Surgical Management of Thoracic Dorsal Arachnoid Webs: A 10-Year Single-Institution Experience

Objective: Thoracic dorsal arachnoid webs are intradural membranes that may cause obstruction of cerebrospinal fluid flow and spinal cord compression. Although well recognized, they are rare and there is a paucity of long-term data on their natural history and prognosis. We reviewed radiographic features, surgical indications, and pathologic specimens of patients diagnosed with focal thoracic dorsal arachnoid webs. Methods: A radiology database and surgical case logs were queried for thoracic arachnoid webs at a single hospital system for a 10-year period. A retrospective chart review was performed on identified cases. Results: We identified 127 patients with dorsal thoracic arachnoid webs. Arachnoid webs were radiographically classified into 3 morphologic types: type 1 (54%) causing spinal cord deformity only, type 2 (32%) producing cord deformity with myelomalacia, and type 3 (14%) with cord deformity, myelomalacia, and syringomyelia. These arachnoid webs were commonly centered at the upper thoracic T4 segmental level. Forty-one cases (32%) required surgery, generally for thoracic myelopathy with gait instability (46%) and lower extremity numbness and pain (39%). In patients who underwent surgery, 79% experienced symptomatic improvement and 21% remained stable, after an average of 21 months follow-up evaluation. Surgical pathology revealed fibrous connective tissue (100%) with calcifications (26%) or inflammation (7%). Conclusions: Most patients in a large series of patients with dorsal arachnoid webs did not undergo surgical intervention, but those with myelomalacia and syrinx experienced radiographic and clinical deterioration without surgery. Surgery to treat symptomatic arachnoid webs results in significant clinical improvement with low surgical morbidity.