Another form of spinal arachnoiditis, in which both the spinal cord and roots are entrapped in thickened pia-arachnoid, sometimes with arachnoid-dural adhesions, is a rare but well known and often idiopathic entity. An account of this condition is included with the spinal cord diseases (see Chap. 43). The etiologic factors have been singularly elusive, although in the past it followed the instillation of iophendylate (Pantopaque) for myelography and corticosteroids (for pain or multiple sclerosis) and other irritative agents, particularly chemically contaminated spinal anesthetics. Our colleagues saw more than 40 cases of the latter type, now rare, dating from the time when vials of anesthetic were stored in detergent sterilizing solutions. Instillation of the anesthetic agent was followed immediately by back pain and a rapidly progressive lumbosacral root syndrome (areflexic paralysis, anesthesia of the legs, and paralysis of sphincters). Several cases have, in our recent experience, followed prolonged spinal anesthesia with the patient in a decubitus position, usually for orthopedic procedures, but the resulting myelopathy or cauda equina radiculopathy was difficult to separate from a direct toxic effect of the anesthetic. The CSF protein rises rapidly in cases that were precipitated by injection of substances into the subarachnoid space, but pleocytosis is minimal. In other instances, protracted back pain lasting days to weeks is the only effect in the post anesthetic period but is followed, after months or years, by a progressive myelopathy. This takes the form of some combination of spinal arachnoiditis with ataxic paraparesis and sensory disturbance, hydrocephalus, or opticochiasmatic arachnoiditis. The point to be made is that there is always some risk attached to the subarachnoid instillation of any foreign agent.
This condition was well known to neurologists during the period when neurosyphilis was a common disease.
It occurs after years of chronic syphilitic meningitis, sometimes in conjunction with tabes dorsalis or meningomyelitis. However, there were always nonsyphilitic cases, the cause of which was never determined. A constriction of visual fields, usually bilateral and asymmetrical (rarely scotomas), developed insidiously and progressed. Pathologically, the optic nerves were found to be enmeshed in thickened, opaque pia-arachnoid. The optic nerves are atrophic in appearance. Idiopathic cases are likely to be confused with multiple sclerosis.
This term refers to a chronic, inflammatory thickening of the dura. The term is somewhat confusing insofar as the pia and arachnoid may be equally involved in the inflammatory thickening and all three membranes are bound together by dense fibrous adhesions. This type of meningeal reaction, which is now uncommon, was first described by Charcot and Joffroy. It occurred mainly in the cervical region (hence the name pachymeningitis cervicalis hypertrophica) and was attributed to syphilis. Indeed, in some instances there was a gummatous thickening of the dura. Involvement of cervical roots and compression of the spinal cord gave rise to variable degrees of paraparesis in association with root pain, paresthesia, sensory loss, and amyotrophy of the upper limbs. In the modern era, rheumatoid arthritis (Fig. 29-7), sarcoidosis, and chronic local infection (fungal, tuberculous, see Chap. 32) have been the main causes, but many cases remain unexplained. Idiopathic hypertrophic pachymeningitis continue to be reported; a summary of published cases and two personally studied ones is given by Dumont and colleagues and by Jimenez-Caballero and coworkers.