Metabolic and degenerative diseases of childhood.

The metabolic and degenerative diseases of childhood are a diverse group of disorders with varied imaging features. Some of the disease processes have characteristic findings and some have no findings at all, but most present with nonspecific abnormalities in white matter. These patchy lesions, seen best on magnetic resonance scanning with T2 weighting, require a good history and a dialogue with the referring physicians to help in narrowing the differential possibilities. The major disease processes involving white matter are the dysmyelinating diseases, in which the abnormal white matter is the result of an inherited enzyme deficiency, and the demyelinating diseases, in which an acquired process such as infection destroys white matter. Several diseases result in gray matter abnormalities, including central pontine myelinolysis, MELAS syndrome (mitochondrial myopathy, encephalopathy, lactic acidosis, and stroke-like symptoms), Batten's disease, Leigh disease, and Wilson's disease.