NEUROPATHOLOGY OF EXPERIMENTAL VITAMIN-B12 DEFICIENCY IN MONKEYS

Severe vitamin B12 deficiency was produced in rhesus monkeys by feeding them a defined experimental diet under controlled conditions. The morphology and counts of peripheral blood and bone marrow were normal 5 yr after instituting the deficient diet. Gross visual impairment appeared in 5 of the monkeys between 33 and 45 mo. after the institution of the vitamin B12 deficient diet. In 3 of the visually impaired animals, a gradually progressive spastic paralysis of their hind limbs developed. Autopsies of 6 deficient animals showed degeneration of the peripheral visual pathway in all and of white matter in the spinal cord in 4. Degeneration of several cranial nerve roots was found in 4 monkeys and a mild diffuse degeneration of cerebral white matter in 4. The lesions in all affected parts of the CNS were bilaterally symmetrical and were indistinguishable from those due to B12 deficiency in the human. No abnormalities were found in any B12 supplemented control animal.