Dr. Jordan Kramer, the VEP Chief Medical Officer, saw an interesting patient in the ED recently and prepared the following case summary.

A 21-year-old college student with no past medical history came to the ED recently with a chief complaint of blurred vision for two days and weakness for one day.  The patient complained of difficulty supporting her weight.

Before reading further, spend a few moments thinking about the differential diagnosis. 

The patient present to the ED with stable vital signs.  She was able to maintain her airway.  Her exam was notable for 6mm, non-reactive pupils, bilateral ophthalmoplegia, and ptosis greater on the right.  She had bilateral facial muscle weakness.  She had mild weakness with shrugging her shoulders.  She could move her extremities, but she could not stand and support her weight.  The remainder of her exam was unremarkable.

Basic laboratory studies were unremarkable.  Her urine toxicology screen was negative.

Before reading further, think about your differential diagnosis again and consider what further testing may be useful.

We initially considered conditions such as Myasthenia Gravis or Guillain-Barre.  However, the eye symptoms are not typical of these conditions.  We consulted our neurologist who evaluated the patient.  LP and MRI of the brain were normal. Nerve conduction studies were compatible with a diagnosis of botulism.  The patient was further questioned and recalled eating ham 5 days earlier that had been bought two weeks earlier and stored.  The patient recalled the ham not tasting right.

Botulism is a neuroparalytic syndrome resulting from the action of a neurotoxin elaborated by the bacterium Clostridium botulinum.  There are several different forms of the disease:

Foodborne Botulism
Infant Botulism
Wound Botulism
Adult Enteric Infectious Botulism
Inhalational Botulism
Iatrogenic Botulism

Foodborne Botulism involves ingestion of food contaminated by preformed toxin.  Infant Botulism involves the ingestion of clostridial spores that colonize the GI tract and release toxin produced in vivo.  Ingestion of honey or soil containing spores is the most common source. The spores are heat resistant.

The toxin disperses via the vascular system.  It binds to a receptor on the presynaptic side of peripheral cholinergic synapses at ganglia and neuromuscular junctions.  It causes an irreversible disruption in acetylcholine release by the presynaptic nerve terminal.  See image below:

Return of synaptic function requires development of a new presynaptic terminal, a process that can take six months.  The toxin does not affect adrenergic synapses.  The toxin does not permeate the blood brain barrier.  LP results are typically negative.

The clinical manifestations of botulism are bilateral cranial neuropathies with symmetric descending weakness.  Cranial nerve involvement usually occurs first.  This can include blurred vision, diplopia, nystagmus, ptosis, dysphagia, dysarthria and facial weakness.  Descending muscle weakness progresses to the trunk and upper extremities followed by the lower extremities.

Urinary retention and constipation are due to smooth muscle paralysis.  Respiratory difficulties requiring intubation and mechanical ventilation are common because of diaphragmatic paralysis, upper airway compromise or both.  The clinical presentation and severity of the illness are variable.

Differential diagnosis is broad.  This includes myasthenia gravis, Lambert-Eaton myasthenic syndrome, tick paralysis, Guillain-Barre, poliomyelitis, stroke, heavy metal intoxication, tetrodotoxin, shellfish poisoning, and antimicrobial-associated paralysis.

Diagnosis may be difficult to make in the ED.  Early consultation with an appropriate specialist or the Poison Control Center can be a helpful.  The State Health Department can assist with the decision to give botulism antitoxin and to obtain a supply.

Demonstration of toxin in the blood is diagnostic.  Toxin has been detected from the serum up to 12 days post ingestion.  However, this test is only conducted at specialized laboratories.  Analysis of stool, vomitus, and suspected food items may reveal toxin.

Patients with suspicion for botulism should be hospitalized and monitored for respiratory failure which is the primary cause of death in these patients.  There are two botulism antitoxin therapies in the US.  Equine serum heptavalent botulism antitoxin is use to treat children older than one year of age and adults.  Human-derived botulism immune globulin is used for infants less than one year of age.  Antibiotics are not recommended for infant or foodborne because lysis of intraluminal C. Botulinum can increase the amount of toxin available for absorption.

Patients with botulism can require hospitalization for up to three months depending on their clinical presentation.  Our patient fortunately did not develop respiratory failure or require intubation.  She was treated with antitoxin.  The patient continues to be symptomatic with blurred vision and weakness.  She has been transferred to an inpatient rehabilitation facility with aggressive physical and occupational therapy.

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