Thallium Toxicity

Thallium poisoning induces a painful sensory neuropathy, particularly at the soles and palms, which may be followed by lower extremity weakness, ataxia, confusion, hallucinations, convulsions, and coma. Neuro-ophthalmic symptoms such as diplopia, abnormal color vision, and impairment of visual acuity may develop early, while dermatologic manifestations such as alopecia, rashes, palmar erythremia, and Mees lines in the nails and gums may be delayed by several weeks. Electrodiagnostic findings include an axonal sen-sorimotor neuropathy with nerves innervating the feet most significantly involved (30).

Management

Gastrointestinal decontamination, activated charcoal, and Prussian blue (potassium ferric hexacyanoferrate) are recommended in thallium ingestions. Activated charcoal and Prussian blue bind thallium decrease the enterohep-atic recycling, and enhance fecal elimination of the metal. Prussian blue binds more thallium than charcoal on a gram-bound per gram-agent basis and should be used instead of charcoal if possible. Prussian blue is available only as a laboratory reagent in the United States and Canada, and is not approved by the FDA as a pharmaceutical agent. Prolonged neurological exposure to thallium, especially in cases of acute poisoning when proper diagnosis is not established and detoxification is delayed almost universally leads to long-term and/or irreversible neurological sequelae (30,31).

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