The California Cerebral Palsy Project

zyxwvuts zyxwvuts Paediatric and Perinatal Epidemiology 1992,6,339-351 The California Cerebral Palsy Project zyx zy Judith K. Grether*, Susan K. Cumminst and Karin 8.Nelson$ *California Birth Defects Monitoring Program and tEnvironmenta1 Epidemiology and Toxicology Branch, California Department of Health Smices, Emeryoille, California, and $National Institute of Neurological Disorders and Stroke, Neuroepidemiology Branch, Bethesda, Mayland, USA Summary. The California Cerebral Palsy Project (CACP) is a population-based study of 192 children with moderate or severe congenital cerebral palsy who were born between 1983 and 1985 in four San Francisco Bay area counties and who were alive and residing in California at age 3 years. Initial ascertainment of cases was based on records of two agencies known to enrol virtually all CACP-eligible children. Final case status was established by standardised clinical examination in 67% of cases and extensive record review in 33%.The 192 cases gave a prevalence at age 3 of 1.23/10oOsurvivors. Twins were 10%of the cases with a prevalence of 6.711000. Overall, 53% of the cases had birthweight 3 2,500 g and 28% had birthweight < 15oog. There was no association between birthweight and severity of functional impairment and no consistent association between birthweight and the presence of associated disabilities. The CACP prevalence is lower than that reported in other studies and is believed to be due to the more stringent case inclusion criteria employed for this research data base. zyxw zyxwv Introduction The California Cerebral Palsy Project (CACP) is a population-based study of children with moderate or severe congenital cerebral palsy (CP) who were born between 1983 and 1985 in four San Francisco Bay area counties. This report describes the methods used to ascertain and diagnose cases and reports the Address for correspondence: Dr J.K.Grether, California Birth Defects Monitoring Program, 5900 Hours Street, Suite A, Emeryvllle, California 94608, USA. 339 340 zyxwvuts zyx 1.K. Grether et al. prevalence of CP as observed at 3 years of age. It also reports the dominant CP subtypes in relation to birthweight and the presence of associated disabilities. Methods Dejinitions zyxwvuts zyxw zy zyxwv zyxwv Cerebral palsy was defrned as a chronic disability of central nervous system origin characterised by aberrant control of movement or posture, appearing early in life and not the result of a progressive disease. Excluded were transient motor disabilities, motor disabilities due to meningomyelocele or other spinal cord lesions, isolated hypotonia, and motor abnormalities due solely to mental deficiency. To be defined as a case, a child must have met all of the following criteria: born between 1983 and 1985; maternal residence as verified on the child's birth certificate in one of four San Francisco Bay area counties (Contra Costa, San Francisco, San Mateo, Santa Clara); child alive and residing in California at age 3 years; moderate or severe congenital CP at age 3 years as determined by a standardised examination or record review conducted by a single CACP physician. The criterion age of 3 years was chosen as the earliest age at which reliable ascertainment was feasible in these moderately and severely affected children. Excluded were children whose CP was acquired through infection, trauma, or other known adverse event after the first 28 days of life or through documented severe head trauma in the first month of life. Assessment of severity of CP was based on functional ability of the most affected limb. CP was classified as severe if that limb had no function, and as moderate if some function was preserved although assistive devices were usually required. Mild CP, with abnormalities oftone and reflexes but no functional impairment, was excluded because it could not be reliably ascertained. CP was categorised as spastic hemiplegia (armand leg of one side of the body affected), spastic diplegia (legs more affected than arms), spastic quadriplegia (involvement of all four limbs, arm involvement at least as severe as legs), dyskinesia (abnormal involuntary movements), ataxia (lack of balance and uncoordinated movement) or mixed (spastic CP with ataxia and/or dyskinesia). The descriptive data used to assign CP subtype are compatible with the Standard Recording of Central Motor Deficit reported by Evans et al.' Information on associated disabilities was obtained through parental interview and classified as follows: vision disability ('some difficulty' or 'blind), hearing disability ('some difficulty' or 'deaf'), speech disability ('difficult to understand, 'non-verbal communication only' or 'no communication'), chronic seizure disorder (parental report of physician diagnosis) and mental retardation (parental report of diagnosis by physician or other