Acute Flaccid Myelitis

Overview

Acute flaccid myelitis is a rare but serious condition affecting the spinal cord that causes sudden muscle weakness. Sudden onset weakness in the arms or legs, muscle flaccidity, and decreased reflexes are the most common symptoms. It is also known briefly as AFM.

"Myelitis" means inflammation of the spinal cord; "flaccid" indicates that the muscles are loose and weak. In this condition, the muscles become limp and weak rather than stiff.

Acute flaccid myelitis generally appears after viral infections. When certain nerve cells in the spinal cord are damaged, communication between the brain and muscles is severed. As a result, the affected arm or leg suddenly becomes unable to move. Sometimes a single arm or leg is affected, while sometimes all four limbs may be involved.

This condition is seen more frequently especially in children and generally begins a few days after experiencing a flu-like illness. Weakness progresses rapidly within hours or days. Realizing that a child was healthy a few days ago but now cannot move their arm or leg is a very shattering experience for the family.

Acute flaccid myelitis can be life-threatening; respiratory failure can develop especially when the respiratory muscles are affected. Rapid diagnosis and appropriate treatment are very important. Some patients fully recover, while others may have persistent weakness.

Symptoms

Acute flaccid myelitis symptoms most often develop very rapidly. A child who is normal in the morning may become unable to lift their arm by evening. This sudden onset puts both the family and healthcare workers on high alert.

Acute flaccid myelitis symptoms include the following:

• Sudden arm or leg weakness. This is the most obvious and earliest symptom. It generally begins in a single arm or leg. The child cannot lift their hand, drags their foot, or cannot stand on their leg. Weakness can progress within hours or days and spread to other limbs.
• Muscles being loose and limp. The affected arm or leg appears without tone. There is no muscle stiffness; on the contrary, the muscles are softer and looser than normal. The arm or leg is in a sort of "lifeless" state.
• Loss of reflexes. When the doctor examines, knee or elbow reflexes cannot be elicited. The automatic withdrawal response seen in normal people when tendons are struck with a hammer is absent. This is an important sign that spinal cord nerve cells have been damaged.
• Pain. Pain may be felt in the arm, leg, neck, or back, especially at the onset of the illness. This pain generally begins a few days before the weakness.
• Fever and flu-like symptoms. Usually an infection such as fever, cough, sore throat, or diarrhea has occurred one to two weeks before weakness begins. After the viral infection passes, the child appears to have recovered; however, a few days later weakness suddenly appears.
• Facial paralysis or drooping eyelid. In some cases, the brainstem may be affected along with the spinal cord. One side of the face may become paralyzed, the eyelid may droop, double vision or difficulty swallowing may develop.
• Loss of bladder and bowel control. Spinal cord damage can also affect bladder and bowel functions. Problems such as urinary or fecal incontinence or inability to urinate may be seen.
• Breathing difficulty. This is the most serious and life-threatening symptom. When respiratory muscles are affected, breathing becomes difficult. Rapid and shallow breathing, difficulty speaking, or bluish discoloration of the lips are signs of respiratory failure. This situation requires emergency intervention.

Symptoms generally begin on one side but can progress to affect both sides. Sometimes only the legs, sometimes only the arms, sometimes all four limbs at once may be involved.

When to See a Doctor

Acute flaccid myelitis is a condition that can progress rapidly. Early diagnosis both increases treatment options and helps prevent complications.

Call to the emergency room immediately in the following situations:

• If your child or you suddenly cannot move your arm or leg
• If there is difficulty breathing, if shortness of breath is rapidly increasing
• If saliva is drooling or there is a risk of choking due to difficulty swallowing
• If drooping eyelids and double vision have started
• If confusion or drowsiness has developed

See a doctor without delay in the following situations:

• If unexplained weakness has started in your child's or your arm or leg
• If weakness in an arm or leg is noticed a few days after experiencing an infection
• If difficulty walking, stumbling, or dragging the foot has started
• If there is loss of sensation or numbness in an arm or leg
• If severe neck, back, or leg pain is being experienced

Sudden onset weakness especially in children should definitely be taken seriously. Reaching a doctor within hours is critically important.

Causes

The exact cause of acute flaccid myelitis may not always be clear, but it is most often associated with viral infections. The virus either directly damages the spinal cord or triggers the immune system to attack the spinal cord.

