is due to the high number of babies who do not live long enough to develop CP, and it disappears when estimating prevalence for neonatal survivors. Changes in perinatal and neonatal mortality accelerated in most countries from the 1960s, with a huge decrease up until the late 1980s, when there was an increase in the absolute number of children with CP. From 1990 there has been a plateauing of mortality rates but a downward trend in CP rate mainly in moderate and VLBW children. 394
© 2008 Elsevier Ltd. All rights reserved.
Symposium: special needs
Percentage of more severe motor impairment, measured using GMFCS and BFMF scales, in children with cerebral palsy from different studies Bilateral spastic (%)
Unilateral spastic (%)
Dyskinetic (%)
Ataxic (%)
Total (%) (number)
GMFCS level IV/V SE Australia4 Norway14 Sweden15 France* BFMF level IV/V
50 38 41 46
1 1 3 0
40 89 79 20
0 0 0 0
34 28 23 31
Norway14 Sweden15 France*
44 31 37
1 1 0
95 50 15
39 0 0
35 (289) 24 (367) 27 (100)
(323) (289) (367) (100)
Gross Motor Function Classification System [GMFCS] (between 4th and 6th birthdays):10
• GMFCS level IV: Children sit on a chair but need adaptative seating for trunk control and to maximize hand function. Children move in and out of a chair,
sitting with assistance from an adult or a stable surface to push or pull up on with their arms. Children may at best walk short distances with a walker and adult supervision but have difficulty turning and maintaining balance on uneven surfaces. Children are transported in the community. Children may achieve self-mobility using a power wheelchair. GMFCS level V: Physical impairments restrict voluntary control of movement and the ability to maintain antigravity head and trunk postures. All areas of motor function are limited. Functional limitations in sitting and standing are not fully compensated for through the use of adaptive equipment and assistive technology. Children have no means of independent mobility and are transported. Some children achieve self-mobility using a power wheelchair with extensive adaptations.
•
Bimanual Fine Motor Function [BFMF]:13
• BFMF level IV: (a) both hands, only able to grasp; (b) one hand, only able to grasp; other hand, only able to hold or worse. Child needs support and/or adapted equipment. • BFMF level V: both hands, only able to hold or worse. *Personal communication, RHEOP, Medecine diploma, L Camel, 2006.
Table 2
In most studies the CP rates in children born at term or with normal birth weight seem rather stable over time (Figure 2a), although a decreasing trend was observed in Sweden and in one UK centre. This finding is particularly relevant since normal birth weight and term children represent at least one-half of children with CP and, thus, it may be related to the persisting stagnation of CP prevalence despite continuous improvement in perinatal care and in mortality rates.7,9,17,18,21 Moderately preterm children and children with a birth weight of 1500–2499 g represent one-fifth of all children with CP. In the early 1990s, a downward trend in CP rate began to emerge for this group (Figure 2b). To analyse CP prevalence rate in VLBW children and to distinguish between children with birth weight 1000–1499 g and less than 1000 g, pooling of data from different centres was necessary and the SCPE Network recently made this practicable (Figure 2c). Overall, the greatest recent change in CP prevalence was observed in children born at less than 32 weeks’ gestation or weighing less than 1500 g. Since 1980, the CP prevalence rate has decreased considerably in the 1000–1499 g birth weight group and in the bilateral spastic clinical subtype group (Figure 2c). To a great extent this can be explained by improvement in perinatal and neonatal management and the decrease in the occurrence of white matter parenchymal lesions in these children.19
PAEDIATRICS AND CHILD HEALTH 18:9
When looking at CP estimates for clinical subtypes, some authors have suggested recently that there might be an increase in the prevalence of the dyskinetic type of CP, independent of birth weight, which counterbalances the encouraging results of the significant trends observed among VLBW and moderate birth weight children. Factors influencing cerebral palsy prevalence Many factors influence the prevalence of CP: 1. Time period: CP prevalence seems to fluctuate over time more than can be explained by simple random variation. This variation may relate to the level of care and the mortality rates in the study areas. 2. Inclusion of mild CP cases: children with CP who show neurological signs but only minor motor function difficulties will walk without limitations, and are not included in studies that focus on ‘disabled’ children only, whatever definition of CP is used. 3. Migration movements out of the area covered: the proportion of children moving out of the area before CP is diagnosed may alter the estimated CP rate. 4. Stillbirths and neonatal mortality rates: children who would have died a few years ago are now surviving despite their VLBW. These children may contribute significantly to the overall number of children with CP since they are at greater risk of developing CP. It can be expected that where mortality rates are high, CP 395
© 2008 Elsevier Ltd. All rights reserved.
Symposium: special needs
a 90
a
80
Rate per 1,000 live births
70
Survivors
60 50 40 30
Live births
20 10 0 < 1000
1000–1499
1500–2500
> 2500
Weight (g)
2.0 1.8 1.6 1.4 1.2 1.0 0.8 0.6 0.4 0.2 0
b
1981 1983 1985 1987 1989 1991 1993 1995 1997 1999
90 80
Birth years
Survivors b
70
Rate per 1,000 live births
60 50 40
Live births
30 20 10 0 < 28
28–31
32–36
> 36
Gestation (weeks)
16 14 12 10 8 6 4 2 0 1981 1983 1985 1987 1989 1991 1993 1995 1997 1999
Figure 1 Prevalence rates of CP per 1000 live births and per 1000 neonatal survivors according to a birth weight (eight centres—SCPE data 1990–1998) and b gestational age (six centres—SCPE data 1990–1998) (SCPE Network, personal communication).
