Neurology of ciguatera

Ciguatera is a widespread ichthyosarcotoxaemia with dramatic and clinically important neurological features. This severe form of fish poisoning may pr esent with either acute or chronic intoxication syndromes and constitutes a global health problem. Ciguatera poisoning is little known in temperate co untries as a potentially global problem associated with human ingestion of large carnivorous fish that harbour the bioaccumulated ciguatoxins of the p hotosynthetic dinoflagellate Gambierdiscus toxicus. This neurotoxin is stor ed in the viscera of fish that have eaten the dinoflagellate and concentrat ed it upwards throughout the food chain towards progressively larger specie s, including humans. Ciguatoxin accumulates in all fish tissues, especially the liver and viscera, of "at risk" species. Both Pacific (P-CTX-1) and Ca ribbean (C-CTX-1) ciguatoxins are heat stable polyether toxins and pose a h ealth risk at concentrations above 0.1 ppb. The presenting signs of ciguate ra are primarily neurotoxic in more than 80% of cases. Such include the pat hognomonic features of postingestion paraesthesiae, dysaesthesiae, and heig htened nociperception. Other sensory abnormalities include the subjective f eatures of metallic taste, pruritis, arthralgia, myalgia, and dental pain. Cerebellar dysfunction, sometimes diphasic, and weakness due to both neurop athy and polymyositis may be encountered. Autonomic dysfunction leads to hy potension, bradycardia, and hypersalivation in severe cases. Ciguatoxins ar e potent, lipophilic sodium channel activator toxins which bind to the volt age sensitive (site 5) sodium channel on the cell membranes of all excitabl e tissues. Treatment depends on early diagnosis and the early administratio n of intravenous mannitol. The early identification of the neurological fea tures in sentinel patients has the potential to reduce the number of second ary cases in cluster outbreaks.