Cerebral palsy

From Biomch-W

Cerebral palsy is a perinatal disorder (occurring before, during or shortly after birth), occuring with an incidence of about 2 per 1000 live births. Although it is more common in babies with low birth weight and prematurity (birth before 32 weeks), due to anoxia and brain trauma, the majority of cases are of idiopathic aetiology, i.e. of no discernible cause.

While the neurological damage is non-progressive (meaning that the brain lesion does not get any worse), secondary problems (muscular contractures and abnormal bone growth) often cause deterioration in function as the child ages. Nevertheless, about 70 % of people with CP can walk and a plethora of therapeutic interventions in recent years have made understanding CP gait one of the main challenges in clinical biomechanics.

There are three main types: spastic (around 70%), involving the pyramidal tracts and causing either hemiplegia or diplegia (bilateral involvement, with lower limbs affected more than upper limbs); athetoid (20%), which affects the extrapyramidal system, causing involuntary movements; and ataxic (10%), involving the cerebellum and resulting in balance problems. Cognitive impairment is present in approximately 40%.

The natural history of cerebral palsy is not entirely clear. Almost all children undergo some form of therapy, so it is difficult to observe their natural progress. The effects of growth further complicate the picture. Two studies in which two gait analyses were performed several years apart showed a decline in function. This is thought to be due to a combination of two processes. Spastic muscles become tighter as the long bones grow, and while muscle strength increases according to the square of its diameter (cross-sectional area), body weight (or volume) increases according to the cube. Thus the child becomes progressively weaker with growth.

There are three fundamental problems in CP: weakness, spasticity, and loss of selective motor control with retained primitive reflexes and postural reactions. Ankle equinus, excessive knee and hip flexion (crouch gait) and jump knee are common gait deviations.