professional). In addition, an informal California Cerebral Palsy Project zyx zyx 341 impression of intellectual functioning was recorded by the CACP physician as part of the clinical examination. No other validation of associated disabilities was conducted. Case ascertainment procedures Children with definite or possible motor disabilities were identified through review of service records of two state-funded agencies: the California Children ServiceslDepartment of Health Services (CCS) and Regional Centers for the Developmentally Disabled/Department of Developmental Services (DDS). Both programmes provide services to children with CP without regard to financial or citizenship status in accordance with statewide guidelines. Community surveys conducted by the California Birth Defects Monitoring Program prior to establishment of the CACP had demonstrated that, in the four study counties, virtually all children with moderate or severe congenital CP were CCS clients, many having dual enroIment with DDS. A very small minority of children with severe disabilities were exclusively DDS clients. Regulatory restrictions on access to confidential data prohibited inclusion of these few DDS clients in the data base. However, as explained below, limited non-confidential information was obtained for these children. Within CCS, the $year birth cohort was tracked until all members were at least 4% years old. Using very broad criteria applied to computerised service records, 1110 possible cases were selected for manual chart review, including children who had moved to other counties within the state and children who were not currently enrolled with CCS (Figure 1). Chart review was conducted by CACP field staff to determine presumptive eligibility. Records in which the diagnosis of CP was ambiguous underwent a second review by a CACP physician. Children with ambiguous aetiological information were retained as presumptive cases, pending review of medical records by the CACP physician. All presumptive cases were then linked to vital statistics records to venfy birthdate, residence and survival to age 3 (Figure 1). To establish the final diagnosis of CP, all CCS children who remained as presumptive cases were invited to undergo a standardised neurological and motor assessment. For children who could not be examined, the final diagnosis was established through extensive review of CCS records, other medical records and, in many cases, personal discussion with therapists or physicians familiar with the child. Physical examinations and record review were performed by a CACP physician (S.K.C.) who was blinded to the previous medical history of the children and who had received special training for this project. Prior to the examination, a brief interview was conducted with a parent or guardian, usually on the telephone, by a CACP field staff member. The interview was used to obtain zyxwvuts zyxwvuts 342 zyxwvutsrq zyxwvutsrq zyxwvu zyxwvuts zyxwvu 1.K. Grether et al. zyxw zyxw n zyxw zyxwvut CCS records of 1110 children initially reviewed I I -Excluded - - 18 children died or moved before age 3 years 369 children had M inellgibie birthdate or birth residence 71 children had another condition that was not CP 51 children had CP acquired after 28 days of age or from head trauma after birth 339 had no evidence of CP I 262 children with possible CP matched to their birth certiflcate i -Excluded -Excluded - 14 children had mild CP 192 children with moderate or severe Figure 1. Case ascertainment process at CCS: CACP 1983-1985. 1 zyxw zyx zy Culifarniu Cerebral Palsy Project 343 information on medical and surgical treatment which might affect examination findingsand on associated disabilities. Intensive procedures were used to locate parents or guardians and solicit consent for participation in the examination. Bilingual translators .were used as needed. Examinations were conducted in CCS clinic facilities or the child’s home or school. Identical procedures were followed for all children residing in California during the study period, whether their residence was inside or outside the study area. Within DDS, clients with possible CP (n=322) were selected from computerised client records which contained non-confidential diagnostic data. Staff at the local DDS Regional Centers then reviewed confidential records to determine birth residence and dual enrolment with CCS. For the few presumptive cases who were exclusively DDS clients, DDS staff attempted to obtain parental consent for CACP staff to review confidential DDS records. This effort was generally unsuccessful because of inability to locate parents of institutionalised children. DDS medical staff then reviewed the complete DDS record on each presumptive case and completed a non-confidential data form querying residency, birthdate, survival and residency in California at age 3, type of motor