Miller Fisher syndrome: What you need to know

Miller Fisher syndrome (MFS) is a rare, autoimmune nerve condition. It is a less-severe form of Guillain-Barré syndrome.

Read on for an overview of Miller Fisher syndrome, including symptoms, treatment, and recovery time.

What is MFS?

MFS is a sudden-onset neurological condition that causes problems with the peripheral nervous system, including:

  • coordination and balance
  • loss of reflexes
  • facial droopiness
  • problems controlling the eyelids

MFS often follows a viral illness, so many people experience symptoms of a cold, mono, diarrhea, or other diseases before MFS appears.

MFS is a milder variant of Guillain-Barré syndrome (GBS). Both are considered to be autoimmune conditions that develop when the immune system attacks the nervous system.

GBS can cause weakness, tingling, and paralysis in the limbs. More severe forms of this syndrome can make it difficult to breathe. An estimated 5 to 10 percent of people with GBS develop respiratory paralysis that requires the use of a breathing tube or ventilator.

MFS usually has a good outlook, and most people begin to recover within 2 to 4 weeks. However, some people experience lasting effects, and relapses can occur.

Alternatively, MFS symptoms could signal the beginning of GBS. Because GBS can cause breathing issues, doctors may hospitalize people with symptoms of MFS.

How common is MFS?

MFS is a rare disorder. Guillain-Barré syndrome affects only 1 in 100,000 people. MFS makes up just 1-5 percent of these cases in Western countries, but more in Taiwan and Japan.

Because MFS is such a rare condition, it can sometimes be challenging to diagnose. A person who thinks they have either of these conditions may need to see a specialist.

The symptoms of MFS usually come on rapidly, which distinguishes it from other gradual-onset nerve conditions.

The three primary symptoms of MFS are:

  • loss of control of body movements, including weakness or uncontrolled movements
  • loss of reflexes, particularly in the knees and ankles
  • weakness in the face, including facial drooping, difficulty keeping the eyes open, and blurred vision

For most people, symptoms begin in the eyes. Many people with MFS struggle to walk and may waddle or walk very slowly. Some people experience other neurological symptoms, such as difficulty urinating.

Because MFS often follows a viral infection, people with this condition may also have symptoms of a viral illness.

Doctors usually diagnose GBS or MFS based on a physical examination and assessment of the symptoms that a person displays, as well as how quickly the symptoms appeared.

It is essential that a doctor rules out other conditions, particularly those that may be medical emergencies, such as stroke or a brain injury. Doctors may perform imaging scans on the brain to test for these conditions, and may also ask about recent illnesses, medical history, and lifestyle.

Blood work can test for a specific antibody called anti-GQ1b antibody, which is typically present in people with MFS or GBS. A nerve test called a nerve conduction velocity test, or a spinal tap that removes a small bit of cerebrospinal fluid may also aid diagnosis.


Most people recover from MFS, some even without treatment. Those who develop GBS, however, may develop serious or even life-threatening complications. A person who thinks they might have MFS should not self-diagnose or assume that symptoms will disappear on their own.

Because other disorders, such as polio, stroke, or nerve damage, can cause symptoms similar to MFS, it is essential to seek comprehensive testing from a doctor who understands neurological health.

Report all symptoms to a doctor, particularly those that indicate neurological issues. Difficulty breathing should always be treated as a medical emergency, so people who experience weakness or numbness and trouble breathing should go to the emergency room.


MFS is a rare and poorly understood condition. Doctors do not yet understand why some people develop MFS following an illness, but most people do not.

Providing a doctor with comprehensive information about health history and symptoms can ensure a proper diagnosis, and may even help medical providers better understand this puzzling syndrome.

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