Cyanide metabolism and vitamin B12 in multiple sclerosis.

In the course of an investigation of vitamin B12 concentrations in body fluids in multiple sclerosis (Basil, Brown, and Matthews, 1965), it was noted that the proportion of total B12 extractable from serum in the absence of added cyanide was higher in cases of multiple sclerosis than in a group of patients with other neurological disorders. This finding might mean that the serum in multiple sclerosis contained an excess of cyanide, or might represent a disturbance in the normal proportions of cyanocobalamin and hydroxocobalamin in the blood (Matthews, 1961, 1962, 1964; Smith, 1961; Anderson, 1964; Basil et al., 1965), and thus sug-gested the possibility of some disturbance in cyanide metabolism. Chronic exposure to cyanide can pro-duce lesions of the central nervous system, and possibly demyelination, in animals (e.g., Hurst, 1942; Lumsden, 1950; Smith, Duckett, and Waters, 1963; Wilson, 1965), and it has been suggested that cyanide is the toxic factor in tobacco amblyopia, producing hydroxocobalamin deficiency by con-verting this substance to the cyano- form (Smith, 1961). Clinical and laboratory studies indicate that there is an abnormality in conversion of cyanide to thiocyanate in Leber's hereditary optic atrophy (Wilson, 1965). The present investigation was undertaken to see whether any abnormality of cyanide metabolism could be detected in multiple sclerosis, and whether there was any disturbance in the relationship between cyanide and vitamin B12 in this condition. METHODS The subjects of the present study comprised seven controls and six patients with multiple sclerosis, in-patients at The National Hospital, Queen Square. The controls, four men and three women, were suffering from a variety of neurological disorders (idiopathic