Parkinson Disease, Guillain-Barré Syndrome, and ALS

These three disorders can all cause weakness, impaired mobility, and swallowing difficulty, but the time course and neuroanatomical pattern point in different directions. Parkinson disease is a chronic central nervous system disorder dominated by bradykinesia—slowness with decrement in movement—plus rigidity, resting tremor, and later postural instability. The tremor is typically most evident when the limb is at rest and may lessen during purposeful movement. The patient may have a reduced arm swing, small shuffling steps, difficulty initiating gait, freezing at doorways, a soft voice, and reduced facial expression. Constipation, anosmia, depression, sleep disturbance, orthostatic hypotension, and cognitive change may precede or accompany the motor findings. Guillain-Barré syndrome (GBS) is an acute immune-mediated peripheral nerve and nerve-root disorder. Weakness often begins in the legs and progresses upward over hours to days. Reflexes are reduced or absent. Facial weakness, dysphagia, neuropathic pain, and autonomic instability can appear as the illness advances. The immediate threat is not the weakness in the legs; it is failure of the respiratory muscles or loss of airway protection. Amyotrophic lateral sclerosis (ALS) causes progressive degeneration of upper...