Birth years UK (Oxford, 17)
West Australia (7)
Sweden (21)
USA (9)
UK (Belfast, 18)
c Birth prevalenceper 1,000 live births
rates are low. However, it may also be that good clinical practice will simultaneously lower mortality rate and CP prevalence rate. 5. Neonatal intensive care practices, including withdrawal of life support, may have an impact on local CP rates over time; this influence is difficult to assess. To date research has mainly focused on children born preterm or with low birth weight. It may be appropriate for epidemiological studies and clinical trials to focus also on the larger group of term children with CP. Finally, an important question for clinicians, public health doctors and policy makers is still open to discussion: do children with CP have more or less severe clinical patterns now than before? Paediatricians from the same or different countries disagree on the answer, and so do epidemiologists, since there is no current consensus on what is a severe, moderate or mild case of CP. Several authors have described trends in severity, with discordant results up to now. The proportion and prevalence of nonambulant children with CP seem to have been stable over time,16 but the trends for children with CP and severe intellectual or vision impairment are less well known.
60 50 40 30 20 10 0 1981
1983
1985
1987
1989
1991
1993
1995
Midpoint birth year Bilateral spastic cerebral palsy in children of birthweight 1,000–1,499 g Bilateral spastic cerebral palsy in children of birthweight < 1,000 g Hemiplegia spastic cerebral palsy in children of birthweight 1,000–1,499 g Hemiplegia spastic cerebral palsy in children of birthweight < 1,000 g Reprinted from Platt MJ et al. Trends in cerebral palsy among infants of very low birthweight (<1500 g) or born prematurely (<32 weeks) in 16 European centres: a database study. The Lancet, 369, 8. Copyright (2007), with permission from Elsevier.
Prevention Prevention comprises a wide range of actions, from efforts to prevent the development of CP in a child to the interventions oriented to reduce its consequences. Preventive actions may then be closely related to the knowledge on aetiology of the disorder or on determinants of the resulting disability.
PAEDIATRICS AND CHILD HEALTH 18:9
70
Figure 2 Cerebral palsy rates in children of a normal birth weight, b birth weight 1500–2499 g, and c very low birth weight 1000–1499 g and < 1000 g. Postneonatal cases excluded.
396
© 2008 Elsevier Ltd. All rights reserved.
Symposium: special needs
cardinal book on CP.22 Thus, it is difficult to envisage specific health actions for each identified influential factor.
Potentially preventable cases of cerebral palsy Acquired or postneonatal cases of CP are defined as an accidental/infectious/hypoxic event that leads to brain lesion in a presumed uninjured brain after the first month of life. Public health and health care actions, such as policies promoting more safety on the roads, meningitis immunization programmes and better management of blood circulation during surgical interventions for heart congenital anomalies, are reducing postnatal cases of CP. These cases of CP account for 5–10% of all cases in developed countries. The increase in multiple births during the 1980s and 1990s, from 1.5% to 3%, has certainly contributed partially to the stability of CP rates. It was recently shown that the risk of developing CP in multiple births was mainly explained by the VLBW/very preterm status of children issuing from multiple births (Table 3).20 Thus, besides recommending that no more than two embryos should be implanted in assisted reproduction treatments, it is also important to remind young women about the risk of multiple births increasing with higher maternal age. Despite consistent efforts in different countries, it seems to be quite difficult to reduce the rate of preterm births. During the prenatal period attention has to be paid to the detection of deviation from normal growth. At present time, antenatal magnetic resonance imaging (MRI) may be performed once a brain anomaly/ lesion is suspected, but antenatal therapeutic strategies following diagnosis contribute more to research programmes than to care implementation.
