eMedicine Specialties > Neurology > Pediatric Neurology

Cerebral Palsy

Author: Ari S Zeldin, MD, FAAP, Senior Clinical Fellow/Clinical Instructor in Autism and Neuro-Developmental Disorders, Division of Pediatric Neurology, Department of Neurosciences, University of California, San Diego, School of Medicine
Coauthor(s): Alicia T F Bazzano, MD, MPH, Consulting Faculty, Division of Pediatric Emergency Medicine, Harbor/UCLA Medical Center; Attending Staff, Department of Emergency Medicine, Children's Hospital Los Angeles; Chief Physician, Westside Regional Center; Boosara Ratanawongsa, MD, Clinical Assistant Professor of Pediatrics, Penn State College of Medicine; Pediatric Neurologist, Pediatric Specialists of Lehigh Valley, Lehigh Valley Physician Group
Contributor Information and Disclosures

Updated: Feb 25, 2010

Introduction

Background

Definition of cerebral palsy

The term cerebral palsy (CP) was originally coined more than a century ago and loosely translates as "brain paralysis." However, a precise definition has remained elusive because CP is not a single diagnosis but an "umbrella" term describing nonprogressive brain lesions involving motor or postural abnormalities that are noted during early development.¹ CP has been described as follows:²

A group of disorders of the development of movement and posture causing activity limitations that are attributed to non-progressive disturbances that occurred in the developing fetal or infant brain. The motor disorders of cerebral palsy are often accompanied by disturbances of sensation, cognition, communication, perception, and/or behavior and/or a seizure disorder.

Age of onset

The brain lesions of CP occur from the fetal or neonatal period to up to age 3 years. Insults to the brain after age 3 years through adulthood may manifest clinically as similar or identical to CP, but, by definition, these lesions are not CP. Although the lesion to the developing brain occurs prior to age 3 years, the diagnosis of CP may not be made until after that time. Some authorities advocate not making a definitive diagnosis in some cases until age 5 years or later. This approach allows the clinical picture to be clear and potentially allows exclusion of progressive diseases.^3,4 In addition, some children have been diagnosed with CP at an early age, only to have the symptoms resolve later.⁵

Lesion location

CP is restricted to lesions of the brain only; diseases specific to the peripheral nerves of the spinal cord (eg, spinal muscular atrophy, myelomeningocele) or to the muscles (eg, muscular dystrophies), although causing early motor abnormalities, are not considered CP.

Associated findings

Approximately 30-50% of patients with CP have mental retardation, depending on the type of CP.^6,7 However, because of oromotor, fine motor, and gross motor difficulties, communication in CP patients may be impaired and expression of intellectual capacity may be limited. However, if CP is approached in a multidisciplinary manner, with physical, occupational, and nutritional therapy to maximize rehabilitative efforts, patients can be more fully integrated academically and socially.

Approximately 15-60% of children with CP have epilepsy, and epilepsy is more frequent in patients with spastic quadriplegia or mental retardation.

Etiology and risk factors

The etiology of CP is not well understood, and brain lesions are thought to be associated with prenatal, perinatal, or postnatal events of varying causes. Risk factors for CP are multifactorial and can include preterm birth, multiple gestation, intrauterine growth restriction, male sex, low Apgar scores, intrauterine infections, maternal thyroid abnormalities, prenatal strokes, birth asphyxia, maternal methyl mercury exposure, and maternal iodine deficiency.^4,5,8

Classification and types

CP is classified according to resting tone and what limbs are involved (called topographic predominance). Spastic CP, due to cortex/pyramidal tract lesions, is the most common type and accounts for approximately 80% of cases.⁴ Spastic CP is characterized by spasticity (velocity-dependent increase in tone), hyperreflexia, clonus, and an upgoing Babinski reflex. Extrapyramidal or dyskinetic CP is characterized more by abnormal involuntary movements. Many patients have characteristics of both spastic and extrapyramidal CP.

