Differences and similarities between botulism and Guillain-Barré syndrome (GBS)
| Botulism | GBS | |
| Preceding illness | No. | Frequent. |
| Symmetry | Yes. | Yes. |
| Preserved consciousness | Yes. | Yes (except with Bickerstaff encephalitis). |
| Sensory involvement | No. | Yes, in most cases. |
| Pattern of symptomatology | Craniobulbar onset and descending paralysis. |
Classic GBS: ascending paralysis, sensory disturbance and areflexia. Miller Fisher syndrome: ataxia, areflexia and ophthalmoplegia. Pharyngeal-cervical-brachial variant: descending paralysis. Bickerstaff brainstem encephalitis: ataxia, ophthalmoplegia and altered consciousness. |
| Cranial nerve palsies and pupillary involvement | Almost ubiquitous. | Uncommon. |
| Dysautonomia | Common. | Common. |
| Respiratory involvement | With severe presentations. | With severe presentations. |
| Cerebrospinal fluid protein | Usually normal. | Elevated (but may be normal in early presentations). |
| Imaging | Normal. | MR scan of the spine with contrast can show nerve root enhancement. |
| Nerve conduction studies | Reduced motor action potentials and/or potentiation with rapid repetitive stimulation (60% of cases). | Reduced action potentials and/or conduction velocities and/or absent F waves (but studies may be normal in early disease). |