condition, whether acquired or congenital, and severity. Because identdymg data were not available to link these children with vital records, they were not included in the CACP data base. zyxwv zyxwvuts zyxwvu Evaluation of cuse ascertainment procedures To evaluate CCS and DDS as adequate sources for initial identification of cases, telephone interviews were conducted with 22 private physical and occupational therapists and with selected public school special education programmes to enquire about children with moderate or severe CP who were born between 1983 and 1985in the study area and who had never been enrolled with CCS and DDS. No such children were identifed. To check the selection of possible cases from the computerised CCS files, all open and closed charts between January 1983 and March 1990 were manually reviewed at two of the four local CCS programmes; all therapy records for the same period were reviewed at a third local CCS programme; all referral diagnoses were reviewed at the remaininglocal CCS programme. Two additional cases were found through these procedures and were added to the data base. To evaluate the exclusion of possible cases through the manual review of records, a second review was conducted by a different reviewer on a 40% sample (n = 100) of the subset of CCS clients who had been excluded because there was no evidence of motor problems at age 3, they had mild CP, developmental delay and hypotonia, or an apparently progressive condition with no specific diagnosis. Inter-rater agreement was 100%. zyxwvutsrqpo 344 zyxwvutsr zyxwvutsrq zyxwvut zyxwvu J.K. Grether et al. To evaluate the assignment of final case status based on physical examination or physician review of records, a sample of cases underwent an informal review by a second CACP physician (K.B.N.). This review indicated that primary diagnoses were reliably established but that the assessment of secondary CP subtypes and degree of severity across subtypes may not be robust. zyxwvut zyxwv Statistical methods A chi-square test of association with sigruhcance level of 0.05 was used. A risk ratio (RR) measure with 95%confidence levels was used to obtain a point estimate of the relative risk of CP among subgroups of survivors to age 3. . I Results The final CACP case series includes 192 children with moderate or severe CP as established by physical examination in 129 cases (67%)and record review in 63 cases (33%).Examined cases averaged 4.9 years of age at the time of examination, with a range from 2.6 to 7 years. Of the 63 cases whose final diagnosis was established through record review, 19 had refused consent or had repeatedly failed to keep appoinbnents for examinations. Nine had died after their third birthday, and three were known to have moved out of the state. The remaining32 cases could not be located and examined within the time frame of the study. The examined cases and record review cases were similar with respect to sex, maternal race, birth type (single or twin) and severity of CP. Examined cases were more often of very low birthweight (<l500g) and had diplegia or mixed CP, compared with record review cases (Table 1).Four children who were exclusively DDS clients and one CCS client were not included because their birth residence could not be verified but they met other case criteria. Prevalence The 192 verified cases gave a prevalence at age 3 of 1.23/1000 suTvivors, 1.36/1000 for males and 1.10/1000 for females (RR=1.2 (0.9,1.6)). Inclusion of the five unverified cases gave a prevalence of 1.27/1000survivors. There were no sigruficant differences in prevalence among the four study counties or the three birth years. Among children identified as singletons on the birth certificate, the prevalence was 1.1/1000; among twins, 6.7/1000 (RR = 5.9 (3.7’9.4)). Twins represented 10% of the cases. There were no cases among 64 triplet survivors. zyxw Description of cases The distribution of singleton and twin cases by dominant subtype is presented in Table 2. For 14cases, there were two spastic subtypes for which dominance of one zyxwv zyx zyxwvuts zyxw California Cerebral Palsy Project 345 zyxwvutsrqp Table 1. Comparison of examined and record review cases, by birthweight and CP subtype: CACP 1983-1985 Examined n Birthweight (grams) 4500 1500-2499 z=2500 Total n Total % 46 11 10 42 17 16 67 54 37 101 28 19 53 129 100 63 100 192 100 24 53 29 6 17 19 41 22 5 13 16 11 26 8 2 25 17 41 13 3 40 19 21 33 29 7 10 129 100 63 100 192 100 CP subtype Hemiplegia Diplegia Quadriplegia Dyskinesialataxia Mixed Total % Record review 43 27 59 33 21 64 55 14 P value zyxw <0.05 .i co.001 subtype was distinguished by the examining physician; these cases have been grouped with the dominant subtype. For an additional six cases with both diplegia and hemiplegia, the dominant subtype could not be established; these cases have been grouped with the diplegia