Arachnoid web presenting with acute myelopathy after minor trauma and subtle imaging findings: illustrative case

BACKGROUND: Arachnoid web (AW) is a rare entity characterized by a thickened band of arachnoid membrane on the dorsal surface of the spinal cord, often producing compressive myelopathy. The diagnosis is sometimes challenging, as imaging findings may be subtle. OBSERVATIONS: The authors report the case of a 29-year-old man who developed paraparesis with bladder and rectal dysfunction following a minor traffic accident. Imaging showed no fractures or intramedullary signal changes, with only subtle spinal cord anterior deviation at T7-8. Surgical exploration revealed a thickened arachnoid band compressing and tethering the spinal cord. Resection of the AW restored cord pulsation, and motor function improved postoperatively. Histopathology confirmed arachnoid tissue with collagen fibers, consistent with AW. LESSONS: Even with subtle imaging findings, AW should be suspected in trauma-related myelopathy, and timely surgical intervention can provide recovery. https://thejns.org/doi/10.3171/CASE25734.