Children with this congenital defect are unable to turn their eyes to either side volitionally or on command. Attempting to look to the right, the child turns the head to the right (there is no associated apraxia of head turning), but the eyes lag and turn to the left. As a result, the patient has to overshoot the mark with the head in order to attain ocular fixation. Once the eyes fixate, the head returns to the primary position. To compensate for the deficiency of eye movements, the patient develops jerky thrusting movements of the head, which characterize all attempts at voluntary gaze. Caloric stimulation of the labyrinth causes tonic movement of the eyes but not nystagmus, as in the normal person. Also, optokinetic nystagmus cannot be induced. Vertical eye movements are normal. A similar ocular condition may occur in conjunction with ataxia-telangiectasia and in Gaucher disease. Children with oculomotor apraxia are slow to walk; Ford observed one such child whose sibling had an absence of the vermis of the cerebellum. Aside from this observation, the anatomic basis of the condition has not been studied.
In this group of congenital disorders, a major disturbance of motor function, usually nonprogressive, has been present since infancy or early childhood. The popular terms for these conditions have been infantile cerebral paralysis (Freud) and cerebral palsy. The latter name is neither appropriate nor useful from the physician’s viewpoint, collocating as it does diseases of widely differing etiologic and anatomic types, wherein the hereditary and acquired and the intrauterine, natal, and postnatal diseases lose their identity. But the name has been adopted as a slogan by fund-raising societies and for rehabilitation clinics throughout the United States, hence it will not soon disappear from medical terminology. The term, often abbreviated CP, is still being used indiscriminately to designate every conceivable cognitive and motor disorder of corticospinal, extrapyramidal, cerebellar, and even neuromuscular type in infants and children.
Etiology of the Congenital Cerebral Motor Disorders
Motor abnormalities that have had their onset early in life are numerous and diverse in their clinical manifestations. Marked prematurity is an associated factor in a large proportion of cases. Each year, approximately 50,000 infants weighing less than 1,500 g are born in the United States; approximately 85 percent survive. Of these, 5 to 15 percent have a motor disorder of cerebral origin and 25 to 30 percent are found to be mentally impaired at school age (Volpe, 1995; also Hack et al). It is helpful to categorize a given case according to the extent and nature of the motor abnormality. A careful history of prenatal, perinatal, or postnatal insults to the developing nervous system must be sought; certain correlations of these factors with the resulting pattern of neurologic deficit are outlined below. Most patients with these motor abnormalities reach adult years. Many but not all have epilepsy in addition to the motor abnormalities and there is an unavoidable overlap in considering the causes and mechanisms of these three clinical states.
The following discussion is given from the perspective of the three major etiologic syndromes: matrix hemorrhages in the immature infant, hypoxic-ischemic encephalopathy, and certain other developmental motor abnormalities including those due to intrauterine stroke.