When a infant or young child presents with motor or cognitive
abnormalities, one of the first questions to answer is whether the condition is
a static or progressive encephalopathy. Both may involve deficits of language,
vision, hearing, and motor function. Likewise, both may result to failure to
obtain certain motor and cognitive milestones. The key
in the diagnosis of a static encephalopathy is that it has a non-progressive
course. Although patients may have delayed motor milestones,
they do not lose milestones, as they do in a
progressive neurologic disorder.
The differentiation is critical as the differential diagnosis and prognosis
are markedly different. A chronic static encephalopathy may be caused by genetic
or acquired etiologies. Some may associated anatomical deformations of the
brain. Among static encephalopathies, cerebral
palsy (CP) is the prototypic disorder. CP is a disorder primarily
affecting motor function and tone. Most often, patients with CP have spasticity
and other upper motor neuron signs. Some patients will
have basal ganglionic dysfunction with dyskineas, chorea or athetosis. The most
common form of CP is a spastic diplegia (of the legs) followed by hemiplegic,
dyskinetic, ataxic and quadriplegic forms. Children with CP may or may not have
intellectual problems or seizures. Indeed, many have above normal intellectual
functon.
CP can be caused by both prenatal and
perinatal insults. Many times the etiology is
unknown. The more common brain abnormalities are intraventricular hemorrhage (IVH)
and periventricular leukomalacia (PVL) in premature infants, and perinatal
hypoxic ischemic encephalopathy (HIE) in term newborns. Other causes are CP
include congenital infections, toxins, maternal infection during pregnancy and
labor, and genetic and metabolic disorders.
Conversely, chronic progressive encephalopathies are ususally caused by
genetic inborn errors of metabolism (e.g., peroxisomal metabolism or lysosomal
storage disorders), leukodystrophies, and rare infections (e.g., HIV, SSPE),
among other uncommon conditions. |