Young infants with CP often present with hypotonia. The differential diagnosis for the floppy infant is vast. The most common etiologies include central nervous system disorders such as CP, neuromuscular disorders, genetic
FIGURE 14.9 Algorithm for the evaluation of the child with CP.
Source: Reprinted with permission from Aswal S, et al. Practice parameter: Diagnostic assessment of the child with cerebral palsy. Report of the Quality Standards Subcommittee of the American Academy of Neurology and the Practice Committee of the Child Neurology Society. Neurology. 2004;62:851-863.
disorders, and metabolic disorders. Clues to a neuromuscular disorder include diminished deep tendon reflexes, weakness (which may result in absent infantile reflexes), or a positive family history. Dysmorphic features may suggest a genetic cause for hypotonia, such as Down syndrome, Prader-Willi syndrome, or Angelman syndrome. Metabolic disorders may present at any age, but are most likely to present in infancy. Metabolic disorders should be considered if a previously healthy child presents with an acute encephalopathy without an adequate explanation. Metabolic acidosis, hypoglycemia, hepatic involvement, or cardiac involvement should also prompt consideration of a metabolic disease. Dystonia and spasticity are present in a number of metabolic disorders, including mitochondrial disorders, glutaric aciduria type I, Lesch-Nyhan syndrome, and homocystinuria. A diagnosis other than CP should always be sought in children who have evidence of progressive disease or loss of previously obtained milestones.
A definitive diagnosis of CP should be made cautiously, especially in the first 6 months of life. Infants who are suspected of having CP should be followed closely with serial developmental evaluations and physical exams until the diagnosis is clear. An early diagnosis is considered best practice, however, because it will allow access to diagnosis-specific early intervention and parental support (29).
CP is defined as a disorder of movement control and posture, and therefore sensory impairments are easily overlooked. Deficits in two-point discrimination, proprioception, and stereognosis have been described (46-48). Sensory deficits are believed to be most common in children with hemiparesis. A study of children with spastic hemiparesis found that 97% of the spastic limbs had a stereognosis deficit, 90% had a two-point discrimination deficit, and 46% had a proprioception deficit, and these sensory deficits were more commonly present in limbs with a greater size discrepancy (48). Sensory deficits can also be found in the limbs that do not appear to be affected by CP (49). Bilateral sensory deficits were found in 88.8% of children with hemiparesis in one study (46). Stereognosis and proprioception deficits were the most common bilateral abnormalities, and the extent of sensory loss did not mirror the motor deficit. Another study identified abnormalities of tactile spatial discrimination in the hands of children with spastic diparesis with apparent normal motor function in their upper extremities (47). Little is known about the significance of right- or left-sided brain injury on sensory deficits in CP. A trend toward children with left hemiparesis to perform worse on spatial-tactile tests has been reported (49). Beyond the brain injury itself, it has been hypothesized that a reduced number of perceptual motor experiences throughout development may contribute to the reorganization of the sensorimotor cortex (50). Sensory deficits are important to recognize because they can significantly affect functional use of the extremity.