The arachnoid is one of the three membranes surrounding the spinal cord and the nerve roots, and arachnoiditis is an inflammation of this membrane.
Normally this membrane is thin and pliable but in arachnoiditis the membrane becomes thicker and thicker, gradually squeezing and compressing the nerves so that they can no longer move freely. The inevitable result is pain, though the pain depends upon which nerves have been affected.

There are several possible ways in which arachnoiditis can develop. Sometimes it develops as a result of spinal surgery, and sometimes as a result of an infection of the membranes surrounding the brain and spinal cord (meningitis).

In the past it was not unknown for arachnoiditis to develop after X-rays of the spine in which contrast dyes were used. These are now known to cause inflammation and are no longer used.

Further information can be found at:

Arachnoiditis Treatment
Husband describes a unique treatment his wife tried. Email list available here.

Article on Arachnoiditis
Hundreds of thousands of back operations are performed yearly yet roughly 25% of these operations fail to help the patients completely. A good portion of this 25% is thought to be related to arachnoiditis.

COFWA
COFWA Arachnoiditis Information and Support Group-
"Circle of Friends With Arachnoiditis" (COFWA). Absolutely FREE!!! We call ourselves the "Arachniacs".

Most Common Complication of Spinal Surgery
y Kevin Rahn, M.D. and Richard T. Holt, M.D.explain a source of Arachnoiditis, where it affects the spinal cord, and treatments used.