Intraoperative ultrasound in spinal tumor surgery

Purpose: Intraoperative ultrasound (ioUS) has become increasingly widespread in brain tumor surgery but it is not yet a standard procedure in spinal surgery. We analyzed intraoperative ultrasonographic findings of different spinal tumors and their influence on the surgical strategy. Methods: We evaluated patients who underwent surgery for spinal tumor (extradural, intradural extramedullary, intradural intramedullary) removal, with ultrasound (US) guidance. Intraoperative standard B-mode images were acquired using a 3-11 MHz linear US probe. Before tumor removal the lesion was identified on the two axes and measured and defined as hyperechoic, isoechoic or hypoechoic. Other characteristics of the lesions were considered: the presence of calcifications, cystic/necrotic areas, diffuse or circumscribed appearance, and the relationships with the surrounding anatomical structures. Results: In all 34 cases it was possible to visualize the lesion, as well as the surrounding neural structures (like dura mater, dentate ligament, arachnoid membranes) and vascular structures. In 9 out of 34 cases, ioUS showed that the surgical approach was not wide enough: therefore it was necessary to enlarge the bony approach before dural opening. In 8 intramedullary cases, ioUS was used to correctly tailor the myelotomy. Conclusions: We present our ioUS series findings along with some pictorial essays of different spinal tumors treated at our institution. IoUS is a valuable tool to detect spinal lesions, evaluate the surgical approach and plan the surgical strategy considering the position and relationships of the lesion with bony, neural and vascular structures.