Use symptom tempo and exposure history to decide whether the evaluation should focus on toxic-metabolic disease, structural CNS mimics, or acute immune neuropathy. Rapid progression should push the workup toward urgent hospitalization.

Urine porphyrins are essential when porphyria is suspected; Heavy metal screening matters when exposure is plausible; MRI helps exclude central mimics like myelopathy or multiple sclerosis; Guillain-Barre syndrome is an acute or subacute autoimmune neuropathy; Rapid weakness with areflexia is a major red flag