Areflexia: Causes, Symptoms, Treatment, Diagnosis

Areflexia is a medical condition in which the muscles stop responding to stimuli. It is the opposite of what happens in hyperreflexia, which is when the muscles overreact to stimuli.^(1,2,3) A reflex is any type of rapid and involuntary movement of a certain part of the body in response to a change in stimuli or environment. People with areflexia, though, do not experience any typical reflexes, such as a knee-jerk reaction.^(4,5)

Areflexia is usually caused by another underlying health condition related to either disease or injury to the nervous system. The treatment and your overall outlook depend on what is the underlying cause of the areflexia.^(6,7)

Areflexia can affect different muscles of the body. For example, detrusor areflexia happens when the detrusor is unable to contract. The detrusor muscle is the bladder muscle that controls the emptying of the bladder.

People with detrusor areflexia are unable to empty their bladders on their own and may need to use a hollow tube known as a urinary catheter to release urine from the bladder. Detrusor areflexia is also known as neurogenic bladder or underactive bladder.^(8,9)

The primary symptom of areflexia is the complete absence of reflexes. Usually, when a muscle-tendon gets tapped briskly, the muscle should immediately contract. In a person with areflexia, the muscle does not contract when it is tapped briskly.

Other symptoms of areflexia depend on the underlying cause, and people with areflexia can also experience the following symptoms:

• Muscle weakness
• Abnormal muscle coordination
• Numbness or tingling in the feet or hands
• Constipation
• Digestive issues
• Clumsiness or regularly dropping things from your hands
• Urinary incontinence due to detrusor areflexia
• Paralysis
• Sexual dysfunction, especially in men
• Respiratory failure

The most common cause of areflexia is peripheral neuropathy.⁽¹⁰⁾ Peripheral neuropathy is a type of disorder that causes the nerves to malfunction because they are destroyed or damaged. Any injury or illness can damage or destroy the nerves. Here are some common conditions that can cause areflexia:

Diabetes: People with diabetes are prone to experience nerve damage due to inflammation, high blood sugar sustained over a long time, and/or problems with thyroid or kidneys (a condition known as diabetic neuropathy).⁽¹¹⁾

Guillain-Barre Syndrome (GBS): In people with Guillain-Barre syndrome, the immune system mistakenly starts to attack the healthy nerve cells that are present in the peripheral nervous system. While the exact cause of this syndrome is not yet known, but it is believed that an infection causes it, such as the Epstein-Barr virus or the stomach flu.⁽¹²⁾

Miller Fisher Syndrome: The Miller Fisher syndrome is a rare nerve disease that is sometimes considered to be a subgroup or variant of Guillain-Barre syndrome itself. Similar to Guillain-Barre syndrome, a viral infection is believed to be the trigger for Miller Fisher syndrome.

Vitamin Deficiencies: Being deficient in vitamins B1, B6, B12, and E can also cause damage to the nerves, leading to areflexia. These vitamins are important for the body and for ensuring nerve health.⁽¹³⁾

Hypothyroidism: Hypothyroidism happens when the body is not able to produce sufficient levels of the thyroid hormone. The condition can cause fluid retention and also increase the pressure surrounding the nerve tissues.

Other Autoimmune Disorders: Autoimmune diseases like rheumatoid arthritis, multiple sclerosis, or amyotrophic lateral sclerosis can cause nerve or tissue damage that can cause weak or absent reflexes. For example, in multiple sclerosis, the body’s immune system starts attacking and damaging the protective layer of the nerve fibers, known as the myelin sheath. This causes injury, inflammation, and scar tissue in the nervous system.⁽¹⁴⁾

Injury to the Spinal Cord Or Nerves: A physical injury or trauma, including from a fall or car accident, is one of the most common causes of injury to the nerves that can lead to areflexia. An injury to the spinal cord can lead to a total loss of sensation and mobility below the injury. This can include areflexia as well. Usually, only the reflexes below the level of the injury area tend to get affected.

Toxins and Alcohol Use: Exposure to toxic levels of heavy metals or chemicals, like mercury or lead, can cause nerve damage. Alcohol abuse can also become toxic to the nerves over time. People who are heavy alcohol drinkers are at a greater risk of having peripheral neuropathy.

