Arachnoiditis
Chronic inflammation and scarring of the spinal nerve root lining
ICD-10: G03.9 · systemic condition
Arachnoiditis is a painful condition caused by inflammation of the arachnoid mater — the middle layer of the three membranes (meninges) surrounding the spinal cord and nerve roots. When the arachnoid membrane becomes inflamed, it can develop scar tissue that binds nerve roots together, tethers them to the dural sac, or restricts their normal gliding movement. The result is often severe, chronic, and refractory pain that is difficult to treat. Arachnoiditis is most commonly caused by prior spinal surgery, epidural steroid injections, spinal infections, or by contrast agents used in older myelography procedures (oil-based myelographic dye was a leading historical cause). It is a distinct entity from the much more common post-surgical pain syndromes, and it is frequently underdiagnosed.
50%
Spinal cord stimulation achieves clinically meaningful pain reduction (≥50%) in approximately 50–60% of carefully selected patients with arachnoiditis.
North American Spine Society,
Prior spinal surgery is now the most common identifiable cause of arachnoiditis, accounting for the majority of current cases since oil-based myelographic contrast was discontinued in the 1980s.
Aldrete JA et al., Pain Practice (2006)Symptoms
- Burning, stinging, or stabbing pain in the lower back, legs, or perineum — often severe
- Leg weakness and sensory changes — numbness, tingling, or hypersensitivity
- Muscle cramps and spasms, particularly in the legs
- Bowel and bladder dysfunction
- Shooting or electric shock-like pains (dysesthesias)
- Symptoms that are variable — worsened by movement, weather changes, or stress
- Neurological deficits — in severe cases, progressive lower extremity weakness
Causes & Risk Factors
- Prior spinal surgery — the most common current cause; inflammation during healing can scar nerve roots
- Multiple epidural steroid injections at the same level — especially when performed without image guidance
- Spinal infection (meningitis, discitis, or epidural abscess) causing reactive scarring
- Oil-based myelography contrast (Pantopaque) — the leading cause prior to the 1980s; now discontinued
- Intrathecal medications (especially when preservatives are present)
- Spinal cord or cauda equina trauma
Treatment Options
Conservative
- Multimodal pain management — gabapentin/pregabalin, tricyclic antidepressants, opioids in carefully selected cases
- Physical therapy — hydrotherapy and gentle movement to maintain function
- Spinal cord stimulation (SCS) — the most evidence-supported interventional treatment for refractory arachnoiditis
- Intrathecal drug delivery (pain pump) for severe, opioid-responsive cases
- Psychological support and pain psychology — essential given the chronic, refractory nature
Surgical
- Surgical lysis of adhesions (adhesiolysis) — technically complex, outcomes variable, risk of worsening
- Spinal cord stimulator implantation — typically classified as interventional rather than "surgical" but requires implantation
When to see a spine specialist
If you have had prior spinal surgery or epidural injections and experience progressive burning leg pain, new neurological deficits, or bowel/bladder dysfunction, see a spine specialist promptly. Arachnoiditis is best evaluated by an experienced spine specialist or pain management physician who can order and interpret MRI with appropriate protocols and rule out other treatable causes of post-procedural pain.
Specialists Who Treat Arachnoiditis
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Search spine specialists →Frequently Asked Questions
How is arachnoiditis diagnosed?
MRI of the lumbar spine with and without contrast is the primary diagnostic tool. Characteristic findings include clumping of nerve roots into a central mass ("empty sac" sign), adhesion of nerve roots to the dural sac peripherally ("pseudocord" sign), or a completely obliterated thecal sac filled with fibrous tissue. These MRI patterns are graded (Type I, II, III) and correlate with symptom severity. Diagnosis requires both the clinical picture and consistent MRI findings.
Is arachnoiditis curable?
Currently there is no cure for arachnoiditis. Once scar tissue has formed around the spinal nerve roots, it cannot be reliably removed without risk of causing further nerve damage. Treatment focuses on pain control and preserving function. Spinal cord stimulation is the most effective long-term intervention, with studies showing 50–60% of patients achieving meaningful pain reduction. The condition does not inevitably worsen — many patients reach a plateau and achieve stable management.
What is the relationship between epidural steroid injections and arachnoiditis?
Single, properly performed, image-guided epidural steroid injections have an extremely low risk of causing arachnoiditis. The risk increases with multiple injections at the same level, injections performed without fluoroscopic or CT guidance (increasing the risk of inadvertent intrathecal injection of particulate steroid), and the use of methylprednisolone acetate (Depo-Medrol) intrathecally, which has documented neurotoxicity. The FDA cautions against epidural injection of particulate corticosteroids. The absolute risk remains very low, but it is a known possible complication.