An advanced navigation protocol for endoscopic transsphenoidal surgery.

OBJECTIVE: To report our clinical experience with an advanced navigation protocol that provides seamless integration into the operating workflow of endoscopic transsphenoidal surgery. PATIENTS AND METHODS: From 32 consecutive cases of endoscopic transsphenoidal surgery, an optimal setup of continuous electromagnetic instrument navigation was created. Additionally, our standard multimodality image navigation of T1-weighted magnetic resonance (MR) images for soft tissue, MR angiogram for vascular structures, and computed tomography (CT) for solid bone was advanced by the addition of a CT surface rendering for fine paranasal sinus structures. The anatomic structures visualized and their clinical impacts were compared between standard and advanced visualization protocol. Bone-windowed CT images served as reference. The accuracy of the navigation setup was assessed by intraoperative landmark tests. Potential tissue shift was calculated by comparing pre- and postoperative MR angiograms of 20 macroadenomas. RESULTS: After a learning curve of 2 cases (1 ferromagnetic interference and 1 dislocation of the patient reference tracker), the advanced navigation protocol was feasible in 30 cases. Advanced multimodality imaging was able to visualize significantly finer paranasal sinus structures than multimodality image navigation without CT surface rendering, equal to bone-windowed CT images (P < 0.001, McNemar test). This was found helpful for orientation in cases of complex sphenoid sinus anatomy. The accuracy of the advanced navigation setup corresponded to standard optic navigation with skull fixation. A tissue shift of median 2 mm (range 0-9 mm) was observed in the posterior genu of the internal carotid arteries after tumor resection. CONCLUSIONS: The advanced navigation protocol permits continuous suction-tracked navigation guidance during endoscopic transsphenoidal surgery and optimal visualization of solid bone, fine paranasal sinus structures, soft-tissue and vascular structures. This may add to the safety of the procedure especially in cases of anatomical variations and in cases of recurrent adenomas with distorted anatomy.

Microsurgery and radiosurgery for brainstem cavernomas: effective and complementary treatment options.

OBJECTIVE: To evaluate treatment options for brainstem cavernous malformations (BSCMs) using the results from a center with long-standing experience in microsurgical resection and Gamma Knife radiosurgery (GKRS) treatment of BSCMs. METHODS: Study participants were 67 symptomatic patients with BSCMs who were treated either microsurgically (n = 29) or radiosurgically (n = 38). Patients were followed for a minimum of 2 years (median, 7.7 years). A recent follow-up was performed. RESULTS: Patients receiving surgical treatment had mainly large, superficially seated lesions and experienced preoperative hemorrhages more often and presented with higher preoperative modified Rankin Scale scores. Patients receiving GKRS harbored smaller, deep-seated lesions, reflecting a selection bias. In both treatment groups, patients presented with significantly better modified Rankin Scale scores at follow-up than before intervention. Overall annual preoperative hemorrhage rates were 3.2% in microsurgery patients and 2.3% in radiosurgery patients. In the preoperative observation period, the rehemorrhage rate was 25.1% for microsurgery patients and 7.2% for radiosurgery patients. Hemorrhage rate after GKRS decreased significantly to 0.6% after 2 years. The postoperative hemorrhage rate was 8.8% but only for microsurgery patients with residual lesions. Advancements in microsurgical techniques improved surgical outcomes, resulting in a high total excision rate in the modern era. CONCLUSIONS: In the treatment of BSCM, patient selection and timing of surgery are crucial. If applied in a multidisciplinary neurosurgical center, microsurgery and radiosurgery are complementary treatment options that both result in reduced bleeding rates and improvement of clinical outcome.

Advanced cranial navigation.

BACKGROUND: Cranial surgical navigation is most commonly performed by registration with fiducial markers, optic tracking, and intermittent pointer-based application. OBJECTIVE: To assess the accuracy and applicability of an advanced cranial navigation setup. METHODS: Continuous electromagnetic instrument navigation was used in 136 neurosurgical cases with a standard navigation system. A phantom head in an intraoperative magnetic resonance imaging environment was used to compare the accuracy of the advanced and standard navigation setups. RESULTS: A navigated suction device was used in 71 cases of intracranial tumor surgery and 46 cases of endoscopic transsphenoidal surgery. The ventriculoscope was navigated in 6 cases and the stereotactic biopsy needle in 4 cases. Electromagnetic tracking was used for catheter placement in 9 cases. The learning curve comprised 6 of the 136 cases during the first month of application. No significant difference was observed at the intracranial target points between the standard navigation setup using optic tracking, fiducial marker registration, and pointer and the advanced navigation setup with electromagnetic tracking, surface-based registration, and navigation of a field-detecting stylet in a standard metal suction tube when performed outside the 5-G line of the 3.0-T intraoperative magnetic resonance imaging. CONCLUSION: Continuous instrument navigation is the prerequisite for seamless integration of navigation systems into the neurosurgical operating workflow. Our data confirm that the application of preoperative imaging, surface-merge registration, and continuous electromagnetic tip-tracked instrument navigation may provide such integration without a significant reduction in accuracy compared with standard navigation.

Brain tumor surgery with 3-dimensional surface navigation.

BACKGROUND: Precise lesion localization is necessary for neurosurgical procedures not only during the operative approach, but also during the preoperative planning phase. OBJECTIVE: To evaluate the advantages of 3-dimensional (3-D) brain surface visualization over conventional 2-dimensional (2-D) magnetic resonance images for surgical planning and intraoperative guidance in brain tumor surgery. METHODS: Preoperative 3-D brain surface visualization was performed with neurosurgical planning software in 77 cases (58 gliomas, 7 cavernomas, 6 meningiomas, and 6 metastasis). Direct intraoperative navigation on the 3-D brain surface was additionally performed in the last 20 cases with a neurosurgical navigation system. For brain surface reconstruction, patient-specific anatomy was obtained from MR imaging and brain volume was extracted with skull stripping or watershed algorithms, respectively. Three-dimensional visualization was performed by direct volume rendering in both systems. To assess the value of 3-D brain surface visualization for topographic lesion localization, a multiple-choice test was developed. To assess accuracy and reliability of 3-D brain surface visualization for intraoperative orientation, we topographically correlated superficial vessels and gyral anatomy on 3-D brain models with intraoperative images. RESULTS: The rate of correct lesion localization with 3-D was significantly higher (P = .001, χ), while being significantly less time consuming (P < .001, χ) compared with 2-D images. Intraoperatively, visual correlation was found between the 3-D images, superficial vessels, and gyral anatomy. CONCLUSION: The proposed method of 3-D brain surface visualization is fast, clinically reliable for preoperative anatomic lesion localization and patient-specific planning, and, together with navigation, improves intraoperative orientation in brain tumor surgery and is relatively independent of brain shift.