Laboratory Studies
No specific laboratory test that confirms tetrodotoxin ingestion exists; thus, dietary history is key for diagnosis.
Mouse bioassays for paralytic shellfish toxin (ie, saxitoxin) exist that are positive with tetrodotoxin. There are research chromatography techniques for tetrodotoxin as well; liquid chromatography–mass spectrometry (LC–MS) and liquid chromatography–tandem mass spectrometry (LC–MS/MS) are the most simple, powerful, and sensitive methods for qualitative and quantitative determination of TTX from human urine, blood, or other fluids. [13] However, neither is available in the acute clinical situation. [14]
Measure routine serum electrolytes, calcium, magnesium, and ABGs to rule out metabolic causes of diffuse sensory and motor neuron dysfunction.
Imaging Studies
Patients with evidence of cyanosis or respiratory insufficiency should have a chest x-ray to exclude local lung pathology (eg, aspiration pneumonia). Obtain a plain film and upright x-ray of the abdomen in patients with persistent vomiting or severe abdominal pain to exclude obstruction or hollow viscus perforation.
Perform a CT scan of the brain if the patient exhibits any focal neurologic dysfunction or seizures.
Staging
The following is the classic grading system for tetrodotoxin poisoning based on symptoms and signs [8] :
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Grade 1 - Perioral numbness and paraesthesia, with or without GI symptoms (mainly nausea)
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Grade 2 - Numbness of tongue, face, and other areas (distal); early motor paralysis and incoordination; slurred speech; normal reflexes
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Grade 3 - Generalized flaccid paralysis, respiratory failure (dyspnea), aphonia, and fixed/dilated pupils; patient still conscious
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Grade 4 - Severe respiratory failure and hypoxia; hypotension, bradycardia, and cardiac dysrhythmias; unconsciousness may occur
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Puffer fish.
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Chemical structure of tetrodotoxin.
