Thoracic dorsal arachnoid web with rapid onset of symptoms: A report of two cases and brief review of the literature

Abstract

Background: Thoracic arachnoid webs are a rare entity and can be challenging to diagnose with sometimes subtle radiographic findings. Arachnoid webs can cause severe cord compression with associated syrinx and resulting myelopathy, weakness, sensory loss, and bowel/bladder dysfunction. There have been a little over 60 cases total reported in the literature with only one systematic review. The cases presented here have unique features including rapid onset of symptoms, symptomatic syrinx extending into the cervical spine, and intraoperative syrinx drainage, all of which are quite rare in the current published literature for arachnoid webs.

Case description: Here, we present two patients, a 73-year-old man and 58-year-old man presenting with different symptoms and timing of symptom progression but both with "scalpel sign" and associated syrinx present on their MRIs. Each patient underwent a laminectomy with resection of arachnoid web with complete resolution of symptoms in the first case and significant improvement in the second case. Postoperative imaging in both cases showed almost complete resolution of the syrinx.

Conclusion: Early clinical evaluation and workup followed by early surgical treatment can lead to dramatic improvement in outcomes after surgery. For patients that are symptomatic from an associated syrinx, a midline myelotomy to facilitate drainage can be considered to be done concomitantly with the arachnoid web resection.

Keywords: Arachnoid web; Dorsal; Review; Spine; Surgery; Thoracic.

Figure 1:

Preoperative (a, b, d, e) and postoperative (c, f) MR images obtained in case 1. Sagittal images (a, d) show syrinx extending up to C7-T1 with “scalpel” configuration at T3. Axial images at the level of C7-T1 (b) show syrinx and at the level of T3 (e) show severe spinal cord compression. Postoperative sagittal images (c and f) show complete resolution of syrinx and spinal cord compression.

Figure 2:

Intraoperative photographs obtained in case 1. (a) The thickened white arachnoid web is apparent at approximately T3 with venous congestion in the spinal cord noted rostrally. (b) Microdissection of the band from the caudal side. (c) Partial resection of thickened arachnoid web with remaining attachment on the right side (top). (d) Complete resection of arachnoid web with resolution of spinal cord venous congestion. C: Caudal, R: Rostral.

Figure 3:

Preoperative MR images obtained in case 2. Sagittal and axial images (a and b) show large syrinx extending up through the cervical cord and primarily on the left side above C7. Thoracic sagittal (c) and axial images at the level of T6 (d) show large 9.4 × 7.1 mm syrinx at its maximum diameter and at the level of T7-T8 (e) show spinal cord compression due to the arachnoid web.

Figure 4:

Intraoperative photographs obtained in case 2. (a) The cloudy thickened arachnoid web is seen caudally. (b) After slightly extending durotomy caudally, the full extent of arachnoid web is appreciated with spinal cord venous congestion inferiorly. (c) Complete resection of arachnoid bed with improvement of venous congestion. (d) Small midline myelotomy (arrow) to allow for drainage of large syrinx. C: Caudal, R: Rostral.

Figure 5:

Postoperative MR images (a-d) and X-rays (e) obtained in case 2. Cervical sagittal (a) and axial images (b) show complete resolution of cervical syrinx with residual severe C5-C6 stenosis. Thoracic images (c and d) show near-complete resolution of syrinx and resolution of spinal cord compression. (e) Interval anterior cervical discectomy and fusion at C5-C6.