The disorder progresses rapidly (from days to a few weeks), causing weakness or paralysis in a symmetrical manner. As weakness starts in the legs and then spreads to the arms, it is referred to as ascending paralysis. At the same time, patients may notice tingling, foot or hand pain, and clumsiness. As paralysis worsens, the patient may require assisted ventilation in order to breathe.

The phases of the illness include an initial phase of rapid worsening that may take only a few hours to reach the most severe symptoms. This phase can last up to 3 weeks. This is followed by a plateau phase of no changes, then a recovery phase where symptoms improve over days to 6 months or longer.

Typical symptoms include the following:

• Muscle weakness or paralysis (the most common symptom) or uncoordinated movements
  • Weakness begins in the feet and legs and may progress upward to the arms and cranial (head) nerves
  • May progress rapidly over 24 to 72 hours
  • May begin in the arms and progress downward
  • May occur in the arms and legs at the same time
  • May occur in the cranial nerves only
  • May not occur (mild cases)
• Sensation changes
  • Numbness, decreased sensation
  • Tenderness or muscle pain (may be a cramp-like pain)
  • Usually accompanies or precedes muscle weakness
  • May not occur at all

• Blurred vision
• Difficulty moving face muscles
• Clumsiness and falling
• Palpitations (sensation of feeling heartbeat)
• Muscle contractions

• Difficulty swallowing
• Drooling
• Difficulty breathing
• Breathing, absent temporarily
• Feeling unable to take a deep breath
• Fainting

A history of increasing muscle weakness and paralysis may indicate Guillain-Barre syndrome, especially if there was a recent illness.

Neurological examination shows muscle weakness and may indicate dysfunction of the control of involuntary (autonomic) body functions such as blood pressure and heart rate. Sensory loss may be minimal, even when sensory changes are present.

There may be evidence of decreased breathing ability caused by paralysis of the breathing muscles and a decrease in deep tendon reflexes in the arms and legs.

• An NCV (nerve conduction velocity) shows demyelination.
• An EMG (a test of electrical activity in muscles) shows lack of nervous stimulation.
• A CSF (cerebrospinal fluid) examination may be abnormal, showing increase in protein without increase in white blood cell count.
• An ECG may show abnormalities in some cases.