Cerebral Palsy

Introduction

The term cerebral palsy ( CP ) has been considered by some to be a nonspecific “wastebasket” and by others a valuable diagnostic tool that provides individuals with greater access to medical care, rehabilitation, educational, and social services. The diagnosis of this heterogeneous syndrome rests upon the presence of a permanent motor disability (movement and posture) causing a functional limitation, that is due to a nonprogressive lesion in the developing fetal or infant brain. Historically, the initial association among prematurity, birth injury, and perinatal asphyxia with CP is attributed to Dr. William John Little in a lecture presented to the Obstetric Society of London. Subsequent major contributions were made by William Osler, who introduced the phrase “cerebral palsy” to describe this nonprogressive disorder, and Sigmund Freud, who extended Little's observations to include factors in early pregnancy, as well as emphasizing the cerebral abnormality in spastic diplegia. Despite these early seminal contributions and the efforts of multiple other investigators, the definition of CP continues to evolve, a widely accepted classifications system remains a goal, the epidemiology of this disorder continues to expand, and its therapy remains a challenge. ^,

A widely cited definition states, “CP describes a group of permanent disorders of the development of movement and posture, causing activity limitation, that are attributed to nonprogressive disturbances that occurred in the developing fetal or infant brain. The motor disorders of CP are often accompanied by disturbances of sensation, perception, cognition, communication and behavior, by epilepsy, and by secondary musculoskeletal problems.” While some have endorsed this definition others are concerned about the term ‘nonprogressive’ recognizing that motor abnormalities, especially tone and posture, are not always fixed even in the presence of underlying static brain lesions. ^, Further, there is no consensus for a required etiology, leading to the inclusion of subjects under this rubric who have diverse etiologies ranging from developmental malformations to metabolic disorders. Proposed classifications for this clinical neurodevelopmental syndrome have included (1) the anatomical site of the lesion (cortex, basal ganglia, cerebellum); (2) the type of movement (chorea, dystonia, ataxic, and mixed) or presence of spasticity; (3) the type of tone abnormality (hypotonia or hypertonia); (4) involvement of extremities (hemiplegia, diplegia, quadriplegia); and (5) the cause and timing of the insult (prepartum, intrapartum, postnatal). In the future, it is likely that the umbrella term CP will be classified based on causal factors with a description of physical alterations and functional impairments.

Epidemiology

CP is the most common cause of disability in children. The overall prevalence of CP is about 1.5 to 3.1/1000 live births. The prevalence is greatest in very low (<1000 gm) birth weight infants (90/1000) vs 1.5/1000 in those weighing 2500 g or more. Despite this high risk in low birth rate infants, term infants still represent more than half of all cases with CP. Compared with singletons, the relative risk of CP in twins is 5.6 and in triplets is 12.6. The death in utero of a co-twin places the surviving twin at high risk for developmental problems. Improvements in obstetric and neonatal care have reduced the incidence of CP in prematures, ^, but the overall prevalence has not changed due to a stable rate in term infants, greater survival in preterm infants, and extended longevity. Most cases of CP have no relationship to prematurity or asphyxia. Although early diagnosis is emphasized in order to implement appropriate intervention, the diagnosis is typically made between age 12 and 24 months. The full extent of the motor disability may not be evident until 3–4 years of age. Most children affected with CP survive into adulthood, but life expectancy is negatively affected by the presence of severe quadriplegia, profound retardation, visual impairments, and lack of appropriate medical care. In addition to the defining motor disabilities, individuals with CP have a variety of nonmovement problems, including intellectual disability (40%–70%), epilepsy (35%–94%), chronic pain (75%), speech and language disorders (50%–60%), behavioral disorders (26%), chronic sleep disorders (23%), functional blindness (11%), and hearing impairment (4%). Children with CP also have more psychological difficulties than do children in the general population. ^, The most common cause of mobility decline in adults with CP is impaired balance. The association between socioeconomic status (SES) and CP is controversial; with some evidence suggesting that the effect of SES goes beyond just mediating factors affecting preterm birth, low birth weight, and postnatal trauma.

Etiology

The etiology of CP is extensive, with heterogeneous risk factors including preconception maternal issues, antenatal, perinatal, and postnatal insults ( Table 20.1 ). ^{, ,} Prenatal factors are estimated to cause approximately 80% of CP with postnatal events responsible for about 10%. Despite the frequent emphasis, hypoxic-ischemic encephalopathy (HIE) represents only a small category within the neonatal encephalopathies and an even smaller contributor to the causes of CP. Criteria supporting an acute intrapartum hypoxic event sufficient to cause CP are presented in Table 20.2 . ^, Nonhypoxia/asphyxia causes of CP are numerous and include cerebral dysgenesis, intrauterine infection, intrauterine growth restriction, preterm birth, ^, coagulation disorders, antepartum hemorrhage, multiple pregnancies, abnormal presentations, neurometabolic diseases, ^, chromosomal anomalies, selected polymorphisms, ^, congenital abnormalities, and many others affecting either the mother or child. Neonatal stroke (ischemic perinatal infarction or sinovenous thrombosis) is also a significant etiology of CP. Postneonatal causes of CP commonly include traumatic brain injury, meningitis, and near drowning. As discussed in subsequent sections and Chapter 17 , treatable inborn errors of metabolism can also present as CP mimics. Animal models have also been used to study and test hypotheses regarding several aspects of CP.

