Criteria for using imaging ultrasound during brain and spinal cord surgery.

Imaging ultrasonography was performed during 23 brain and five spinal cord operations with real-time B-mode instruments. Criteria for the utilization of ultrasound at neurosurgical procedures were identified in terms of assistance in the diagnosis or better definition of lesions. The diagnosis criteria were detection and exclusion. Because of the accuracy of preoperative imaging, usually little further help was provided by operative ultrasonography in detecting previously totally unknown abnormalities or excluding lesions found on positive studies. The definition criteria were localization, distinction of tissue features, and assessment of spatial relations. Operative ultrasonography was most useful when applied on the basis of these definition criteria. Operative ultrasonography was considered to be useful in 22 of 28 operations (79 per cent) in which it assisted in exposing, accessing, and extirpating disease.