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Objective: Image-guidance systems are widely available for surgical planning and intraoperative navigation. Recently, three-dimensional volumetric image rendering technology that increasingly applies in navigation systems to assist neurosurgical planning, e.g., for cranial base approaches. However, there is no systematic clinical study available that focuses on the impact of this image-guidance technology on outcome parameters in suboccipital craniotomies., Methods: A total of 200 patients with pathologies located in the cerebellopontine angle were reviewed, 100 of whom underwent volumetric neuronavigation and 100 of whom underwent treatment without intraoperative image guidance. This retrospective study analyzed the impact of image guidance on complication rates (venous sinus injury, venous air embolism, postoperative morbidity caused by venous air embolism) and operation times for the lateral suboccipital craniotomies performed with the patient in the semi-sitting position., Result: This study demonstrated a 4% incidence of injury to the transverse-sigmoid sinus complex in the image-guided group compared with a 15% incidence in the non-image-guided group. Venous air embolisms were detected in 8% of the image-guided patients and in 19% of the non-image-guided patients. These differences in terms of complication rates were significant for both venous sinus injury and venous air embolism (P < 0.05). There was no difference in postoperative morbidity secondary to venous air embolism between both groups. The mean time for craniotomy was 21 minutes in the image-guided group and 39 minutes in non-image-guided group (P = 0.036)., Conclusion: Volumetric image guidance provides fast and reliable three-dimensional visualization of sinus anatomy in the posterior fossa, thereby significantly increasing speed and safety in lateral suboccipital approaches.

Objective: Being situated close to the transverse and sigmoid sinus, the asterion has traditionally been viewed as a landmark for surgical approaches to the posterior fossa. Cadaveric studies, however, have shown its variability in relation to underlying anatomic structures. We have used an image-guidance technology to determine the precise anatomic relationship between the asterion and the underlying transverse-sigmoid sinus transition (TST) complex in patients scheduled for posterior fossa surgery. The applicability of three-dimensional (3-D) volumetric image-rendering for presurgical anatomic identification and individualization of a surgical landmark was evaluated., Methods: One-millimeter computed tomographic slices were combined with venous computed tomographic angiography in 100 patients, allowing for 3-D volumetric image-rendering of the cranial bone and the dural vasculature at the same time. The spatial relationship between the asterion and the TST was recorded bilaterally by using opacity modulation of the bony surface. The location of both the asterion and the TST could be confirmed during surgery in all of these patients., Results: It was possible to accurately visualize the asterion and the sinuses in a single volumetrically rendered 3-D image in more than 90% of the patients. The variability in the anatomic position of the asterion as shown in cadaveric studies was confirmed, providing an individualized landmark for the patients. In this series, the asterion was located from 2 mm medial to 7 mm lateral and from 10 mm inferior to 17 mm superior to the TST, respectively., Conclusion: Volumetric image-rendering allows for precise in vivo measurements of anatomic distances in 3-D space. It is also a valuable tool for assessing the validity of traditional surgical landmarks and individualizing them for surgical planning.

Objective: The most important treatment options for meningiomas are microsurgery, radiotherapy, and gamma knife radiosurgery (GKRS). The efficacy of GKRS in terms of local tumor control and tumor volume (TV) reduction can best be determined by accurate analysis of changes in tumor size in pre- and post-GKRS images. In this prospective study, we set the focus on evaluating TV changes and treatment outcome of meningiomas using a quantitative volumetric follow-up protocol after GKRS., Methods: Consecutive patients with World Health Organization Grade I and II meningiomas were included in this study. Most patients underwent a microsurgical TV reduction before being treated with GKRS. Follow-up examinations were performed according to a standardized protocol and included magnetic resonance imaging and quantitative volumetric tumor analyses as well as thorough neurological examinations., Results: Complete follow-up data was available for 211 patients (243 tumors) with a mean age of 57.9 years. TVs ranging from 0.1 to 48.3 cm3 were treated with GKRS using prescription doses ranging from 10 to 22 Gy. The achieved overall tumor control rate determined with quantitative TV analyses after GKRS was 93.4%; a mean TV reduction of 42.1% was achieved in 74.5% of all treated patients., Conclusion: Results of this study show that a quantitative volumetric follow-up study of meningiomas is a useful method to demonstrate the efficacy of GKRS for meningiomas. Statistically significant TV reductions with a low rate of side effects can be achieved with GKRS.

Objective: Most of the endoscopes used for endonasal transsphenoidal surgery use 4-mm diameter lenses. The applicability of a newly developed neuroendoscope with a lens diameter of only 2 mm was tested in endonasal transsphenoidal pituitary surgery., Methods: The newly developed rigid-rod neuroendoscope with a 2-mm lens and an endoscope with a 4-mm lens were coupled with a navigation system and used for this comparative study. Comparison between the views obtained with these two devices was performed in a model and in formalin-fixed cadaver heads. A pure endonasal approach was used to reach and explore the sellar and parasellar regions. The navigation system was used to locate the same position in both lenses for image comparison., Results: The sellar and parasellar regions could be reached and explored using the new endoscope with the 2-mm lens and an oval-shaped irrigation and suction channel. The visual field appeared to be reduced compared with that of the 4-mm lens. However, this reduction was compensated by greater mobility and easier introduction and maneuvering of the instruments at the sellar level. Reduced image size and brightness were also found using the 2-mm lens compared with the 4-mm lens. These differences could be overcome by increasing the amount of light and enlarging the image but with subsequent reduction in image resolution., Conclusion: The small diameter of this neuroendoscope resulted in good maneuverability and maintained a fine quality of vision. Children and patients with small nostrils are good candidates for the use of such a device.

Because of electrical and thermal spread to healthy nervous tissue, the application of electrosurgical tools in neurosurgery has specific limitations. This is true for both bipolar and monopolar devices. These limitations are not inherent to an instrument in which action is based on electromagnetic interaction with human tissue. We evaluated the indications and the clinical applicability of a new radiofrequency electrosurgical unit that works on this biophysical principle. The system was found to be a useful addition for the resection of morphologically tougher tissue with keyhole approaches in which the ultrasound aspirator cannot easily be applied.