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Classifying types of cerebral palsy
There are two main factors in describing the disability of a child with cerebral palsy (CP). These are where the disability
is located (topography) (e.g., hemiplegia, all four extremities, etc.) and the type of abnormality in motor ability (e.g.,
hypotonia, weakness, dystonia, spasticity, etc.). It is important to determine these for each child with CP because:
Children with CP are diagnostically classified by their abnormalities in tone. The most commonly used terms are:
Topographical classification of spastic CP:
- Classification focuses the etiologic evaluation;
- Classification predicts associated conditions;
- Different treatment approaches are effective for different kinds of motor problems;
- Topography is important in functional prognosis; and
- Accurate description of patients' tonal abnormalities and topography allows
for easier identification of changes in status and for better communication between clinicians (e.g., "a 7 year old with mental
retardation and cerebral palsy" vs. "a 7 year old with diplegia and moderate cognitive challenges who uses a walker to assist
in ambulation").
Children with CP are diagnostically classified by their abnormalities in tone. The most commonly used terms are:
- spastic CP: the child with spastic CP has increased muscle tone – muscles feel rigid and exhibit exaggerated reflexes. This type of CP is due to damage to the main motor control system of the brain, the pyramidal system, made up of the precentral gyrus and the corticospinal pathway.
- extrapyramidal CP: the child with extrapyramidal CP may have a variety of motor problems, due to damage to the basal ganglia and associated areas of the brain, the so called extrapyramidal motor system. These might include dystonia, which is variable muscle rigidity that disappears in sleep, hypotonia, and/or choreoathetosis. A child with extrapyramidal CP generally has whole body involvement, although some differences may exist in severity and extent between the two sides of the body and upper and lower extremities. Children with purely extrapyramidal feature are rare – historically, kernicterus produced this pattern with basal ganglia-specific toxicity.
- ataxic CP: The child with ataxic CP generally has difficulty walking and balancing. This may mainfest as truncal titubation (swaying) in non-ambulatory children. Children with ataxic CP may also exhibit dysmetria (impaired ability to accurately control the range of movement in muscular actions for instance when reaching for an object).
- The majority of children have mixed tonal abnormalities. Common patterns include central hypotonia with spasticity of the
extremeties and spasticity mixed with dystonia. A common approach is to use the term which identifies the most functionally
significant abnormality in tone (i.e., spasticity or extrapyramidal) and use the term mixed when both components are prominent.
- When present, spasticity is present regardless of the patient's state (e.g., agitated, calm, or asleep). Dystonia varies significantly with the patient's state and goes away during sleep. Children with spasticity are more likely to require surgery or botox/phenol injections for contractures as their muscles don't relax during sleep.
- In spasticity, when range of motion is tested, the degree of resistance to movement varies depending on the rate at which the extremity is moved. If flexed or extended slowly, the extremity will move with much less resistance than if moved quickly. The clasp knife effect, where there is no resistance at the start but it kicks in when the extremity has been moved enough to activate stretch receptors, may also be found in spasticity. In dystonia, the resistance is constant and not rate dependent.
- Sustained ankle clonus suggests spasticity.
- Observe the child's posture and movement patterns. Spasticity results in an upper extremity flexion pattern with lower extremities extended. Extrapyramidal features result in overflow movements and extension (e.g., arching).
- Watch the child's face. Children with extrapyramidal features often display choreoathetotic facial movements. These are observed as involuntary tongue thrusting or writhing, a smile that overflows to a huge caught-up grin, or scrunching of the eyes when attempting other voluntary facial movements.
- Examination can vary over time, particularly if there are extrapyramidal components. Repeat your examine multiple times. The exam will change with fever or agitation. You may only be able to identify spasticity underneath severe dystonia when the child is very calm or asleep.
Topographical classification of spastic CP:
- Children with hemiplegia have unilateral motor impairments, with the arm affected more than the leg. Hemiplegia is often the result of an in utero middle cerebral artery stroke or a focal brain malformation.
- Children with diplegia demonstrate bilateral involvement with legs affected more than hands. Hand involvement may be observed in gross motor movements or may be more subtle, affecting only fine motor control. (The presence of hand involvement distinguishes diplegia from paraplegia in which only the bottom half of the body is affected, for example after a spinal cord injury). Asymmetries are common. Diplegia is most commonly the result of prematurity with injury to the periventricular area. The incidence of spastic diplegia has not decreased with the advent of improved survival of premature infants.
- Children with quadriplegia have full body involvement with arms more or equally involved as lower extremities. Generally this reflects diffuse brain injury or malformation and extrapyramidal features are also substantial (i.e., mixed CP). A common etiology for this pattern is asphyxia near term or after birth.
- Children with triplegia have one extremity substantially spared, usually an arm.
- Children with monoplegia have only one extremity involved.
For more information on tonal abnormalities and topography, see MD Virtual University: Pediatric Movement Disorders (with annotation in the Resources section).
Resources
Information & Support
For Professionals
MD Virtual University: Pediatric Movement Disorders
Created by WE MOVE (World Wide Education and Awareness for Movement Disorders); movement and tone abnormalities are discussed,
with extensive information regarding identification, evaluation, and treatment. The information is not specific to CP, but
includes information about CP.