Follow-up programmes Follow-up programmes for children with CP have been established recently in several countries. It has been shown that efforts toward early identification of hip subluxation should be performed in bilateral spastic CP, allowing conservative measures and preventive surgery. Studies are needed to identify which support therapeutic strategies bring longer term benefits to the children, including psychological (e.g. parental stress) and educational dimensions. The present availability of better tools for identifying and classifying CP, and for assessing its severity, will certainly help in the evaluation of clinical practices. ◆
References 1 Surveillance of Cerebral Palsy in Europe. Surveillance of cerebral palsy in Europe: a collaboration of cerebral palsy surveys and registers. Dev Med Child Neurol 2000; 42: 816–824. 2 Bax M, Goldstein M, Rosenbaum P, et al. Proposed definition and classification of cerebral palsy, April 2005. Dev Med Child Neurol 2005; 47: 571–576. 3 Cans C, Guillem P, Fauconnier J, Rambaud P, Jouk PS. Disabilities and trends over time in a French county, 1980–91. Arch Dis Child 2003; 88: 114–117. 4 Howard J, Soo B, Graham HK, Boyd RN, et al. Cerebral palsy in Victoria: motor types, topography and gross motor function. J Paediatr Child Health 2005; 41: 479–483. 5 Cans C, Dolk H, Platt MJ, Colver A, Prasauskiene A, KragelohMann I. Recommendations from the SCPE collaborative group for defining and classifying cerebral palsy. Dev Med Child Neurol 2007; 109(suppl): 35–38. 6 Surveillance of Cerebral Palsy in Europe. Prevalence and characteristics of children with cerebral palsy in Europe. Dev Med Child Neurol 2002; 44: 633–640. 7 Watson L, Blair E, Stanley F. Report of the Western Australian cerebral palsy register. To birth year 1999, Perth: Institute for Child Health Research, 2006. 8 Shevell MI, Majnemer A, Morin I. Etiologic yield of cerebral palsy: a contemporary case series. Pediatr Neurol 2003; 28: 352–359. 9 Winter S, Autry A, Boyle C, Yeargin-Allsopp M. Trends in the prevalence of cerebral palsy in a population-based study. Pediatrics 2002; 110: 1220–1225. 10 Palisano R, Rosenbaum P, Walter S, Russell D, Wood E, Galuppi B. Development and reliability of a system to classify gross motor function in children with cerebral palsy. Dev Med Child Neurol 1997; 39: 214–223. 11 Available from:http://www.canchild.ca/ 12 Available from:http://www.macs.nu/ 13 Beckung E, Hagberg G. Neuroimpairments, activity limitations, and participation restrictions in children with cerebral palsy. Dev Med Child Neurol 2002; 44: 309–316. 14 Andersen G, Irgens LM, Haagaas I, Skranes JS, Meberg A, Torstein V. Cerebral palsy in Norway: prevalence, subtypes and severity. Eur J Paediatr Neurol 2008; 12: 4–13. 15 Himmelmann K, Beckung E, Hagberg G, Uvebrant P. Gross and fine motor function and accompanying impairments in cerebral palsy. Dev Med Child Neurol 2006; 48: 417–423.
Cases of cerebral palsy not yet preventable or difficult to prevent The proportion of cases of CP of unknown origin is still high, at least 30%,21 despite improvements in understanding following from the recommendation of systematically performing MRI in children with CP. A multifactorial origin is frequent in cases of CP. For example, it is possible to observe a cascade of adverse events such as a genetic susceptibility plus maternal age (grater than 38 years old), plus multiple births, plus congenital heart anomaly, without being sure of what the main cause of CP is. The causal pathways of CP have been clearly described and the complexity of the different situations highlighted in the latest edition of a
Multiple births, low birth weight/low gestational age and cerebral palsy in children born between 1975 and 1990 in Europe*20
Among live births
CP rates
Proportion of VLBW Proportion of less than 32 weeks In all live births* In VLBW births*
Multiple births
Singletons
7.7%
0.71%
7.9%
0.79%
7.6 per 1000 41 per 1000
1.8 per 1000 38 per 1000
* 12 SCPE centres.
Table 3
PAEDIATRICS AND CHILD HEALTH 18:9
397
© 2008 Elsevier Ltd. All rights reserved.
Symposium: special needs
16 Beckung E, Hagberg G, Uldall P, Cans C, Surveillance Palsy in EuropeProbability of walking in children with cerebral palsy in Europe. Pediatrics 2008; 121: e187–e192. 17 Surman G, Newdick H, King A, Gallagher M, Kurinczuk JJ. Annual report including data for births 1984 to 2000. Four Counties Database of Cerebral Palsy, Vision Loss and Hearing Loss in Children. Berkshire, Buckinghamshire, Northamptonshire, Oxfordshire, December 2006. National Perinatal Epidemiology Unit, Oxford. 18 Dolk H, Parkes J, Hill N. Trends in the prevalence of cerebral palsy in Northern Ireland, 1981–1997. Dev Med Child Neurol 2006; 48: 406–412. 19 Platt MJ, Cans C, Johnson A, et al. Trends in cerebral palsy among infants of very low birthweight (less than1500 g) or born prematurely (less than 32 weeks) in 16 European centres: a database study. Lancet 2007; 369: 43–50. 20 Topp M, Huusom LD, Langhoff-Roos J, Delhumeau C, Hutton JL, Dolk H. Multiple birth and cerebral palsy in Europe: a multicenter study. Acta Obstet Gynecol Scand 2004; 83: 548–553. 21 Himmelmann K, Hagberg G, Beckung E, Hagberg B, Uvebrant P. The changing panorama of cerebral palsy in Sweden. IX. Prevalence and origin in the birth-year period 1995–1998. Acta Paediatr 2005; 94: 287–294. 22 Stanley F, Blair E, Alberman E. Causal pathways to the cerebral palsies: a new aetiological model. In: Bax MCO, Hart HM, eds. Cerebral palsies: epidemiology and causal pathways. London: Mac Keith Press, 2000, p. 40–47.
