Incidence

• Over 1 Million Scorpion Stings Occur Worldwide Annually
  • Most Cases are Minor with Only Localized Pain and Minimal Systemic Involvement
  • Only 10% of Scorpion Stings Result in Severe Systemic Envenomation

Age

• Most Severe Envenomation Cases Occur in Children

Taxonomy

• Buthidae Family: scorpions from this family account for most clinically serious scorpion stings
  • Genus Centruroides: North America/Central America
  • Genus Tityus: South America
  • Genus Leiurus: near East/Middle East
  • Genus Androctonus or Buthus: North Africa
  • Genus Mesobuthus: Asia (especially India)
  • Genus Parabuthus: South Africa
• Liochlidae Family
  • Hemiscorpius Lepturus: endemic in areas of Iran

Stinger Apparatus

• Scorpions Have a Venom Gland-Containing Stinger (Telson) in Their Tail (Terminal Segment)

Scorpion Venom

• General Comments: contains small peptide toxins which target ion channels in mammals and insects
• α-Toxins: bind to mammalian voltage-gated sodium channel -> inhibits inactivation of the channel, resulting in prolonged depolarization and neuronal excitaton
  • Sympathetic Excitation: contributes to complications such as myocardial infarction, pulmonary edema, and cardiogenic shock
  • Parasympathetic Excitation: usually occur soon after the sting, are generally less severe, but may contribute to respiratory impairment
  • Induction of Massive Endogenous Catecholamine Release (Epinephrine, Norepinephrine): contributes to complications such as myocardial infarction, pulmonary edema, and cardiogenic shock
    • Catecholamine-Induced Myocarditis and Myocardial Ischemia: may complicate severe androctonus/buthus/mesobuthus/tityus envenomations
    • Myocardial Ischemia (Due to Coronary Vasoconstriction)
  • Induction of Release of Vasoactive Peptide Hormones (Neuropeptide Y, Endothelin)
  • Possible Direct Effect of the Toxin on the Myocardium: which contributes to cardiac dysfunction
• Other Toxins: act on potassium and calcium channels
  • These toxins appear to be less importan tin human envenomations

Physiologic Effects

Time Course of Cardiovascular Effects

• Initial Increase in Cardiac Output and Blood Pressure, Followed by Decreased Left Ventricular Function and Hypotension

Parasympathetic/Cholinergic Effects (see Cholinergic Intoxication)

• General Comments: tend to occur early
• Bronchorrhea (see Bronchorrhea)
• Bronchospasm (see Obstructive Lung Disease)
• Diaphoresis (see Diaphoresis)
• Diarrhea (see Diarrhea)
• Hypotension (see Hypotension)
• Lacrimation (see Lacrimation)
• Miosis (see Miosis)
• Priapism (see Priapism)
• Sialorrhea (Hypersalivation) (see Sialorrhea)
• Sinus Bradycardia (see Sinus Bradycardia)
• Vomiting (see Nausea and Vomiting)

Sympathetic Effects

• General Comments: tend to persist because of the release of catecholamines
• Agitation
• Hyperglycemia (see Hyperglycemia)
• Hypertension (see Hypertension)
• Hyperthermia (see Fever)
• Mydriasis (see Mydriasis)
• Restlessness
• Tachycardia (see Sinus Tachycardia)

Neuromuscular Excitation (Characteristic of Centruroides Envenomations)

• General Comments: due to direct effects of toxin on neuronal sodium channels in somatic and cranial nervous system
  • Central nervous system effects are uncommon, as the toxins cannot cross the blood-brain barrier
• Muscle Spasms
• Oculomotor Abnormalities
• Paralysis
• Uncoordinated Neuromuscular Activity
• Visual Disturbances

General Comments

• Epidemiology: adults are more commonly envenomated, but children are more likely to develop severe illness
• Centruroides Suffusus Envenomation is Clinically Similar
• Onset of Symptoms
  • Symptoms begin immediately and progress to maximum severity within 5 hrs
  • Infants can reach peak severity of symptoms within 15-30 min
• Duration of Symptoms: variable (based on age of victim and grade of envenomation)
  • Grade III/IV Envenomations: symptoms usually abate within 9-30 hrs without antivenom therapy (although pain/parasthesias may persist for up to 2 wks)
• Presence of Intact Mental Status: this finding may be useful to rule out other intoxications where delirium is common (such as methamphetamine intoxication, phencyclidine intoxication, etc)

Grade I Envenomation

• Local Pain/Parasthesias at Sting Site with No Local Inflammation (see Parasthesias)
  • Puncture Site is Usually Too Small to Be Seen
  • Angioedema (see Angioedema): may occur in some cases
  • Tap Test: gently tap the site (with patient looking away) -> this greatly exacerbates the pain (this is unique to envenomation by this scorpion species)

Grade II Envenomation

• Local Pain/Parasthesias at Sting Site see Parasthesias)
  • Angioedema (see Angioedema): may occur in some cases
• Remote Pain/Parasthesias (see Parasthesias)
  • May radiate proximally up the affected limb
  • May occur at more remote body sites or as generalized parasthesias
• Unexplained Agitation/Crying: may occur in children
• Hypertension (see Hypertension): common and occurs early in course

