Anatomic Pathology: Neuropathology

• Leigh syndrome is a severe progressive neurodegenerative disorder that typically arises in the first year of life. This condition is characterized by progressive loss of mental and movement abilities. Leigh-type lesions are the result of metabolic defects of mitochondrial origin. X-linked mutations in the pyruvate dehydrogenase complex can be present.

• In Leigh disease, many necrotic lesions distributed symmetrically are present. The lesions are characterized by foamy macrophages, astrocytosis, prominent congested and hypertrophic capillaries, and collapse of the neuropil. Chronic lesions appear as fibrous or cavitated gliotic scars.

• Hepatolenticular degeneration or Wilson disease is an autosomal recessive disorder causing accumulation of copper in the liver, brain, and other organs. The putamen and caudate nucleus are more severely affected with neuronal loss, macrophages, and reactive astrocytes.

• Vitamin B12 deficiency can cause subacute combined degeneration of the spinal cord and peripheral neuropathy. Degeneration of the white matter in the posterior columns is initially seen, followed by the corticospinal and spinocerebellar tracts in the lateral columns.

• Central pontine myelinolysis occurs as a complication of rapid correction of hypo- or hypernatremia. Active demyelination is seen microscopically characterized by reactive astrocytes and large numbers of foamy, lipid-laden macrophages in the pons.

• Thiamine deficiency causes Wernicke encephalopathy, which produces atrophy of the mammillary bodies. It can also involve the hypothalamus, dorso-medial anterior thalamic nuclei, floor of the third ventricle, the periaqueductal region, the colliculi, and the cerebral cortex.