Patient history is important in diagnosis. The progression of ascending paralysis – starting with feet or hands and advancing upward – is a typical presentation. About 50% of cases also include a history of a recent mild infection or illness like a sore throat, a cold, the flu, or diarrhea. Several tests are commonly used to diagnose or confirm the disease and, sometimes, to monitor recovery.
- Cerebrospinal fluid (CSF) analysis – to identify the presence of increased protein; for this test, a needle is inserted into the spine between vertebrae and a small amount of fluid is withdrawn. While some protein is normally present, an increased amount without an increase in the white blood cells in the CSF may be indicative of Guillain Barré syndrome.
- Nerve conduction velocity – tests the speed at which impulses travel through a nerve; the nerve conduction velocity test uses electrodes placed on the skin over peripheral nerves and measures the amount of time it takes for an impulse to travel between electrodes.
- Electromyography (EMG) – measures the electrical activity of muscles fibers; the EMG test measures the electrical activity within muscle fibers by placing a needle electrode through the skin directly into the muscle and measuring the electrical activity of that muscle. It is usually done in conjunction with a nerve conduction velocity test.
There are several variants of GBS that are associated with specific signs and symptoms and with the production of different types of antibodies directed against gangliosides. Rarely, ganglioside autoantibody tests may be ordered.
Other testing may be performed to help distinguish GBS from other causes of weakness, neuropathy, and immune dysfunction and to monitor the person's health status during illness and recovery.