Table 2

Differential diagnosis of myasthenic crisis

DiagnosisPrinciple signsInvestigations
Guillain–Barré syndromeInitial proximal weakness, some distal sensory symptoms, absent reflexesLumbar puncture, nerve conduction studies
Myopathies (eg, acid maltase)Proximal weakness, no sensory changesRaised serum creatine kinase, electromyography, muscle biopsy
Cervical myelopathy (structural or inflammatory)Usually subacute onset, sensory level, urinary retentionMR scan, lumbar puncture
Motor neuron diseaseUsually with clear preceding history, muscle fasciculation and wasting, brisk reflexesElectromyography
Brainstem stroke/inflammationCranial nerve signs, altered consciousness, brisk reflexes, sensory signsMR scan, lumbar puncture
BotulismHistory of intravenous drug abuse, weakness spreading caudally, autonomic disturbances (sluggish pupillary responses, dry eyes)Electromyography
Lambert–Eaton myasthenic syndromeRare; subacute proximal leg weakness, autonomic symptomsElectromyography, voltage gated calcium channel antibodies
Organophosphate poisoningHistory of pesticide use, chemical warfare, symptoms similar to cholinergic crisisRed cell acetylcholinesterase levels
Cholinergic crisisSalivation, lacrimation, diarrhoea, urinary incontinence, bradycardia, miosis, bronchospasm (in addition to muscle weakness and respiratory failure)Drug history and clinical signs