Typical types of cerebral palsy

• Spastic hemiplegia - CP predominantly affecting one side of the body, with upper extremity spasticity more than lower extremity spasticity (eg, right side involved with right arm more so than right leg)
• Spastic diplegia - CP affecting bilateral lower extremities more than upper extremities
• Spastic quadriplegia - CP affecting all 4 extremities (full body)
• Dyskinetic CP (athetoid CP, choreoathetoid CP, and dystonic CP) - CP with extrapyramidal signs characterized by abnormal movements; hypertonicity often is associated
• Mixed CP - CP with no single specific tonal quality predominating; typically characterized by a mixture of spastic and dyskinetic components
• Hypotonic CP - CP with truncal and extremity hypotonia with hyperreflexia and persistent primitive reflexes; thought to be rare

Functional classification systems generally divide patients into mild, moderate, and severe types (depending on functional limitations). Alternatively, patients may be categorized more comprehensively by their abilities and limitations, as was proposed by the World Health Organization in 2001. See International Classification of Functioning, Disability and Health.

CP is generally considered a static encephalopathy (ie, nonprogressive in nature). However, the clinical presentation of CP changes as children and their developing nervous systems mature.

Pathophysiology

The clinical presentation of CP may result from an underlying structural abnormality of the brain; early prenatal, perinatal, or postnatal injury due to vascular insufficiency; toxins or infections; or the pathophysiologic risks of prematurity. Evidence suggests that prenatal factors result in 70-80% of cases of CP. In most cases, the exact cause is unknown but is most likely multifactorial.⁵

Major events in human brain development and their peak times of occurrence⁹ include the following:

• Primary neurulation - Weeks 3-4 of gestation
• Prosencephalic development - Months 2-3 of gestation
• Neuronal proliferation - Months 3-4 of gestation
• Neuronal migration - Months 3-5 of gestation
• Organization - Month 5 of gestation to years postnatal
• Myelination - Birth to years postnatal

Given the complexity of prenatal and neonatal brain development, injury or abnormal development may occur at any time, resulting in the varied clinical presentations of CP (whether due to a genetic abnormality, toxic or infectious etiology, or vascular insufficiency). For example, cerebral injury before the 20th week of gestation can result in a neuronal migration deficit; injury between the 26th and 34th weeks can result in periventricular leukomalacia; injury between the 34th and 40th weeks can result in focal or multifocal cerebral injury.

Brain injury due to vascular insufficiency depends on various factors at the time of injury, including the vascular distribution to the brain, the efficiency of cerebral blood flow and regulation of blood flow, and the biochemical response of brain tissue to decreased oxygenation.

The physical stress on premature infants and the immaturity of the brain and cerebral vasculature likely explain why prematurity is a significant risk factor for CP. Prior to term, the distribution of fetal circulation to the brain results in the tendency for hypoperfusion to the periventricular white matter. Hypoperfusion can result in germinal matrix hemorrhages or periventricular leukomalacia. Between weeks 26 and 34 of gestation, the periventricular white matter areas near the lateral ventricles are most susceptible to injury. Because these areas carry fibers responsible for the motor control and muscle tone of the legs, injury can result in spastic diplegia (ie, predominant spasticity and weakness of the legs, with or without arm involvement of a lesser degree).

When larger lesions extend past the area of descending fibers from the motor cortex to involve the centrum semiovale and corona radiata, both the lower and upper extremities may be involved. Periventricular leukomalacia is generally symmetric and thought to be due to ischemic white matter injury in premature infants. Asymmetric injury to the periventricular white matter can result in one side of the body being more affected than the other. The result mimics a spastic hemiplegia but is best characterized as an asymmetric spastic diplegia. The germinal matrix capillaries in the periventricular region are particularly vulnerable to hypoxic-ischemic injury because of their location at a vascular border zone between the end zones of the striate and thalamic arteries. In addition, because they are brain capillaries, they have a high requirement for oxidative metabolism.

Many authorities grade the severity of periventricular hemorrhage-intraventricular hemorrhage using a classification system originally described by Papile et al in 1978¹⁰ (see Periventricular Hemorrhage-Intraventricular Hemorrhage).

