Cerebral Palsy

Bruce K. Shapiro

Arnold J. Capute

Cerebral palsy is a disorder of movement and posture that results from an insult to or anomaly of the immature central nervous system (CNS). This definition recognizes the central origin of the dysfunction and differentiates cerebral palsy from neuropathies and myopathies. The definition implies that the cause is static and excludes progressive neurologic disorders. The simplicity of the definition belies the diversity of the dysfunctions that result from diffuse neurologic damage.

Although a static encephalopathy, cerebral palsy is not unchanging. As the CNS matures, peripheral manifestations of the central lesions change. Some children improve, some require bracing and surgery, and others reach a plateau.

HISTORICAL PERSPECTIVE

Just as the disorder changes with time, so has the approach to cerebral palsy. Although known from ancient and biblical times, cerebral palsy was not differentiated from other crippling disorders until William John Little described spastic diplegia and related it to birth injury. Little treated the handicap that resulted from cerebral palsy, and others, including Sigmund Freud and William Osler, focused on classification and clinicopathologic associations.

At the turn of the twentieth century, the emphasis had shifted to the prevention of handicaps. Bronson Crothers and his coworkers are credited with initiating the first programs of physical therapy for cerebral palsy. Winthrop Phelps, an orthopedic surgeon, expanded the treatment for children with cerebral palsy using a comprehensive method of treatment that addressed nonmotor and motor dysfunctions. As scientific capabilities have increased, two major trends have emerged: reevaluation of clinicopathologic correlations with noninvasive techniques to define anatomy and physiology and, objective quantification of movement to define therapy more reliably. Early identification and intervention are mandated.

EPIDEMIOLOGY

Cerebral palsy is the most common movement disorder of childhood. Estimates of its frequency vary from 1 to 6 per 1,000, but most recent studies report a prevalence of 1 to 2 per 1,000. The lower rate should be regarded as a minimum estimate because milder cases are not included; more severe cases may be obscured by other developmental disabilities, such as seizure disorders or mental retardation, and patients with the most severe cases may die.

Traditionally, spastic cerebral palsy has been the most frequent type, accounting for approximately 50% of cases. It is followed by athetosis (approximately 20% of cases), rigidity, ataxia tremor, and mixed forms (approximately 25% of cases). However, obtaining good estimates of the frequency of cerebral palsy is difficult. Time trends have not been consistent, with some researchers reporting an increase and others a decrease. Disagreement ensues about whether to include children with acquired cerebral palsy (e.g., owing to neurotrauma or infection) and at what age cerebral palsy should be diagnosed because the diagnosis is less stable in infants.

The causes of cerebral palsy have changed. Acute infantile hemiplegia, which was a common occurrence during the late nineteenth century, has become rare. Modern obstetric techniques have diminished major birth trauma markedly. The understanding and successful prevention of hemolytic disease of the newborn have changed the spectrum of extrapyramidal cerebral palsy of the choreoathetoid type.

Most cerebral palsy is found in children who do not possess identifiable risk factors. Traditional risk factors associated with cerebral palsy are birth asphyxia, prematurity, and intrauterine growth retardation. When risk factors are analyzed in a multivariate fashion, the strongest determinants of cerebral palsy are found not to be related to events of labor or delivery. Data from the perinatal collaborative study more strongly support the hypothesis that abnormal antenatal events yield difficult pregnancies, labors, and deliveries and that perinatal difficulties are associated with, not the cause of, cerebral palsy.

The impact of prematurity on the incidence of cerebral palsy is not clear. As neonatal care has improved, the incidence of cerebral palsy in heavier-birth-weight groups has decreased. Very low-birth-weight infants (less than 1,500 g) may have a higher incidence of cerebral palsy, but the lower number of children at this birth weight should modify the contribution that these children make to the total pool of cerebral palsy cases.

Some studies have reaffirmed the relationship between maternal infection and cerebral palsy. Multiple gestation markedly increases the incidence of cerebral palsy. Some researchers have suggested that cytokines are the mediators that tie together infection, asphyxia, multiple births, and prematurity.

CLASSIFICATION

The classification of cerebral palsy is multiaxial and includes the type of dysfunction (e.g., physiologic), the site of dysfunction (e.g., topographic), associated dysfunctions (e.g., supplemental), and etiologic, neuroanatomic, functional, and therapeutic axes. Only the first three axes are used and discussed here. The neuroanatomic axis awaits definition, and the etiologic, functional, and therapeutic axes have been abandoned. The current classification is most useful for older infants and children. All patients with cerebral palsy pass through a hypotonic phase, and attempts at early classification must be viewed as tentative until the evolution of the neurologic syndrome stabilizes. The changing peripheral manifestations also limit prognostication.

