The role of intraoperative ultrasound in surgery of occult spinal dysraphisms

Background: Occult spinal dysraphism (OSD) leading to tethered cord syndrome can determine neurological deficits during growth. Despite the complexity of some untethering procedures, especially in complex lipomas, partial surgery may lead to re-tethering and delayed deterioration. We aimed to evaluate the role of intraoperative ultrasounds (IOUS) in a surgical series of children harboring OSD, to investigate the benefits of intraoperative ultrasonographic guidance during the different subgroups of dysraphic lesions. Methods: All consecutive children affected by OSD who underwent surgery from 2019 to 2021 were evaluated. When possible, the Pang's classification was used. Intraoperative standard B-mode images were acquired using a dedicated linear or microconvex probe. The lesions were identified and measured, and defined as hyperechoic, isoechoic or hypoechoic. We also considered the presence of calcifications, the relationships with the surrounding anatomical structures, mainly the conus and caudal roots, the presence of syringomyelia, the level of conus descendance. Results: Eleven children with spinal dysraphism who underwent surgical repair were examined, comprising a wide spectrum of OSD, from filum terminalis lipoma, limited dorsal myeloschisis, diastematomyelia, up to transitional, dorsal, and chaotic lipomas. Visualization of the cystic compartments, identification of the neural structures, and identification and localization of the associated lesions were all reliably achieved in all cases. Intraoperative ultrasonographic guidance could determine the type of lesion and the associated lipomas, ectopic tissues, dermoid and epidermoid cysts, and doubling of the spinal cord, and locate diastematomyelic spurs, bands, and adhesions. Components filled with cerebrospinal fluid appeared as anechoic areas and lipomas as hyperechoic. The exact characteristics of each subtype of OSD and the role of IOUS per every single case will be detailed. Conclusion: Intraoperative ultrasonographic guidance could help to correlate the complex anatomy identified on preoperative neuroimaging to the surgical site during the operation and the neurophysiological monitoring results.