Conventional versus Ultrasound Neuronavigation in the Surgery of Cerebral Metastases

Introduction The proportion of metastatic lesions in the neurosurgical practice is constantly rising in the last decade thanks to the aggressive treatment and prolonged survival of oncological patients. Although cerebral metastases are usually not considered surgical challenge, the variety of locations, sizes, consistence, and numbers of these tumors frequently require individualized approach to every case.

Objective To assess the application of ultrasound neuronavigation in metastatic cranial neurosurgery in comparison with conventional navigation based on preoperative images only.

Material and Methods In a series of 96 patients, navigated intraoperative ultrasound with or without preoperative images (Sonowand Invite, Sonowand) was used to locate metastatic lesions and to confirm total removal. Another 65 patients harboring cerebral metastases underwent surgery during the same period with the aim of conventional neuronavigation (Vector Vision 2, BrainLab). Tumor size and location, number of metastases, and preoperative condition of patients, measured according to the Karnofsky performance scale (KPS), were analyzed in both groups. Surgical results were assessed in respect to the extent of resection, postoperative complications, and local recurrence of the disease.

Results Gross-total resection was achieved in nearly all patients (97%) in both groups. Higher rates of major postoperative complications were observed in the ultrasound navigation group (14.6 vs. 10.8%). Mortality was also higher in the ultrasound group, although most of the deaths could be attributed to the patient's poor preoperative condition (average KPS 50). Local recurrence rates were higher in the conventional navigation group (7.69 vs. 5.21%, respectively). In few cases, operated using the Sonowand system, considerable brain shift was observed that would have hampered the surgery in case conventional navigation was used.

Conclusion No major differences were found in the surgical results when comparing ultrasound navigation to conventional navigation in the resection of cerebral metastases. Nevertheless in cases of deep-seated tumors, small metastases, or multiple lesions, the intraoperative ultrasound navigation gives the surgeon confidence and facilitates the surgery by elimination of the factors that would affect neuronavigation accuracy (brain shifting, patient to image coregistration, etc.).

Keywords cerebral metastases; neuronavigation; ultrasound navigation