Apart from these conditions and factors, there are also some rare disorders that can cause areflexia. These include:

Cerebellar Ataxia, Neuropathy, And Vestibular Areflexia (CANVAS) Syndrome: CANVAS syndrome is an inherited and slowly progressive neurological disorder that causes ataxia (meaning loss of coordination), areflexia, and other types of nerve-related impairments over time. The average age of onset for CANVAS syndrome is usually 60 years.⁽¹⁵⁾

Chronic Inflammatory Demyelinating Polyneuropathy (CIDP): Chronic inflammatory demyelinating polyneuropathy is a long-term condition that is characterized by the destruction of the nerve fibers in the brain. This condition is very similar to Guillain-Barre syndrome and can ultimately lead to a complete loss of muscle reflexes.⁽¹⁶⁾

Cerebellar Ataxia, Areflexia, Pes Cavus, Optic Atrophy, And Sensorineural Hearing Loss (CAPOS) Syndrome: CAPOS syndrome is a rare disease that is believed to be hereditary. It is commonly observed in young children between the ages of six months and five years. CAPOS syndrome usually occurs after a disease that causes the child to spike a high fever. The child is likely to suddenly find themselves having difficulty walking or coordinating. Other symptoms of CAPOS syndrome can include muscle weakness, trouble swallowing, hearing loss, unusual eye movements, and areflexia. The majority of the symptoms of CAPOS syndrome tend to improve once the fever disappears, but some symptoms can continue to linger.⁽¹⁷⁾

Your doctor will take a detailed medical history and ask you questions about your symptoms. These will include:

• When did the symptoms begin?
• How quickly the symptoms started to get worse?
• If you were sick right before the symptoms began?

Your doctor will also perform a physical examination and along with a reflex test to find out the severity of your symptoms. A reflex test will help your doctor assess the reaction between your sensory responses and motor pathways.

During the reflex test, your doctor will use a tool known as a reflex hammer to test your response to being briskly tapped on the deep tendons. Your doctor is also likely to tap some spots on or near your fingers, biceps, knees, or ankles. In people with areflexia, the muscles will not react to the tap from the reflex hammer.

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

• Blood tests to measure your blood sugar and vitamin levels.
• A spinal tap, also known as a lumbar puncture, is a procedure in which a needle is inserted into the lower back for withdrawing spinal fluid. The fluid is then sent to a laboratory for further analysis.⁽¹⁸⁾
• Electromyography is a diagnostic test that assesses the health of the muscles and the nerve cells that control them.
• A nerve conduction study is a diagnostic test that checks for nerve dysfunction and damage.
• MRI or CT scans are imaging tests that are used to check to see if anything is pressing down on a nerve.

There are various treatments for areflexia. Treatments prescribed will depend on the underlying cause. Treatment typically involves medications, physical therapy, and sometimes both.

The exact medications for areflexia again vary depending on what is the cause of your symptoms. For example, your doctor may prescribe insulin for treating diabetes. Or, if you have Guillain-Barre syndrome, your doctor will prescribe plasmapheresis and immunoglobulin therapy. You may be prescribed steroids to help bring down the inflammation.⁽¹⁹⁾

Similarly, hypothyroidism will be treated with thyroid replacement hormones, and there are a variety of medications that are used for treating the symptoms of autoimmune diseases.⁽²⁰⁾

However, there is currently no specific medication available for the treatment of detrusor areflexia. People with detrusor areflexia will need to urinate regularly to ensure that their bladder does not become too full.

In case of detrusor areflexia, your doctor may also recommend using a urinary catheter to help you empty the bladder. In a catheterization procedure, there will be a thin, flexible tube inserted into your bladder to help release urine directly into an attached bag.

Physical therapy is necessary for people with areflexia as it helps strengthen the affected muscles. You will be taught how to perform certain exercises in a safe manner to help improve your walking, running, and overall muscle strength. You will be working with an occupational therapist who will also help you learn how to perform daily activities with more ease.

The outlook for areflexia again depends on the underlying cause. Conditions like multiple sclerosis and rheumatoid arthritis that are triggers for areflexia have no cure at present, and so the goal of treatment revolves around reducing the severity of the symptoms and improving the overall quality of life. Most people with Guillain-Barre syndrome and Miller Fisher syndrome will go on to make full, or at least nearly full, recoveries from areflexia.

If you are experiencing any muscle weakness, numbness, or any type of abnormal sensations of the nerves or muscles, you should consult your doctor right away. The earlier these symptoms are diagnosed and the condition treated, the better is your outlook.

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