Stereotactic accuracy and frame mounting: A phantom study.

BACKGROUND: Frame mounting is considered one of the most critical steps in stereotactic neurosurgery. In routine clinical practice, the aim is to mount the frame as symmetrical as possible, parallel to Reid's line. However, sometimes, the frame is mounted asymmetrically often due to patient-related reasons. METHODS: In this study, we addressed the question whether an asymmetrically mounted frame influences the accuracy of stereotactic electrode implantation. A Citrullus lanatus was used for this study. After a magnetic resonance imaging scan, symmetric and asymmetric mounting of the frame, which could occur in clinical scenarios, was performed with computed tomography (CT). Three different stereotactic software packages were used to analyze the results. In addition, manual calculations were performed by two different observers. RESULTS: Our results show that an asymmetrically mounted frame (deviated, tilted, or rotated) does not affect the accuracy in the mediolateral axis (X-coordinate) or the anteroposterior axis (Y-coordinate). However, it can lead to a clinically relevant error in the superoinferior axis (Z-coordinate). This error was largest with manual calculations. CONCLUSION: These results suggest that asymmetrical frame mounting can lead to stereotactic inaccuracy in the superoinferior axis (Z coordinate).

Microelectrode Recording for Deep Brain Stimulation of the Subthalamic Nucleus in Patients with Advanced Parkinson's Disease: Advantage or Loss of Time?

AIM: To investigate the effect of using microelectrode recording (MER) on the length of time required to carry out a deep brain stimulation (DBS) procedure of the subthalamic nucleus in patients with Parkinson's disease (PD). MATERIAL AND METHODS: The time required to include MER in the DBS operation was calculated for the first and second sides in 24 patients with PD. The number of microelectrodes used on each trajectory for the first and second sides, and the percentage of permanent electrodes implanted on each trajectory for the first and second sides, were quantified. RESULTS: The average times taken to use MER were 23.4 ± 6.2 minutes, 17.4 ± 6.5 minutes, and 41.2 ± 6.3 minutes for the first side, second side and total procedure, respectively. In 75% of patients, the permanent electrode was implanted at the planned target site for the first side, and in 61% of patients for the second side. CONCLUSION: MER extends the time required to carry out the DBS procedure. However, during surgery, it provides real-time information on the electrodes' neurophysiological locations and helps the surgical team choose an alternative target if the planned target does not produce satisfying results.

Perioperative Technical Complications in Deep Brain Stimulation Surgeries.

AIM: Deep brain stimulation (DBS) surgeries are multi-faceted and the various steps are interconnected. Since its first implementation, the method of DBS surgery has undergone changes. We have encountered several expected and also non-expected perioperative technical complications in the past seventeen years. Here, we describe the stereotactic frame, stereotactic localizer and planning station related complications and how we have managed them as much as possible. MATERIAL AND METHODS: This study is a retrospective qualitative analysis of the documented technical events encountered during DBS surgeries from 1999 onwards. We have collected these events from a cohort of approximately 921 DBS electrodes implantations from the centers of the authors. RESULTS: Stereotactic frame related complications included movement related fixation problems, head anatomy related problems, and lack of maintenance related issues. Localizer related complications were compatibility issues of the stereotactic localizer and planning station, field of view effect on fiducials, air bubbles in localizers using liquid solutions, and disengaged localizer effect. Planning station related complications included image fusion failures and cerebrospinal fluid signal effect on image fusion. CONCLUSION: The road to success in DBS therapy passes through the ability to cope with surgical and technical complications. Each step is unconditionally connected to the other, and detection of the problems that can be encountered in advance and preparations for these negative conditions are the key to success for the group responsible for executing the therapy. We are still learning from these events and advance our surgical approaches.

Does probe's eye subthalamic nucleus length on T2W MRI correspond with microelectrode recording in patients with deep brain stimulation for advanced Parkinson's disease?

AIM: Subthalamic nucleus (STN) deep brain stimulation (DBS) has become a well-accepted treatment for patients with advanced Parkinson's disease (PD). During surgical planning for DBS, the length of the STN is taken into account and verified during microelectrode recording (MER) intraoperatively. Here, we addressed the question to which extent the length of the STN measured with the T2 weighted MRI in the probe's eye view corresponded with the intraoperatively determined length of the STN with MER. MATERIAL AND METHODS: We included 10 consecutive Parkinson's disease patients who underwent STN DBS surgery. The length of the STN in the probe's eye view mode was calculated along the trajectory of the central MER electrode crossing the STN. RESULTS: Our analysis showed no statistical difference between the length of the STN measured with the T2 weighted probe's eye view mode and the MER (right STN length 5.8 ± 0.9 mm MRI vs. 6.3 ± 0.5 mm MER, p > 0.05; left STN length 5.6 ± 0.4 mm MRI vs 5.8 ± 1 mm MER, p > 0.05). CONCLUSION: This means that the entry and the exit of the STN can be adequately estimated using the probe's eye view preoperatively.

Conversion of local anesthesia-guided deep brain stimulation of the subthalamic nucleus to general anesthesia.

BACKGROUND: Deep brain stimulation of the subthalamic nucleus (STN) is a widely applied procedure in the treatment of patients with advanced Parkinson disease and is generally performed under local anesthesia. Here we report our experience with the conversion to general anesthesia in two patients with advanced Parkinson disease because of fear reactions intraoperatively. CASE DESCRIPTION: Patients received general anesthesia with propofol and were implanted with electrodes at the level of STN guided by multiple-microelectrode electrophysiological recordings after obtaining informed consent. During the recordings the propofol levels were reduced. Postoperative clinical assessments showed marked improvements of motor disability with significant reductions of dopaminergic medication. CONCLUSION: Our case observations document the possibility of fear reactions intraoperatively and show the possibility of conversion to general anesthesia with a successful outcome.

Targeting thalamic tremor cells in deep brain stimulation for multiple sclerosis-induced complex tremor.

BACKGROUND: Tremor is an important cause of disability in patients with multiple sclerosis (MS). It is an ongoing debate as to which brain region should be targeted in MS patients with complex tremors. CASE DESCRIPTION: Here, we describe our experience with targeting thalamic tremor cells in the ventro-intermediate/ventro-oralis posterior (Vim/Vop) region in a patient with MS related complex tremor. Intraoperative multiple-microelectrode recordings showed the existence of tremor cells. Test stimulation produced the best effect when performed at the regions where tremor cells were recorded. Postoperative examination revealed a substantial improvement of the tremor. CONCLUSION: Our case observation reveals the existence of a neurophysiological target for deep brain stimulation (DBS) in MS related tremor.