category because their birthweight distribution was similar to that for cases with isolated diplegia and dissimilar to that for cases with isolated hemiplegia. Diplegia was the most common subtype, occurring in 33%of the cases (Table 2). Subtypes which included dyskinesia and/or ataxia were least common, occurring in 7% (dyskinesiaiataxia) and 10% (mixed) of the total cases. Twins were Table 2. Singleton and twin cases, by CP subtype: CACP 1983-1985 Singleton n CP subtype Hemiplegia Diplegia Quadriplegia Dyskinesialataxia Mixed Total % Twin n % P value Total 37 55 49 14 17 22 32 28 8 10 3 9 6 0 2 15 45 30 0 10 40 64 55 14 19 21 33 29 7 10 172 100 20 100 192 100 NS 346 zyxwvutsrq zyxwvu zyxwvuts J.K. Grether et al. zyxwvu zyxwvu zyxwv somewhat over-represented among diplegics and under-represented among hemiplegics but overall differences between twins and singletons in subtype distribution were not statistically significant. Isolated right-sided hemiplegia occurred in 24 cases and was more than twice as frequent as isolated left hemiplegia (n = lo), a pattern consistent with previous reports.25 A predominance of right hemiplegia was not found for hemiplegia which occurred in combination with diplegia. Among the unverified cases (not included in the tables), two had quadriplegia, two had mixed CP, and for one the subtype was unknown. Severity was moderate in 54% of the verified cases and severe in 46%. Quadriplegia and mixed CP together comprised 73% of the severely impaired children and 9% of the moderately impaired. All nine children who died after age 3 had had spastic quadriplegia. Birthweight distribution by dominant subtype is presented in Table 3. Overall, a majority of the cases (53%) had birthweight 2 2500 g, while 19% were born weighing 15W2499 g, and 28% were of very low birthweight, < 1500g. Among the subgroup of diplegics, 28% had birthweight 32500 g and nearly half (48%) had birthweight < 1500g. Of all children with very low birthweight, more than half (57%)had diplegia. For total cases and within the hemiplegia and diplegia subgroups, children with moderate CP and children with severe CP had similar birthweight distributions. Among children with quadriplegia, all the moderately affected children and half (52%)of the severely affected children had birthweight 32500 g. Associated disabilities - Among examined children, 20% were reported to have no associated disabilities, 24% to have one, and 56% to have two or more. All examined children with dyskinesidataxia, 87%with mixed CP,and 78% with quadriplegia were reported Table 3. Three birthweight categories by CP subtype: CACP 1983-1985 <1mg CP subtype n Hemiplegia Diplegia Quadriplegia Dyskinesidataxia Mixed 31 12 1 4 Total 54 6 1500-2499 g Total &!5oog zyx zyxwvuts R n % 15 18 23 20 7 21 7 15 11 0 4 28 37 19 48 22 21 n 27 18 32 13 11 % 68 28 58 93 58 101 53 n % 40 100 64 loo 55 100 14 100 19 100 192 100 zyx zyx zyxw zyxw California Cerebral Palsy Project 347 to have two or more associated disabilities, in contrast with 36% of children with hemiplegia and 40% with diplegia. Examined children with severe CP more often had two or more associated disabilities compared with those with moderate CP (P < 0.01), although almost half (44%)of moderately affected children were reported to have two or more associated disabilities and 27% of severely affected children had one or none (Table 4). Two or more associated disabilitieswere somewhat more fequent in children with birthweight < 1000g or 3 2500 g compared with children with birthweight 1000-1499 g or 1500-2499 g (Table 4). The differences were not statistically significant, nor was this birthweight pattern consistent for all specific disabilities 6r within CP subtypes (data not shown). Small cell frequencies prohibited rigorous analysis. zyxwvu zyxwv Discussion The CACP is the largest population-based study of CP in North America in more than 2 decades of major changes in perinatal health care. The project was designed by the California Birth Defects Monitoring Program explicitly to address questions of aetiology, including the possible reIationship between congenital structural anomalies and CP. To facilitatethese research objectives, very stringent inclusion criteria were used which are not comparable to case inclusion criteria in other CP studies. zyx Table 4. Associated disabilities among examined children by severity of CP and by birthweight: CACP 1983-1985 ~ ~ ~~~ Associated disabilities Total 22 0-1 n n % n % Severity of CP Moderate Severe 35 13 56 27 27 35 44 73 62 100 48 loo Birthweight <lo00 g 1000-1499 g 1500-2499g 22500 g 3 3 3 14 52 10 45 21 40 6 13 12 31 67 48 55 60 9 27 22 52 loo loo 100 Total 4 8 4 4 62 56 110 loo P value % 100 <0.01 NS 348 zyxwvutsr zyxwvu zyxwvu zyxw 1.K. Grether et al. The CACP prevalence estimate of 1.23/1000 survivors at age 3 is lower than that reported in other studies