CLASSIFICATION AND CLINICAL FEATURES

The term cerebral palsy is not a diagnosis, nor does its use denote a specific etiology or degree of severity. The term defines a condition whose cause is no longer active and that occurred during brain development. The cerebral palsies are a heterogeneous group of clinical syndromes that are characterized by motor and postural dysfunction caused by a nonprogressive lesion in the developing brain. Although the disorder itself is nonprogressive, the appearance of neuropathological lesions and their clinical expression change over time as the brain matures.¹

Classification of the cerebral palsy syndromes is based on the type and distribution of the motor abnormality (Table 121-1). An overlap of findings can occur, but the principal features are usually evident by age 5 years. Patients with a spastic syndrome have the features of an upper motor neuron syndrome. These include the positive signs of spastic hypertonia, hyperreflexia, extensor plantar responses, clonus, and contractures. Negative signs include slow, effortful, uncoordinated voluntary movements; poor fine motor function; difficulty isolating individual movements; and fatigability. The spastic syndromes are subdivided according to the distribution of abnormal signs. In spastic diplegia, the legs are more affected than the arms. In spastic quadriplegia, the arms are involved equally or more than the legs, and in hemiplegia, one side of the body is involved.

TABLE 121-1 Cerebral Palsy Syndromes

From Miller G: Cerebral palsies: an overview. In Miller G, Clark GD, eds: The Cerebral Palsies. Causes, Consequences, and Management. Boston: Butterworth-Heinemann, 1998, pp 1-36.

Dyskinetic signs may be found in all the spastic syndromes. Spastic diplegia can occur in both full-term and preterm infants, but it is associated particularly with prematurity, the risk increasing with the degree of prematurity, and is often associated with periventricular leukomalacia and ventriculomegaly. Patients with mild leukomalacia have relatively good hand function and fewer associated disabilities. Those with more severe involvement have compromised hand function, contractures, cortical sensory impairment, and involuntary movements and are more likely to have strabismus and visual impairment. Poor growth, particularly below the waist, is usually present. Asymmetrical diplegia, which can be found in preterm infants after unilateral hemorrhagic infarction, is associated with more severe disabilities than is symmetrical spastic diplegia. Spastic hemiplegia typically affects full-term infants of normal birth weight and may be caused by prenatal cerebrovascular events, neonatal stroke, or cerebral dysgenesis. Postnatal causes include arterial and venous stroke, trauma, infection, and vasculopathies.² The condition may be missed during early infancy without careful examination and may manifest later as early hand dominance and reduced movement or abnormal posturing on one side. A focal seizure, or a secondarily generalized one, may be the first indication of its presence. The typical hemiplegic gait is noted when the child begins to walk or run; walking and running usually begin within the normal age range, or are only mildly delayed, unless marked mental retardation is present. In general, frank disorders of language are related more closely to cognitive abilities than to the side of the lesion. Cortical sensory deficits on the affected side are correlated with poor growth, although not with the severity of the motor deficit.³ Spastic quadriplegia¹ is the most severe form of spastic cerebral palsy. Causes include prenatal infection or cerebral dysgenesis occurring in full-term infants who are small for gestational age, severe perinatal or postnatal diffuse brain insults, and extreme prematurity.

