CEREBRAL PALSY DEFINITION, ETIOLOGY & CLASSIFICATION

Cerebral palsy is defined as a disorder of movement and posture caused by a nonprogressive defect or lesion in an immature brain. In the neurological literature, cerebral palsy is referred to as a "static encephalopathy."

Three distinctive features common to all patients with cerebral palsy:

 (1) Some degree of motor impairment is present, which distinguishes it from other conditions, such as global developmental delay or autism

 (2) an insult to the developing brain has occurred, making it different from conditions that affect the mature brain in older children and adults

(3) a neurological deficit is present that is non progressive, which distinguishes it from other motor diseases of childhood, such as the muscular dystrophies

Although the neurological deficit is permanent and non progressive, the effect it can have on the patient is dynamic, and the orthopaedic aspects of cerebral palsy can change dramatically with growth and development. Growth, along with altered muscle forces across joints, can lead to progressive loss of motion, contracture, and eventually joint subluxation or dislocation, resulting in degeneration that may require orthopedic intervention.

Worldwide, the prevalence ranges from 0.6 to seven cases per 1000 live births

Injury to the developing brain can occur anytime from gestation to early childhood and typically is categorized as prenatal, perinatal, or postnatal

Prenatal period

·        Risk factors inherent to the fetus (most commonly genetic disorders)

·        Factors inherent to the mother (seizure disorders, mental retardation, and previous pregnancy loss)

·        Factors inherent to the pregnancy itself (Rh incompatibility, polyhydramnios, placental rupture, and drug or alcohol exposure)

·        External factors, such as TORCH (toxoplasmosis, other agents, rubella, cytomegalovirus, herpes simplex)

Perinatal period (from birth until a few days after birth) 

·        Asphyxia or trauma that occurs during labor

·        Oxytocin augmentation,

·        Umbilical cord prolapsed

·        Breech presentation

·        Only 10% of cases of cerebral palsy occur during this time period.

·        Low-birth-weight infants (<1500 g) are at dramatically increased risk of cerebral palsy, with an incidence of 60 per 1000 births compared with two per 1000 births in normal-weight infants.

·        This increased incidence is believed to be due to the fragility of the periventricular blood vessels, which are highly susceptible to physiological fluctuations during pregnancy which include hypoxic episodes, placental pathology, maternal diabetes, and infection, which can injure these vessels and lead to subsequent intraventricular hemorrhages.

These injuries are graded on a scale

I

Bleeding confined to germinal matrix

II

Bleeding extends into ventricles

III

Bleeding into ventricles with dilation

IV

Bleeding into brain substance

An increased incidence of neurological consequences such as hydrocephalus and cerebral palsy in grade III and grade IV

Postnatal period- causes are

·        Hypoxic-ischemic encephalopathy, which is characterized by hypotonia, decreased movement, and seizures, is a common cause of cerebral palsy during the postnatal period. Meconium aspiration and persistent fetal circulation with true ischemia are the most common causes of hypoxic-ischemic encephalopathy.

·        Infections such as encephalitis and meningitis, most commonly caused by group B streptococcus and herpes, can lead to cerebral palsy during this period.

·        Traumatic brain injury from accidents or child abuse also accounts for a significant number of cases of cerebral palsy that develop in the postnatal period.

CLASSIFICATION

Geographical classification

Monoplegia

·        Monoplegia is very rare and usually occurs after meningitis.

·        Most patients diagnosed with monoplegia actually have hemiplegia with one extremity only very mildly affected.

Hemiplegia

·        In hemiplegia, one side of the body is involved, with the upper extremity usually more affected than the lower extremity.

·        Patients with hemiplegia, approximately 30% of patients with cerebral palsy, typically have sensory changes in the affected extremities as well.

·        Severe sensory changes, especially in the upper extremity, are a predictor of poor functional outcome after reconstructive surgery.

·        Hemiplegic patients also may have a leg-length discrepancy, with shortening on the affected side.

Diplegia

·        Diplegia is the most common anatomical type of cerebral palsy, constituting approximately 50% of all cases.

·        Patients with diplegia have motor abnormalities in all four extremities, with the lower extremities more affected than the upper.

