Arachnoiditis ossificans

Posted By Wael Nemattalla
Arachnoiditis ossificans

55 years old male with remote history of spinal fixation after trauma.

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  • Wael Nemattalla 2014-02-18 12:09:31

    Small calcified plaques of the dura mater are frequently encountered at surgery and autopsy. Kaufman and Dunsmore have emphasized that these patchy, thin, isolated asymptomatic calcifications should be distinguished from intrathecal ossification associated with chronic meningeal inflammation (or arachnoiditis), for which the term arachnoiditis ossificans should be reserved.

    Arachnoiditis ossificans is frequently associated with a significant, often progressive, neurologic deficit [1,2,3,4, 7, 8]. Specifically, patients tend to present with symptoms of progressive compressive myelopathy. However, this presentation is variable, and clinical symptoms may be relatively mild or seemingly unrelated [5].

    Prior trauma, surgery, subarachnoid hemorrhage, myelography (particularly using oil-based contrast agents), and spinal anesthesia have all been implicated as causes of arachnoiditis ossificans [1,2,3,4,5,6,7,8].

    Various mechanisms have been proposed for the development of the ossification including intradural hematoma, which organizes and ossifies; seeded bone fragments; and osseous metaplasia associated with chronic inflammation [1, 8]. The latter is probably the most likely cause, with arachnoiditis ossificans representing end-stage chronic arachnoiditis, as suggested by Kaufman and Dunsmore [1]. They found chronic fibroblastic proliferative change to the leptomeninges associated with the osseous metaplasia in all the cases they reviewed. However, a high prevalence of vascular abnormalities of the spinal cord was also seen in their series. They suggested that vascular shunting or pressure effects might contribute to the development of the disorder, possibly complicated by bleeding into the abnormal tissues.

    Conventional radiographs rarely show the abnormality, and then only when it is extensive. Myelography may show the features of arachnoiditis, but the ossification can be overlooked because of obscuration by the contrast agent. Dennis et al. [4] indicated that myelography, in fact, might be misleading; their case report indicated that the myelogram suggested spinal stenosis rather than an intradural ossific mass.

    Although unenhanced CT has been well shown to be exquisitely sensitive for the disorder [2,3,4,5,6, 8], it is being used less frequently for the routine evaluation of lower back pain. In all four of the patients in our series who underwent CT, the intrathecal ossification could be readily identified.


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