PAEDIATRICS AND CHILD HEALTH 18:9
Practice points • There is widespread consensus on what constitutes CP, and it is recognized that children with CP often present associated impairments that may strongly influence their activity, participation and quality of life • Standardized procedures are now available for ascertaining and describing children with CP, and it is possible to determine motor impairment severity with validated scales • Collaborative efforts are required to monitor CP trends and to evaluate treatment efficiency. Epidemiology of CP has changed during the past 10 years, mainly among moderate low birth weight and bilateral spastic very low birth weight children • CP is most often the result of multifactorial events rather than one, a situation which impedes its prevention
Acknowledgement We acknowledge the collaborating partners of the SCPE Network.
398
© 2008 Elsevier Ltd. All rights reserved.
Epidemiology of cerebral palsy
loss of motor function. A child with spina bifida is not included among CP cases unless his/her brain has suffered at birth, a very unlikely coincidental event. Progressive motor disorders, spinal, nerve or muscular diseases and also brain metabolic disorders fall outside the scope of CP, although the special needs of these children may be very similar. A decision tree has been developed to promote the consistent implementation of these criteria.1
Christine Cans Javier De-la-Cruz
Public health perspective
Marie-Ange Mermet
CP is the most prevalent severe disability in childhood after severe intellectual impairment. In school age children it is twice as common as Down syndrome and it accounts for 60% of severe motor disabilities.3 Other motor disabilities are neuromuscular diseases, spinal cord disorders and some rare tissue and skeletal diseases (dermatomyositis, arthrogryposis). Although used as an umbrella term for different diseases, some of them infrequent, CP itself is not usually considered to be a rare disease due to its overall prevalence, around 2 per 1000 live births. It can be estimated that 650 000 families in Europe (EU 25) either have a child with CP or support an adult with CP. Many persons with CP have associated impairments such as intellectual impairment, sensorial impairment or epilepsy. Most children with CP require some specific help during their schooling period. As adults, half of them will face difficulties in getting a job and living independently. Among the elderly population with CP, more than one-third will be institutionalized for permanent medical assistance. An increase in life-expectancy for children with CP has been shown over the last decades. Nevertheless, their 20-year survival rate is lower than that for the general population.
Abstract Definition of cerebral palsy (CP) has become more precise in recent years and, even if CP remains an umbrella term, a simple classification system for CP types has been proposed. CP is the commonest motor impairment in childhood. New validated motor scales for gross and fine motor functions describe a third of children with CP as severely impaired. Children with CP may also have associated impairments, other than motor, that deserve particular attention and support at school and work, and which are responsible for lower survival rates. The prevalence of CP, 2 per 1000 children, has remained remarkably stable over the last 30 years, particularly for term children who represent half of all children with CP. However, recently, a consistent downward trend has been seen in moderately and very low birth weight children. Prevention measures still seems difficult to define since CP is the result of multifactorial events. Decreasing multiple births and specific health actions during early infancy may have an impact. Followup programmes have been implemented to assess how the consequences of CP are best reduced.
Keywords cerebral palsy; classification; disability; epidemiology; impairment; motor function; prevalence
Classification of cerebral palsy To obtain a complete clinical pattern of CP (based on phenotypical expression), children can be described according to observed neurological signs, current loss of motor function and associated impairments.
Definition Cerebral palsy (CP) is the commonest motor impairment in childhood. It affects 1 in 500 children, and is responsible for permanent limitation of activity and participation. The prevailing definitions of CP have common elements: CP is a group of permanent, but not unchanging, disorders of movement and/or posture and of motor function due to a nonprogressive interference, lesion or abnormality of the developing/immature brain.1 Recently, the changing concepts of impairment and limitation of activity were taken into consideration, and it was also highlighted that children with CP often show accompanying impairments.2 It is worth pointing out conditions that are not CP. For example, a child with dyspraxia may face activity limitation and a learning disability but he/she does not show neurological signs or
Classification based on neurological signs Spasticity is one of the main neurological signs in the clinical description of a case of CP. To discriminate subgroups of CP with spasticity, classification systems often used to refer to the localization of the motor function loss, with terms such as diplegia, double hemiplegia, quadriplegia, tetraplegia and hemiplegia. However, it has been shown, and recently confirmed, that the distinction between these terms is not sufficiently reliable.4 A European network of population-based surveys and CP registers adopted a simple classification of CP types to ensure data comparability between centres. This research collaboration reached a consensus between professionals with different background and skills for the very simple classification of CP subtypes into four main groups: unilateral spastic, bilateral spastic, dyskinetic and ataxic. To promote this standardized way of classifying CP types, SCPE (Surveillance of Cerebral Palsy in Europe) developed a classification tree1 and a reference and training manual in CD format including video sequences of the different clinical patterns of neurological signs and motor function impairments.5 Table 1 shows very similar proportions of CP subtypes when
Christine Cans MD PhD is Senior Epidemiologist at RHEOP-SCPE ThEMAS, Grenoble University Hospital, France. Javier De-la-Cruz MD is Clinical Epidemiologist at CIBERESP, Hosp Univ 12 de Octubre, Madrid, Spain. Marie-Ange Mermet MSc is a member of the ThEMAS Team, UJF Faculté de Médecine de Grenoble, Grenoble, France.