·        This type of cerebral palsy is most common in premature infants; intelligence usually is normal.

·        Most children with diplegia walk eventually, although walking is delayed usually until around age 4 years.

Quadriplegia

·        In quadriplegia, all four extremities are equally involved, and many patients have significant cognitive deficiencies that make care more difficult.

·        Head and neck control usually are present, which helps with communication, education, and seating.

·        Treatment goals for patients with quadriplegia include a straight spine and level pelvis, located mobile hips with 90 degrees of flexion for sitting and 30 degrees of extension for pivoting, plantigrade feet that can fit in shoes, and an appropriate wheelchair.

Total Body

·        Patients with total body involvement typically have profound cognitive deficits in addition to loss of head and neck control.\

·        These patients usually require full-time assistance for activities of daily living and specialized seating systems to assist with head positioning.

·        Drooling, dysarthria, and dysphagia also are common and complicate care.

Physiological Classification

Physiologically, cerebral palsy can be divided into 

·        Spastic type, which affects the corticospinal (pyramidal) tracts

·        An extrapyramidal type, which affects the other regions of the developing brain. The extrapyramidal types of cerebral palsy include

·        Athetoid

·        Choreiform

·        Ataxic

·        Rigid

·        Hypotonic 

Spastic

·        Most common form of cerebral palsy, constituting approximately 80% of cases.

·        Associated with injury to the pyramidal tracts in the immature brain.

·        Spasticity, or the velocity-dependent increase in muscle tone with passive stretch, is caused by an exaggeration of the normal muscle passive stretch reflex.

·        Often, patients have simultaneous cocontraction of normally antagonistic muscle groups leading to fatigue, loss of dexterity and coordination, and balance difficulties.

·        Joint contractures, subluxation, and degeneration are common.

Athetoid

·         Injury to the extrapyramidal tracts

·        Characterized by dyskinetic, purposeless movements that may be exacerbated by environmental stimulation.

·        Joint contractures are uncommon, and the results of soft-tissue releases, in contrast to those seen in spastic cerebral palsy, are unpredictable, and the procedures have a high complication rate

·        Dystonia, characterized by increased overall tone and distorted positioning in response to voluntary movements, or hypotonia also can occur with athetoid cerebral palsy.

Choreiform

·        Characterized by continual purposeless movements of the patient's wrists, fingers, toes, and ankles.

·        This continuous movement can make bracing and sitting difficult

.

Rigid

·         Most hypertonic of all cerebral palsy patients.

·        This hypertonicity occurs in the absence of hyperreflexia, spasticity, and clonus, which are common in spastic cerebral palsy.

·        These patients have a “cogwheel” or “lead pipe” muscle stiffness that often requires surgical release.

Ataxic

·        Ataxic cerebral palsy is very rare and probably is the most often misdiagnosed type. It is characterized by the disturbance of coordinated movement, most commonly walking, as a result of an injury to the developing cerebellum. It is important to distinguish true ataxia from spasticity because with treatment many children with ataxia are able to improve their gait function without surgery. Overaggressive tendon lengthening in patients with ataxia can lead to iatrogenic weakness, which further interferes with gait function.

Hypotonic

·        Characterized by weakness in conjunction with low muscle tone and normal deep tendon reflexes.

·         Persistent hypotonia can lead to difficulties with sitting balance, head positioning, and communication.

 Mixed

·        Have features of more than one type

·        Show signs of pyramidal and extrapyramidal deficits.

Palisano et al. developed the Gross Motor Function Classification System to help resolve these classification difficulties .This five-level numeric grading system, which has been found to be a reliable and stable method of classification and prediction of motor function for children 2 to 12 years old, takes into account functional limitations for assistive devices, such as walkers and wheelchairs, and the quality of movement based on age. The emphasis of this scale is on self-initiated movement and walking and sitting function

Gross Motor Function Classification System

I

Has nearly normal gross motor function

II

Walks independently, but has limitations with running and jumping

III

Uses assistive devices to walk and wheelchair for long distances

IV

Has ability to stand for transfers, but minimal walking ability; depends on wheelchair for mobility

V

Lacks head control, cannot sit independently, is dependent for all aspects of care

From :

R.T.Vipul