Causes that can lead to acute flaccid myelitis are as follows:

• Enteroviruses. This is the most common cause of acute flaccid myelitis. Enterovirus D68 (EV-D68) and Enterovirus A71 in particular have been strongly associated with this condition. These viruses generally cause respiratory tract infections or hand-foot-mouth disease; however, rarely they can also jump to the spinal cord causing severe paralysis. They are generally seen more frequently in autumn months.
• West Nile virus. This virus carried by mosquitoes can lead to brain and spinal cord inflammation. Acute flaccid myelitis is a rare but serious complication of this infection.
• Poliovirus. This was the most important cause of childhood paralysis (polio) in the past. Thanks to vaccination, it has almost completely disappeared in developed countries. However, it can still be seen in unvaccinated regions.
• Other viruses. Adenoviruses, herpes viruses (herpes simplex, varicella zoster), influenza virus, and even rarely the COVID-19 virus can also lead to acute flaccid myelitis.
• Autoimmune reactions. In some cases, after a viral infection passes, the immune system mistakenly attacks spinal cord nerve cells. This autoimmune damage can continue even after the virus has been cleared from the body.
• Rare causes. Very rarely, some vaccines (especially the old-type live polio vaccine), toxins, or other neurological conditions can also lead to an acute flaccid myelitis-like picture.

Cases generally increase in autumn and winter months because respiratory tract viruses are more prevalent during this period. Outbreaks can appear in waves every few years.

Risk Factors

Risk factors for acute flaccid myelitis are as follows:

• Being a child. Although the condition can be seen at any age, it is much more frequently encountered especially in children under 10 years old. Most cases are between ages 2-8.
• Recently experiencing a viral infection. Risk increases especially in children who have had a respiratory tract infection or diarrhea. The risk rises significantly after enterovirus infections.
• Being unvaccinated. Children without the polio vaccine carry the risk of flaccid myelitis due to poliovirus. This risk is higher in developing countries or in regions where vaccination rates are low.
• Weakened immune system. People taking immune system suppressing medications or those with immune deficiency are more vulnerable to viral infections.
• Season. Since enterovirus infections are more frequent in autumn and winter months, acute flaccid myelitis cases also increase during this period.
• Geographic location. In some regions, the West Nile virus is transmitted more widely through mosquito bites. Living in these regions increases risk.

Acute flaccid myelitis is a very rare condition. Of the millions of children who experience enterovirus infection, only a very small portion develop this serious complication. Why some children are affected is not fully known; genetic predisposition and immune system characteristics likely play a role.

Diagnosis

Acute flaccid myelitis is diagnosed with clinical examination and various tests. Ruling out other conditions that cause similar symptoms is also important because treatment approaches may differ.

The methods used in the diagnosis of acute flaccid myelitis are as follows:

• Neurological examination. The doctor tests arm and leg strength, checks reflexes, and evaluates muscle tone. In flaccid myelitis, reflexes cannot be elicited or are very weak, muscles appear loose and without tone. Determining at what level the weakness started and how much it has spread is important for the treatment plan.
• Spinal cord MRI (magnetic resonance imaging). This is the most valuable diagnostic tool. It shows inflammation and damage in the spinal cord. In acute flaccid myelitis, damage is seen in the specific region of the spinal cord called "gray matter"; this shows itself as bright areas on the MRI. The MRI also helps rule out other causes that lead to similar symptoms (tumor, bleeding, partial paralysis).
• Lumbar puncture (spinal tap). A sample is taken from the fluid surrounding the spinal cord (cerebrospinal fluid). An increase in white blood cells in the fluid is an indicator of infection or inflammation. Special tests are performed on the fluid for virus detection.
• Blood tests. Blood samples are taken to look for viral infection. Tests are done for enterovirus, West Nile virus, and other viruses. However, the virus may not always be detected because by the time weakness begins, the virus may have been cleared from the body.
• Throat swab and stool sample. Enteroviruses can remain in the throat and stool for a longer time. Virus detection can be done from these samples.
• Electromyography (EMG) and nerve conduction study. Small electrodes are placed on muscles and nerves to test nerve and muscle functions. These tests help distinguish whether the damage is in the spinal cord or in the nerves. Since the problem is in the spinal cord in acute flaccid myelitis, the EMG shows a specific pattern.
• Respiratory function tests. If respiratory muscles are affected, lung capacity and respiratory strength are measured regularly. These tests help determine when respiratory support will be needed.

The diagnostic process can sometimes take time because acute flaccid myelitis is a rare condition and there are many other conditions that cause similar symptoms. Guillain-Barré syndrome, transverse myelitis, and spinal cord tumors are other conditions that should be considered in differential diagnosis.

Treatment

There is no approved specific treatment for acute flaccid myelitis. Treatment focuses on supportive care and preventing complications. Some treatments can be tried but their efficacy has not been fully proven.

