Spastic Cerebral Palsy: Risk Factors, Botulinum Toxin Use and Prevention of Hip Dislocation
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Background: Cerebral palsy (CP) is a clinical diagnosis encompassing a heterogeneous group of disorders in movements and posture resulting from disturbance in the developing brain. The aetiology of CP is poorly understood in most cases despite numerous studies on the risk factors for CP. Labour induction has rarely been evaluated as an independent risk factor for CP and the combined effect of multiple risk factors, although likely to increase the risk, has rarely been estimated. The most prominent motor disorder in CP is spasticity which is the dominating clinical feature in 80% of all patients. Spasticity is the main cause of the musculoskeletal deformities in CP and thereby it worsens the child’s motor disability. Moreover, spasticity together with mal-positioning leads to joint instability as in hip displacement. Hip displacement is usually painless but may gradually progress to painful hip dislocation in severe cases. Treatment with intramuscular botulinum neurotoxin (BoNT) injections and intrathecal baclofen (ITB) has revolutionized spasticity management in the last two decades. Aims: The aims of this research were to investigate the association between labour induction and CP and to examine the effect of multiple risk factors on the risk of developing CP. Furthermore, we aimed to study the proportions and the clinical characteristics of children who received BoNT compared with those who did not receive such treatment. Finally, we wanted to study if a specifically designed follow-up programme was able to prevent hip dislocation among children with CP, or if a general improvement in regular care and treatment was equally effective. Methods: Antenatal and perinatal data were obtained from the Medical Birth Registry of Norway (MBRN) on 176 591 infants born 1996 – 1998 who survived the early neonatal period. Neurodevelopmental data were available in the CP Register in Norway (CPRN) on 241 children with CP born during that time period. The exposure measures were the different single or combined antenatal and perinatal risk factors. The main outcome measures were the total CP and spastic CP subtypes. The use of BoNT in 411 children with CP born 1999–2003 was recorded in the CP Register. Gross motor function was assessed using the Gross Motor Classification System (GMFCS). Data obtained from CPRN for seven Norwegian counties providing conventional “regular” care were compared with data in the CP Register in Southern Sweden for one Swedish healthcare region where a hip surveillance programme (CPUP) was introduced in 1994. In all, 119 Norwegian and 136 Swedish children were born 1996 – 2003 with moderate to severe CP (GMFCS levels III – V). In Norway, data on hip operations and radiographs of the hips were collected from medical records. The hip migration percentage (MP) was measured on the recent radiographs and hip dislocation was defined as MP of 100%. Results: Induction of labour was associated with a threefold excess risk of bilateral spastic CP. The risk of CP increased exponentially with increasing number of the combined pre- and perinatal risk factors. In one third of children born at term none of the studied risk factors were identified. Multiple risk factors were more common in premature infants where 70% had two or more additional risk factors. However, only few children were exposed to the same combination of factors. We found that two thirds of all children with CP in Norway had received BoNT. The proportion of children treated with BoNT was directly related to the level of motor impairment to the highest proportion at GMFCS IV. However, smaller proportion of children with the most severe physical and cognitive disabilities received BoNT. The hip surveillance resulted in significant reduction in prevalence of hip dislocation compared with areas providing conventional follow-up. Radiological screening led to early identification and surgical treatment of hips at risk without increasing the total number of hip operations. Interpretation: The potential risk of CP associated with induction of labour should be considered when induction is requested without clear medical indication. Multi-causal pathways were more common among children born preterm suggesting more alternatives for preventive strategies at various stages. In children born at term, alternatives for prevention may be more limited. Our results raise the question whether the need for BoNT-treatment in children with minor motor impairments might be overestimated, while children with severe CP forms might be undertreated. Our results support that an intensive follow-up (surveillance) programme prevents hip dislocation and reduces the need for salvage surgery.
SerieDoktoravhandlinger ved NTNU, 1503-8181; 2012:253
Dissertations at the Faculty of Medicine, 0805-7680; 568