Your GP may be able to diagnose Guillain-Barré syndrome by examining you and checking your symptoms. They will usually test your knee-jerk reflex to see if this is lost. The knee-jerk reflex is where your lower leg ‘kicks out’ in response to your GP tapping your leg just below your knee cap.
Guillain-Barré syndrome can sometimes be difficult to diagnose because the symptoms vary from person to person. The symptoms can also be very similar to those of other brain and nervous system disorders. Therefore, two tests are used to confirm the diagnosis of Guillain-Barré syndrome. They are:
- electromyography
- lumbar puncture
You may also have a blood test to rule out any other possible causes.
Electromyography (EMG)
Electromyography is a test that measures the health of the muscles and the nerves that control them.
Testing the muscles
To test the muscles, a needle electrode is inserted through the skin and into the muscle to give an electrical recording of your muscle activity. This helps to determine whether your muscles respond when certain nerves are stimulated. In Guillain-Barré syndrome, the muscles may not respond due to nerve damage.
Testing the nerves
To test the nerves, a surface electrode (small metal disc) is stuck to your skin to stimulate the nerves with a small electric shock. The response from them is measured. It measures how quickly your nerves conduct electric signals. If you have Guillain-Barré syndrome, nerve conduction will be slower than normal.
Lumbar puncture (spinal tap)
A lumbar puncture involves inserting a needle into the spinal canal (usually in the lower back), under local anaesthetic (painkilling medication). This is done to:
- determine the pressure of the spinal fluid inside
- take a sample of the spinal fluid and test it for evidence of bleeding in the brain and spinal cord
- check the protein levels in the spinal fluid (this is often raised in Guillain-Barré syndrome) and look for any bacteria or fungi
See the Health A-Z topic about Lumbar punctures for more information about this procedure.
Blood tests
Possible blood tests include:
- testing for antibodies – antibodies are infection fighting proteins that are produced by the immune system; in Guillain-Barré syndrome specific antibodies may be present that are known to react to your peripheral nerves
- erythrocyte sedimentation rate (ESR) – this measures how long it takes the red blood cells in a sample of blood to sink to the bottom of a test tube; the time it takes indicates how much inflammation (swelling) there is in your body