which average approximately 2.0/1000.G*5 The CACP diagnostic criteria excluded children with mild involvement, those with hypotonia only, and those with acquired CP. Also excluded were children who died or moved out of state before age 3. These exclusions are the probable explanation for the relatively low prevalence obtained. Because of these differences, the prevalence figures cannot be compared directly with other prevalence figures, many of which were developed for service planning purposes. The CACP data do not provide a basis for judging changes in CP prevalence in the United States or differences between the US and elsewhere. Children with CP who died before the age of 3, and are thus excluded from the project, are likely to have been severely affected children whose motor disability contributed to their death;16 all nine children who died uffer age 3 had had quadriplegia and had been severely impaired. Major strengths of the CACP for research purposes are that it is populationbased and incorporates a high level of consistency in the diagnostic information. Using standardised criteria and procedures, all diagnoses of CP, subtype and severity were established by one trained observer who examined two-thirds of the cases and conducted extensive record review for the remainder. Such validation of reported diagnoses through use of a standardised protocol has received ‘surprisingly little attention’ in previous population studies of CP.I7 Further, the CACP data are translatable into the Standard Recording of Central Motor Deficit1 protocol, making collaborative investigations feasible. A major limitation of the CACP is that it covered only a 3-year period, and there are no comparable data permitting time trend estimates. Although in important respects the CACP data are not comparable to those reported elsewhere, there is clear similarity bhtween the CACP and other population-based series with respect to epidemiological characteristics of the cases. In the CACP, as elsewhere, males were at slightly higher risk for CP, with the RR of 1.2 reported here at the low end of the reported range.a10J4J5,18 The six-fold higher risk for CP for twins compared with singletons in the CACP is the highest reported to date but an elevation in risk for multiple births has also been reported study of CP in twins in this series is under in other s t u d i e ~ . ~ J ~ JA5 detailed J~ way. The predominance of low birthweight among children with diplegia and of normal birthweight among children with other CP subtypes is a familiar pattern.9,1sz The distribution of birthweight among children with diplegia in the CACP can best be described as bi-modal, with a small mode above 25oOg. A similar but even more dramatic bi-modal pattern for diplegia is reported by Pharoah et uLzo Spastic diplegia associated with low birthweight may have different causal patterns than spastic diplegia associated with normal birthweight;= .. zyxw zyx California Cerebral Palsy Project zyxw 349 even the underlying anatomy, as revealed by neuroimaging, may be different in premature and term children with d i ~ l e g i a . * ~ Although this and other studies have demonstrated that low birthweight is an important risk factor for CP,s14Jp-23 there is no evidence in the CACP data for an overall association between birthweight and the severity of CP. Nor is there consistent evidence for an association between birthweight and the presence of associated disabilities. These findings are inconsistent with other reports of an increased frequency of associated disabilities and increased severity of motor problems in children with term compared with preterm diplegia.= The CACP findings must be interpreted with caution given the imprecise nature of the -4 measure of assodated disabilities. The finding that associated disabilities were common in children with dyskinesidataxia or mixed CP is consistent with the previously reported high incidence of associated disabilities in the current generation of children with extrapyramidal CP.= The aetiology of CP is imperfectly understood. The CACP has constructed a population-based series of children with congenital CP using service agency records as the foundation for initial ascertainment of cases, with verification of case status through standardised examination of accessible children. This project will provide a resource for case-control studies of aetiology. The expense and cumbersome nature of prospective studies limit the use of a prospective study design for the investigation of CP. While the particular organisation of service agencies in California may offer some special advantages, the approach used in this project may be one of the few study designs currently feasible for broad-based investigations of CP and other low prevalence but important disorders. Acknowledgements zyxw zyx zyx zyx zyxwv This study was supported in