Neurologic symptoms are characteristically bilateral and symmetric, beginning with the cranial nerves and followed by descending weakness or paralysis. Common initial symptoms and signs include dry mouth, diplopia, ptosis, loss of accommodation, and diminished or total loss of pupillary light reflex. Dysphagia can lead to aspiration pneumonia. Muscles of the extremities and trunk and of respiration progressively weaken in a descending pattern. There are no sensory disturbances, and the sensorium usually remains clear.
Fever is absent, and the pulse remains normal or slow unless intercurrent infection develops.
Routine studies of the blood, urine, and CSF are usually normal. Constipation is common after neurologic impairment appears. Major complications include respiratory failure caused by diaphragmatic paralysis and pulmonary infections. Wound botulism is manifested by neurologic symptoms, as in foodborne botulism, but there are no GI symptoms or evidence implicating food as a cause. A history of a traumatic injury or a deep puncture wound in the preceding 2 wk may suggest the diagnosis.