PAEDIATRICS AND CHILD HEALTH 18:9
393
© 2008 Elsevier Ltd. All rights reserved.
Symposium: special needs
Distribution of cerebral palsy types in different countries (postneonatal cases included)
Europe6 Western Australia7 Quebec8 Atlanta, USA9 South-east Australia4
Number
Bilateral spastic (%)
Unilateral spastic (%)
Dyskinetic (%)
Ataxic (%)
Other (%)
6174 1599 217 815 323
50 44 54 56 56
30 39 31 23 30
7 8 1
6 8 6 21 3
7 1 8
2
9
Table 1
applying this classification system to data from Europe, North America and Australia.
should be considered when giving information to parents about their child’s prognosis. It has been shown, for example, that severe intellectual impairment has a strong influence on walking ability in children with unilateral spastic CP type.16
Classification based on motor function Until recently, severity of motor impairment was commonly assessed by describing walking ability. Data comparison was hindered by different underlying definitions of ‘walking ability’, which could mean walking a few meters only, walking outdoors or just being able to walk without actually walking in everyday life. The assessment of motor function has improved significantly with specific motor scales for gross and fine motor functions. The Gross Motor Function Measurement Scale (GMFMS, 88 or 66 items) was developed for clinical use, reduced to a five-point scale for epidemiological purposes (the Gross Motor Function Classification System [GMFCS]),10 and extended and revised in 2007. More recently, similar scales for fine motor abilities have been developed: the Manual Ability Classification System (MACS) and the Bimanual Fine Motor Function (BFMF) scales. GMFCS and MACS are both validated in depth and available online.11,12 BFMF offers the advantages that it takes account of asymmetry and allows data to be extracted from medical records. BFMF validation is pending.13 The use of these scales has greatly increased comparability of results between centres. Table 2 shows that the proportion of more severely impaired children on either scale (level IV/V) is around 25–35% of all CP cases. The dyskinetic group shows the highest variability between studies, suggesting residual difficulties in classifying mixed forms.
Early determinants of cerebral palsy The risk of developing CP for children born preterm is 10–50 times higher than for term children. A third of children with CP are born very preterm or with a very low birth weight (VLBW), whilst half of children with CP are born at term. The risk of developing CP is also higher for children born with a congenital anomaly or growth deviation, and for children admitted, for whatever reason, to a neonatal intensive care unit (NICU). At least 15% of children with CP have a congenital anomaly (brain or nonbrain). Growth retardation in singleton children (born at 32–42 weeks’ gestation) increases the risk of developing CP 4–6 times, and macrosomy 2–3 times. This is particularly relevant because growth deviation is not infrequent in the general population (6%), i.e. 3% have a low birth weight and 3% an excessive birth weight. Some authors are trying to identify babies who might later develop CP from their early movement pattern. There is a consensus about the usefulness of follow-up programmes for newborns admitted to NICUs to ensure early diagnosis. However, and despite promising results, further studies are needed to establish the benefit of intensive early therapy on longer term abilities.
Frequency and trends over time
Associated impairments in cerebral palsy cases The importance of impairments other than motor, commonly observed in children with CP, has recently been highlighted. For epidemiological and quality of care purposes, a severity measurement of each associated impairment should distinguish between, for example, a child with CP and strabismus and a child with total blindness, or between a child with CP and severe mental retardation (IQ less than 50 following WHO classification cut-off point) and a child with CP and mild mental retardation (IQ 50–69). Hearing impairment is rarely associated with CP, whilst other types of impairment are frequent. Severe intellectual impairment occurs in one-third of children with CP, blindness or nearblindness in 1 in every 10, and epilepsy in up to one-third. The proportion of children with CP without any severe associated impairment varies from one-third to one-half, depending on CP type and birth weight. The impact of these and of other associated impairments (speech, communication and feeding impairments)
PAEDIATRICS AND CHILD HEALTH 18:9
CP prevalence is around 2 per 1000 live births in both developed and developing countries (even if for very different reasons). For term children CP prevalence is 1 per 1000 live births. For moderately preterm children (32–36 weeks’ gestation) estimates are 6–10 times higher and for very preterm children (less than 32 weeks’gestation) prevalence is 10 times higher than in moderately preterm children (Figure 1). CP rates for live births show a lower prevalence for babies of birth weight less than 1000 g than for those with a birth weight of 1000–1499 g. This paradoxical effect is due to the high number of babies who do not live long enough to develop CP, and it disappears when estimating prevalence for neonatal survivors. Changes in perinatal and neonatal mortality accelerated in most countries from the 1960s, with a huge decrease up until the late 1980s, when there was an increase in the absolute number of children with CP. From 1990 there has been a plateauing of mortality rates but a downward trend in CP rate mainly in moderate and VLBW children. 394
© 2008 Elsevier Ltd. All rights reserved.
