Arachnoiditis

What happens in arachnoiditis

The spinal cord and the bundle of nerve roots below it (the cauda equina) are wrapped in three membranes: the dura (outermost), the arachnoid, and the pia. Cerebrospinal fluid circulates between the arachnoid and pia, letting the nerve roots float freely.

When the arachnoid is irritated, inflammation develops. In some people this leads to scar tissue that glues nerve roots to each other and to the membrane. The roots can no longer move normally with the body, and blood flow and fluid circulation around them are disturbed. In rare cases, fluid-filled cysts form or the scar tissue calcifies (arachnoiditis ossificans).

Causes

• Spinal surgery, particularly repeated operations on the lower back
• Myelograms with older oil-based contrast dyes (such as iophendylate), which were widely used before the late 1980s. Modern water-soluble contrast has much lower risk
• Infections: bacterial, fungal or tuberculous meningitis, and spinal infections
• Bleeding into the spinal fluid, such as after a subarachnoid hemorrhage or traumatic lumbar puncture
• Injections into the spinal fluid (intrathecal), including some chemotherapy drugs, and rarely complications of epidural steroid injections or anesthesia, particularly if medicine is accidentally injected into the wrong space
• Spinal trauma
• Chronic disc disease and spinal stenosis, in some cases

Many people with these exposures never develop arachnoiditis. Symptoms can begin months or years after the trigger.

Symptoms

Symptoms vary widely, from mild to disabling:

• Chronic pain in the lower back, buttocks and legs: burning, stinging, aching, or electric-shock-like
• Numbness and tingling in the legs and feet
• A sensation of insects crawling on the skin or water trickling down the legs
• Muscle cramps, spasms and twitching
• Leg weakness
• Pain worse with sitting or prolonged standing, sometimes eased by lying down
• Bladder, bowel and sexual dysfunction, which overlap with cauda equina syndrome and need prompt assessment if new
• Headache, vision or hearing disturbances in some people
• Fatigue, sleep disturbance and depression, which often accompany chronic pain

Diagnosis

Arachnoiditis is difficult to diagnose because its symptoms overlap with other spinal conditions such as spinal stenosis and failed back surgery syndrome.

• MRI of the lumbar spine with contrast is the main test. Characteristic findings include nerve roots clumped together in the center of the canal, roots stuck to the walls of the dural sac (an "empty sac" appearance), or a soft-tissue mass of matted roots.
• CT myelogram may be used if MRI is not possible.
• Nerve conduction studies and EMG assess nerve damage.
• Blood tests and spinal fluid analysis may be done if infection or another cause is suspected.

A neurologist, neurosurgeon or pain specialist usually makes the diagnosis by combining symptoms, history and imaging.

Treatment

There is no treatment that reliably reverses the scarring. Care focuses on controlling pain and maintaining function.

Medicines

• Nerve pain medicines such as gabapentin, pregabalin, duloxetine or amitriptyline
• NSAIDs for inflammatory flares, following the label dose for over-the-counter versions
• Muscle relaxants for spasms
• Opioids are used cautiously, if at all, because of limited long-term benefit and risks

Rehabilitation and self-management

• Physical therapy: gentle movement, stretching, aquatic therapy and graded activity to maintain strength and mobility
• Hydrotherapy and heat
• Pacing: balancing rest and activity to avoid flares
• Psychological therapy: CBT and pain management programs help with the stress, sleep problems and depression that often accompany chronic neuropathic pain

Procedures

• Spinal cord stimulation: an implanted device that sends mild electrical pulses to the spinal cord may reduce pain in some people
• Surgery to remove scar tissue generally has poor and short-lived results because new scarring forms. It is reserved for specific complications such as cysts compressing the cord

Avoiding further spinal procedures, unless clearly needed, is usually advised, since each may worsen inflammation.

Outlook

Arachnoiditis is a long-term condition. Its course is unpredictable: some people have stable, manageable pain, while others have progressive symptoms. It does not usually shorten life. A combined approach of medicines, rehabilitation and psychological support offers the best quality of life. Support groups can help people living with this rare condition.

Frequently asked questions

What is arachnoiditis?

Arachnoiditis is inflammation of the arachnoid membrane that surrounds the spinal nerves. It can lead to scarring that makes nerve roots stick together, causing chronic burning pain, numbness and other nerve symptoms in the back and legs.

What causes arachnoiditis?

Common causes are spinal surgery, infections such as meningitis, bleeding into the spinal fluid, older oil-based myelogram dyes, injections into the spinal fluid, and spinal trauma. It is rare, and most people who have these exposures do not develop it.

How is arachnoiditis diagnosed?

The main test is an MRI of the lower spine, which can show nerve roots clumped together or stuck to the lining of the spinal canal. Doctors combine this with your symptoms and history of spinal procedures or infection.

Can arachnoiditis be cured?

There is currently no cure. Treatment focuses on managing pain and maintaining function through nerve pain medicines, physical therapy, psychological support and sometimes spinal cord stimulation. Many people find a combination that allows them to stay active.