Enhanced torque-based impedance control to assist brain targeting during open-skull neurosurgery: a feasibility study.

BACKGROUND: Cooperatively-controlled robotic assistance could provide increased positional accuracy and stable and safe tissue targeting tasks during open-skull neurosurgical procedures, which are currently performed free-hand. METHODS: Two enhanced torque-based impedance control approaches, i.e. a variable damping criterion and a force-feedback enhancement control, were proposed in combination with an image-based navigation system. Control systems were evaluated on brain-mimicking phantoms by 13 naive users and 8 neurosurgeons (4 novices and 4 experts). RESULTS: In addition to a 60% reduction of user effort, the combination of the proposed strategies showed comparable performances with respect to state-of-the-art admittance controller, thus satisfying the clinical accuracy requirements (below 1 mm), reducing the hand tremor (by a factor of 10) and the tissue's indentation overshooting (by 80%). CONCLUSION: Although the perceived reliability of the system should be improved, the proposed control was suitable to assist targeting procedures, such as brain cortex stimulation, allowing for accurate, stable and safe contact with soft tissues. Copyright © 2015 John Wiley & Sons, Ltd.

A method for the assessment of time-varying brain shift during navigated epilepsy surgery.

PURPOSE: Image guidance is widely used in neurosurgery. Tracking systems (neuronavigators) allow registering the preoperative image space to the surgical space. The localization accuracy is influenced by technical and clinical factors, such as brain shift. This paper aims at providing quantitative measure of the time-varying brain shift during open epilepsy surgery, and at measuring the pattern of brain deformation with respect to three potentially meaningful parameters: craniotomy area, craniotomy orientation and gravity vector direction in the images reference frame. METHODS: We integrated an image-guided surgery system with 3D Slicer, an open-source package freely available in the Internet. We identified the preoperative position of several cortical features in the image space of 12 patients, inspecting both the multiplanar and the 3D reconstructions. We subsequently repeatedly tracked their position in the surgical space. Therefore, we measured the cortical shift, following its time-related changes and estimating its correlation with gravity and craniotomy normal directions. RESULTS: The mean of the median brain shift amount is 9.64 mm ([Formula: see text] mm). The brain shift amount resulted not correlated with respect to the gravity direction, the craniotomy normal, the angle between the gravity and the craniotomy normal and the craniotomy area. CONCLUSIONS: Our method, which relies on cortex surface 3D measurements, gave results, which are consistent with literature. Our measurements are useful for the neurosurgeon, since they provide a continuous monitoring of the intra-operative sinking or bulking of the brain, giving an estimate of the preoperative images validity versus time.

Surgical treatment of cavernoma-related epilepsy.

Cerebral cavernous malformations (CCMs) are frequently associated with a seizure disorder, and the risk of developing drug-resistant epilepsy (DRE) is substantial, especially for temporal lobe lesions. This article includes a review of the literature on the surgical treatment of epilepsy associated to CCMs in the magnetic resonance imaging (MRI) era, as well as an analysis of the Authors' experience in this field. It is concluded that microsurgery is a valuable treatment option, which may provide excellent results on seizures, with 76% of patients on average being seizure-free after surgery. Nevertheless, the optimal surgical strategy to achieve seizure control has not been clearly identified, and several attitudes have been reported in the literature. The choice of lesionectomy, associated or not to removal of surrounding hemosiderin, versus resections extended to epileptogenic cortex depends on the accurate scrutiny of several factors, which should be investigated through an adequate epileptological presurgical workup. This should include an epilepsy-oriented brain MRI study, integrated by an appropriate neurophysiological and clinical assessment, and if needed by other functional evaluations. Besides representing the optimal option in CCM-related DRE cases, microsurgery should be considered also at seizure presentation or in cases with recent-onset sporadic seizures, to protect the patient from both the possible development of drug resistance and the risk of haemorrhage.

Multi-trajectories automatic planner for StereoElectroEncephaloGraphy (SEEG).

PURPOSE: StereoElectroEncephaloGraphy (SEEG) is done to identify the epileptogenic zone of the brain using several multi-lead electrodes whose positions in the brain are pre-operatively defined. Intracranial hemorrhages due to disruption of blood vessels can cause major complications of this procedure ([Formula: see text]1%). In order to increase the intervention safety, we developed and tested planning tools to assist neurosurgeons in choosing the best trajectory configuration. METHODS: An automated planning method was developed that maximizes the distance of the electrode from the vessels and avoids the sulci as entry points. The angle of the guiding screws is optimized to reduce positioning error. The planner was quantitatively and qualitatively compared with manually computed trajectories on 26 electrodes planned for three patients undergoing SEEG by four neurosurgeons. Quantitative comparison was performed computing for each trajectory using (a) the Euclidean distance from the closest vessel and (b) the incidence angle. RESULTS: Quantitative evaluation shows that automatic planned trajectories are safer in terms of distance from the closest vessel with respect to manually planned trajectories. Qualitative evaluation performed by four neurosurgeons showed that the automatically computed trajectories would have been preferred to manually computed ones in 30% of the cases and were judged good or acceptable in about 86% of the cases. A significant reduction in time required for planning was observed with the automated system (approximately 1/10). CONCLUSION: The automatic SEEG electrode planner satisfied the essential clinical requirements, by providing safe trajectories in an efficient timeframe.