Perspective/short review: Diagnosis and surgery for mostly dorsal thoracic spinal arachnoid webs with/ without Syrinxes and/or Spinal Arachnoid Cysts

Background: Predominantly Dorsal Thoracic Spinal Arachnoid Webs (DAW/SAW: 90%-100%), attributed to arachnoidal scarring obstructing cerebrospinal fluid (CSF) dynamics, typically cause dorsal cord compression. Their multiple etiologies include; trauma, idiopathic/post-surgical, inflammatory/infection, subarachnoid hemorrhage, and/or congenital defects. Methods: Patients with DAW/SAW are typically in their early/mid-fifties, and present with; back pain (i.e., 41.2%-88.9%), motor deficits (i.e. 59%-77.8%), sensory loss (i.e., numbness 65%-66.7%), and/or sphincter dysfunction (i.e., 33.3%). Results: MR and Myelo-CT studies for DAW/SAW classically demonstrate the positive scalpel sign (i.e., single or multilevel dorsally compressive “fluid” collections often containing multiple loculations/fenestrations usually accompanied by Syrinxes (i.e., 44 - 83%), and/or Spinal Arachnoid Cyst (SAC) formation. Conservative treatment is rarely effective. Alternatively, surgery consisting of laminectomy/decompression, resection/ lysis, marsupialization and/or fenestration of loculated collections including attendant SAC resections, and decompression/shunting of Syrinxes, results in postoperative improvement in up to 91% of patients. Conclusion: Patients with DAW/SAW typically present with MR/Myelo-CT studies that demonstrate the dorsal thoracic positive scalpel sign in conjunction with Syrinxes, and/or SAC. Surgery typically includes laminectomy/ decompression, lysis/resection of arachnoidal adhesions with marsupialization/fenestration, and/or shunting, to achieve up to a 91% incidence of postoperative neurological improvement.