part by the California Birth Defects Monitoring Program, California Department of Health Services, in part by co-operative agreement with the Center for Environmental Health and Injury Control, Centers for Disease Control, and in part by funds from the Comprehensive Environmental Response, Compensation and Liability Act trust fund through an interagency agreement with the Agency for Toxic Substances and Disease Registry, US Public Health Service. The authors would like to express sincere appreciation to the children who participated in this study and to their families, to the many therapists and physicians who contributed valuable information, and to the staff and leadership of California Children Services, the Regional Centers for the Developmentally Disabled, and the Department of Developmental Services. The authors are also deeply indebted to Virginia Heffeman and Kathy Haas, 350 zyxwvutsr zyxwvutsrq zyxwvu zyxwvut zy J.K. Grether et al. the fieldwork assistants whose hard work and loving spirits contributed so much to this project, and to Denise Connors for her invaluable secretarial support. References zyxwvuts zyxw 1 Evans, P., Johnson, A., Mutch, L. et al. Standard recording of central motor deficit. Developmental Medicine and Child Neurology 1989;31:119-129. 2 Brockway, A. The problem of the spastic child. Journal of the American Medical Association 1936;1061635-1638. 3 Perlstein, M.A., Hood, P.N. Infantile spastic hemiplegia, I. Incidence. Pediatrics 1954; 14436-441. 4 Crothers, B., Paine, R.S. TheNatural HistoryofCerebral Palsy. Cambridge, MA: Harvard University Press, 1959; pp. 38, 81. 5 Barmada, M.A., MOOSSY, J., %human, R.M. Cerebral infarcts with arterial occlusion in neonates. Annuls of Neurology 1979;6:495. 6 Yeargin-Allsopp, M., Murphy, C.C., Trevathan, E. Cerebral palsy in Atlanta: preliminary results from the Atlanta Developmental Disabilities Study. Annuls of Neurology 1988; 24348. 7 Rikonen, R., Raumavirta, S., Sinivuori, E. et al. Changing pattern of cerebral palsy in the southwest region of Finland. Acta Paediutrica Scandinavicu 1989;78581-587. 8 Evans, P., Elliott, M., Alberman, E . et al. Prevalence and disabilities in 4 to 8 year olds with cerebral palsy. Archives of Disease in Childhood 1985;m940-945. 9 Emond, A., Golding, J., Peckham, C. Cerebral palsy in two national cohort studies. Archives of Diseuse in Childhood 1989;64:848-852. 10 Pharoah, P.O.D., Cooke, T., Rosenbloom, I. et al. Trends in birth prevalence of cerebral palsy. Archives of Disease in Childhood 1987;62379-384. 11 Hagberg, B., Hagberg, G., Olow, I. etal. The changing panorama of cerebral palsy in Sweden. Acta Paediatrica Scundinuuica 1989;78283-290. 12 Stanley, F. J., Watson, L. The cerebral palsies in Western Australia: trends, 1968 to 1981.American Journal of Obstetrics and Gynecology 1988;158:89-93. 13 Dowding, V.M.,Barry, C. Cerebral palsy? changing patterns of birthweight and gestational age (1976181).Irish Medical Journal 1988;81:25-29. 14 Kudxjavcev, T., Schoenberg, B.S., Kurland, L.T. et al. Cerebral palsy - trends in incidence and changes in concurrent neonatal mortality: Rochester, MN, 1950-1976.Neurology 1983;3314S1438. 15 Nelson, K.B., Ellenberg, J.H. Epidemiology ofcerebral palsy. Advances in Neurology 1978;19421435. 16 Evans, P.M., Evans, S.J.W., Alberman, E. Cerebral palsy: why we must plan for survival. Archives of Disease in Childhood 1990;65:1329-1333. 17 Stanley, F., Alberman, E. (eds) Epidemiology of the Cerebral Palsies. Philadelphia, PA: J.B. Lippincott, 1984: p. 50. 18 Peterson, B., Stanley, F., Henderson, D. Cerebral palsy in multiple births in Western Australia: genetic aspects. American toumnl of Medical Genetics 1990;37:34&351. 19 Ellenberg, J.H., Nelson, K.B. Birthweight and gestational age in children with cerebral palsy or seizure disorders. American Journal of Diseases of Children 1979; 1331044-1088. 20 Pharoah, P.O.D., Cooke, T., Rosenbloom, L. et al. Effects of birthweight, gestational age, and maternal obstetric history on birth prevalence of cerebral palsy. Archives of Disease in Childhood 1987;621035-1040. zyxw zyxw zy zyxwvut California Cerebral Palsy Project 351 21 Jarvis, S.N.,Holloway, J.S., Hey, E.N.Increase in cerebral palsy in normal birthweight babies. Archives of Disease in Childhood 1985;60:1113-1121. 22 Stanley, F.J. Spastic cerebral palsy: changes in birthweight and gestational age. Early Human Development 1981;5:167-178. 23 Veelken, N.,Hagberg, B., Hagberg, G. et al. Diplegic cerebral palsy in Swedish term and preterm children. Neurogediatrics 1983;1420-28. 24 Koeda, T.,Suganuma, I., Yohno, Y. etaf. MRimagingof spasticdiplegia: comparative study between preterm and term infants. Neurorudiology 1990;32187-190. 25 Marquis, P., Palmer, F.B., Mahoney, W.J. ef al. Extrapyramidal cerebral palsy: a changing view. Developmental and Behavioral Pediatrics 1982;3(2):65-68. zyxwvuts