Common associated features include marked mental retardation, profound motor disability, dysarthria or anarthria, seizures, hip deformity, scoliosis, and limb contractures. Sensory impairment, in particular visual, may be present, in addition to microcephaly. The dyskinetic cerebral palsy syndromes¹ typically affect full-term infants and can follow severe acute full-term perinatal asphyxia because of selective basal ganglia damage and status marmoratus.⁴ These syndromes are divided into two types: mainly athetoid, in which the abnormal movements are a combination of athetosis and chorea, and mainly dystonic. Dysarthria and oropharyngeal difficulties are present in conjunction with facial grimacing. Retained primitive reflexes are a feature. Emotion, change in posture, or intended movement may worsen or induce the abnormal movements. Those with the mainly dystonic form tend to be more severely disabled, with anarthria and poor feeding, and are unable to ambulate. Manifestation in early infancy is with delayed psychomotor development, decreased tone, drooling, grimacing, and abnormal retention of primitive reflexes. The involuntary movements develop with time and may not be clearly apparent until ages 2 to 3 years. Contractures usually do not develop unless they are positional. Patients with ataxic cerebral palsy usually are born at term, and most cases are caused by early prenatal events,¹ including genetic causes.⁵ They manifest with congenital hypotonia and delayed language and gross motor skills. The development of speech, which is typically slow, jerky, and explosive, is related to intellectual ability. The ataxia usually improves with age. The diagnosis is made by exclusion, with the recognition that all patients with cerebral palsy have some degree of incoordination and disturbed posture. The condition should also be distinguished from metabolic and degenerative disorders, which may manifest with some of the same features.

The atonic syndromes are a form of cerebral palsy that is not often described. Affected infants are born at term with severe hypotonia. Many have cerebral dysgenesis, microcephaly, and profound mental retardation. Development is extremely delayed, and the children never stand or walk. Those findings that characterize other cerebral palsy syndromes are absent. Tone remains decreased for one to two years and then becomes variable and paratonic.

ASSOCIATED DISORDERS

Other disorders of brain function frequently accompany the motor abnormalities that characterize cerebral palsy.⁶ These include mental retardation, epilepsy, and abnormalities of vision, hearing, language, cortical sensation, attention, learning, and behavior. Dyspraxias and agnosias may interfere with skilled tasks, independently from the severity of gross motor dysfunction. Mental retardation often, but not always, is correlated with the severity of motor handicap, and patients with atonic cerebral palsy or spastic quadriplegia are the most severely affected. Seizures are also most common in atonic cerebral palsy and spastic quadriplegia, in addition to acquired hemiplegia, and least common in mild symmetrical spastic diplegia and mainly athetoid cerebral palsy.¹ Ocular and visual abnormalities are common and include refractive error, strabismus, amblyopia, field defects, cortical visual impairment, and eye movement abnormalities. Disorders of speech and language are frequent and often complex, and it is important to assess for hearing loss. Although failure to thrive and poor nutrition may be related to nonnutritional factors, poor nutrition often plays a significant role in the severity of cerebral palsy and can be combated by the early use of a gastrostomy.⁷ Palatopharyngeal incoordination and gastroesophageal reflux contribute to chronic respiratory disease in patients with severe cerebral palsy, and this is further worsened by respiratory muscle incoordination, chest deformity, and sleep apnea. Immobile patients are at risk for osteopenia and fractures, and orthopedic disorders, including hip dislocation and scoliosis, are common. Although the primary neuropathological lesion is static, neurological signs may change or worsen with increasing age.⁸ However, sometimes the changes are caused by a spondylotic myelopathy. Drug reactions may also be cause of new or worsening neurological signs: for example, they may follow intake of carbamazepine or phenytoin.

DIAGNOSIS

Early diagnosis can be made on the basis of a combination of history and clinical findings. These include motor delay, abnormal or delayed postural responses, persistence of primitive reflexes, and abnormal neurological signs. The finding of an isolated abnormality such as mild hypertonia or hyperreflexia in the setting of normal development and behavior is an indication to observe closely. In most cases, if these findings remain isolated, they resolve during the first year of life. A diagnosis may be suspected if there is abnormal behavior such as undue irritability or excessive docility, abnormal oromotor or oculomotor findings, and developmental delay. Primitive reflexes may be asymmetrical or persistent, and postural reactions delayed. Accompanying abnormal neurological signs may include hypotonia and hyperreflexia. Spasticity may not be evident until 6 months of age, whereas dyskinesias may not be obvious until the second year and ataxia even later. By definition, definite diagnosis requires serial examinations.