Physiologic Classification

Cerebral palsy can be divided into two major types, the pyramidal (spastic) and the extrapyramidal (nonspastic). Extrapyramidal cerebral palsy can be subdivided into choreoathetoid,
ataxic, dystonic, and rigid forms. These groups are clinically useful but are not well correlated with neuropathologic findings.

The neurologic findings of the pyramidal type are consistent and persistent, varying little with movement, tension, emotion, or sleep. Variability is the main feature of extrapyramidal types; findings are increased with activity, tension, and emotions and are decreased with sleep or relaxation.

The characteristic type of hypertonus seen in spasticity is clasp knife, similar to the opening and closing of a penknife with a consistent hitch. The tone in extrapyramidal types varies from hypotonic to hypertonic. Extrapyramidal hypertonus is of the lead pipe or candle-wax type, but it is variable and can be diminished by repetitive movement (i.e., “shaking it out”). The persistence of spastic hypertonus may be a factor in the development of contractures. The variability of extrapyramidal tone may protect against such development.

Pathologic reflexes, such as Babinski or Chaddock, are elicited readily in patients with spastic forms. A true Babinski reflex must be differentiated from the extensor plantar response that is seen as part of athetotic posturing. Sustained ankle clonus usually is associated with spasticity. Primitive reflexes are more evident in the extrapyramidal forms.

Topographic Classification

The topographic classification is limited to the spastic types. Generally, it is not used with extrapyramidal types because these types show four-limb involvement and are classified by the nature of the movement disorder. The topographic axis includes hemiplegia, diplegia, quadriplegia, and bilateral hemiplegia.

Hemiplegia (i.e., hemiparesis) describes involvement of either lateral side of the body. The upper extremities are more severely impaired than are lower ones, and upper extremity dysfunction usually brings the child to attention.

Diplegia refers to four-limb involvement, with the upper limbs involved only minimally, although significant lower extremity impairment is present. The good upper extremity function seen in diplegia is of major assistance to habilitative efforts. The designation paraplegia is reserved for spinal and lower motor neuron dysfunctions, such as myelodysplasia.

Spastic quadriplegia is four-limb involvement with significant impairment of all extremities. Upper limbs may be less severely impaired than are lower ones, but substantial functional limitations exist. Some researchers consider quadriplegia a furtherance of diplegia.

Bilateral hemiplegia designates significant spasticity of both sides of the body, with upper extremities significantly more severely impaired. Monoplegia and triplegia are formes frustes or combinations of hemiplegia and quadriplegia.

The value of physiologic or topographic classification is that syndromes emerge that are related to patterns of neurologic deficit. For example, hemiplegia may be associated with growth arrest, a visual field defect (e.g., homonymous hemianopia), sensory impairment (e.g., astereognosis, deficiencies in two-point discrimination, position sense), and seizures. Cerebral palsy resulting from bilirubin encephalopathy has been associated with choreoathetoid movements that evolve into dystonia during adolescence, brown-green discoloration and dentin dysplasia of the deciduous teeth, upward-gaze apraxia, and high-frequency hearing loss, often associated with central auditory processing dysfunction.

Supplemental Classification

The child with cerebral palsy has an abnormally functioning CNS. The problem is expressed in many ways, all of which are associated with the primary problem. Cognitive, communicative, and behavioral disturbances are common. Seizures, sensory loss, and visual and auditory occurrences influence treatment programs.

Cerebral palsy rarely occurs without associated deficits. The diagnosis of cerebral palsy alone is not sufficient. In some cases, the cerebral palsy is not the most limiting condition. Associated dysfunctions alter treatment and affect long-term outcomes. An understanding of the interaction of the motor components and associated deficits is necessary for setting realistic goals. Evaluation and delineation of the associated deficits comprise part of the evaluation of cerebral palsy.

The presence of associated deficits, each with its own spectrum of severity, senders each case of cerebral palsy unique. A complete description of the child’s areas of strength and weakness must be obtained because no “garden variety” of cerebral palsy exists. Failure to define a developmental profile usually results in incomplete habilitation, unrealistic goals, and therapeutic frustration.

Mental retardation coexists with cerebral palsy in approximately 60% of patients. In spastic forms of cerebral palsy, mental retardation occurs more frequently and more severely in proportion to the number of limbs involved. However, motor impairment does not always mean that the child also has mental retardation.

Children who escape mental retardation are nonetheless brain damaged and have processing impairments that may present as communicative disorders in the preschool child or as learning disabilities in the older child. The communicative disorders are of central origin and must be differentiated from the speech disorders that result from oral motor dysfunction.