The methods used in acute flaccid myelitis treatment are as follows:

• Supportive care. This is the cornerstone of treatment. The patient is closely monitored, vital functions are supported. Nutrition, fluid balance, and general health status are maintained.
• Respiratory support. If respiratory muscles are affected, a mechanical ventilator (breathing machine) may be needed. This ensures the lungs take in oxygen and expel carbon dioxide. Some patients need temporary respiratory support, others need it long-term.
• Physical therapy and rehabilitation. This is the most important treatment component. Physical therapy started early prevents muscle atrophy (wasting), prevents joint stiffness, and helps maintain existing strength. Active exercises, stretching, and strengthening programs are organized. The rehabilitation process can take months or even years.
• Intravenous immunoglobulin (IVIG). This is high-dose antibody treatment given intravenously. It is thought to reduce damage by modulating the immune system. It is used in some centers but its efficacy has not been definitively proven.
• Corticosteroids. High-dose steroids may be given to reduce inflammation. However, there is no definitive evidence that steroids are beneficial in acute flaccid myelitis; in fact, some studies have shown them to be ineffective.
• Plasmapheresis (plasma exchange). A blood cleaning procedure can be done to remove harmful antibodies from the blood. This is generally tried in cases that don't respond to IVIG.
• Antiviral medications. Antiviral treatments are available for some viruses. However, there is limited evidence that antivirals are effective in acute flaccid myelitis because by the time weakness begins, the virus has usually been cleared from the body.
• Bladder and bowel management. If there is inability to urinate, a catheter is inserted. Bowel movements are regulated, constipation is prevented.
• Orthoses and assistive devices. If there is leg or foot drop, special shoes or orthoses are used. These devices make walking easier and reduce the risk of falling. A wheelchair, walker, or cane may be needed.
• Psychological support. Experiencing sudden paralysis is a traumatic experience for both patient and family. Child psychologist or psychiatrist support is very important. Family counseling is also beneficial.

The treatment process begins with hospitalization. After the acute period passes, the patient is generally referred to a rehabilitation center. Long-term physical therapy and follow-up are needed.

Complications

Acute flaccid myelitis can lead to serious and permanent complications. With early diagnosis and treatment, some complications can be prevented or mitigated.

Complications that may be seen in acute flaccid myelitis are as follows:

• Permanent muscle weakness or paralysis. This is the most commonly seen complication. When spinal cord nerve cells are severely damaged, full recovery may not occur. The affected arm or leg remains permanently weak or becomes completely nonfunctional. Some patients can walk but limp; others become dependent on a wheelchair.
• Respiratory failure. When respiratory muscles are paralyzed, long-term mechanical ventilator support may be needed. Some patients may have to use a breathing device at home with a tracheostomy (a hole opened from the throat to the windpipe).
• Muscle atrophy (wasting). Muscles that are not used shrink and waste away over time. This makes weakness even more pronounced in later periods.
• Joint stiffness and contractures. Joints that cannot move gradually stiffen and become rigid. This condition called contracture leads to loss of normal range of motion. Regular physical therapy and stretching exercises help prevent this complication.
• Pain. Chronic nerve pain (neuropathic pain) can develop. This type of pain may be felt as burning, tingling, or electric shock and may not respond to normal painkillers.
• Bladder and bowel problems. Long-term loss of urinary control or bowel dysfunction seriously affects quality of life.
• Scoliosis (spinal curvature). Especially in children, one-sided muscle weakness can lead to curvature of the spine. This curvature can progress during the growth period.
• Psychological problems. Sudden paralysis and the long treatment process can lead to depression, anxiety, and post-traumatic stress disorder. School performance and social relationships can be negatively affected especially in children.
• Risk of recurrence. Although very rare, acute flaccid myelitis can recur, especially when a new viral infection is experienced.

Living with Acute Flaccid Myelitis

Life after acute flaccid myelitis is a major adaptation process for both patient and family. The course of the illness varies greatly from person to person; some patients fully recover while others have serious persistent weakness. This uncertainty is one of the most challenging aspects of the process.

The Recovery Process and What to Expect

Recovery from acute flaccid myelitis is a slow process requiring patience. In the first few months, weakness may remain stable or slight improvement may be seen. Real recovery generally becomes clear after 6-12 months. In some patients, recovery can continue for years; nerve cells try to reconnect and develop new pathways.

Recovery levels vary greatly. Some children gain full function and return to their normal lives. Some learn to live with mild weakness or a limp. Another group must cope with severe persistent weakness. Unfortunately, at the beginning of the illness it is very difficult to predict who will fully recover and who will carry permanent damage.

