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Botulism: Diagnosis & Laboratory Guidance for Clinicians

  • Clinical diagnosis of botulism is confirmed by specialized laboratory testing that often requires days to complete. Routine laboratory test results are usually unremarkable. Therefore, clinical diagnosis is the foundation for early recognition of and response to a bioterrorist attack with botulinum toxin, and all treatment and management decisions should be made based on clinical diagnosis.
  • Botulism is frequently misdiagnosed, most often as a polyradiculoneuropathy (Guillain-Barre or Miller-Fisher syndrome), myasthenia gravis, or other diseases of the central nervous system.
  • In the United States, botulism is more likely than Guillain-Barre syndrome, chemical poisoning, or poliomyelitis to cause a cluster of cases of acute flaccid paralysis.
  • Botulism differs from other flaccid paralyses in that it always manifests initially with prominent cranial paralysis and its invariable descending progression, in its symmetry, and in its absence of sensory nerve damage.

Differential Diagnosis

Differential Diagnosis for Adults

  • Guillain-Barre syndrome
  • Myasthenia gravis
  • Cerebrovascular accident (CVA)
  • Bacterial and/or chemical food poisoning
  • Tick paralysis
  • Chemical intoxication (e.g., carbon monoxide)
  • Mushroom poisoning
  • Poliomyelitis
  • Psychiatric illness

Differential Diagnosis for Infants

  • Sepsis
  • Meningitis
  • Electrolyte-mineral imbalance
  • Reye’s syndrome
  • Congential myopathy
  • Werdnig-Hoffman disease
  • Leigh disease

Laboratory Studies

  • Initial diagnosis is based on clinical symptoms. Treatment should not wait for laboratory confirmation.
  • Routine lab tests (CBC, electrolytes, LFTs, urinalysis) are generally not helpful in diagnosis as these tests show no characteristic abnormalities.
  • CSF studies are essentially normal although occasionally a borderline elevation in protein level is seen.
  • A normal Tensilon test helps to differentiate botulism from myasthenia gravis; borderline positive tests can occur in botulism.
  • Normal CTs and MRIs help to rule out CVA.
  • Laboratory confirmation is done by demonstrating the presence of toxin in serum, stool, or food, or by culturing C. botulinum from stool, a wound or food.
  • Laboratory testing may take hours or days. Initial diagnosis and appropriate treatment depend on clinical diagnosis through a thorough history and physical examination.

For more information:

  • Page last reviewed October 06, 2006
  • Page last updated June 14, 2006
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