Review of Arachnoiditis Ossificans with a Case Report
Archana C. Lucchesi, MD*
William L. White, MD
Joseph E. Heiserman, MD†
Richard A. Flom, MD†
Division of Neurological Surgery, †Division of Neuroradiology, Barrow Neurological Institute, St. Joseph’s Hospital and Medical Center, Phoenix, Arizona
*Current Address, East Valley Diagnostic Imaging, Mesa, Arizona
Arachnoiditis ossificans is a rare type of arachnoiditis, with about 46 cases reported in the world literature today. It has received little attention in the neurosurgical literature. Spinal arachnoiditis ossificans can present with a wide variety of signs and symptoms, depending on the location, morphology, and size of the lesion. Predisposing factors for the development of the disease are similar to those for adhesive arachnoiditis and include trauma, hemorrhage, and meningeal irritation. Unlike adhesive arachnoiditis, arachnoiditis ossificans has been treated successfully with surgery. Surgery, however, remains a controversial treatment option. Consequently, the literature and available case reports on arachnoiditis ossificans were reviewed to gain a better understanding of the disease, its presentation, etiology, treatment options, and prognosis. The disease is optimally evaluated by noncontrast computed tomography. Treatment decisions are based on the location and morphology of the calcifications and their contribution to compression of the spinal cord or nerve roots. Most patients with arachnoiditis ossificans do undergo surgery and most improve.
Key Words: arachnoiditis, back pain, CT myelography, magnetic resonance imaging, ossificans
Figure 1. (A) Sagittal T2-weighted and (B) axial T1-weighted magnetic resonance images show only changes associated with arachnoiditis.
Spinal arachnoiditis ossificans is a rare entity, and its true incidence is unknown.1
Virchow first differentiated between symptomatic and asymptomatic calcifications, and Puusepp25
is credited with describing and treating the first four cases of the disease in 1931. In 1971 Kaufman and Dunsmore9
proposed the term arachnoiditis ossificans for the more ominous manifestation of the disease with clinical symptoms. Incidental
arachnoid calcifications, which are found in as many as 76% of spines at autopsy, differ from the symptomatic, progressive form of arachnoiditis ossificans, which can lead to devastating neurological sequel-ae.9
These distinct clinicopathological entities differ in terms of their etiology, clinical course, and prognosis.9
Arachnoiditis ossificans, which forms the basis of this article, applies to the latter manifestation. The case reports on arachnoiditis ossificans in the literature were individually reviewed and analyzed in an attempt to clarify the role of surgery in the treatment of these patients. An additional case is also presented.
A computerized search of the medical database Medline (1966 to current), performed using the key words arachnoiditis, ossificans, and calcifications, provided 16 articles (21 case reports).1,4,6,8,12,17,18,27-29,32-34,36,39,40 The reference lists that followed these articles provided 11 additional articles (17 case reports) dating to the early 1900s.2,5,9,10,13-15,20,21,25,37 A Japanese article32 included a table in English that provided information on four additional case reports from the Japanese literature. Foreign articles that could be translated were included in the study.2,15,27 Articles were obtained from the medical library at St. Joseph’s Hospital and Medical Center or by interlibrary loan.
Figure 2. (A) Plain film myelogram and (B) computed tomographic myelogram confirm the findings of arachnoiditis.
The following exclusion criteria were established after these articles were reviewed: (1) asymptomatic patients or autopsy reports,7,11,24,30,31
(2) information unavailable in English or not readily translated,3,16,41
(3) pertinent information not reported,26,38
and (4) compression due to an osseous anomaly.22
Our patient (presented below) was also included in the analysis.
Patients were evaluated in terms of age, sex, location of the calcifications, and treatment. Patients treated surgically were further evaluated for level of surgery and surgical outcome. One patient with disease at T10-L2 was characterized as having lumbar disease because the nerve roots of the cauda equina were involved.40
Another patient had two isolated sites of disease, which were considered separately as thoracic and lumbar arachnoiditis ossificans.10
Patients were diagnosed either by computed tomographic (CT) examination or at surgery, some of whom also had a diagnosis based on pathological analysis.
Figure 3. Plain noncontrast computed tomography scan confirms the presence of intradural calcifications.
In October 1996, a 64-year-old female with a 2-year history of back pain sought treatment at our institution. She subsequently developed right back pain and numbness in the right lower extremity. She also experienced mild urinary retention. In 1950 she had undergone a lumbar discectomy with spinal fusion at L4-5 and L5-S1.
Magnetic resonance (MR) imaging showed changes associated with arachnoiditis (Fig. 1). There was no mass and no evidence of herniated nucleus pulposus or stenosis of the spinal canal. Lumbar myelography with CT confirmed the findings (Fig. 2). However, the calcific nature of the disease was not apparent until a follow-up noncontrast CT was performed 9 days after the myelography (Fig. 3). The calcifications, which were very fine and scattered throughout the dural sac from L4 through S1, involved the nerve roots of the cauda equina. Because calcifications were present, surgery was considered a viable treatment option.
Because the densities were so small, however, and because she also had concomitant medical conditions, surgery did not seem indicated. The patient was placed on ongoing pain medication, and physical therapy was recommended to improve her ability to ambulate. She continues to have pain and urinary dysfunction, which are attributed to the arachnoiditis ossificans.