Deficiency in some food nutrients can cause disorders of the body systems. The Nervous system is not an exception and disorders such as Myelopathy, Encephalopathy, Visual disturbances, Malnutrition and slow development of the Brain are all nutritional disorders of the nervous system.
Demyelination may occur in the posterior and lateral columns of the spinal cord as a result of deficiency of vitamin B12. Though mostly seen as a complication of the pernicious anaemia, it may develop in vitamin B12 deficiency resulting from any causes. Myelopathy manifests as subacute combined degeneration, ie, dysfunction of the pyramidal tracts and posterior columns. The other parts of the nervous system affected include peripheral nerves and optic nerves. The neurological lesion and hematological abnormalities (macrocytic anemia) coexist in many cases, but in some, the neurological lesion may precede the anemia. Treatment with vitamin B12 always corrects the anemia, but the neuropathy is irreversible if the condition is advanced.
Thiamine deficiency causes the classical example of nutritional encephalopathy, I.e, Wernicke’s encephalopathy. The pathological changes include demyelination and petechial hemorrhages in and around the mammilary bodies and around the third ventricle and aqueduct. Wernicke’s encephalopathy may manifest as altered consciousness, ataxia, nystagmus and ocular palsies. An acute encephalopathy may develop in alcoholics and malnourished individuals who are given large doses of carbohydrates (especially parenteral glucose therapy) without concurrent administration of thiamine. The response to parenteral administration of 100mg thiamine is dramatic in such cases. Encephalopathy is a feature of pellagra (niacin deficiency). This manifest as dementia, spasticity of the limbs, ataxia, and extrapyramindal disturbances.
Nutritional amblyopia may develop in deficiency of multiple nutrients, including vitamin B12. This sets in insidiously with dimness of vision, photophobia, and retrobulbar discomfort on moving the eyes. Visual acuity is reduced. Central or parenteral scotomas develop, but the peripheral fields of vision may remain intact. Stracham syndrome is the combination of visual disturbances, ataxia, deafness and mucocutaneous lesions.
Malnutrition and development of the brain
The human brain shows spurts of development between the 15th to 20th weeks of gestation and the growth continues for about two years after birth. The major events are proliferation of neurons and glial cells, and myelination of the tracts. Severe malnutrition (protein and energy) occurring during fetal life and in the early parts of infancy may leave behind damage which is not correctable by subsequent therapy. This condition is quite prevalent in developing countries. Though the problem of infant malnutrition is closely linked with socio-economic and geographic factors, it is of utmost public health importance to ensure proper nutrition during pregnancy and infancy.