Arachnoiditis (types)

Arachnoidal Adhesions
Adhesive Arachnoiditis

Known Potential Etiologic Agents

Irritants, Non-Foreign Bodies (i.e. air, blood)
Injury, Local (i.e. trauma, surgery)
Foreign Body Substances
Local Anesthetics
Steroid Preparations
Myelographic agents


Adhesive arachnoiditis represents the most severe form of an inflammatory disease process involving the pia-arachnoid membranes of the brain and spinal canal. The inflammatory process itself represents a disease spectrum separable as follows:

Arachnoid adhesions- a very common entity. Frequently present following injury, spine surgery or infection. It is highly unlikely to be of clinical significance.

Arachnoiditis- a more advanced but uncommon entity. It may, when focal be associated with significant clinical problems.

Adhesive arachnoiditis- a much less common entity, but potentially serious in nature due to the possibility of dramatic anatomic change, disability related to constant and incapacitating pain and sometimes associated with progressive neurologic impairment.

In the case of specific toxic agents such as iophendylate incidence level can be quite high. Not all patients with anatomically documented adhesive arachnoiditis have associated clinical symptoms. The scientific explanation for this phenomenon has not yet been documented but the most plausible explanation seems to relate to severity of nutrient nerve vascular impairment and nerve anoxia produced by the pattern of the encapsulating collagenous scar tissue. It is well documented that when the scar tissue of adhesive arachnoiditis becomes calcified it can progressively compress nerve rootlets of the cauda equina leading to irreversible neurologic impairment such as loss of bowel and bladder function.

Neural tissue anoxia is known to be associated with a particularly disabling condition referred to as "causalgia". Neurologist, Weir Mitchell, during the U.S. Civil War, coined the term "causalgia" as a attempt to explain the horrible agony suffered by many of the soldiers experiencing partial peripheral nerve injuries. In causalgia the direct nerve injury produces a disruption in the normal flow of sensory information passing from the nerve to the brain. This change in information is confusing to the brain and interpreted as a uniquely disabling pain state, which is constant, and of a "agonal" quality. Causalgic pain syndromes are highly resistant to normal forms of medical therapy.

The most common causes of incapacitating, clinically significant, adhesive arachnoiditis (over the past 50 years internationally), based on our ILBNC experience in the U.S. are as follows:

93% - Myelography with iophendylate (i.e. Lipiodol®, Pantopaque®, Myodil®)

04% Trauma, segmental to spine from motor vehicle accidents

01% Trauma, segmental to spine occurring at surgery

01% Inadvertent deposition of foreign body substance into sub-arachnoid space usually for the purpose of epidural steroid deposition.  The neurotoxic preparation most commonly involved has been Depo-Medrol® (also known as Depo-Medrone®; and more recently as "methyl prednisolone suspension" containing the highly neurotoxic agent polyethylene glycol..

01% All other causes

Over the past decade, following the cessation of use of oil-based myelographic agents in the 1980s,  the most common cause of incapacitating, clinically significant, adhesive arachnoiditis in the world population has now become the subarachnoid deposition of substances containing polyethylene glycol.

Charles V. Burton, M.D.
Senior Medical Director
The Institute for Low Back and Neck Care Arachnoiditis Sufferers Action and Monitoring Society (ASAMS) Dr Charles Burton

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