Arachnoiditis ossificans associated with syringomyelia: An unusual cause of myelopathy

ABSTRACT

Objective: The pathophysiology of arachnoiditis ossificans (AO) and its association with syringomyelia remains a rare and poorly understood phenomenon. Here, we present a case of AO associated with syringomyelia, a review of literature, and a discussion of current understanding of disease pathophysiology.

Methods: A literature review was performed using MEDLINE (January 1900–May 2010) and Embase (January 1900–May 2010) to identify all English-language studies that described AO with syringomyelia. The current report was added to published cases.

Results: Over 50 cases of AO are reported in literature, of which only eight are associated with syringomyelia. The various presumptive etiologies of syrinx formation include abnormalities in blood circulation, ischemia, hydrodynamic alternations in cerebrospinal fluid (CSF) flow, tissue damage, or incidental coexistence. Changing CSF dynamics related to decreased compliance of the subarachnoid space and subsequent paracentral dissection of the spinal cord may be implicated in the disease process. magnetic resonance imaging (MRI) scanning may identify the syrinx but fail to diagnose the calcified arachnoid. Five patients, including the current case, improved clinically following laminectomy and decompression.

Conclusions: Syringomyelia in association in AO is a rare phenomenon. A high index of suspicion is required and both MRI and computed tomography (CT) are recommended for diagnosis. The pathophysiology of syringomyelia in AO remains an area of ongoing research.

ABBREVIATIONS LIST AO Arachnoiditis ossificans CSF Cerebrospinal fluid CT Computed tomography MRI Magnetic resonance imaging

References

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Acknowledgements:

The authors thank Steve Lunny for his help in formatting the figures included in the manuscript.

POINT OF VIEW:
EVIDENCE-BASED CARE APPROACH

Author Osmar Moraes

Institution Neurosurgical Department, Saint’s Marceline University Hospital, Sao Paulo, Brazil

Arachnoiditis calcificans (or „ossificans”) remains poorly understood and is a rare condition [1, 2]. With the advent of MRI, chances for its diagnosis have improved and the development of microsurgical treatment increases prospects for safe surgical intervention. There is still not enough data in the literature to determine if we can define a ‘best therapy’ at this pointing time. Further cases likely stand to influence our understanding of this condition and its recommended treatment substantially.

The association of calcifying or ossifying arachnoiditis with syringomyelia is even more rare, as shown with the eight cases described in this article, in addition to two cases described by Mello et al.

Operative treatment does not interrupt the ossification process, which continues over time, and frequently seems to result in an unfortunate progressive deterioration of an affected patient. Spinal cord cavitations can occur due to spinal cord tethering, stretching, and central cord edema formation, accompanied by cerebrospinal fluid flow impairment and pulse pressure changes. The results of surgical interventions are generally described as poor, offering short-term recovery with subsequent later deterioration. Multiple pathogenic factors are involved in this clinical syndrome including complex metabolic changes.

Laminectomy or laminotomy and decompression with or without syrinx drainage and shunting remain the standard of care as the authors stated. Little or nothing is known as to adjuvant therapies to limit recurrence of the calcification process.

Dominicucci and colleagues suggested a classification into three categories based on three cases and their review of the literature. They used the morphology of the calcification as the foundation of their classification, and found this to help determine the best surgical tactic.

As we analyze the current accepted pathophysiology of arachnoid calcification and its possible influence on spinal cord function, in addition to my personal anecdotal (unpublished) experience in two personal cases, the best available data we have to date suggests the following:

The case presented is a Domenicucci type 1, representing a case with one or more surgically resectable compressions caused by a calcified arachnoid. The recommended treatment consists of resection of the calcification for decompression and duraplasty as necessary. In the absence of improvement or with progression of symptoms associated with a concurrent syringomyelia, myelotomy for cerebrospinal fluid drainage and shunting had been recommended.

The case described in the preceding text is the first one in the literature treated with decompression alone, and is very well documented. The demonstrated decrease in the syrinx size-in addition to a good clinical outcome-supports the recommendation of drainage surgery to be performed only in presence of progression of symptoms.

As a final observation this case has only 9-months of follow up, which is a short time from which to draw conclusions as to eventual surgical success.

Additional references:

1. Mello LR, Bernardes CI, Feltrin Y, et al (2001) Thoracic spine arachnoid ossification with and without cord cavitation: report of three cases. J Neurosurg; 94 (1 Suppl):115–120.

2. Faure A, Khalfallah M, Perrouin-Verbe B, et al (2002) Arachnoiditis ossificans of the cauda equina Case report and review of the literature. J Neurosurg; 97 (2 Suppl):239–243.

EDITORIAL STAFF PERSPECTIVE

Case reports have been frequently touted as representing the ‘bottom of the food chain’ in the evidence pyramid. The preceding case report explicitly presents a classic indication for a meaningful case report even in this day and age of insistence on ‘higher levels of evidence’. This exceedingly rare condition was luckily identified and after thorough review treated by expert surgeons armed with skill set and expertise to handle even the rarest and most unusual of cases.

We all continue to gain by case reports in these settings, especially if they go through the extra effort to summarize the past publication history in the topic in a mini metanalysis-as was done in this case. Caution should, however, be exercised in the over application of greater inferences for larger patient populations based on such case reports.