Scorpion envenomation

Background

Arizona Bark Scorpion, (Centruroides sculpturatus)

• Most scorpion stings in North America result only in local pain.
• Arizona Bark Scorpion, Centruroides sculpturatus, found in AZ, NM, TX, and CA, can cause systemic toxicity.

Clinical Features

Local reaction

• Immediate and severe pain
  • "Tap" test: severe local tenderness when affected area is lightly tapped

Systemic reaction

• Uncommon but can be severe, particularly in children
• Cranial nerve and somatic motor dysfunction can develop:
  • Abnormal roving eye movements (pathognomonic) , blurred vision, pharyngeal muscle incoordination
  • Can occasionally lead to respiratory compromise (excessive secretion)
• Tachycardia and severe agitation can also be present
• Without antivenom, symptoms typically last 24-48 hrs

Grades of Centruroides envenomation

• Grade 1 - Local pain and/or paresthesias at site of envenomation
• Grade 2 - Pain and/or paresthesias remote from the site of the sting, in addition to local findings
• Grade 3 - Either cranial nerve/autonomic dysfunction or somatic skeletal neuromuscular dysfunction
  • Cranial nerve dysfunction - Blurred vision, roving eye movements, hypersalivation, tongue fasciculations, dysphagia, dysphonia, problems with upper airway
  • Somatic skeletal neuromuscular dysfunction - Restlessness, severe involuntary shaking or jerking of the extremities that may be mistaken for a seizure
• Grade 4 - Combined cranial nerve/autonomic dysfunction and somatic nerve dysfunction

Differential Diagnosis

Envenomations, bites and stings

• Hymenoptera stings (bees, wasps, ants)
• Mammalian bites
  • Closed fist infection (Fight bite)
  • Dog bite
• Marine toxins and envenomations
  • Toxins (ciguatera, neurotoxic shellfish poisoning, paralytic shellfish poisoning, scombroid, tetrodotoxin
  • Stingers (stingray injury)
  • Venomous fish (catfish, zebrafish, scorpion fish, stonefish, cone shells, lionfish, sea urchins)
  • Nematocysts (coral reef, fire coral, box jellyfish, sea wasp, portuguese man-of-war, sea anemones)
  • Phylum porifera (sponges)
  • Bites (alligator/crocodile, octopus, shark)
• Scorpion envenomation
• Reptile envenomation
  • Snake bites
    • Crotaline (Pit Vipers)
    • Elapidae (Coral Snakes)
  • Lizard bites
• Spider bites
  • Black widow
  • Brown recluse
  • Tarantula
  • Funnel-web spider bite
  • Armed spider bite

Diagnosis

• Usually clinical

Treatment

1. Apply ice to area of sting
2. Atropine
   • May be given for hypersalivation and respiratory distress caused
     • Contraindicated for foreign scorpion stings because may exacerbate adrenergic effects
3. Anascorp Antivenom - Only available in Arizona, Nevada, and Utah
   • Resolves clinical syndrome within 4hr
   • Common side effects: vomiting, pyrexia, rash, nausea, and pruritus
   • Serious side effects: anaphylaxis
   • Costs approx $8000 over vial, needing 3-4 vials for treatment

See Also

• Bites and Stings