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Introduction: The aim of this study was to present a novel technique for subthalamic nucleus (STN) deep brain stimulation (DBS) implantation under general anesthesia by using intraoperative motor-evoked potentials (MEPs) through direct lead stimulation and determining their correlation to the thresholds of postoperative stimulation-induced side effects. Methods: This study included 22 consecutive patients with advanced Parkinson's disease who underwent surgery in our institution between January 2021 and September 2023. All patients underwent bilateral implantation in the STN (44 leads) under general anesthesia without microelectrode recordings (MERs) by using MEPs with electrostimulation directly through the DBS lead. No cortical stimulation was performed during this process. Intraoperative fluoroscopic guidance and immediate postoperative computed tomography were used to verify the electrode's position. The lowest MEP thresholds were recorded and were correlated to the postoperative stimulation-induced side-effect threshold. The predictive values of the MEPs were analyzed. Five DBS leads were repositioned intraoperatively due to the MEP results. Results: A moderately strong positive correlation was found between the MEP threshold and the capsular side-effect threshold (RS = 0.425, 95% CI, 0.17–0.67, p = 0.004). The highest sensitivity and specificity for predicting a side-effect threshold of 5 mA were found to be at 2.4 mA MEP threshold (sensitivity 97%, specificity 87.5%, positive predictive value 97%, and negative predictive value 87.5%). We also found high sensitivity and specificity (100%) at 1.15 mA MEP threshold and 3 mA side-effect threshold. Out of the total 44 leads, 5 (11.3%) leads were repositioned intraoperatively due to MEP thresholds lower than 1 mA (4 leads) or higher than 5 mA (1 lead). The mean accuracy on postoperative CT was 1.05 mm, and there were no postoperative side-effects under 2.8 mA. Conclusion: Intraoperative MEPs with electrostimulation directly through the contacts of the DBS lead correlate with the stimulation-induced capsular side effects. The lead reposition based on intraoperative MEP may enlarge the therapeutic window of DBS stimulation. [ABSTRACT FROM AUTHOR]

Introduction: The orientation in the intracranial space remains a neurosurgical challenge and transition from slices to threedimensional (3D) imaging makes surgeon closer to the reality. New developments in magnetic resonance imaging (MRI) and the release of free softwares as 3DSlicer, Freesurfer and FSL improved dramatically the quality of 3D reconstruction. Our aim to present the possibilities of 3D cortico-vascular and stereotactic electroencephalography (SEEG) reconstructions using common MRI sequences and free softwares. Methods: This study has included fifty-five consecutive epilepsy patients operated on during the period between January 2015 and December 2016. All patients underwent 1.5 T preoperative MRI and DICOM data postprocessing using FSL, Freesurfer and 3DSlicer. Intraoperative neuronavigation was performed in 40 patients and SEEG was performed in 15 patients using postprocessed images and raw data. Results: Three-dimensional reconstruction improve preoperative planning and intraoperative orientation especially in extratemporal epilepsy patients where the sulcal pattern is more complex and tailored SEEG implantations and cortical resctions are needed. Conclusion: Postprocessing of raw MRI and CT DICOM sets could provide useful preoperative and intraoperative information. [ABSTRACT FROM AUTHOR]

Background: Stereo-electroencephalography (SEEG) requires high quality angiographic study because avascular trajectory planning is a prerequisite for the safety of this procedure. Some epilepsy surgery groups have started to use computed tomography angiography (CTA) and magnetic resonance T1- weighted sequence with contrast enhancement (CE T1). To the best of our knowledge there are no reports of avascular trajectory planning of SEEG based on magnetic resonance angiography (MRA). Objective: The goal of our study was to assess the quality and safety of MRA for avascular trajectory planning of SEEG. Methods: Thirty-six SEEG explorations for drug-resistant focal epilepsy have been performed from January 2013 to December 2015 in the Epilepsy Surgery Center in Sofia. MRI included MRA with modified contrast enhanced magnetic resonance venography (MRV) protocol with short acquisition delay allowing simultaneous arterial and venous visualization. Our criteria for satisfactory MRA were visualization of at least first-order branches of the angular artery, paracentral and calcarine artery and thirdorder tributaries of superficial Sylvian vein, vein of Labbe and vein of Trolard. Results: Thirty-four patients underwent thirty-six SEEG explorations with 369 electrodes carrying 4321 contacts. Contrast enhanced MRA using MRVprotocol was judged satisfactory for SEEG planning in all explorations. Postoperative complications were not observed in our series of 36 SEEG explorations. Conclusions: MRA using MRV protocol may be applied for avascular trajectory planning during SEEG procedures and appears to have satisfactory safety profile. This technique provides simultaneous visualisation of cortical arteries and veins without need of additional radiation exposure or intra-arterial catheter placement. [ABSTRACT FROM AUTHOR]

Objective: Stereoelectroencephalography (SEEG)-guided radiofrequency thermocoagulation (RFTC) has the advantage of producing a lesion in the epileptogenic zone (EZ) at the end of SEEG. The majority of published SEEG-guided RFTCs have been bipolar and usually performed between contiguous contacts of the same electrode. In the present study, the authors evaluate the safety, efficacy, and benefits of monopolar RFTC at the end of SEEG., Methods: This study included a series of 31 consecutive patients who had undergone RFTC at the end of SEEG for drug-resistant focal epilepsy in the period of January 2013-December 2019. Post-RFTC seizure control was assessed after 2 months and at the last follow-up visit. Twenty-one patients underwent resective epilepsy surgery after the SEEG-guided RFTC, and the postoperative seizure outcome among these patients was compared with the post-RFTC seizure outcome., Results: Four hundred forty-six monopolar RFTCs were done in the 31 patients. Monopolar RFTCs were performed in all cortical areas, including the insular cortex in 11 patients (56 insular RFTCs). There were 31 noncontiguous lesions (7.0%) because of vascular constraints. The volume of one monopolar RFTC, as measured on T2-weighted MRI immediately after the procedure, was between 44 and 56 mm3 (mean 50 mm3). The 2-month post-RFTC seizure outcomes were as follows: seizure freedom in 13 patients (41.9%), ≥ 50% reduced seizure frequency in 11 (35.5%), and no significant change in 7 (22.6%). Seizure outcome at the last follow-up visit (mean 18 months, range 2-54 months) showed seizure freedom in 2 patients (6.5%) and ≥ 50% reduced seizure frequency in 20 patients (64.5%). Seizure freedom after monopolar RFTC was not significantly associated with the number or location of coagulated contacts. Seizure response after monopolar RFTC had a high positive predictive value (93.8%) but a low negative predictive value (40%) for seizure outcome after subsequent resective surgery. In this series, the only complication (3.2%) was a limited intraventricular hematoma following RFTC performed in the hippocampal head, with spontaneous resolution and no sequelae., Conclusions: The use of monopolar SEEG-guided RFTC provides more freedom in terms of choosing the SEEG contacts for thermocoagulation and a larger thermolesion volume. Monopolar thermocoagulation seems particularly beneficial in cases with an insular EZ, in which vascular constraints could be partially avoided by making noncontiguous lesions within the EZ.