CHRONIC CYANIDE POISONING IN RELATION TO BLINDNESS AND TROPICAL NEUROPATHY

Within a group of 20 patients showing optic atrophy and macula degener ation, 14 patients could be examined for neurological and audiometric defects. In 6 patients neurological signs and symptoms were observed. Nine patients reported loss of hearing and in 3 of them a severe perce ptive deafness was seen in the audiogram. In 3 of the 14 patients a co mbination of severe neurologic and audiologic symptoms developed and i n two of them a high thiocyanate concentration in serum was observed. The occurrence of perceptive deafness and posterior column sensory los s in the lower extremities in four of the patients made the diagnosis of polyneuropathy the most plausible. Although a similarity to chronic myelopathies caused by nutritional cyanide poisoning cannot be denied , the mean thiocyanate concentration in plasma 24 mu mol/L (1.39 mg/L) , and the cyanide levels in the blood 0.09 mu mol/L (2.3 mu g/L) were substantially lower than those found in other individuals during perio ds of extreme drought in which food only consisted of the bitter varie ty of cassava. The role of cyanide in the etiopathology of this polyne uropathy is unknown.