Diagnosis

The essential motor dysfunction criteria, required for the diagnosis of CP, is reduced or neurologically abnormal movement patterns due to a static lesion in the developing fetal or infant brain. CP is usually evident in the first 12–18 months of life, but systematic reviews have provided a basis for an accurate and earlier (before 5 months corrected age) diagnosis of CP. The latter is based on a combination of clinical history, physical examination, use of standardized neuromotor assessments, and findings on magnetic resonance imaging (MRI). In addition, if the clinical diagnosis is suspected but cannot be made with certainty, an interim diagnosis of “high risk of CP” has been recommended to assure referral to appropriate centers for follow up. More specifically, the diagnosis of high risk for CP requires motor dysfunction and either an abnormality on MRI scan and/or a clinical history indicating risk for CP. However, as emphasized by others, the diagnosis of CP is generally more reliable after age 2 years, recognizing that early signs and symptoms may be a normal variation or developmental lag that resolve. The involvement of a highly trained and experienced team, knowledgeable in the use of assessment measures, is required for the early and accurate diagnosis. Lastly, despite the extensive list of potential risk factors ( Table 20.1 ), it is not unusual to fail to identify a clear etiology.

One ongoing challenge in children presenting with motor delays or impairment early in life is to identify those that are due to neurogenetic disorders masquerading as CP. The possibility of identifying a treatable genetic or metabolic etiology further emphasizes the need for identifying the underlying cause. Clinical and imaging indicators that suggest a need to consider additional evaluation for an impersonator or “masquerader” for CP include: a normal MRI; abnormal imaging restricted to the globus pallidus; severe symptoms in the absence of a history of perinatal insult; a positive family history; progressive worsening of symptomatology or neurodevelopmental regression; and physical findings of isolated muscle hypotonia, rigidity, and paraplegia.

History and Physical Examination

Like other movement disorders, the history and physical examination are essential for the diagnosis and classification of CP. The clinical history should seek evidence for prenatal, perinatal, and postnatal risks for CP (see Table 20.1 ). The typical presentation is a delay in attaining motor milestones, or findings of asymmetric motor function or abnormalities of muscle tone. Serial neurodevelopmental evaluations are often required for proper classification of the subtype, recognizing that findings on examination may be affected by the state of alertness, emotional stress, and irritability. Additionally, neurologic findings that are considered abnormal in adults may be physiologic during the first months of life (e.g., ankle clonus, brisk reflexes, and extensor plantar responses). Several early indicators of significant motor disability include delay in the appearance of motor milestones, early hand preference, and exaggerated or persistent primitive reflexes. ^, In some children, clinical findings suggestive of CP may continue to evolve up to 4–5 years of age. Gross motor function tends to improve in most children up to the age of 6–7 years which then tends to remain stable at least until early adolescence.

Assessment Scales

Several standardized developmental assessment scales are available to monitor the development of motor function in children with CP. Some scales focus narrowly on the physical impairment rather than functional consequence, some evaluate capability rather than actual performance of functional activities, and others miss important items, or include unimportant information. In a review, the scales with the best predictive validity for detecting CP before age 5 months corrected age were the Hammersmith Infant Neurological Examination (HINE) and Prechtl Qualitative Assessment of General Movements (GMs) and for infants after 5 months the HINE and the Developmental Assessment of Young Children. In children age two and older, severity has been reliably classified using the Gross Motor Function Classification System (GMFCS) and the Manual Ability Classification System. Other recommended classification systems include the Communication Function Classification System and the Eating and Drinking Ability Classification System.

The Hammersmith Infant Neurological Examination ( HINE ) is a standardized neurological assessment that is available for children between the ages of 2 and 24 months. It consists of 37 items and is subdivided into three sections: physical exam, documentation of motor development, and evaluation of the behavior state. The HINE has a high (about 90%) sensitivity and specificity for detecting CP. ^,

Prechtl Qualitative Assessment of General Movements (GM): This is a standardized motor assessment used in children under age 5 months corrected age. The GM observes the quality of spontaneous movements in infants while lying supine. Cramped-synchronized GMs and the absence of fidgety movements between 9 and 20 months reliably predict CP. It has a 98% sensitivity and 89%–93% interrater reliability.

Gross Motor Function Classification System ( GMFCS ) for CP : The GMFCS, a five-level ordinal rating scale based on the severity of motor disability (e.g., ambulation), has good reliability and good prognostic utility ( Fig. 20.1 ). ^{, ,} In brief, children in the GMFCS level I have some difficulty with speed, balance and coordination, but do all activities; level II do well on flat surfaces but need support on stairs or uneven surfaces; level III are independent walkers, but require a cane, crutch, or walker; level IV are nonambulatory, but can weight bear for transfers and use a walker; and level V are nonambulatory with no functional weight-bearing and are totally dependent. Stability was higher for the Gross Motor Function Classification System than the Manual Ability Classification System.

Manual Ability Classification System ( MACS ): The MACS was developed to classify how children with CP use their hands when handling objects in daily activities. It classifies the collaborative use of both hands together and is designed to reflect the child's typical manual performance, not the child's maximal capacity. ^, Subsequent reports have supported the reliability, validity, and stability of this evaluation.

Clues for Determining the Motor CP Type

Cerebral Palsy Syndromes

Conventionally CP has been classified into two major groupings based on: (1) the predominant motor disability: spastic (about 50%–80%); dyskinetic (about 20%); ataxic (about 10%); and mixed (about 20%). Hypotonia, with or without associated spasticity, is also used by some. Many CP patients are mixed in type to some degree, for example, mild dyskinetic signs are often present in subtypes of spastic CP and (2) the topographic involvement (hemiplegia, diplegia, and quadriplegia). While these classifications continue to have clinical utility, in terms of prognosis they are not very reliable or predictable.