It appears that the anatomic subarachnoid space was first “discovered” by Egyptians practicing mummification in 3,500 B.C. It was not until the the the 1920s however that the epidural space was rediscovered by the medical profession and the outlining of it became a diagnostic study (epidurography). Initially air and then Lipiodol (an iodinated poppy seed oil, first developed by Sicard and Forestier in Paris, France), were used to outline this space. Epidurography was soon recognized as being an inexact diagnostic study unable to provide good clinically valuable information regarding the spinal cord or nerve roots, but an excellent means of locating and identifying the epidural space.
Epidurography was soon replaced by contrast agents being introduced, by needles, directly into the subarachnoid (intrathecal) space as a hopefully better diagnostic study. Thus the field of myelography was born. It was appreciated, from the beginning, that myelography was much more informative than epidurography. Lipiodol was soon found to be not only a relatively poor contrast agent because of its high viscosity but was also seriously neurotoxic to the delicate tissues and nerves of the subarachnoid space. Due to this Lipiodol then “fell into disuse.”
The medical profession has not yet appeared to recognize that the epidural and subarachnoid spaces are very different in their response to foreign body substances. The epidural space is highly resistant to insult while the subarachnoid space is not. It has also not been well appreciated that when potentially neurotoxic substances are introduced into the epidural space for diagnostic or therapeutic purposes great care is required to assure that these substances are not actually placed into the more fragile and pristine subarachnoid space.
The physician’s responsibility is not to create clinically significant adhesive arachnoiditis which in the case of “epidural steroids gone wrong” can be associated with a lifetime of continuing agony. Clinically significant adhesive arachnoiditis represents a serious potential disaster for any unsuspecting patient in whom unsafe materials are injected. Despite the seriousness of this problem and good scientific documentation actually available in the medical literature on this subject there does not yet exist a general level of awareness among the medical profession regarding this potential patient disaster. Given this fact it is unlikely that many patients have had, prior to epidural steroid injection, legitimate informed consent.
Some procedurists have attempted to justify the ill-advised introduction of toxic substances into the epidural space by blind technique as being a “standard of care.” It must be clearly pointed out to the reader however that a harmful procedure can never be considered a “standard of care” by the medical profession.
A summary illustration of the process of adhesive arachnoiditis is shown above to demonstrate its separation from the epidural space.. It seems that only when physicians, or their patients, have firsthand experience with this disease do they come to any real understanding of it. In 1977, a symposium on the “Complications From Methylprednisolone Acetate (Depo-Medrol®) concluded that the only way to prevent the unfortunate complications was to completely discontinue the use of “Depo-Medrol within the spinal canal” (D Nelson et al, Delaware Medical Journal, Vol. 49, No. 6, 1977).
Methylprednisolone is a synthetic glucocoticoid (steroid). It wasn’t known by Nelson and his associates in 1977 that Depo-Medrol®, as a suspension, also contained preservatives and potentiators such as polyethylene glycol, known better as a anti-freeze in car cooling systems.
Ethylene glycol has turned out to be the primary toxic agent in producing adhesive arachnoiditis.
How did substance end up so frequently in the subarachnoid space? It appears that the intraspinal (subarachnoid) instillation of methylprednisolone suspension (Depo-Medrol®, Upjohn Company, Kalamazoo MI) began in 1960 as a ill-advised attempted treatment of adhesive arachnoiditis (created by oil myelography) and demyelinating disease (i.e. multiple sclerosis). Complications relating to this use began to be documented in the medical literature within 10 years and this particular practice then basically fell into disuse.
How then historically, given this checkered background, did epidural steroid injections (ESI) become such a widespread non-specific treatment for low back pain? There can be no question but that this “shotgun” therapy is commonly used in the United States, as well as other countries. It’s popularity seems to relate, to a large degree, to be a “knee-jerk” means of providing short-term back pain relief. The only rationale for ESI use is the generalized anti-inflammatory action of steroids and also the observation that many patients with back pain can recover spontaneously if their initial pain is moderated. Statistics demonstrate however that the same result can be achieved with most forms of other non-invasive therapies such as physical therapy and chiropractic manipulation. as well as specific injections and blocks.
In a 1999 review of 13 studies published on the use of epidural steroids 8 of the reports showed no measurable benefits (Rozenberg S et al: Efficacy of epidural steroids in low back pain and sciatica, Rev. Rhum. Engl. Ed., 66:79-85, 1999 (Feb)). In a review editorial published in the British Medical Journal the authors pointed out that randomized controlled studies and the systematic reviews of randomized trials have not shown convincing evidence that ES injections provide predictable relief for sciatica and/or back pain (Samanta A, SamanthaJ: Is epidural injection of steroids effective for low back pain? BMJ, 328:1509-10, 2004).
A remarkable amount of ignorance exists today regarding ESI. Many physicians performing epidural steroid injections on a regular basis do not even understand the relationship of this procedure to the possibility of creating adhesive arachnoiditis months later. The only sensible approach at this point in time is to require medical professionals to fully explain the procedure and other options before it is carried out. Only this approach provides true informed consent . ES steroid injection has been, in fact, just another example of the New Guinea Syndrome.
Some societies learn from past history, while others do not. Presented above is another example of the “New Guinea Syndrome” which hopefully pass from the scene in the future.