Arachnoid web of the spine: a systematic literature review

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OBJECTIVE

An arachnoid web of the spine (AWS) is a rare and oftentimes challenging lesion to diagnose, given its subtle radiographic findings. However, when left untreated, this lesion can have devastating effects on a patient’s neurological function. To date, only limited case reports and series have been published on this topic. In this study, the authors sought to better describe this lesion, performing a systematic literature review and including 2 cases from their institution’s experience.

METHODS

A systematic literature search was performed in September 2018 that queried Ovid MEDLINE (1946–2018), PubMed (1946–2018), Wiley Cochrane Library: Central Register of Controlled Trials (1898–2018), and Thompson Reuters Web of Science: Citation Index (1900–2018), per PRISMA guidelines. Inclusion criteria specified all studies and case reports of patients with an AWS in which any relevant surgery types were considered and applied. Studies on arachnoid cysts and nonhuman populations, and those that did not report patient treatments or outcomes were excluded from the focus review.

RESULTS

A total of 19 records and 2 patients treated by the senior authors were included in the systematic review, providing a total of 43 patients with AWS. The mean age was 52 years (range 28–77 years), and the majority of patients were male (72%, 31/43). A syrinx was present in 67% (29/43) of the cases. All AWSs were located in the thoracic spine, and all but 2 (95%) were located dorsally (1 ventrally and 1 circumferentially). Weakness was the most frequently reported symptom (67%, 29/43), followed by numbness and/or sensory loss (65%, 28/43). Symptoms predominated in the lower extremities (81%, 35/43). It was found that nearly half (47%, 20/43) of patients had been experiencing symptoms for 1 year or longer before surgical intervention was performed, and 35% (15/43) of reports stated that symptoms were progressive in nature. The most commonly used surgical technique was a laminectomy with intradural excision of the arachnoid web (86%, 36/42). Following surgery, 91% (39/43) of patients had reported improvement in their neurological symptoms. The mean follow-up was 9.2 months (range 0–51 months).

CONCLUSIONS

AWS of the spine can be a debilitating disease of the spine with no more than an indentation of the spinal cord found on advanced imaging studies. The authors found this lesion to be reported in twice as many males than females, to be associated with a syrinx more than two-thirds of the time, and to only have been reported in the thoracic spine; over 90% of patients experienced improvement in their neurological function following surgery.

ABBREVIATIONS AWS = arachnoid web of the spine.

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Article Information

Correspondence Ali A. Baaj: Weill Cornell Medicine Center for Comprehensive Spine Care, New York, NY. alb9140@med.cornell.edu.

INCLUDE WHEN CITING Published online April 19, 2019; DOI: 10.3171/2019.1.SPINE181371.

Disclosures Dr. Härtl: consultant for DePuy-Synthes, Ulrich, and Brainlab; and royalties from Zimmer Biomet. Dr. Baaj: consultant for DePuy and Stryker.

© AANS, except where prohibited by US copyright law.

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Figures

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    Flow diagram for selection of articles for AWS systemic review. Figure is available in color online only.

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    Preoperative MR images and CT myelograms obtained in 2 patients with AWS. A–D: Case 1. E–H: Case 2. Sagittal MR images (A and E) and CT myelograms (C and G) demonstrating the “scalpel sign” at the T4 and T5 levels, characterized by an indentation in the dorsal aspect of the spinal cord without an obvious intradural mass. Axial MR images (B and F) and CT myelograms (D and H) demonstrating ventral displacement of the cord due to the arachnoid web, again without an appreciable dorsal mass. The dorsal collection is isointense with CSF. Figure is available in color online only.

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    Intraoperative photographs obtained in case 1 (A–C) and case 2 (D–F). A: A Woodson dissector and 11-blade scalpel are used for midline durotomy. B: The arachnoid web is apparent at the caudal aspect of the durotomy, appearing as a cloudy web of thickened arachnoid. The normal spinal cord is visualized rostral to the web. C: Microsurgical dissection of the arachnoid web using Rhoton instruments to gently lift and separate the web from the spinal cord and microscissors for release and excision. D: Planned midline durotomy. Note that there are no extradural indications of the location of the arachnoid web. E: A similar cloudy mass of thickened arachnoid representing the arachnoid web. F: Microsurgical intradural exploration and dissection using 5-F Fukushima suction and a bayonet to separate the arachnoid web from the underlying spinal cord. C = caudal; D = dorsal; R = rostral; V = ventral. Figure is available in color online only.

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    Case 1. Postoperative images obtained at the 1-month follow-up. A: Sagittal MR image slice with the thoracic levels of T3, T4, and T5 represented at the corresponding vertebral levels. The dotted line at the T4 level is where the arachnoid web was originally located; complete resolution of scalpel sign is demonstrated, with no signs of recurrence. B: Corresponding axial image obtained at the location of the T4 dotted line, also showing no indentation of the spinal cord. Figure is available in color online only.

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