Arachnoiditis is a pain disorder caused by inflammation of the arachnoid, one of the membranes that surrounds and protects the nerves of the spinal cord. The inflammation may occur due to irritation from chemicals; infection; direct injury to the spine; chronic compression of spinal nerves; or complications from spinal surgery or other spinal procedures. It may result in scar tissue and adhesions, which cause the spinal nerves to “stick” together. If arachnoiditis affects the function of nerves, it can cause symptoms such as numbness, tingling, and a characteristic stinging and burning pain in the lower back or legs. In some people. it may affect the bladder, bowel, and sexual function. Very severe arachnoiditis can result in paralysis of the legs. Treatment aims to relieve pain and improve symptoms that impair function. Treatment may include pain medications, physical therapy, and psychotherapy. Surgical treatment is controversial because it offers only short-term relief and may increase formation of scar tissue.

Arachnoiditis has many possible causes, including:

• mechanical injury during spinal surgery, or complications from spinal surgery (about 60% of cases)
• trauma to the spinal cord
• one or more spinal taps
• steroid epidural injections or other injections
• spinal and epidural anesthesia
• myelography
• bacterial or viral spinal infections

The initial symptoms of arachnoiditis are caused by inflammation of the arachnoid, and the formation of scar tissue and adhesions later cause the more severe symptoms as the condition progresses.

Arachnoiditis can cause a number of symptoms including numbness; tingling; loss of temperature sensation; and a characteristic stinging and burning pain in the lower back, limbs, and trunk. Pain is often made worse by activity. Some people have debilitating muscle cramps or spasms; loss of balance; tinnitus; problems with vision and hearing; or bladder, bowel, or sexual dysfunction. In severe cases, arachnoiditis may lead to paralysis of the legs.

Arachnoiditis causes chronic pain and neurological deficits. The disease does not improve significantly with treatment and does not have a predictable pattern of symptoms, severity, or progression. Some people with arachnoiditis may have milder symptoms which do not get much worse over time, although the aging process usually does add to the severity of the symptoms.  Others may quickly progress to severe neurological symptoms that lead to paralysis. The majority of people with arachnoiditis appear to fall somewhere between these extremes. 

Arachnoiditis is generally not an inherited condition and typically results from inflammation due to prior spinal surgery, other procedures on the spine (such as injections), trauma, or infection. Familial cases of arachnoiditis have very rarely been reported. To our knowledge, only two families with multiple affected family members have been described in the literature, with possible autosomal dominant or multigenic inheritance (due to the interaction of multiple genes).