Symposium: special needs
Percentage of more severe motor impairment, measured using GMFCS and BFMF scales, in children with cerebral palsy from different studies Bilateral spastic (%)
Unilateral spastic (%)
Dyskinetic (%)
Ataxic (%)
Total (%) (number)
GMFCS level IV/V SE Australia4 Norway14 Sweden15 France* BFMF level IV/V
50 38 41 46
1 1 3 0
40 89 79 20
0 0 0 0
34 28 23 31
Norway14 Sweden15 France*
44 31 37
1 1 0
95 50 15
39 0 0
35 (289) 24 (367) 27 (100)
(323) (289) (367) (100)
Gross Motor Function Classification System [GMFCS] (between 4th and 6th birthdays):10
• GMFCS level IV: Children sit on a chair but need adaptative seating for trunk control and to maximize hand function. Children move in and out of a chair,
sitting with assistance from an adult or a stable surface to push or pull up on with their arms. Children may at best walk short distances with a walker and adult supervision but have difficulty turning and maintaining balance on uneven surfaces. Children are transported in the community. Children may achieve self-mobility using a power wheelchair. GMFCS level V: Physical impairments restrict voluntary control of movement and the ability to maintain antigravity head and trunk postures. All areas of motor function are limited. Functional limitations in sitting and standing are not fully compensated for through the use of adaptive equipment and assistive technology. Children have no means of independent mobility and are transported. Some children achieve self-mobility using a power wheelchair with extensive adaptations.
•
Bimanual Fine Motor Function [BFMF]:13
• BFMF level IV: (a) both hands, only able to grasp; (b) one hand, only able to grasp; other hand, only able to hold or worse. Child needs support and/or adapted equipment. • BFMF level V: both hands, only able to hold or worse. *Personal communication, RHEOP, Medecine diploma, L Camel, 2006.
Table 2
In most studies the CP rates in children born at term or with normal birth weight seem rather stable over time (Figure 2a), although a decreasing trend was observed in Sweden and in one UK centre. This finding is particularly relevant since normal birth weight and term children represent at least one-half of children with CP and, thus, it may be related to the persisting stagnation of CP prevalence despite continuous improvement in perinatal care and in mortality rates.7,9,17,18,21 Moderately preterm children and children with a birth weight of 1500–2499 g represent one-fifth of all children with CP. In the early 1990s, a downward trend in CP rate began to emerge for this group (Figure 2b). To analyse CP prevalence rate in VLBW children and to distinguish between children with birth weight 1000–1499 g and less than 1000 g, pooling of data from different centres was necessary and the SCPE Network recently made this practicable (Figure 2c). Overall, the greatest recent change in CP prevalence was observed in children born at less than 32 weeks’ gestation or weighing less than 1500 g. Since 1980, the CP prevalence rate has decreased considerably in the 1000–1499 g birth weight group and in the bilateral spastic clinical subtype group (Figure 2c). To a great extent this can be explained by improvement in perinatal and neonatal management and the decrease in the occurrence of white matter parenchymal lesions in these children.19
PAEDIATRICS AND CHILD HEALTH 18:9
When looking at CP estimates for clinical subtypes, some authors have suggested recently that there might be an increase in the prevalence of the dyskinetic type of CP, independent of birth weight, which counterbalances the encouraging results of the significant trends observed among VLBW and moderate birth weight children. Factors influencing cerebral palsy prevalence Many factors influence the prevalence of CP: 1. Time period: CP prevalence seems to fluctuate over time more than can be explained by simple random variation. This variation may relate to the level of care and the mortality rates in the study areas. 2. Inclusion of mild CP cases: children with CP who show neurological signs but only minor motor function difficulties will walk without limitations, and are not included in studies that focus on ‘disabled’ children only, whatever definition of CP is used. 3. Migration movements out of the area covered: the proportion of children moving out of the area before CP is diagnosed may alter the estimated CP rate. 4. Stillbirths and neonatal mortality rates: children who would have died a few years ago are now surviving despite their VLBW. These children may contribute significantly to the overall number of children with CP since they are at greater risk of developing CP. It can be expected that where mortality rates are high, CP 395
© 2008 Elsevier Ltd. All rights reserved.
Symposium: special needs
a 90
a
80
Rate per 1,000 live births
70
Survivors
60 50 40 30
Live births
20 10 0 < 1000
1000–1499
1500–2500
> 2500
Weight (g)
2.0 1.8 1.6 1.4 1.2 1.0 0.8 0.6 0.4 0.2 0
b
1981 1983 1985 1987 1989 1991 1993 1995 1997 1999
90 80
Birth years
Survivors b
70
Rate per 1,000 live births
60 50 40
Live births
30 20 10 0 < 28
28–31
32–36
> 36
Gestation (weeks)
16 14 12 10 8 6 4 2 0 1981 1983 1985 1987 1989 1991 1993 1995 1997 1999
Figure 1 Prevalence rates of CP per 1000 live births and per 1000 neonatal survivors according to a birth weight (eight centres—SCPE data 1990–1998) and b gestational age (six centres—SCPE data 1990–1998) (SCPE Network, personal communication).
