Guillain-Barré syndrome (GBS) may be difficult to diagnose in the early stages of the disease. A detailed examination of your nervous system is needed to diagnose the condition. Your health professional will ask questions about your symptoms, including when they started and how they have changed over time. A history of recent infection (especially respiratory or gastrointestinal illness) may also be an important clue in the diagnosis.

The two signs that must be present to diagnose GBS are:

• Progressive weakness in both arms and both legs.
• Loss of reflexes.

When these two signs are present, a diagnosis of GBS may be more likely if:

• The symptoms developed over a period of days to several weeks.
• The symptoms affect both sides of your body equally.
• Mild sensory symptoms are present, such as numbness and tingling.
• The muscles on each side of your face are affected.
• You begin to recover 2 to 4 weeks after symptoms have stabilized.
• You did not have a fever when symptoms first started.

Some testing may be necessary to rule out other conditions, such as electrolyte imbalances and certain types of poisoning, that could also be causing the symptoms and to help confirm the diagnosis of GBS. These tests include:

• A lumbar puncture, which is an analysis of the fluid around the spine. If you have GBS, this test may show increased amounts of protein in your spinal fluid without other signs of infection.
• Nerve conduction studies, which use electrical impulses to indicate how well the nerves are working. If you have GBS, the results may show a slowing of nerve function, which usually suggests that damage to the covering (myelin sheath) of the peripheral nerves has occurred.

In the very early stages of GBS, the results of these tests may be normal. Abnormal results may not show up for a week or more after symptoms begin.

If the diagnosis is unclear, you may be referred to a doctor who specializes in brain and nervous system disorders (neurologist).