Ultrasound-guided surgery of deep seated brain lesions.

OBJECTIVE Computer aided navigation systems have been introduced to optimize the neurosurgical strategies minimizing the damage to the healthy brain tissue. As the loss of cerebrospinal fluid and surgical manipulation alter the position of the lesion in the external reference system, there is a risk of being misguided to deep seated brain tumors. In this context we present our experiences with intraoperative ultrasound which represents a real-time navigation system. PATIENTS AND METHODS 45 patients with subcortical intracerebral lesions were operated on with the support of ultrasound imaging. Tumor depth from the surface measured 5 (superficial) to 68 mm. The minimum size of a cavernoma was 8 mm. Histopathological diagnoses included 17 cavernomas, 12 metastases and 16 gliomas. Ultrasound localization was achieved by two perpendicular projections and the surgical trajectory of the lesion secured by catheter placement. RESULTS Intraoperative ultrasound allowed an easy identification of all brain lesions. Additionally, a reliable localization of the tumor margins, including gliomas and metastases, was reached in 23 of 28 (82%) cases. The remaining 17 cavernomas were located all by intraoperative ultrasound, even the deep seated brain lesions of less than 10 mm in diameter could be easily detected. The real-time mode enabled a control of the surgical procedure. Technical problems arose from irregular and vaulted cortex surface, head positioning and surgical manipulation causing air artefacts with distal reduction of the signal intensity. CONCLUSION Intraoperative ultrasound is a reliable intraoperative guidance tool in the localization of deep seated brain tumors because it operates in real-time, thus increasing the safety of the surgical procedure and of the tumor resection.