• Grade I - This is subependymal and/or germinal matrix hemorrhage.
• Grade II - This is subependymal hemorrhage with extension into the lateral ventricles without ventricular enlargement.
• Grade III - This is subependymal hemorrhage with extension into the lateral ventricles with ventricular enlargement.
• Grade IV - A germinal matrix hemorrhage that dissects and extends into the adjacent brain parenchyma, irrespective of the presence or absence of intraventricular hemorrhage, is also referred to as an intraparenchymal hemorrhage when found elsewhere in the parenchyma. Hemorrhage extending into the periventricular white matter in association with an ipsilateral germinal matrix hemorrhage/intraventricular hemorrhage is termed a periventricular hemorrhagic venous infarction.

At term, when circulation to the brain most resembles adult cerebral circulation, vascular injuries at this time tend to occur most often in the distribution of the middle cerebral artery, resulting in a spastic hemiplegic CP. However, the term brain is also susceptible to hypoperfusion, which mostly targets watershed areas of the cortex (eg, end zones of the major cerebral arteries), resulting in spastic quadriplegic CP. The basal ganglia also can be affected, resulting in extrapyramidal or dyskinetic CP.

Dyskinetic (extrapyramidal) CP is associated with several unique etiologies. Historically, kernicterus, or acute neonatal bilirubin encephalopathy, was a major cause. With improvement in early management of hyperbilirubinemia, the vast majority cases of dyskinetic CP are currently associated with presumed hypoxic ischemic injury rather than with hyperbilirubinemia.¹¹ In the absence of hypoxia, hyperbilirubinemia, or prematurity, the possibility of a metabolic or neurodegenerative disorder as a basis for this presentation must be considered.

In summary, no set rules exist as to where or when the brain injury can occur, and injury may occur at more than one stage of fetal brain development. Additionally, causes are multiple and potentially multifactorial, including vascular insufficiency, infection, maternal factors, or underlying genetic abnormalities. Regardless of the etiology, however, the underlying brain anomaly in CP is static, although the motor impairment and functional consequences may vary over time. By definition, cases associated with underlying disorders of a progressive or degenerative nature are excluded when diagnosing CP.

Frequency

International

In developed countries, the overall estimated prevalence of CP is 2-2.5 cases per 1000 live births.¹² The prevalence of CP among preterm and very preterm infants is substantially higher.^13,14 In the developing world, the prevalence of CP is not well established but estimates are 1.5-5.6 cases per 1000 live births. These figures may represent an underestimation because of a paucity of data, the lack of health care access, an overrepresentation of severe cases, and inconsistent diagnostic criteria.⁴

Mortality/Morbidity

See Complications.

Race

CP affects persons of all races. Lower socioeconomic status may be an increased risk factor for CP.¹⁵

Sex

Male sex may be a risk factor for CP.⁴

Clinical

History

CP diagnosis begins with a history of gross motor developmental delay in the first year of life (see Developmental history for milestones). CP frequently manifests as early hypotonia for the first 6 months to 1 year of life, followed by spasticity.

• Prenatal history
  • This should include information on pregnancy, such as prenatal exposure to illicit drugs, toxins, or infections; maternal diabetes; acute maternal illness; trauma; radiation exposure; prenatal care; and fetal movements.
  • A history of early frequent spontaneous abortions, parental consanguinity, and a family history of neurological disease (eg, hereditary neurodegenerative disease) also is important.
• Perinatal history: This should include gestational age (ie, degree of prematurity), presentation of the child and delivery type, birth weight, Apgar score, and complications in the neonatal period (eg, intubation time, presence of intracranial hemorrhage on neonatal ultrasound, feeding difficulties, apnea, bradycardia, infection, and hyperbilirubinemia).
• Developmental history
  • This should review gross motor, fine motor, language, and social milestones from birth until the time of evaluation.
  • Gross motor milestones of concern with CP include head control at age 2 months, roll at age 4 months, sit at age 6 months, and walk at age 1 year. Infants with CP may have significantly delayed gross motor milestones or show an early hand preference when younger than 1.5 years, suggesting relative weakness of one side (eg, reaching unilaterally).
  • The presence of an unexplained regression would be more suggestive of a hereditary neurodegenerative disease than CP.
  • Current social skills, academic performance, and participation in an early intervention program (if <3 y) or school support (if >3 y) should be reviewed, including resource room assistance; physical, occupational, and speech and language therapy; and adaptive physical education.
  • Standardized cognitive and educational testing and a current individualized education plan can be used to determine whether speech therapy, occupational therapy, and physical therapy are in place or whether referrals for these are needed.
• Need for adaptive equipment: Review the patient's equipment or need for equipment such as adaptive and communication devices (eg, computer-assisted speech programs), orthotics (eg, ankle-foot orthoses, walkers, wheelchair), and/or seating (may require straps to keep in place).
• General medical history: This should include a review of systems to evaluate for the multiple complications that can occur with CP (see Complications).

