Miller Fisher syndrome (MFS) is a subgroup of a more common — yet still rare — nerve disorder known as Guillain-Barré syndrome (GBS).

While GBS affects just 1 person in 100,000, MFS is even more uncommon. It makes up just 1 to 5 percent of Guillain-Barré cases in the Western world. According to the GBS/CIDP Foundation International, most cases of MFS progress into full-fledged GBS.


Both GBS and MFS are triggered by a viral infection, most commonly the flu or a stomach bug. Symptoms generally start appearing from one to four weeks after infection with the virus.

No one is entirely sure why GBS and MFS develop in response to these common illnesses. Some researchers speculate that the viruses may somehow change the structure of cells in the nervous system, causing the body’s immune system to recognize them as foreign and fight them off. When this happens, nerves can’t transmit signals well. The muscle weakness that’s a characteristic of both diseases can result.


While GBS tends to produce muscle weakness that starts in the lower body and travel upward, MFS generally begins with a weakness in the eye muscles and progresses downward. Common symptoms of MFS include:

Anyone can develop MFS, but some are more prone than others. They include:

  • Men. The Journal of the American Osteopathic Association notes that men are twice as likely to have MFS as women.
  • People who are of middle age. The mean age of developing MFS is 43.6 years.
  • People who are Taiwanese or Japanese. According to a case report published in the Hawai‘i Journal of Medicine & Public Health, 19 percent of GBS cases in Taiwan fall under the MFS category. That number jumps to 25 percent in Japan.

The first thing your doctor will do is take a thorough medical history. To distinguish MFS from other neurological disorders, your doctor will ask you:

  • when your symptoms started
  • how quickly the muscle weakness progressed
  • if you were sick in the weeks before the onset of symptoms

If your doctor suspects MFS, they’ll order a spinal tap, or lumbar puncture. This is a procedure in which a needle is inserted into the lower back to withdraw spinal fluid. Many people with MFS have elevated proteins in their spinal fluid.

A blood test looking for MFS antibodies (proteins made by the body and used by the immune system to fight off infection) can also help confirm the diagnosis.

There’s no cure for MFS. The aim of treatment is to lessen the severity of symptoms and speed recovery.

The two main forms of treatment are immunoglobulin therapy and plasmapheresis. These are the same treatments used for GBS.

Immunoglobulin therapy

This treatment involves delivering (through an injection into a vein) high doses of proteins the immune system uses to attack infections. Researchers aren’t exactly sure why this helps to lessen the immune system’s attack on the nervous system, but it does seem to speed recovery.


This is a procedure in which red and white blood cells are removed from the plasma (or liquid) portion of the blood. These cells are then reintroduced into the body, without the plasma.

Both these procedures seem to be equally effective in improving the disorder. However, intravenous immunoglobulin therapy is easier to administer. It may be the first therapy tried.

Physical therapy to help the affected muscles regain strength may also be recommended.

MFS symptoms tend to progress for several weeks, plateau, and then start to improve. Typically, MFS symptoms begin to improve within four weeks. Most people recover within six months, although some residual weakness can linger.

Because the muscle weakness of MFS can also affect the heart and lungs, resulting in cardiac and breathing problems, hospitalization and careful medical supervision are necessary during the course of the illness.

MFS is an exceedingly rare condition that is, fortunately, short-lived. While there can be serious complications, such as breathing issues, most people are successfully treated and make full, or nearly full, recoveries.

Relapses are rare, occurring in less than 3 percent of cases. Learn about two women diagnosed with GBS who went on to have normal lives.

Talk to your doctor at the first sign of symptoms. Early treatment can help speed recovery.