The localized lumbar arachnoiditis associated with repeated disc surgery (the common variety seen in pain clinics) is characterized by back and or leg pain with other inconstant signs of radiculopathy (loss of tendon reflexes, weakness, and variable degrees of sensory loss), usually bilateral.
The CSF is abnormal during the acute stage in practically all cases that ultimately result in adhesive arachnoiditis. In some there is a moderate lymphocytic pleocytosis, occurring soon after the inciting event. In the localized lumbar arachnoiditis, referred to earlier, the CSF may be normal or show only a slight increase in protein content. The prominent finding with imaging is a partial or complete obliteration of the spinal subarachnoid space. The loculated myelographic appearance of arachnoiditis is characteristic (patchy dispersion of the column of dye and a “candle-guttering” appearance that was most evident with oil-based contrast media); MRI reveals a loss of the normal ring of CSF or localized loculations of CSF (see Fig. 10-6).
Treatment In the early stages of arachnoiditis, corticosteroids have been given to control the inflammatory reaction and to prevent progress of the disease, but their value is questionable. Surgery may be effective in the case of localized “cyst” formation and cord compression. Severe radicular pain can be effectively relieved by posterior rhizotomy, but there is a strong tendency for the pain to return after an interval of several months or 1 or 2 years so that this approach has been all but abandoned. For chronic adhesive lumbar arachnoiditis in which diffuse back and limb pain is the most distressing symptom, there is little effective surgical or medical treatment, although relief has reportedly been provided in isolated instances by painstaking microsurgical dissection of the lumbar roots. In some cases, the loculations return. Administration of corticosteroids, systemic and epidural, has not been consistently beneficial but may be tried. Immune-suppressant medication such as azathioprine or interferons have been tried but not studied systematically. Transcutaneous stimulator treatment and gabapentin have also been used with inconsistent results.
Herniation of the Cord Through a Dural Tear
Violent trauma to the spinal canal or skull such as a fall or blow to the back can cause arachnoidal and dural tears. The associated neural injury dominates the picture and the dural tear may require repair so as to minimize the development of meningitis. More difficult to understand is the occurrence of spinal cord herniation through a spontaneous rent in the adjacent dura with no preceding injury. In view of the fact that we have encountered five such instances in a decade, without trauma having occurred, it is probably not rare.
In the typical case, a vertically oriented tear of limited extent occurs in the ventral dura overlying the midor high-thoracic region, and a segment of the spinal cord protrudes through it into the epidural space. The result is a painless, subacute, and incomplete spinal cord syndrome, which reaches a plateau and leaves the patient with an asymmetrical spastic paraparesis and variable sensory loss. There are reports of a Brown-Séquard hemi-cord syndrome and variations of it as described in the small series by Watters and colleagues. Orthostatic headache of low-CSF pressure is not usually part of the syndrome. MRI or CT myelopathy demonstrates the protruded segment of the cord where it buckles through the dura. Presumably the herniation creates a sufficient degree of local ischemia or mechanical disturbance to account for the myelopathic symptoms. Surgical restoration of the cord to its proper position and repair of the tear, have resulted in partial or complete return of neurologic function (Vallee et al).
As to the cause of this condition, a congenital duplication of the dura membranes combined with herniation through the inner layer has been observed in some cases at operation. The abnormal configuration of the membrane has been proposed as a cause of the propensity for the fibers to separate and create an aperture.