Which of the following is not a feature of botulism: diarrhea, extensor plantar (extensor plantar response), post-tetanic potentiation, or circumoral paresthesias?

Diarrhea is NOT a Feature of Botulism

Diarrhea is NOT a typical feature of botulism, occurring in only 16% of cases, while constipation is actually more common. 1, 2

Clinical Features of Botulism

Botulism is characterized by a classic triad:

1. Symmetric descending flaccid paralysis with prominent bulbar palsies (93% of cases)
2. Afebrile presentation (99% of cases)
3. Clear sensorium (mental status typically preserved)

Common Neurological Manifestations

• Descending paralysis (93%)
• Dysphagia (85%)
• Weakness or fatigue (85%)
• Ptosis (81%)
• Blurred vision (80%)
• Difficulty speaking/dysarthria (78%)
• Diplopia (75%)
• Change in voice (69%)
• Shortness of breath (65%)
• Extraocular muscle palsy (60%)

Gastrointestinal Features

• Dry mouth (63%)
• Constipation (30%) - more common than diarrhea
• Nausea (43%)
• Vomiting (33%)
• Diarrhea (16%) - notably rare in botulism

Sensory Symptoms

• Sensory deficits and paresthesias occur in only 17% of cases 1, 2
• Circumoral paresthesias can occur as part of these sensory deficits

Analysis of Answer Options

Let's analyze each option:

1. Diarrhea - This is NOT a typical feature of botulism. According to CDC guidelines, diarrhea occurs in only 16% of cases, while constipation is actually more common (30%) 1, 2. This is the correct answer.

2. Extensor plantar - Not mentioned in the guidelines as a feature of botulism. Botulism causes flaccid paralysis with decreased reflexes, not upper motor neuron signs like extensor plantar responses.

3. Post-tetanic potentiation - This is a feature of botulism. Electrophysiologic testing in botulism typically shows post-tetanic facilitation in affected muscles 3.

4. Circumoral paresthesias - While sensory deficits and paresthesias are less common (17%), they can occur in botulism and would be consistent with the cranial nerve involvement pattern seen in the disease 2.

Pathophysiology Explanation

Botulinum toxin inhibits acetylcholine release at the neuromuscular junction by cleaving the synaptic Vesicle Associated Membrane Protein (VAMP). This mechanism explains the predominantly motor symptoms and the characteristic descending paralysis 2.

The rarity of diarrhea in botulism is notable because gastrointestinal symptoms in foodborne botulism are typically caused by other clostridial products or non-clostridial substances related to food spoilage, rather than the botulinum neurotoxin itself 2.

In fact, constipation is much more commonly reported than diarrhea in botulism cases, particularly in children, and is often an early symptom of the disease 2.