What is arachnoiditis?
The arachnoid membrane is one of the three meninges (protective membranes) that surround and protect the brain and spinal cord. Inflammation of the arachnoid membrane is known as arachnoiditis. Inflammation and swelling of the arachnoid lining causes irritation, leading to the development of scar tissue. This scar tissue can adhere to nerve roots or blood vessels and bind them together. The most common symptom of arachnoiditis is constant, severe pain in the lower back or lower limbs.
Arachnoiditis can be difficult to diagnose as many of its symptoms are shared with other nerve conditions of the lower back. The diagnostic process typically begins with a thorough medical history, including information about any previous spinal traumas, spinal surgeries, spinal infections, spinal taps, or epidural injections. A physical exam, including a neurological exam to check reflexes and look for areas of weakness, is also performed.
Additional medical tests that may be ordered include, but are not limited to, the following:
- Magnetic resonance imaging (MRI)
An axial view with contrast can be used to confirm an arachnoiditis diagnosis, especially when the three key signs of nerve root inflammation are present: displacement, enlargement and clumping.
- Computerized axial tomography (CT) scan
A CT scan is also often used to confirm an arachnoiditis diagnosis or to eliminate the possibility of other medical conditions.
- Electromyogram (EMG)
An EMG can be used to measure the severity of nerve root damage.
- Spinal tap
A spinal tap, also known as a lumbar puncture, may be ordered to check for the presence of infection in the spinal fluid.
- Blood tests
Elevated erythrocyte sedimentation rates (ESR) and especially high C-reactive protein (CRP) levels may indicate arachnoiditis. Interleukins, myeloperoxidase (MPO), a1-antitrypsin, and tumor necrosis factor may also be elevated.