Deafness has been reported in approximately 10% of people with cerebral palsy, with the athetoid type having the highest incidence. Strabismus occurs in 50%, although it is seen less commonly in children with hemiplegia. However, visual field cuts occur in 25% of children with hemiplegia. Refractive errors also occur more commonly in cerebral palsy.

Abnormal neural control of oral motor mechanisms may result in speech and articulation problems, swallowing abnormalities, and repeated episodes of aspiration. Drooling, poor articulation, and difficulties in breath control are more evident in nonspastic forms of cerebral palsy. Most children can be managed successfully with oral motor treatment techniques and appropriate positioning. Swallowing abnormalities and aspiration are seen in children who have severe rigidity or dystonia. Severe oral motor dysfunction may be complicated by gastroesophageal reflux and may cause growth failure. In treating the child with severe oral motor dysfunction, the nutritional and motor aspects should be assessed separately. If the child is failing to grow appropriately, has repeated episodes of dehydration, or has gastroesophageal reflux, a feeding gastrostomy with or without an antireflux procedure should be considered.

Sensory impairments associated with hemiplegia are thought to be caused by parietal lobe dysfunction. A limb with sensory impairment (i.e., a blind limb) is functionally useless. Fine testing of cortical sensory function is not possible in children younger than 7 years of age, and sensory impairment should be suspected in the child who uses the more motor-involved limb for function.

Seizures occur in one-third of children with cerebral palsy. Most seizures are controlled easily with standard approaches. Recalcitrant seizure disorders, such as infantile spasms or Lennox-Gastaut syndrome, are associated more commonly with increased motor dysfunction. Hemiplegia is associated most commonly with seizures.

Behavioral disturbances occur in many children with cerebral palsy. Neurobehavioral disturbances, such as short attention span, impulsivity, distractibility, perseveration, and
self-stimulation, may be seen. Emotional disturbances may intensify as the child nears adolescence, when issues of independence and peer-group interactions cannot be resolved successfully.

Expanded Classification

The traditional definition of cerebral palsy does not specify that motor impairment is present to a handicapping degree, nor does it allow for temporal changes. If the physician concentrates only on the children with obvious motor handicap, a larger, more mildly dysfunctioning group of children will be overlooked. This oversight is unfortunate because many of these children have lasting developmental problems outside the motor area and require surveillance and tailoring of treatment programs.

Children who have subclinical forms of cerebral palsy require neither motor therapy nor orthopedic surgical procedures for their motor dysfunctions. These children demonstrate clumsiness, awkwardness, transitory abnormalities of tone or postural responses, and other minor neuromotor signs. These signs are markers of central processing dysfunction and place the child at risk for having a preschool learning disorder or a specific learning disability. The term cerebral palsy should not be used with the parents because it does not assist in counseling and may cause the focus to be placed on the basis of the motor disturbance rather than on the processing dysfunction.

The current definition of cerebral palsy is incomplete because it does not address the entire spectrum of motor dysfunction in children. Although the motor dysfunction may not be handicapping, deviations in motor development are markers for other developmental dysfunctions in cognitive and behavioral domains. Table 396.1 is a classification scheme that expands the definition of cerebral palsy to include the entire spectrum of motor dysfunction of childhood.

TABLE 396.1. EXPANDED CLASSIFICATION OF CEREBRAL PALSY

Rates of Motor Development	Motor Signs	Associated Dysfunction
Minimal normal: MQ 75–100 Qualitative abnormalities only	Subtle, transient abnormalities of tone Persistence, exaggeration of some primitive reflexes to a mild degree Soft signs reflected as clumsy or awkward motor performance	Communicative disorders Specific learning disabilities ADHD
Mild: MQ 50–74	Transient abnormalities of tone Occasional “hard” signs Persistent primitive reflexes; delayed postural responses Soft signs may be present to functionally important degree (i.e., tremor, synkinesis, poor coordination)	Communicative disorders Specific learning disabilities ADHD
Moderate: MQ 40–50 Assisted ambulation May need bracing Usually does not require assistive devices Pharmacotherapy or nerve blocks may be used	Traditional neurologic findings Many exaggerated obligatory primitive reflexes, some obligatory Postural responses delayed or absent	Mental retardation Communicative disorders Specific learning disabilities Seizures ADHD+ Stereotypic behaviors
Severe, profound: MQ <35 Wheelchair mobility Usually requires bracing, assistive devices, and surgery	Traditional neurologic signs predominate Obligatory primitive reflexes Absent postural reponses	Mental retardation Seizures ADHD++ Stereotypic behaviors
ADHD, attention-deficit hyperactivity disorder; MQ, motor quotient. Modified from Shapiro BK, Palmer FB, Capute AJ. Cerebral palsy: history and state of the art. In: Gottlieb M, Wilhams J, eds. Textbook of developmental pediatrics. New York: Plenum Publishing, 1987.