Protein energy malnutrition and the nervous system.
Protein-energy malnutrition (PEM), a natural ramification of poverty, continues to be a perennial source of concern to a large segment of the world population. The developing nervous system of a child is specially vulnerable to deprivations in nurture. Peripheral nerve and muscle derangements are clinically evident by weakness, hypotonia and hyporeflexia in accordance with severity and duration of PEM. Motor and sensory nerve conduction studies exhibit significant abnormalities and often furnish useful and ominous correlation with grades of PEM. The human sural nerve histology in cases of severe PEM is characterized by persistence of small myelinated fibres, striking failure of internodal elongation and significant segmental demyelination. Young rhesus monkeys are ideal experimental PEM models and they show myopathic EMG changes amenable to rehabilitation. Muscle pathology comprises obliteration of cross-striations, streaming of Z bands, increased interfibrillary spaces, mitochondriomegaly and small-for-age fibres. Radioisotope assays reveal anomalous incorporation into various nerve and muscle constituents. Central nervous system, specially the neuropsychological functions are affected in a lasting manner. Learning deficits, behavioural problems and manual indexterity are most obtrusive features.