What Is Arachnoiditis?

Overview

The brain, spinal cord and nerves of the central nervous system are covered by three protective membranes, known as the meninges. The arachnoid lies superficial to the pia mater but deep to the dura mater, acting as the intermediate membranous layer that surrounds the nerves of your spinal cord. Inflammation of the arachnoid membrane causes arachnoiditis. Arachnoiditis is a long-lasting and severe condition that causes chronic pain and neurological symptoms, such as muscle weakness and numbness. Irritating chemicals, spinal injury and infections caused by bacteria or viruses can cause this condition. Medical procedures that involve the injection of substances may also put one at risk of developing arachnoiditis.¹

Causes of arachnoiditis

Numerous factors can be responsible for the occurrence of arachnoiditis, including:¹

• Spinal tap 
• Infections, such as meningitis, AIDS, and tuberculosis   
• Spinal injury from a fall or vehicle accident
• Epidural injections (which are used to provide pain relief during childbirth)
• Injection of radiographic contrast media used for imaging tests 
• Chemical irritation 

Arachnoiditis is characterised by the inflammation of the arachnoid membrane, which leads to:

• The thickening and adhesion of the arachnoid membrane 
• The formation of scar tissue
• The clumping of nerve roots 

As the disease progresses, the scar tissue surrounds and traps the nerves, obstructing the flow of cerebrospinal fluid (the fluid surrounding your brain and spinal cord). As a result, the spinal nerves clump together, leading to chronic adhesive arachnoiditis.² Over time, the arachnoid membrane hardens and presses down on the soft tissues that it envelopes. This complication is known as arachnoiditis ossificans.³ 

Signs and symptoms of arachnoiditis

People suffering from arachnoiditis show a variety of symptoms, depending on the stage and severity of the disease. Some may experience symptoms a few days into developing the disease, whereas others may not show signs of arachnoiditis for years. The symptoms can vary based on which part of your spine is affected, ranging from mild to severe. Although arachnoiditis is asymptomatic in most cases, a common symptom is nerve pain in the lower back and legs (lumbar spine).

Epidural steroid injections may worsen the condition by aggravating existing inflammation of the arachnoid. Hence, epidural injections should be avoided if a patient is suspected to suffer from arachnoiditis. 

Adhesive arachnoiditis can present with several clinical symptoms. These may include: 

• Radicular syndrome, which is characterised by burning pain along the distribution of the sciatic nerve and the presence of the Lasegue sign ⁴ 
• Lower back pain 
• Limited mobility in the lower back and sacral region
• Neurological deficits, such as reduced mobility and numbness in the legs 

In more severe cases, involvement of secondary organ systems can arise. This can lead to:

• Bladder dysfunction (Neurogenic bladder)
• Bowel dysfunction 
• Sexual dysfunction
• Sensory disturbances of the skin ⁵

In worst cases, patients may lose the ability to produce volitional movement in their lower limbs (paraplegia) and will need to use a wheelchair for the rest of their lives.

Management and treatment for arachnoiditis

For acute and chronic cases of arachnoiditis, there are four main ways of managing the disease:

• Inhibition and control of neuroinflammation (inflammation of the nervous tissue) 
• Prevention of adhesion formation 
• Pain relief
• Protection of a person’s mental state 

Adhesion arachnoiditis may progress and get severe if neuroinflammation is not inhibited. It is a complicated condition to treat as long-term outcomes cannot be predicted. The treatment focuses on relieving chronic pain and managing symptoms that negatively impact on a person’s daily life. A combination of pain relief medications, exercise, physiotherapy, and psychotherapy are recommended by doctors.² 

Diagnosis of arachnoiditis

Diagnosis of arachnoiditis typically involves a physical examination and diagnostic imaging. Additional diagnostic tests may also be necessary.^2,6

• Physical examination: The healthcare provider will evaluate the neurological function of the patient by assessing their range of motion, reflexes, and muscle strength. The doctor will also look out for any indications of neurological abnormalities associated with arachnoiditis ^1,7
• Diagnostic imaging: Performing an MRI is important to diagnose arachnoiditis. MRIs can generate detailed images of the spinal cord and nerve roots, identifying any signs of inflammation, scarring, or adhesions that may suggest arachnoiditis ^6,8,9 
• Other diagnostic tests: Electromyography (EMG) may be used to assess muscle activity and detect any irregularities or nerve damage. In some cases, a lumbar puncture may be performed to analyse the cerebrospinal fluid for evidence of inflammation or infection ^2,6,8 

To ensure an accurate diagnosis, it is crucial to seek help from a healthcare professional who has expertise in spinal disorders, as the symptoms of arachnoiditis can overlap with those of other spinal conditions.

FAQs

Can arachnoiditis be prevented?

Arachnoiditis cannot be prevented. However,  avoiding unnecessary invasive spinal procedures, such as surgeries or injections, and minimising exposure to potential triggers, such as contrast agents, may lower the risk of developing arachnoiditis.

Is arachnoiditis life-threatening?

No, arachnoiditis is not considered a life-threatening condition. However, the symptoms and complications associated with arachnoiditis, such as chronic pain, neurological deficits, and impaired quality of life, can significantly impact a person's well-being and daily functioning.^1,10

How common is arachnoiditis?

The exact prevalence of arachnoiditis is difficult to determine as it is an underdiagnosed and rare disease. However, in recent years, it has been found that arachnoiditis is the third most frequent complication of failed back surgeries.

Who is at risk of arachnoiditis?

Individuals who have undergone spinal surgeries or procedures, particularly those involving the spinal cord and nerve roots, are at a higher risk of developing arachnoiditis. Additionally, those who have had spinal injections with certain substances, such as contrast agents, or those who have experienced spinal infections or trauma may also be at an increased risk of developing arachnoiditis.

When should I see a doctor?

If you are experiencing chronic pain in your back or legs, along with neurological symptoms, such as numbness, weakness, or changes in bladder or bowel function, it is important to seek medical attention promptly. A doctor can evaluate your symptoms, perform necessary tests, and provide appropriate treatment or a referral to a specialist if arachnoiditis is suspected.

Summary

Arachnoiditis is the inflammation of the arachnoid membrane surrounding the nerves in the spinal cord. It is often caused by infections, post-surgery complications and chemical irritation. It can lead to symptoms such as chronic pain, muscle cramps, bladder and bowel dysfunction, sexual dysfunction, and in severe cases, paralysis of the lower limbs. A physical examination and diagnostic imaging is performed to diagnose arachnoiditis. Treatment focuses on managing symptoms. This includes pain relief, inhibition of inflammation and the maintenance of physical and mental health. Prevention of the disease is challenging but minimising unnecessary invasive spinal procedures and reducing exposure to potential triggers, such as certain contrast agents, may help lower the risk of developing arachnoiditis. Early medical attention is necessary if you experience persistent back or leg pain, neurological symptoms, or changes in bladder or bowel function.