Birth years UK (Oxford, 17)
West Australia (7)
Sweden (21)
USA (9)
UK (Belfast, 18)
c Birth prevalenceper 1,000 live births
rates are low. However, it may also be that good clinical practice will simultaneously lower mortality rate and CP prevalence rate. 5. Neonatal intensive care practices, including withdrawal of life support, may have an impact on local CP rates over time; this influence is difficult to assess. To date research has mainly focused on children born preterm or with low birth weight. It may be appropriate for epidemiological studies and clinical trials to focus also on the larger group of term children with CP. Finally, an important question for clinicians, public health doctors and policy makers is still open to discussion: do children with CP have more or less severe clinical patterns now than before? Paediatricians from the same or different countries disagree on the answer, and so do epidemiologists, since there is no current consensus on what is a severe, moderate or mild case of CP. Several authors have described trends in severity, with discordant results up to now. The proportion and prevalence of nonambulant children with CP seem to have been stable over time,16 but the trends for children with CP and severe intellectual or vision impairment are less well known.
60 50 40 30 20 10 0 1981
1983
1985
1987
1989
1991
1993
1995
Midpoint birth year Bilateral spastic cerebral palsy in children of birthweight 1,000–1,499 g Bilateral spastic cerebral palsy in children of birthweight < 1,000 g Hemiplegia spastic cerebral palsy in children of birthweight 1,000–1,499 g Hemiplegia spastic cerebral palsy in children of birthweight < 1,000 g Reprinted from Platt MJ et al. Trends in cerebral palsy among infants of very low birthweight (<1500 g) or born prematurely (<32 weeks) in 16 European centres: a database study. The Lancet, 369, 8. Copyright (2007), with permission from Elsevier.
Prevention Prevention comprises a wide range of actions, from efforts to prevent the development of CP in a child to the interventions oriented to reduce its consequences. Preventive actions may then be closely related to the knowledge on aetiology of the disorder or on determinants of the resulting disability.
PAEDIATRICS AND CHILD HEALTH 18:9
70
Figure 2 Cerebral palsy rates in children of a normal birth weight, b birth weight 1500–2499 g, and c very low birth weight 1000–1499 g and < 1000 g. Postneonatal cases excluded.
396
© 2008 Elsevier Ltd. All rights reserved.
Symposium: special needs
cardinal book on CP.22 Thus, it is difficult to envisage specific health actions for each identified influential factor.
Potentially preventable cases of cerebral palsy Acquired or postneonatal cases of CP are defined as an accidental/infectious/hypoxic event that leads to brain lesion in a presumed uninjured brain after the first month of life. Public health and health care actions, such as policies promoting more safety on the roads, meningitis immunization programmes and better management of blood circulation during surgical interventions for heart congenital anomalies, are reducing postnatal cases of CP. These cases of CP account for 5–10% of all cases in developed countries. The increase in multiple births during the 1980s and 1990s, from 1.5% to 3%, has certainly contributed partially to the stability of CP rates. It was recently shown that the risk of developing CP in multiple births was mainly explained by the VLBW/very preterm status of children issuing from multiple births (Table 3).20 Thus, besides recommending that no more than two embryos should be implanted in assisted reproduction treatments, it is also important to remind young women about the risk of multiple births increasing with higher maternal age. Despite consistent efforts in different countries, it seems to be quite difficult to reduce the rate of preterm births. During the prenatal period attention has to be paid to the detection of deviation from normal growth. At present time, antenatal magnetic resonance imaging (MRI) may be performed once a brain anomaly/ lesion is suspected, but antenatal therapeutic strategies following diagnosis contribute more to research programmes than to care implementation.
Follow-up programmes Follow-up programmes for children with CP have been established recently in several countries. It has been shown that efforts toward early identification of hip subluxation should be performed in bilateral spastic CP, allowing conservative measures and preventive surgery. Studies are needed to identify which support therapeutic strategies bring longer term benefits to the children, including psychological (e.g. parental stress) and educational dimensions. The present availability of better tools for identifying and classifying CP, and for assessing its severity, will certainly help in the evaluation of clinical practices. ◆
References 1 Surveillance of Cerebral Palsy in Europe. Surveillance of cerebral palsy in Europe: a collaboration of cerebral palsy surveys and registers. Dev Med Child Neurol 2000; 42: 816–824. 2 Bax M, Goldstein M, Rosenbaum P, et al. Proposed definition and classification of cerebral palsy, April 2005. Dev Med Child Neurol 2005; 47: 571–576. 3 Cans C, Guillem P, Fauconnier J, Rambaud P, Jouk PS. Disabilities and trends over time in a French county, 1980–91. Arch Dis Child 2003; 88: 114–117. 4 Howard J, Soo B, Graham HK, Boyd RN, et al. Cerebral palsy in Victoria: motor types, topography and gross motor function. J Paediatr Child Health 2005; 41: 479–483. 5 Cans C, Dolk H, Platt MJ, Colver A, Prasauskiene A, KragelohMann I. Recommendations from the SCPE collaborative group for defining and classifying cerebral palsy. Dev Med Child Neurol 2007; 109(suppl): 35–38. 6 Surveillance of Cerebral Palsy in Europe. Prevalence and characteristics of children with cerebral palsy in Europe. Dev Med Child Neurol 2002; 44: 633–640. 7 Watson L, Blair E, Stanley F. Report of the Western Australian cerebral palsy register. To birth year 1999, Perth: Institute for Child Health Research, 2006. 8 Shevell MI, Majnemer A, Morin I. Etiologic yield of cerebral palsy: a contemporary case series. Pediatr Neurol 2003; 28: 352–359. 9 Winter S, Autry A, Boyle C, Yeargin-Allsopp M. Trends in the prevalence of cerebral palsy in a population-based study. Pediatrics 2002; 110: 1220–1225. 10 Palisano R, Rosenbaum P, Walter S, Russell D, Wood E, Galuppi B. Development and reliability of a system to classify gross motor function in children with cerebral palsy. Dev Med Child Neurol 1997; 39: 214–223. 11 Available from:http://www.canchild.ca/ 12 Available from:http://www.macs.nu/ 13 Beckung E, Hagberg G. Neuroimpairments, activity limitations, and participation restrictions in children with cerebral palsy. Dev Med Child Neurol 2002; 44: 309–316. 14 Andersen G, Irgens LM, Haagaas I, Skranes JS, Meberg A, Torstein V. Cerebral palsy in Norway: prevalence, subtypes and severity. Eur J Paediatr Neurol 2008; 12: 4–13. 15 Himmelmann K, Beckung E, Hagberg G, Uvebrant P. Gross and fine motor function and accompanying impairments in cerebral palsy. Dev Med Child Neurol 2006; 48: 417–423.
