Chapter 134. Botulism (Part 3)

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Diagnosis A diagnosis of botulism must be considered in patients with symmetric descending paralysis who are afebrile and mentally intact. The bulbar musculature is involved initially, but sensory findings are absent and, early on, deep tendon reflexes remain intact. The differential diagnosis of botulism and distinguishing features are listed in Table 134-2. Depending on season and other epidemiologic factors, West Nile virus infection may also be a consideration. Table 134-2 Selected Mimics that May Lead to Misdiagnosis of Botulism Condition Features Distinguishing Condition from Botulism Common Misdiagnoses Guillain-Barré syndromea and its History of antecedent infection ...

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Chapter 134. Botulism (Part 3) Diagnosis A diagnosis of botulism must be considered in patients with symmetric descending paralysis who are afebrile and mentally intact. The bulbar musculature is involved initially, but sensory findings are absent and, early on, deep tendon
reflexes remain intact. The differential diagnosis of botulism and distinguishing features are listed in Table 134-2. Depending on season and other epidemiologic factors, West Nile virus infection may also be a consideration. Table 134-2 Selected Mimics that May Lead to Misdiagnosis of Botulism Condition Features Distinguishing Condition from Botulism Common Misdiagnoses Guillain-Barré syndromea and its History of antecedent infection; variants, especially Miller-Fisher variant paresthesias; often ascending paralysis; early areflexia; eventual CSF protein increase; EMG findings Myasthenia gravisa Recurrent paralysis; EMG findings; sustained response to anticholinesterase
Strokea Paralysis often asymmetric; abnormal CNS image Intoxication with depressants History of exposure; excessive (e.g., acute alcohol intoxication), drug levels detected in body fluids organophosphates, carbon monoxide, or nerve gas Lambert-Eaton syndrome Increased strength with sustained contraction; evidence of lung carcinoma; EMG findings similar to botulism Tick paralysis Paresthesias; ascending paralysis; tick attached to skin Other Misdiagnoses Poliomyelitis Antecedent febrile illness; asymmetric paralysis; CSF pleocytosis
CNS infections, especially of the Mental status changes; CSF and brainstem EEG abnormalities CNS tumor Paralysis often asymmetric; abnormal CNS image Streptococcal pharyngitisb Absence of bulbar palsies; positive rapid antigen test result or throat culture Psychiatric illnessa Normal EMG in conversion paralysis Viral syndromea Absence of bulbar palsies and flaccid paralysis Inflammatory myopathya Elevated creatine kinase level
Diabetic complicationsa Sensory neuropathy; few cranial nerve palsies Hyperemesis gravidaruma Absence of bulbar palsies and acute flaccid paralysis Hypothyroidisma Abnormal thyroid function tests Laryngeal traumaa Absence of flaccid paralysis; dysphonia without flaccid paralysis Overexertiona Absence of bulbar palsies and acute flaccid paralysis a Misdiagnoses made in a large outbreak of botulism (St. Louis ME et al: Botulism from chopped garlic: Delayed recognition of a major outbreak. Ann Intern Med 108:363, 1988).
b Pharyngeal erythema can occur in botulism. Note: CNS, central nervous system; CSF, cerebrospinal fluid; EEG, electroencephalogram; EMG, electromyogram. Source: Reproduced with permission of the publisher from Arnon et al, 2002. The demonstration of toxin in serum by bioassay in mice is definitive, but this test may give negative results, particularly in wound and infant botulism. It is performed only by specific laboratories, which can be identified through regional public health authorities. Other assays are being developed and remain experimental. The demonstration of C. botulinum or its toxin in vomitus, gastric fluid, or stool is strongly suggestive of the diagnosis because intestinal carriage is rare. Isolation of the organism from food without toxin is insufficient grounds for the diagnosis. Wound cultures yielding the organism are suggestive of botulism. The edrophonium chloride (Tensilon) test for myasthenia gravis may be falsely positive in botulism but is usually less dramatically positive than in the former condition. Nerve conduction velocity is normal, but compound muscle action potentials on routine nerve stimulation studies are decreased with a supramaximal stimulus, and facilitation is evident after repetitive stimulation at high frequency. Single-fiber electromyography may be helpful. The white blood cell count and erythrocyte sedimentation rate are normal.