Guillain-Barré is a rare disorder in which the body's own immune system mistakes parts of the peripheral nerves for an infection and sends out antibodies that attack those nerves. The most common result is a weakness and numbness that starts at the tips of the fingers and toes and spreads inward toward the body.
About 30% of the time, this weakness becomes so severe that the patient cannot breathe on their own. They also cannot swallow food or saliva without it going "down the wrong tube" into their lungs. For these reasons, Guillain-Barré can be life-threatening, and requires close attention by medical professionals, usually in a hospital setting. Here you will find how doctors determine whether a patient has Guillain-Barré syndrome.
Beyond listening to your story to decide if it sounds like you may have Guillain-Barré, the doctor will look for certain findings on the physical exam. Because the peripheral nerves are damaged in Guillain-Barré, reflexes, such as the common knee-jerk reflex, are usually absent. The doctor will also test the arms and legs to see if they are weak, and do sensory tests to see whether there is any kind of numbness as well. Doctors concerned about Guillain-Barré will pay close attention to the cranial nerves because when these are damaged, it may lead to a need for intubation or mechanical ventilation to ensure that the patient keeps breathing.
Electromyography and Nerve Conduction Studies (EMG/NCS)
When the peripheral nervous system is afflicted by a disease, it changes the nature of the electrical signals sent and received in the peripheral nervous system. By measuring these changes with special equipment, physicians can not only tell if something is wrong, but they can tell what parts of the nerves are suffering most. This information can help guide decisions about treatment options, as well as give the doctor an idea of how severe the illness is and how long it will take someone to recover.
For example, if someone has weakness that is spreading upward like Guillain-Barré can, these electrodiagnostic studies can help determine if the axon or the myelin sheath of the nerve is being attacked. Myelin surrounds the axon and helps electrical signals move faster than they otherwise would. If electricity flows unusually slowly through the nerve, then, physicians might suspect the myelin is being attacked, in which case the most common form of Guillain-Barré is probably the cause.
On the other hand, if the axon is attacked, less electrical signal will make it through. If this is measured by nerve conduction studies, then one of the less common axonal types of Guillain-Barré might be responsible. If this is affecting both sensory and motor neurons, the patient could have acute motor and sensory axonal neuropathy (AMSAN), a more aggressive variant requiring strong treatments and a lot of physical therapy for recovery.
In autoimmune disorders affecting the nervous system, the amount of of protein in the body's cerebrospinal fluid (CSF) can be high. For this reason, a lumbar puncture may be performed. Doing a lumbar puncture can also help rule out other potential mimickers of Guillain-Barré, such as infections.
It is not uncommon for physicians to order blood tests for Guillain-Barré syndrome. In some cases, this can help find the antibody responsible for the trouble. For example, the Miller-Fisher variant of Guillain-Barré is usually associated with an antibody called GQ1b. Finding this antibody confirms a diagnosis of Miller-Fisher variant, and can make the physician especially cautious about a future need for intubation.
Blood tests are also helpful in ruling out other potential mimickers of Guillain-Barré syndrome. Depending on the initial interview and physical exam, the physician may test for signs of cancer, infection, or toxins, such as mercury.
It is important to know exactly what is causing a problem in order to avoid giving improper therapies. Cinching the diagnosis of Guillain-Barré allows medical professionals to focus on proper treatment, and can give you more information about what to expect as the disease progresses, how quickly you will recover, and what kind of assistance you will need to get back on your feet again.
Ropper AH, Samuels MA. Adams and Victor's Principles of Neurology, 9th ed: The McGraw-Hill Companies, Inc., 2009. McCabe MP, O'Connor EJ.
Yuen T. So, Continuum: Peripheral Neuropathies, Immune-Mediated Neuropathies, Volume 18, Number 1, February 2012