Neurological Disturbances of Ciguatera Poisoning: Clinical Features and Pathophysiological Basis, 2020, L'Herondelle et al

Killian L’Herondelle,1 Matthieu Talagas,1,2 Olivier Mignen,3Laurent Misery,1,2 and Raphaele Le Garrec1,*
(French researchers)

Abstract

Ciguatera fish poisoning (CFP), the most prevalent seafood poisoning worldwide, is caused by the consumption of tropical and subtropical fish contaminated with potent neurotoxins called ciguatoxins (CTXs). Ciguatera is a complex clinical syndrome in which peripheral neurological signs predominate in the acute phase of the intoxication but also persist or reoccur long afterward.

Their recognition is of particular importance in establishing the diagnosis, which is clinically-based and can be a challenge for physicians unfamiliar with CFP. To date, no specific treatment exists. Physiopathologically, the primary targets of CTXs are well identified, as are the secondary events that may contribute to CFP symptomatology.

This review describes the clinical features, focusing on the sensory disturbances, and then reports on the neuronal targets and effects of CTXs, as well as the neurophysiological and histological studies that have contributed to existing knowledge of CFP neuropathophysiology at the molecular, neurocellular and nerve levels.
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https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7602189/
free access

 

The paper mentions voltage-gated sodium channels (Nav) as the primary target of the toxins. Downstream effects include an increase in intracellular calcium concentration by various mean, including calcium influx through transient receptor potential (TRP) channels.

A blood transcriptomic study suggested activation of inflammatory pathways and genetic variants of the adaptive immune system are involved in the persistence of CFP disturbances.

I thought this was interesting - the idea that the toxins bind to the sodium channels and are difficult to dislodge. And more toxin might be released over time from other binding sites (tissue or plasma proteins or lipoproteins):

It's known that ciguatera poisoning can develop gradually over time - with small exposures building up the toxin levels.


Further to triggers of symptoms

Even if none of the findings about ciguatera poisoning are helpful for us, it's good to be aware of it as a differential diagnosis. It sounds as though it is often mis-diagnosed as chronic fatigue syndrome.

 

One of the studies referenced by this paper is
https://pmj.bmj.com/content/75/889/678

Ciguatera fish poisoning, 1999

That ciguatera toxin acts as a cholinesterase inhibitor has been disputed - saying that while it acts so in vitro, it does not act so in vivo.

However, a document on suggested treatments
https://www.ciguatera.pf/index.php/en/la-ciguatera/les-traitements
says
pralidoxime (Contrathion®…; 200 to 1000 mg, slow infusion) for its cholinesterase reactivator property.

cholestyramine (Questran®…), an anticholesteremic, which seems to be a ciguatoxins-antagonist, demonstrated some efficiency on neurological symptoms improvement in numerous patients.