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Arachnoiditis and back pain.
Medical expert of the article
Last reviewed: 08.07.2025
Arachnoiditis is thickening, scarring, and inflammation of the arachnoid membrane. These changes may be localized or may compress nerve roots and the spinal cord. In addition to pain, patients may experience numbness, weakness, decreased reflexes, and bladder and bowel dysfunction. The exact cause of arachnoiditis is unknown, but it may be associated with disc herniation, infection, tumor, myelography, spinal cord surgery, or intrathecal drug administration. Arachnoiditis has been reported following epidural or subarachnoid methylprednisolone administration.
[ Symptoms of Arachnoiditis
Patients with arachnoiditis complain of pain, numbness, tingling, and paresthesia in the distribution of the affected nerve root or roots. Weakness and loss of coordination in the affected limb may be present; muscle spasms, back pain, and pain radiating to the buttocks are common. Physical examination may reveal decreased sensation, weakness, and altered reflexes. Occasionally, patients with arachnoiditis develop compression of the lumbar spinal cord, spinal roots, and cauda equina roots, leading to lumbar myelopathy or cauda equina syndrome. These patients present with varying degrees of weakness in the lower limb and symptoms of bladder and bowel dysfunction.
Survey
MRI provides the most comprehensive information about the lumbar spine and its contents and should be performed in all patients with suspected arachnoiditis. MRI is highly informative and can identify pathology that threatens the development of lumbar myelopathy. For patients who cannot undergo MRI (presence of pacemakers), CT and myelography are reasonable alternatives. If a fracture or bone pathology such as metastatic disease is suspected, radionuclide bone scanning or plain radiography is indicated.
While MRI, CT, and myelography provide useful neuroanatomical information, electromyography and nerve conduction velocity studies provide neurophysiological data on the current status of each nerve root and lumbar plexus. Electromyography can also differentiate plexopathy from arachnoiditis and identify coexisting entrapment neuropathy, which can complicate diagnosis.
If the diagnosis is in doubt, laboratory testing should be performed, including a complete blood count, ESR, antinuclear antibodies, HLA B-27 antigen, and blood biochemistry to identify other causes of pain.
Differential diagnosis
Arachnoiditis is a clinical diagnosis confirmed by a combination of history, physical examination, radiography and MRI. Conditions that can mimic arachnoiditis include tumor, infectious diseases and pathology of the lumbar spine, roots, plexus and nerves.
Treatment of arachnoiditis
There is no consensus on the most effective treatment for arachnoiditis; most efforts are directed toward decompression of the nerve roots and spinal cord and treatment of the inflammatory component of the disease. Epidural neurolysis or caudal steroids may relieve nerve root compression in localized lesions. Generalized arachnoiditis requires surgical laminectomy. The results of such treatment are poor at best. Sleep disturbances due to depression are best treated with tricyclic antidepressants such as amitriptyline, which can be started at 12.5 mg once daily at bedtime. Neuropathic pain associated with arachnoiditis may respond to gabapentin. Spinal cord stimulation may also result in symptomatic relief. Opioid analgesics should be used with caution, if at all.
Complications and diagnostic errors
Failure to diagnose arachnoiditis promptly may increase the risk of developing lumbar myelopathy or cauda equina syndrome, which, if left untreated, may progress to paraparesis or paraplegia.