Spinal arachnoiditis ossificans: Report of three cases

OBJECTIVE AND IMPORTANCE: Although the clinical and histological features of the pathological entity of spinal arachnoiditis ossificans (AO) have been established for some time, less attention has been paid to the treatment. We propose a classification of spinal AO evaluating the possibilities and indications for surgical or conservative treatment. CLINICAL PRESENTATION: Type III has a lumbar localization, presents with less neurological involvement, and usually requires conservative treatment. In Types I and II, which are usually thoracic, clinical worsening justifies surgical decompression or partial removal, whereas total removal is rarely achievable. INTERVENTION: The literature was reviewed, and the reports on three patients were added to the published cases. On the basis of a reappraisal of the computed tomographic and magnetic resonance imaging documentation and the surgical descriptions, the cases of AO were classified into three types: semicircular (Type I), circular (Type II), and englobing the caudal fibers (Type III). The indications for treatment were evaluated in terms of surgical possibilities and outcome. CONCLUSION: The classification proposed on the basis of radiological findings allows sufficient clinical differentiation of AO and evaluation of the possibilities for surgical treatment. The latter is conditioned by the type of arachnoiditis, degree of neurological involvement, and presence of any concomitant pathological findings.