Demyelinating Polyneuropathy Following Scorpion Sting Envenomation; a Case Report and Review of Literature

Background: Scorpion sting envenomation generally causes treatable local and systemic effects; however, in rare cases, the victims might experience sequels in end organs such as central nervous system. In the present paper, a case of relatively self-limiting demyelinating polyneuropathy following a Butidae sting is presented and the possible mechanisms are discussed.  Case Presentation: A 19-year-old man presented to emergency department of Sultan Qaboos University Hospital, Oman with severe throbbing pain at the base of his right big toe after a scorpion sting. His initial examination revealed normal vital signs and the systemic examinations were unremarkable. Few minutes later, he developed profuse sweating, slurred speech, blurred vision, increased salivation and restlessness. Repetition of measurement of vital signs showed a blood pressure of 160/100 mmHg, heart rate of 140 beat per minute and a respiratory rate of 18 per minute. The patients received scorpion antivenom and cholinergic hyperactivity manifestations. Shortly after, the patient developed involuntary jerky movements in both lower associated with fasciculation. Nerve conduction study was suggestive of demyelinating polyneuropathy. In later days, involuntary jerky movements of lower limbs improved gradually but fasciculation remained. On a follow-up visit after four months, the patient still complained of occasional fasciculation. Discussion: One explanation for the development of peripheral nerves demyelination in our patient is the inflammatory response triggered by scorpion venom. In addition, this complication can be attributed to direct cytotoxic effects of scorpion venom toxins. Antimicrobial peptides in scorpion venoms are shown to be highly toxic to human cells, which in our case might have damaged the nerve sheet. Conclusion: Severe scorpion sting envenomation may lead to severe systemic effects and end organ damage. Medical toxicologists should be prepared to diagnose and treat such sequels.