[Subacute myelo-optic-neuropathy (S.M.O.N.) following treatment with clioquinol (author's transl)]

2 patients, who were treated with clioquinol after radical resection of carcinoma of the rectum and colostomy, developed symmetrical sensorimotor polyneuropathy, mild posterior tract ataxia, bilateral pyramidal tract lesions and optic neuropathy, a clinical picture compatible with subacute myelo-optic-neuropathy (S.M.O.N.). One patient had neurological symptoms after having received 750 g of clioquinol, 3 years after treatment started, and impairment of vision was noted after having received 1200 g. The other patient had neurological symptoms 6 weeks after clioquinol was first given, having received 65 g, the average daily dose being 1.5 g, and vision was impaired after 765 g had been administered. On examination 12 and 14 months after clioquinol had been discontinued, the first patient's vision was slightly improved, but he was otherwise unchanged, while the vision of the other patient was unchanged, but she had otherwise deteriorated slightly neurologically. Electrophysiological examinations confirmed the clinical observations. A multifactor etiology of the syndrome: neurotoxicity of clioquinol, paraneoplastic neuropathy and malabsorption, is discussed.