Physical

The initial presentation of CP includes early hypotonia, followed by spasticity. Generally, spasticity does not manifest until at least 6 months to 1 year of life. The neurological evaluation includes close observation and a formal neurological examination.

• Prior to the formal physical examination, observation may reveal abnormal neck or truncal tone (decreased or increased, depending on age and type of CP); asymmetric posture, strength, or gait; or abnormal coordination.
• Patients with CP may show increased reflexes, indicating the presence of an upper motor neuron lesion. Patients with CP also present with the persistence of primitive reflexes, such as the Moro (startle reflex) and asymmetric tonic neck reflexes (ie, fencing posture with neck turned in same direction when one arm extended and other flexed). CP may also include the underdevelopment or absence of postural or protective reflexes (extending arm when sitting up). For a good discussion of this topic, see Developmental Disabilities in Infancy and Childhood, pages 95-100, by Capute et al.¹¹
• Patients with spastic CP evidence spasticity (ie, a velocity-dependent increase in tone). It may be evident by a tendency to keep the elbow in a flexed position or the hips flexed and adducted with the knees flexed and the valgus and ankles in equinus, resulting in toe walking.
• Patients with dyskinetic or extrapyramidal CP may have decreased head and truncal tone and defects in postural control and motor dysfunction such as the following:
  • Athetosis (ie, slow, writhing, involuntary movements, particularly in the distal extremities)
  • Chorea (ie, abrupt, irregular, jerky movements) or choreoathetosis (ie, combination of athetosis and choreiform movements)
  • Dystonia (ie, slow, sometimes rhythmic movements with increased muscle tone and abnormal postures, eg, in the jaw and upper extremities)
• Classic physical presentations of the different types of CP include the following:
  • Spastic hemiplegic CP
    • One-sided upper motor neuron deficit
    • Arm generally affected more than leg; possible early hand preference or relative weakness on one side; gait possibly characterized by circumduction of lower extremity on affected side
    • Specific learning disabilities
    • Oromotor dysfunction
    • Possible unilateral sensory deficits
    • Visual-field deficits (eg, homonymous hemianopsia) and strabismus
    • Seizures
  • Spastic diplegic CP
    • Upper motor neuron findings in the legs more than the arms
    • Scissoring gait pattern with hips flexed and adducted, knees flexed with valgus, and ankles in equinus, resulting in toe walking
    • Learning disabilities and seizures less commonly than in spastic hemiplegia
  • Spastic quadriplegic CP
    • All limbs affected, either full-body hypertonia or truncal hypotonia with extremity hypertonia
    • Oromotor dysfunction
    • Increased risk of cognitive difficulties
    • Multiple medical complications (see Complications)
    • Seizures
    • Legs generally affected equally or more than arms
    • Categorized as double hemiplegic if arms more involved than legs
  • Dyskinetic (extrapyramidal) CP
    • Early hypotonia with movement disorder emerging at age 1-3 years
    • Arms more affected than legs
    • Deep tendon reflexes usually normal to slightly increased
    • Some spasticity
    • Oromotor dysfunction
    • Gait difficulties
    • Truncal instability
    • Risk of deafness in those affected by kernicterus

Causes

The etiology may be multifactorial; however, in most cases, it is unknown. Interpretation of the literature is limited by the lack of strict definitions in studies attempting to define a pathogenesis of CP and the relatively small size of certain studies. An increasing amount of literature suggests a link between various prenatal, perinatal, and postnatal factors and CP. Epidemiologic studies suggest that prenatal factors play a predominant role in the etiology of CP.

