Intraoperative Ultrasound in the Management of Rare Lesions Involving the Intradural Extramedullary Spinal Compartment: A Quick, but Effective Helping Hand to Define the Optimal Surgical Strategy.

Intraoperative ultrasound (IOUS) is an increasingly adopted adjunctive intraoperative visualization method in spinal tumor surgery, offering real-time imaging that improves lesion localization, exposure planning, and resection control. This paper focuses on IOUS findings in rare intradural entities (neuroenteric/respiratory cysts, chronic spinal subdural hematoma, tethered cord/scarring, intradural extramedullary hemangioblastomas, and arachnoid cysts) where evidence remains limited. Across these lesions, IOUS typically depicts cysts as anechoic or hypoechoic cavities with definable walls and occasional septations; CSSDH is also delimited by hypoechoic subdural collections bounded by echogenic membranes; hemangioblastomas, as well as circumscribed, homogeneous nodules often with cystic components; and arachnoid webs/cysts with their boundaries and subtle subarachnoid communications. Doppler and micro-Doppler can delineate feeding and draining vessels in highly vascular tumors, while shear wave elastography provides quantitative stiffness changes that support effective detethering. IOUS complements preoperative MRI, shortens exposure, helps tailor bone and dural openings, and allows immediate assessment of residual disease. Taken together, current data and our experience support IOUS as a safe, cost-effective, and versatile intraoperative tool for rare intradural spinal pathology, while underscoring the need for prospective studies to refine sonographic criteria and validate outcome benefits.