The Histopathology of Neuromalacia and ‘Curled Toe’ Paralysis in the Chick Fed Low Riboflavin Diets

Abstract

It has been demonstrated that a low riboflavin diet may cause two types of a nutritional deficiency. One of these produces a rapidly acute paralysis characterized as neuromalacia and a more slowly developing form which causes ‘curled toe’ paralysis in the growing chick. These symptoms can be prevented by the addition of crystalline riboflavin to the basal diet. This nutritional deficiency disease is accompanied by specific neuropathology of the main peripheral nerve trunks. In the acute form there is hypertrophy and change in appearance which can be readily observed by gross inspection. Degenerative changes appear in the myelin of the nerves, accompanied by Schwann cell proliferation and axis cylinder swelling and fragmentation. Histologic changes also occur in the spinal cord where myelin changes, gliosis, and chromatolysis have been observed. Neuro-muscular end plate degeneration and muscle fiber degeneration frequently accompany the paralysis. Histologic examination of the sciatic nerve from chicks fed artificially dried young grass shows that a 6% level of oat grass was marginal in its flavin content for the growing chick. It was found that addition of the antidermatitis factor to the low flavin basal diet considerably reduced the histopathology of the spinal cord. This suggests that the low riboflavin diet used in this series of experiments may also be low or marginal in the antidermatitis factor. Chicks fed ration 241H also showed improvement in the histopathology of the spinal cord when the antidermatitis factor was fed but the sciatic nerve was not protected. The latter was protected by the addition of crystalline riboflavin. Histologic examination also indicates that the addition of 300 micrograms of riboflavin to each 100 gm. of the basal diet was inadequate for complete protection of the chick during the early weeks of life. It is concluded from these studies that riboflavin is necessary in the growing chick for the normal function and maintenance of the nervous system, particularly the main peripheral nerve trunks and it may be specifically associated with myelin metabolism.