Delta Cord as a Radiological Localization Sign of Postoperative Adhesive Arachnoiditis: A Case Report and Literature Review

Postoperative adhesive arachnoiditis is an inflammatory response of the spinal leptomeninges that occurs after surgery and results in scar formation in the avascular nature of the arachnoid layer. Clinical manifestations of postoperative adhesive arachnoiditis include pain, sensory deficits, motor dysfunction, reflex abnormalities, and bladder or bowel impairment. In magnetic resonance imaging scans, signs of postoperative adhesive arachnoiditis can vary; however, some indicators can assist surgeons in locating the lesion accurately and, thus, in planning effective surgical interventions. This paper reports the case of a 37-year-old man with postoperative adhesive arachnoiditis after two surgeries for Chiari I malformation. This case illustrates the progressive development of the "delta cord sign", which refers to the formation of a thick arachnoid band causing the spinal cord to adopt a triangular shape in the axial view. This phenomenon is accompanied by the sequential occurrence of syringomyelia. During intraoperative examination, we identified the presence of the delta cord sign, which had been formed by an arachnoid scar that tethered the dorsal spinal cord to the dura. This discovery enabled us to precisely pinpoint the location of the arachnoid scar and thus provided us with guidance that enabled us to avoid unnecessary exploration of unaffected structures during the procedure. Other localization signs were also reviewed.