Cases of cerebral palsy not yet preventable or difficult to prevent The proportion of cases of CP of unknown origin is still high, at least 30%,21 despite improvements in understanding following from the recommendation of systematically performing MRI in children with CP. A multifactorial origin is frequent in cases of CP. For example, it is possible to observe a cascade of adverse events such as a genetic susceptibility plus maternal age (grater than 38 years old), plus multiple births, plus congenital heart anomaly, without being sure of what the main cause of CP is. The causal pathways of CP have been clearly described and the complexity of the different situations highlighted in the latest edition of a
Multiple births, low birth weight/low gestational age and cerebral palsy in children born between 1975 and 1990 in Europe*20
Among live births
CP rates
Proportion of VLBW Proportion of less than 32 weeks In all live births* In VLBW births*
Multiple births
Singletons
7.7%
0.71%
7.9%
0.79%
7.6 per 1000 41 per 1000
1.8 per 1000 38 per 1000
* 12 SCPE centres.
Table 3
PAEDIATRICS AND CHILD HEALTH 18:9
397
© 2008 Elsevier Ltd. All rights reserved.
Symposium: special needs
16 Beckung E, Hagberg G, Uldall P, Cans C, Surveillance Palsy in EuropeProbability of walking in children with cerebral palsy in Europe. Pediatrics 2008; 121: e187–e192. 17 Surman G, Newdick H, King A, Gallagher M, Kurinczuk JJ. Annual report including data for births 1984 to 2000. Four Counties Database of Cerebral Palsy, Vision Loss and Hearing Loss in Children. Berkshire, Buckinghamshire, Northamptonshire, Oxfordshire, December 2006. National Perinatal Epidemiology Unit, Oxford. 18 Dolk H, Parkes J, Hill N. Trends in the prevalence of cerebral palsy in Northern Ireland, 1981–1997. Dev Med Child Neurol 2006; 48: 406–412. 19 Platt MJ, Cans C, Johnson A, et al. Trends in cerebral palsy among infants of very low birthweight (less than1500 g) or born prematurely (less than 32 weeks) in 16 European centres: a database study. Lancet 2007; 369: 43–50. 20 Topp M, Huusom LD, Langhoff-Roos J, Delhumeau C, Hutton JL, Dolk H. Multiple birth and cerebral palsy in Europe: a multicenter study. Acta Obstet Gynecol Scand 2004; 83: 548–553. 21 Himmelmann K, Hagberg G, Beckung E, Hagberg B, Uvebrant P. The changing panorama of cerebral palsy in Sweden. IX. Prevalence and origin in the birth-year period 1995–1998. Acta Paediatr 2005; 94: 287–294. 22 Stanley F, Blair E, Alberman E. Causal pathways to the cerebral palsies: a new aetiological model. In: Bax MCO, Hart HM, eds. Cerebral palsies: epidemiology and causal pathways. London: Mac Keith Press, 2000, p. 40–47.
PAEDIATRICS AND CHILD HEALTH 18:9
Practice points • There is widespread consensus on what constitutes CP, and it is recognized that children with CP often present associated impairments that may strongly influence their activity, participation and quality of life • Standardized procedures are now available for ascertaining and describing children with CP, and it is possible to determine motor impairment severity with validated scales • Collaborative efforts are required to monitor CP trends and to evaluate treatment efficiency. Epidemiology of CP has changed during the past 10 years, mainly among moderate low birth weight and bilateral spastic very low birth weight children • CP is most often the result of multifactorial events rather than one, a situation which impedes its prevention
Acknowledgement We acknowledge the collaborating partners of the SCPE Network.
398
© 2008 Elsevier Ltd. All rights reserved.