Intraoperative sonography of intra- and extramedullary tumors.

Intraoperative ultrasound (IOUS) was used in planning the operative resection of intradural spinal tumors, to define its diagnostic potential and limitations. Since 1997, 78 patients diagnosed with an ependymoma (n = 24), astrocytoma (n = 7), hemangioblastoma (n = 7), neurinoma (n = 15), meningioma (n = 17) and filum terminale ependymoma (n = 8) were examined using intraoperative transdural sonography. Intramedullary tumors turned out to show a heterogeneous image with occasional cystic alterations and an indistinct demarcation to the myelon of comparable echogenicity. Intramedullary tumors are easily distinguishable from their extramedullary counterparts, which display a homogeneous signal intensity and sharp demarcation on IOUS. In conclusion, IOUS allows a reliable diagnosis of intraspinal tumors, allowing the distinction between intra- and extramedullary tumors through their respective signal characteristics. Using IOUS, the extension of the neurosurgical approach can be adopted to the true extent of the tumor; thus, avoiding further bone work while the dura is already opened and the frequently edematous spinal cord protrudes through the opening. Our experiences have shown that IOUS may reduce the procedure-related morbidity and should, therefore, be used as a standard intraoperative tool in these high-risk surgical entities. (E-mail: ).