Arachnoiditis: Taming the Painful Shrew

Author: Forest Tennant

The arachnoid is the middle layer of the covering of the spinal cord and brain. The covering is usually called meninges when referring to the brain, and the lower spine covering is usually referred to as the theca or thecal sac. The outer layer of the covering is the dura and the inner layer the pia mater. The middle layer, arachnoid, was so named over a century ago because it resembles a spider web. Arachnoiditis simply means inflammation of the arachnoid. Heretofore, arachnoiditis has been a taboo subject in medical circles as it was thought to be a rare disease usually caused by medical procedures. Pain caused by arachnoiditis has sometimes been referred to as the "world's worst" and the condition so hopeless that treatment wasn't even considered.

In centuries past arachnoiditis was most often diagnosed only at autopsy. Tuberculosis was a common cause. Today it is now clear that arachnoiditis is neither rare nor primarily caused by medical procedures such as spinal taps, epidural injections, or surgery. Furthermore, effective treatment regimens have been developed. Arachnoiditis may be the end result of almost all the common causes of lumbar and cervical spine pain including herniated discs, degenerative arthritis, and osteoporosis (Table 1). Genetic connective tissue diseases, such as Ehlers-Danlos, are prone to develop arachnoiditis. While a medical procedure may accelerate the development of arachnoiditis, some causative, underlying pathology initiates the disease. Arachnoiditis is now diagnosed by a typical symptom profile, physical exam, the presence of serum inflammatory markers, and magnetic resonance imaging (mri). Although its precise incidence and prevalence are unknown, arachnoiditis cases are now being discovered in every community and clinical practice that deals with low back pain. It is often overlooked and referred to by such names as low back or neck syndrome, failed back surgery syndrome, or degenerative spine disease. Practitioners are just beginning to understand and diagnose the condition. This article is to raise awareness that the condition can no longer be considered "rare," and every pain practitioner must now recognize and treat it.

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