nervous system disorder eye disorder subacute myelo-opticoneuropathy 2022-03-14T15:01:03Z MedDRA:10058009 SMON Nicolas Bosc Zoe May Pendlington Subacute myelo-optico-neuropathy (SMON) is a neuro-degenerative disorder caused by poisoning due to over-dose and prolonged oral administration of clioquinol. This was shown by an epidemiological study in Japan in 1971, and confirmed by a series of animal experiments. It is characterized by symptoms of severe myelo-neuropathy: painful dysesthesia and paresthesia (such as tingling, stinging, fastening, cold, and sticking sensations) initiating in and moving upwards from the feet, loss of sensations, gait disturbance with ataxic and spastic paraplegia, autonomic disorders, and visual impairment, which almost invariably followed a severe abdominal pain (and sometimes led to loss of consciousness and opisthotonus), constipation, and diarrhea.