Respiratory paralysis in neurotoxic envenoming.

<p>Sri Lankan patient with severe neurotoxicity and respiratory paralysis being ventilated following a cobra (<i>Naja naja</i>) bite. (Photograph courtesy of Prof. S. A. M. Kularatne, University of Peradeniya, Sri Lanka. The purpose of the photograph has been explained to the patient, and consent obtained for potential publication.)</p

Sites of action of snake neurotoxins and other substances on the neuromuscular junction.

<p>Schematic representation of the neuromuscular junction showing different sites of action of snake neurotoxins, other toxins, and pharmacological substances, and sites of involvement in disease states (examples indicated where relevant). 1. <b>Synaptic vesicular proteins</b>: <i><u>Snake toxins</u></i>: beta-bungarotoxin (<i>Bungarus</i> spp.), taipoxin (<i>O. scutellatus</i>); <i><u>Other toxins</u></i>: botulinum toxin, tetanus neurotoxin. 2. <b>Voltage-gated calcium channel</b>: <i><u>Snake toxins</u></i><u>:</u> calciseptine (<i>Dendroaspis</i> spp.), beta- bungaratoxin (<i>Bungarus</i> spp.); <i><u>Other toxins</u></i>: omega-conotoxin (marine snail, <i>Conus</i> spp.); <i><u>Disease states</u></i>: Lambert-Eaton myaesthenic syndrome. 3. <b>Pre-synaptic membrane</b>: <i><u>Snake toxins</u></i>: phospholipase A2 toxins. 4. <b>Pre-synaptic ACh receptor</b>: <i><u>Snake toxins</u></i>: candoxin (<i>Bungarus candidus</i>); <i><u>Other toxins</u></i>: curare; <i><u>Pharmacological substances</u></i><u>:</u> non-depolarising blocking drugs (atracurium). 5. <b>Voltage-gated potassium channels</b>: <i><u>Snake toxins</u></i>: dendrotoxins (<i>Dendroaspis</i> spp.); <i><u>Disease states</u></i>: neuromyotonia, Isaacs' syndrome; <i><u>Pharmacological substances</u></i>: magnesium sulphate, aminoglycosides. 6. <b>Acetylcholine</b>: Lysis by exogenous acetylcholinesterase in <i><u>snake venom</u></i>: cobra venom (<i>Naja</i> spp.). 7. <b>Acetylcholinesterase</b>: Inhibitors of endogenous AChE in <i><u>snake venom</u></i>: fasiculins (<i>Dendroaspis</i> spp.). 8. <b>Post-synaptic ACh receptors</b>: <i><u>Snake toxins</u></i>: alpha-bungaratoxin (<i>Bungarus</i> spp.), candoxin (<i>B. candidus</i>), azemiopsin (<i>A. feae</i>), waglerin (<i>T. wagleri</i> ); <i><u>Other toxins</u></i>: alpha-conotoxin (marine snail, <i>Conus</i> spp.); <i><u>Disease states</u></i>: myasthenia gravis; <i><u>Pharmacological substances</u></i>: depolarising blocking agents (e.g., succinylcholine), non-depolarising blocking drugs (e.g., atracurium). 9. <b>Voltage-gated sodium channels</b>: <i><u>Snake toxins</u></i>: crotamine (<i>Crotalus</i> spp.); <i><u>Other toxins</u></i>: pompilidotoxin (wasps), delta-conotoxin (<i>Conus</i> spp.), tetradotoxin (pufferfish).</p

Bilateral ptosis and facial weakness in neurotoxic envenoming.

<p>Sri Lankan patient with bilateral ptosis and facial weakness following a Krait (<i>Bunagrus caeruleus</i>) bite. (Photograph courtesy of Prof. S. A. M. Kularatne, University of Peradeniya, Sri Lanka. The purpose of the photograph has been explained to the patient, and consent obtained for potential publication.)</p

Some examples of toxin diversity in snake venom.

<p>Some examples of toxin diversity in snake venom.</p

Neurotoxicity in Russell's viper envenoming.

<p>Sri Lankan farmer with Russell's viper (<i>Daboia russelii</i>) envenoming: tissue necrosis at bite site, haematuria, and bilateral ptosis. (Photographs courtesy of Prof. S. A. M. Kularatne, University of Peradeniya, Sri Lanka. The purpose of the photographs has been explained to the patient, and consent obtained for potential publication.)</p

Some human studies with neurophysiological findings in snake neurotoxicity.

<p>(CMAP, compound muscle action potential; RNS, repetitive nerve stimulation; EMG, electromyography; SNAP, sensory nerve action potential).</p

Summary table of some key studies with descriptions of neurotoxicity.

<p>(N/A – not available).</p

Summary of some key animal studies with individual snake neurotoxins.

<p>Summary of some key animal studies with individual snake neurotoxins.</p

Characteristics of the snakebite victims who responded to the invitation and non-responders.

<p>NS – not significant.</p

Correlation with post-traumatic stress disorder symptom (PTSD) score.

<p>**Correlation is significant at the 0.01 level.</p