Intraoperative ultrasound imaging features in high-grade metastatic spinal cord compression treated with separation surgery.

Objective: The aim of this study was to identify and characterize intraoperative ultrasound (iUS) findings during separation surgery for treatment of high-grade malignant epidural spinal cord compression that correlate with adequate decompression and prognostication of functional status.

Methods: A retrospective review identified 24 iUS images and videos obtained in 8 patients (age range 48-68 years) who underwent separation surgery for high-grade epidural compression. The following iUS parameters were assessed: the ventral and dorsal distances between the dura mater and spinal cord (i.e., subarachnoid compartments), the distance between the spinal cord and residual tumor, anteroposterior and lateral diameters of the spinal cord, presence of spinal cord deformation, presence of hyperechoic signal within the spinal cord, and measurement of the angular deformation of the spinal cord on the sagittal plane. Additionally, surgical data, such as perioperative neurological status, estimated blood loss, neurophysiological changes, and procedure type, were documented.

Results: The minimum distance between the residual tumor and the spinal cord was 5 mm (mean 6.9, range 5-10 mm). The mean spinal cord sagittal deformation angle after decompression was 172°. The mean widths of the dorsal and ventral subarachnoid compartments were 1.5 mm and 3.3 mm, respectively. The mean anteroposterior and transverse diameters of the spinal cord were 5.6 mm and 9.2 mm, respectively. All patients with hyperechoic punctate areas in the white matter of the spinal cord experienced new or persistent neurological deficits, which improved during hospitalization.

Conclusions: Intraoperative US is a practical and effective tool for assessing the extent of separation achieved during surgery for spinal metastases. The ultrasonographic features described in this study are easily reproducible and could be used to develop a standardized approach for evaluating spinal cord decompression in cases of separation surgery. Future longitudinal studies are needed to validate if intramedullary hyperechoic signal has prognostic value for neurological recovery and if the distance from the spinal cord to residual disease serves as a predictor of local control.