Parkinson Disease, Guillain-Barré Syndrome, and ALS

Parkinson disease, Guillain-Barré syndrome (GBS), and amyotrophic lateral sclerosis (ALS) can all produce weakness, impaired mobility, dysphagia, and falls, but the pattern and time course separate them. Parkinson disease is a chronic central movement disorder caused by progressive loss of dopaminergic neurons in the substantia nigra pars compacta. GBS is an acute immune-mediated disorder of peripheral nerves and nerve roots. ALS is a progressive degeneration of upper and lower motor neurons. The first clinical question is therefore not simply, “Is this patient weak?” It is, “How quickly did the change occur, which motor pathways are involved, and is breathing or swallowing becoming unsafe?” A patient whose hand tremor and slowness have progressed over years suggests Parkinson disease. Symmetric leg weakness progressing to the arms over days or weeks suggests GBS, particularly when reflexes are reduced. Months of focal weakness with muscle wasting, fasciculations, spasticity, or brisk reflexes raises concern for ALS. A rapid decline in any patient changes the priority to airway and breathing assessment, regardless of the eventual diagnosis.