subarachnoiditis

Subarachnoiditis is an inflammatory condition involving the subarachnoid space, the area between the arachnoid and pia mater that contains cerebrospinal fluid. In many cases the inflammation leads to scarring (adhesions) and disruption of CSF dynamics and nerve root function. The term is sometimes used interchangeably with adhesive arachnoiditis, and when it occurs in the spinal subarachnoid space it is often referred to as spinal adhesive arachnoiditis.

Causes include infection (bacterial, fungal, tuberculous meningitis), chemical irritation from intrathecal drugs or imaging contrast agents, spinal surgery or trauma, and hemorrhage into the subarachnoid space. Oil-based contrast used in older myelography or other neurotoxic substances are historical risk factors. In many cases the exact trigger remains unidentified.

Symptoms include chronic, often severe back or neck pain with radicular distribution, sensory disturbances, weakness, and altered reflexes. Autonomic symptoms such as bladder, bowel, or sexual dysfunction can occur. The presentation can be persistent, with periods of fluctuation.

Diagnosis relies on MRI as the favored imaging test, which may show nerve root clumping, arachnoid thickening, or scar tissue; CT myelography can be helpful in some cases. CSF analysis is variable. Management focuses on symptom control: physical therapy, pain medications, neuropathic agents, and lifestyle modification. Injections may help some patients but can worsen others; adhesiolysis or surgical exploration has limited and inconsistent benefit. Prevention emphasizes minimizing intrathecal irritants and treating infections promptly.

Prognosis varies widely; many individuals experience chronic pain and disability, while others stabilize with treatment. The condition is relatively rare, and evidence for disease-modifying therapies is limited.