Families must strike a balance between having realistic expectations and maintaining their hopes. Every small bit of progress should be celebrated, but continuous disappointment should not be experienced with expectations of miraculous recovery.

Physical Therapy and Rehabilitation

Physical therapy is the backbone of acute flaccid myelitis treatment. It should be started at the earliest possible time and continue for a long period. Intensive physical therapy sessions are generally done several times a week in the first months.

The goals of physical therapy are as follows: maintaining and increasing existing strength, sustaining joint mobility, preventing contractures, improving balance, and increasing independence in daily life activities. Exercises are personalized according to the child's age and the degree of weakness.

Exercises done in water (hydrotherapy) are especially beneficial. Since the buoyant force of water supports the muscles, movement becomes easier. This both increases motivation and develops muscle strength.

Implementing a daily exercise program at home is essential. The physiotherapist works together with families and teaches exercises that can be done at home. Continuing these exercises regularly significantly affects recovery.

Orthoses, Prostheses, and Assistive Devices

If there is foot or wrist drop, orthoses make daily life easier. The support called AFO (ankle-foot orthosis) keeps the foot straight and makes walking easier. Night orthoses prevent the foot from contracting during sleep.

A wheelchair, walker, or cane may be needed for independent movement. Especially in children, an electric wheelchair increases independence and self-confidence. Accessibility arrangements may be needed at home and at school — such as ramps, grab bars, and widened doorways.

Technological assistive devices can also make a big difference. Voice-controlled devices, special keyboards, or software make daily life easier.

School and Social Life

The return to school for children who have experienced acute flaccid myelitis should be carefully planned. School administration, teachers, and the healthcare team should work in cooperation. The child's special needs should be identified and necessary arrangements should be made.

Physical accessibility should be provided: elevator, ramp, accessible toilet. Classroom arrangements may be needed: sitting up front, extra time, note-taking support. When permission from school is needed for physical therapy sessions, this process should be made easier.

Social support is very important. Interaction with peers is critical for the child's mental health. School staff and other parents should be informed in a way that helps them understand the child's situation, but the child should not be stigmatized or turned into an object of pity.

Sports and physical activities should be encouraged as much as possible. Activities such as swimming, cycling (three-wheeled or supported), table tennis support both physical development and self-confidence.

For Families

Watching your child experience sudden paralysis deeply affects all members of the family. Parents may feel guilt, anger, fear, and deep sadness. Siblings may feel neglected or jealous. The entire family needs emotional support.

Family counseling or support groups are very valuable. Connecting with families who have had similar experiences provides both practical information and emotional support.

Parents should not neglect their own health. Burnout is a real risk; coping with prolonged fatigue, stress, and uncertainty is very challenging. Taking turns providing care, taking regular breaks, and seeking professional support are important.

Setting aside special time for siblings, allowing them to express their feelings as well, and explaining the situation in an age-appropriate way helps maintain family balance.

Long-term Follow-up

Patients who have experienced acute flaccid myelitis require regular neurology follow-up. Frequent examinations are recommended in the first year, and once or twice yearly thereafter. During follow-ups, strength assessment, joint mobility measurement, and MRI imaging may be done.

Respiratory functions should be checked regularly. Even in patients with mild weakness in respiratory muscles, lung capacity can decrease over time.

Growth and development monitoring is important. Especially in children with one-sided weakness, the affected arm or leg may grow more slowly than normal.

Preparing for Your Appointment

What you can do:

• Note in detail exactly when symptoms started and how they progressed
• Mention illnesses experienced in the last few weeks (fever, cough, diarrhea)
• Write down the vaccinations you have received and their dates (especially polio vaccine)
• Note which arm or leg the weakness started in and its spread
• Make a video recording; if the child's walking, arm movements, and daily activities are recorded, this is very valuable information for the doctor
• Mention if there is a similar illness history in the family
• Write your questions down in advance

Questions you can ask your doctor are as follows:

• Is this acute flaccid myelitis or another condition?
• Can the cause be determined exactly?
• What are the treatment options, which is most effective?
• What is the chance of full recovery?
• How long until recovery can be seen?
• When should physical therapy start and how long should it last?
• Is there a risk of needing respiratory support?
• What is the likelihood of spread to other limbs?
• When can return to school occur?
• Is there a risk of recurrence?

Questions your doctor may ask you are as follows:

• When exactly did symptoms start?
• Did weakness progress within hours or days?
• Was fever, cough, or diarrhea experienced in the last 1-2 weeks?
• Is there pain, where?
• Is there difficulty breathing?
• Is there a problem with urinary or fecal control?
• Was the polio vaccine given?
• Has there been recent travel?
• Is there a family history of a similar condition?