Areflexia is a condition in which your muscles don’t respond to stimuli. Areflexia is the opposite of hyperreflexia. That’s when your muscles overreact to stimuli.

A reflex is an involuntary and rapid movement of a part of your body in response to a change in environment (stimuli). People with areflexia don’t have typical reflexes, such as a knee-jerk reaction.

Areflexia is usually caused by an underlying condition related to disease or injury to the nervous system. Your treatment and overall outlook will depend on the underlying cause.

Detrusor areflexia occurs when the detrusor muscle can’t contract. The detrusor muscle is the muscle in your bladder that controls the emptying of your bladder.

People with detrusor areflexia can’t empty their bladders on their own. They need to use a hollow tube called a urinary catheter to release urine from the bladder. Detrusor areflexia may also be called underactive bladder or neurogenic bladder.

The main symptom of areflexia is complete absence of reflexes. Typically, when a muscle tendon is tapped briskly, the muscle immediately contracts. In someone with areflexia, the muscle doesn’t contract when tapped.

Other symptoms will depend on the underlying cause. People with areflexia may also experience symptoms such as:

  • tingling or numbness in the hands or feet
  • abnormal muscle coordination
  • muscle weakness
  • clumsiness or regularly dropping things from your hands
  • sexual dysfunction, especially in men
  • constipation
  • digestive issues
  • urinary incontinence (detrusor areflexia)
  • paralysis
  • respiratory failure

The most common cause of an absent reflex response is peripheral neuropathy. Peripheral neuropathy is a disorder in which the nerves malfunction because they’re damaged or destroyed.

An illness or injury can destroy or damage your nerves. Here are some of the conditions that can cause areflexia:

Diabetes

People with diabetes can experience nerve damage resulting from:

  • high blood sugar levels sustained over a long period of time
  • inflammation
  • problems with the kidneys or thyroid (diabetic neuropathy)

Vitamin deficiencies

Deficiencies of vitamins E, B-1, B-6, and B-12 can cause nerve damage and lead to areflexia. These vitamins are essential to nerve health.

Guillain-Barré syndrome (GBS)

In Guillain-Barré syndrome, the immune system mistakenly attacks healthy nerve cells in the peripheral nervous system. The exact cause of this condition isn’t known. It’s thought that an infection triggers it, such as the stomach flu or Epstein-Barr virus.

Miller Fisher syndrome

Miller Fisher syndrome is a rare nerve disease. It’s sometimes considered a variant or subgroup of GBS. Like GBS, a viral infection usually triggers it.

Other autoimmune diseases

Autoimmune diseases, like multiple sclerosis (MS), rheumatoid arthritis (RA), or amyotrophic lateral sclerosis (ALS), can result in nerve or tissue damage that can lead to weak or absent reflexes. In MS, for example, the body’s immune system attacks and damages the protective layer of the nerve fibers. This causes inflammation, injury, and scar tissue in the nervous system.

Hypothyroidism

Hypothyroidism occurs when the body doesn’t produce enough thyroid hormone. It can cause fluid retention and increase the pressure surrounding nerve tissues.

Injury to the nerves or spinal cord

A physical trauma or injury, such as from a car accident or fall, is a common cause of injury to the nerves. An injury to the spine usually results in total loss of sensation and mobility below the injury. This includes areflexia. Typically, only the reflexes below the level of the injury are affected.

Toxins and alcohol use disorder

Exposure to toxic levels of chemicals or heavy metals, like lead or mercury, can result in nerve damage. Alcohol can also be toxic to the nerves. People who misuse alcohol are at a higher risk of having peripheral neuropathy.

There are also a few rare disorders that can cause areflexia. These include:

Chronic inflammatory demyelinating polyneuropathy (CIDP)

CIDP is a long-term condition characterized by destruction to the nerve fibers in the brain. CIDP is closely related to GBS. The condition eventually causes a loss of muscle reflexes.

Cerebellar ataxia, neuropathy, and vestibular areflexia (CANVAS) syndrome

CANVAS syndrome is an inherited, slowly progressive neurologic disorder. It leads to ataxia (loss of coordination), areflexia, and other impairments over time. The average age of onset for CANVAS syndrome is 60 years.

Cerebellar ataxia, areflexia, pes cavus, optic atrophy and sensorineural hearing loss (CAPOS) syndrome

CAPOS syndrome is a rare genetic disease. It usually occurs in young children between the ages of 6 months and 5 years.

CAPOS syndrome may occur after an illness that causes a high fever. The child may suddenly have a hard time walking or coordinating. Other symptoms include:

  • muscle weakness
  • hearing loss
  • trouble swallowing
  • unusual eye movements
  • areflexia

Most of the symptoms of CAPOS syndrome improve once the fever goes away, but some symptoms may linger.

Your doctor will first take a thorough medical history and ask you about your symptoms, including:

  • when your symptoms started
  • how quickly your symptoms got worse
  • if you were sick right before the onset of symptoms

Your doctor will then perform a physical exam. They may do a reflex test to determine the severity of your symptoms. This type of exam helps assess the reaction between your motor pathways and sensory responses.

During a reflex test, a doctor uses a tool called a reflex hammer to test your response to being tapped on your deep tendons. The doctor may tap spots on or near your knees, biceps, fingers, or ankles. If you have areflexia, your muscles won’t react to the tap from the reflex hammer.

Your doctor may also run some tests to help distinguish between all of the potential causes of areflexia. Depending on your symptoms, these tests may include:

  • Spinal tap. This test is also known as a lumbar puncture. In this procedure, a needle is inserted into the lower back to withdraw spinal fluid. It’s then sent to a laboratory for analysis.
  • Blood tests. These tests measure your vitamin and blood sugar levels.
  • Nerve conduction study. This test checks for nerve damage and dysfunction.
  • Electromyography. This test assesses the health of muscles and the nerve cells that control them.
  • CT scan or MRI. These imaging tests will check to see if anything is pressing on a nerve.

Treatment for areflexia depends on the underlying cause. It may involve medications, physical therapy, or both.

Medications

The exact medication that your doctor prescribes will depend on what’s causing your symptoms. For example, doctors may prescribe insulin to treat diabetes. If you have GBS or CIDP, your doctor may prescribe immunoglobulin therapy and plasmapheresis. Your doctor may prescribe steroids to help reduce the inflammation.

Hypothyroidism is treated with thyroid replacement hormones. There are also many medications available to treat the symptoms of autoimmune diseases.

Physical therapy

Physical therapy aims to strengthen the affected muscles. You’ll learn how to perform exercises safely to improve walking, running, and overall muscle strength. An occupational therapist can help you with daily activities.

Treatment for detrusor areflexia

There are no current specific medications available to treat detrusor areflexia. People with detrusor areflexia will need to urinate at regular intervals to make sure that the bladder doesn’t get too full.

A doctor may recommend using a urinary catheter to make sure that the bladder is emptied. During a catheterization procedure, a thin, flexible tube is inserted into the bladder to release urine.

The outlook for people with areflexia depends on the underlying cause. Some of the conditions that trigger areflexia, such as MS and RA, have no current cure. The aim of treatment is to lessen the severity of symptoms and improve quality of life. Most people with MFS and Guillain-Barré syndrome will make full, or nearly full, recoveries.

If you’ve been experiencing any numbness, weakness, or abnormal sensations of the muscles or nerves, see your doctor for a diagnosis right away. Usually, the earlier these problems are diagnosed and treated, the better your outlook.