Protein Calorie Malnutrition is also known as Protein–energy malnutrition.The effect of deficiency of proteins and calories on the nervous system has not yet been defined. Infants who suffer from protein-calorie deficiency are less easily conditioned, their performance on standard psychological tests is often impaired and they commonly exhibit less curiosity and exploratory behavior, being apathetic, irritable, and drowsy. Weakness, hypotonia, diminished to absent deep tendon reflexes, seizures, and coarse tremor of the extremities have been described in kwashiorkor. The electroencephalogram is said to be abnormal in 40 per cent of severely afflicted children. There have been few critical neuropathologic studies.
Experimentally induced protein calorie malnutrition in newborn pigs causes retardation of gait development. The learning ability of weanling rats fed a diet devoid of protein is markedly impaired and, in addition, spasmodic trembLing of the head and forepaws may develop. Neurologic signs are said to be striking in puppies born of malnourished bitches. Neonatal death occurs 11 in 50 per cent of the pups, and the development of the survivors is retarded. Athetoid movements of the head and neck, ataxia of gait, and seizures may develop after weaning.
Few of the large number of biochemical investigations in laboratory animals and in patients suffering from protein-calorie deficiency have dealt with the nervous system. Protein and amino acid metabolism is generally impaired; the levels of free essential amino acids are reduced in the plasma, and an adaptive reduction in enzyme activity ensues. The brains of rats fed a low- protein diet have shown a decrease in the content of gamma-aminobutyric acid, and the activity of enzymes concerned with its formation is reduced. The- levels of alanine, glutamic acid, glutamine and aspartic acid are decreased.
Severe malnutrition during fetal growth and in early infancy affects the normal structural and biochemical development of the nervous system in an irreversible manner. Intrauterine malnutrition influences the rate of cell division, resulting in decreased, brain size and cellularity. Severe malnutrition in the immediate neonatal period retards the growth of the brain as well as the metabolism of cerebral DNA, RNA, and protein, and has a marked influence on the rate of synthesis of myelin lipids.
Cerebrosides, plasmalogens, sulfatides, cholesterol, and proteolipids are significantly decreased in the white matter of malnourished infants. In the cortex the content of RNA and protein per cell is normal, yet the total number and size of cells are reduced. The younger the child, the more marked is the abnormality. Evidence gleaned from the study of laboratory animals suggests that the deficit persists despite adequate nutritional replenishment. Thus profound nutritional deprivation occurring at a particularly vulnerable period of brain development permanently and adversely affects ultimate intellectual development and behavior.