Grade III Envenomation

Either of the Following Neurologic Manifestations

• Cranial Nerve Dysfunction
  • Abnormal Eye Movements: involuntary, conjugate, slow, roving
    • Chaotic, multi-directional conjugate saccades (resembling opsoclonus and unsustained primary positional nystagmus) may be seen in some cases
    • Patient may prefer to keep their eyes closed
  • Dysarthria (see Dysarthria)
  • Sialorrhea (Hypersalivation) (see Sialorrhea): due to cholinergic stimulation
  • Tongue Fasciculations (see Fasciculations)
  • Blurred Vision (see Blurred Vision)
• Somatic Skeletal Neuromuscular Dysfunction
  • Agitation/Akathisia (Motor Restlessness) (see Akathisia)
  • Emprosthotonos (see Emprosthotonos): tetanic forward flexion of the body (may be mistaken for seizures, although these movements are more undulating/writhing than seizure activity and patient remains alert)
  • Fasciculations (see Fasciculations)
  • Myoclonus/Jerking of Extremities (see Myoclonus)
  • Opisthotonos (see Opisthotonos): arching of the back (may be mistaken for seizures, although these movements are more undulating/writhing than seizure activity and patient remains alert)
  • Shaking of Extremities: may be mistaken for seizures, although these movements are more undulating/writhing than seizure activity and patient remains alert
• Hypertension (see Hypertension): common and occurs early in course

Grade IV Envenomation

Both of the Following Neurologic Manifestations

• Cranial Nerve Dysfunction
  • Abnormal Eye Movements: involuntary, conjugate, slow, roving
    • Chaotic, multi-directional conjugate saccades (resembling opsoclonus and unsustained primary positional nystagmus) may be seen in some cases
    • Patient may prefer to keep their eyes closed
  • Dysarthria (see Dysarthria)
  • Hypersalivation (see Hypersalivation): due to cholinergic stimulation
  • Tongue Fasciculations (see Fasciculations)
  • Blurred Vision (see Blurred Vision)
• Somatic Skeletal Neuromuscular Dysfunction
  • Agitation/Akathisia (Motor Restlessness) (see Akathisia)
  • Emprosthotonos (see Emprosthotonos): tetanic forward flexion of the body (may be mistaken for seizures, although these movements are more undulating/writhing than seizure activity and patient remains alert)
  • Fasciculations (see Fasciculations)
  • Myoclonus/Jerking of Extremities (see Myoclonus)
  • Opisthotonos (see Opisthotonos): arching of the back (may be mistaken for seizures, although these movements are more undulating/writhing than seizure activity and patient remains alert)
  • Shaking of Extremities: may be mistaken for seizures, although these movements are more undulating/writhing than seizure activity and patient remains alert

Cardiovascular Manifestations

• Conduction Abnormalities: occur in 33-50% of severe envenomation cases (likely related to autonomic effects of toxins, with vagal effects or sympathetic stimulation)
  • Atrial Tachycardia
  • Bundle Branch Blocks: less common
  • ST Changes
  • T-Wave Inversion
  • Ventricular Extra Systoles
• Hypotension (see Hypotension)

Gastrointestinal Manifestations

• Abdominal Pain (see Abdominal Pain): common (due to cholinergic stimulation)
• Acute Pancreatitis (see Acute Pancreatitis): rarely occurs with Centruroides envenomation (in contrast to Tityus and Leiurus Quinquestriatus scorpion envenomations) and is typically transient
• Diarrhea (see Diarrhea): common (due to cholinergic stimulation)
• Nausea/Vomiting (see Nausea and Vomiting): common (due to cholinergic stimulation)

Pulmonary Manifestations

• Acute Respiratory Distress Syndrome (ARDS) (see Acute Respiratory Distress Syndrome)
• Acute Respiratory Failure (see Respiratory Failure)
  • Mechanisms
    • Bronchorrhea/Increased Bronchial Secretions
    • Bronchospasm
    • Uncoordinated Respiratory Muscle Activity
• Bronchorrhea (see Bronchorrhea): due to cholinergic stimulation
• Stridor (see Stridor)
• Wheezing (see Obstructive Lung Disease)

Other Manifestations

• Cerebrospinal Fluid Pleocytosis (see Lumbar Puncture)
• Coagulopathy/Disseminated Intravascular Coagulation (DIC) (see Disseminated Intravascular Coagulation): may occur in some cases
• Fever/Hyperthermia (see Fever): due to excessive muscle activity
• Metabolic Acidosis (see Metabolic Acidosis-Elevated Anion Gap)
• Rhabdomyolysis (see Rhabdomyolysis)

General Comments

• Generally Less Severe Than Centruroides Exilicauda (Sculpuratus) and Centruroides Suffusus Envenomations

Neurologic Manifestations

• Local Pain/Parasthesias at Sting Site (see Parasthesias)
• Systemic Neurologic Manifestations: occur in 20% of cases
  • Chills
  • Diaphoresis (see Diaphoresis)
  • Dysgeusia (Altered Taste) (see Dysgeusia)
  • Dysphagia (see Dysphagia)
  • Facial Parasthesias (see Parasthesias): face, tongue, peri-oral region
  • Fasciculations (see Fasciculations)
  • Nausea/Vomiting (see Nausea and Vomiting)

Other Manifestations

• Local Bleeding at Sting Site
• Local Erythema/Edema/Pruritus/Urticaria at Sting Site

General Comments

• Produces a Cytotoxic Syndrome: similar to that from Loxosceles (recluse) spider bite

Dermatologic Manifestations

• Absence of Immediate Severe Pain at Sting Site
• Erythema/Purpuric/Bullous Lesions at Sting Site: generally resolve
  • However, in 20% of cases, delayed necrosis occurs over a period of hours-days

Gastrointestinal Manifestations

• Nausea/Vomiting (see Nausea and Vomiting)

Hematologic Manifestations

• Hemolytic Anemia (see Hemolytic Anemia)

Renal Manifestations

• Acute Kidney Injury (AKI) (see Acute Kidney Injury)

Other Manifestations

• Fever/Hyperthermia (see Fever)
• Minor Autonomic Effects