• The following maternal and prenatal risk factors statistically correlate with CP:
  • Long menstrual cycle
  • Previous pregnancy loss
  • Previous loss of newborn
  • Maternal mental retardation
  • Maternal thyroid disorder, especially iodine deficiency
  • Maternal seizure disorder
  • History of delivering a child weighing less than 2000 g
  • History of delivering a child with a motor deficit, mental retardation, or a sensory deficit
• The following factors during pregnancy also correlate statistically with CP:
  • Polyhydramnios
  • Treatment of the mother with thyroid hormone
  • Treatment of the mother with estrogen or progesterone
  • Maternal seizure disorder
  • Maternal severe proteinuria or high blood pressure
  • Maternal methyl mercury exposure
  • Congenital malformations in the fetus
  • Male sex of fetus
  • Bleeding in third trimester
  • Intrauterine growth retardation
  • Multiple gestation: The apparent overrepresentation of CP in multiple gestation pregnancies may relate more to the presence of prematurity or intrauterine growth retardation. Multiple gestations may not be an added risk for CP. The exception is when one twin dies; the surviving twin has a higher chance than a singleton of developing CP.
• The following perinatal factors are associated with an increased risk of CP:
  • Prematurity
  • Chorioamnionitis
  • Nonvertex and face presentation of the fetus
  • Birth asphyxia
    • In 10% or less of cases of CP, birth asphyxia can be determined as the definitive cause.
    • Even when birth asphyxia is thought to be associated clearly with CP, abnormal prenatal factors (eg, intrauterine growth retardation, congenital brain malformations) may have contributed to perinatal fetal distress.
    • Cases of CP attributed to birth asphyxia must document clear evidence of acidosis, moderate-to-severe neonatal encephalopathy, restriction to spastic quadriplegia, dyskinetic or mixed types of CP, and exclusion of other etiologies. Additionally, an intrapartum event must be suggested by a sentinel event, fetal heart rate changes, Apgar score less than 4 at 5 minutes, organ system damage related to tissue hypoxia, and early imaging abnormalities.¹⁶
    • While Apgar scores provide a method for documenting cardiopulmonary and neuromotor status in the minutes following birth, low scores alone cannot be used as an indicator of birth asphyxia. Such scores may reflect circumstances unrelated to birth asphyxia, such as infections and other preexisting prenatal conditions.
• The following postnatal factors may contribute to CP:
  • Infections (eg, meningitis, encephalitis)
  • Intracranial hemorrhage (eg, due to prematurity, vascular malformations, or trauma)
  • Periventricular leukomalacia (in premature infants)
  • Hypoxia-ischemia (eg, from meconium aspiration)
  • Persistent fetal circulation or persistent pulmonary hypertension of the newborn
  • Kernicterus
• Possible causes of CP by type include the following:
  • Spastic hemiplegic
    • Of all cases, 70-90% are congenital and 10-30% are acquired (eg, vascular, inflammatory, traumatic).
    • In unilateral lesions of the brain, the vascular territory most commonly affected is the middle cerebral artery; the left side is involved twice as commonly as the right.
    • Other structural brain abnormalities include hemibrain atrophy and posthemorrhagic porencephaly.
    • In premature infants, this may result from asymmetric periventricular leukomalacia.
  • Spastic diplegic
    • In premature infants, spastic diplegia may result from parenchymal-intraventricular hemorrhage or periventricular leukomalacia.
    • In term infants, no risk factors may be identifiable or the etiology might be multifactorial.
  • Spastic quadriplegic
    • Approximately 50% of cases are prenatal, 30% are perinatal, and 20% are postnatal in origin.
    • This type is associated with cavities that communicate with the lateral ventricles, multiple cystic lesions in the white matter, diffuse cortical atrophy, and hydrocephalus.
    • The patient often has a history of a difficult delivery with evidence of perinatal asphyxia.
    • Preterm infants may have periventricular leukomalacia.
    • Full-term infants may have structural brain abnormalities or cerebral hypoperfusion in a watershed (ie, major cerebral artery end zone) distribution.
  • Dyskinetic (extrapyramidal)
    • This type may be associated with hyperbilirubinemia in term infants or with prematurity without prominent hyperbilirubinemia.
    • Hypoxia affecting the basal ganglia and thalamus may affect term infants more than preterm infants.

• Search for CME/CE on This Topic »

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