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The Origin of the Term "Arachnoid" Arachnoid. Arachne (Gk)= spider, and -oeides (Gk) = shape. This word, referring to the very "tenuous and cob-web like membrane lying between the pia and dura mater" was first introduced by the Anatomical Society of Amsterdam in 1664. |
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"Arachnoiditis" and "Meningitis" The term "Arachnoiditis" refers only to inflammation of the arachnoid membrane. The word "meningitis" refers to a diffuse inflammation of the spinal membranes but typically (as in meningitis caused by an infectious agent) involves only the pia mater and arachnoid membranes. Chemical meningitis (leading to adhesive arachnoiditis), on the other hand, typically causes diffuse involvement of all three membranes. Post-traumatic meningitis may also cause focal involvement of all three membranes. It can be appreciated that the term "arachnoiditis" is very non-specific as all known meningitis entities (acute and chronic) involve the arachnoid membrane. |
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"Adhesive Arachnoiditis" This entity, in all of its phases and types, represents an advanced form of inflammation where prominent fibrosis (scarring) involving nerve structures has occurred. It is important to clarify this neuropathologic entity because it can lead to a lifetime of suffering due to intractable pain, neurologic deficit, and even death. Aside from autopsy it can only be reliably diagnosed by high-resolution MRI scanning. In the 20th century the most common cause of clinically significant adhesive arachnoiditis (that associated with signs and symptoms) has been ill-advised myelography with oil based agents such as Pantopaque and Myodil. In the 21st century ill-advised epidural steroid injections have now become the primary etiology of new cases. History of Adhesive Arachnoiditis The first description of what we now know to be adhesive arachnoiditis appears to have been the report, in 1898, by Dr. H. Schlesinger in Germany of a case of paraplegia examined at autopsy. In 1907 Prof. F. Krause presented to the German Surgical Society a series of cases thought initially to be spinal tumors where "meningitis serosa spinalis" was found to be the cause of paraplegia. In 1909 Sir Victor Horsley published, in the British Medical Journal (1:513-517), his work on the differential diagnosis of "chronic spinal meningitis" and pointed out that causation was often difficult to determine. We now know that essentially all of these cases were of an infectious or parasitic etiology. It wasn't until the 1926 publication of "Myélite nécrotique subaiguë by Foix and Alajouanine that it was first appreciated that adhesive arachnoiditis could be due to something other than an infectious process. We now know that these cases represent congenital arteriovenous malformations of the spinal cord where repeated subarachnoid hemorrhage has caused the adhesive arachnoiditis. With the subsequent introduction of spinal anesthesia and spinal myelography the subarachnoid space then became a "highway" for the introduction of foreign body substances. |
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Spinal Meningitis At the beginning of the 20th century almost all spinal meningitis was related to infection. Most bacterial infections (i.e. meningococcal meningitis) were of an acute nature while others (i.e. tuberculous and syphilitic meningitis) could be chronic. In the early days of neurosurgery the differential diagnosis of chronic meningitis from tumor was often a difficult task. |
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The Tower of Babel |
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Because descriptions and understanding of the process of meningeal inflammation have evolved for over a century a common nomenclature did not exist. For this reason arachnoiditis-related terminology has been another, more modern, Tower of Babel. The situation has not been helped by some who have endeavored to maintain the confusion for their own ends. The following is a list of terms which are consistent with Sir Victor Horsely's original description of chronic spinal meningitis where the terms used have shown consistency with the neuropathologic process referred to as with "adhesive arachnoiditis." |
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Meningitis Serosa
Spinalis |
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The problem for the medical profession, and their patients, has been that when these terms were used they were not accompanied by a clearly understandable dialogue as to what these entities really meant. A neuropathologic entity is one thing. A disease process producing disability is a separate entity. This has been particularly true in regard to the subject of chronic chemical meningitis where the real dangers inherent in introducing foreign body substances into the subarachnoid space, for diagnosis or treatment are not spelled out. Because of this the term severe adhesive arachnoiditis has been introduced to clarify that there are associated active clinical problems. |
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