- Most scorpion stings in North America result only in local pain.
- Arizona Bark Scorpion (Centruroides sculpturatus), found in AZ, NV, NM, TX, and CA, is the only neurotoxic species found in North America and can cause systemic toxicity.
- Four neurotoxins (toxins I to IV) have been isolated from C. exilicauda
- Toxins target excitable membranes, especially at the neuromuscular junction, by opening sodium channels → repetitive depolarization of nerves in both sympathetic and parasympathetic nervous systems → catecholamine and acetylcholine release.
- Pain and paresthesias near envenomation site.
- "Tap" test: severe local tenderness when affected area is lightly tapped
- Uncommon but can be severe, particularly in children
- Cranial nerve and somatic motor dysfunction can develop:
- Abnormal roving eye movements, blurred vision, pharyngeal muscle incoordination
- Hypersalivation, noncardiac pulmonary edema (can → respiratory distress/failure)
- Tongue fasciculations and uncoordinated motor agitation (flailing or jerking extremities)
- Tachycardia, other dysautonomias, 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 skeletal neuromuscular dysfunction
- Hymenoptera stings (bees, wasps, ants)
- Mammalian bites
- Closed fist infection (Fight bite)
- Marine toxins and envenomations
- Scorpion envenomation
- Snake bites
- Spider bites
- Generally clinical diagnosis
- Be aware that a discrete scorpion bite mark may not be clinically apparent.
- Supportive care
- Cold compress to area of sting
- Analgesic and anti-inflammatory medications
- Benzodiazepines may help with agitation and muscle spasm
- May be given for hypersalivation and respiratory distress caused
- Contraindicated for scorpion stings not indigenous to US (may exacerbate adrenergic effects)
- Anascorp antivenom (Centruroides immune Fab) - Only stocked by certain hospitals in Arizona, Nevada, and Utah
- Grade I or II envenomation may generally be discharged after 6 hours of observation in the ED without progression of symptoms.
- Grade III or IV envenomation likely requires antivenom administration and/or admission.
- Boyer LV, Theodorou AA, Berg RA, Arizona Envenomation investigators, et al. Antivenom for critically ill children with neurotoxicity from scorpion stings. N Engl J Med. 2009 May 14;360(20):2090-8.
- Nelson, Lewis, and Lewis R. Goldfrank. Goldfrank's Toxicologic Emergencies. New York: McGraw-Hill Medical Division, 2014. Print.
- http://www.anascorp-us.com/hospital/ Accessed 08/03/15