Adequate control of seizures in a case of lead migration and neuromodulation of the posterior Sylvian junction: A case report.

Background: This report aims to describe the neuromodulation effect on seizure control in a patient with a left hippocampal migrated electrode to the Posterior Sylvian Junction (PSJ) during a follow-up of 17 years. Case Description: We report a case of a female patient with drug-resistant epilepsy who initiated at seven years old and underwent a stereotactic frame-based insertion of a left hippocampal electrode for deep brain stimulation (DBS). Posterior migration of the electrode was identified at PSJ by postoperative magnetic resonance imaging one month after surgery. A consistent seizure reduction (Engel IC) was obtained with 2v-120 uS-145 Hz, contacts 0-3 negative, casing positive DBS parameters and maintained to this day. Patient data were collected from electronic medical records preceded by obtaining an informed consent for research and publication purposes. Stimulation parameter adjustments were confirmed with the digital records of the local device provider (Medtronic). Results: PSJ is a connectivity confluence point of white matter pathways in the posterior quadrant of the hemispheres. White mater DBS could be considered for research as a potential complementary target for neuromodulation of refractory epilepsy.

Validating EEG source imaging using intracranial electrical stimulation.

Electrical source imaging is used in presurgical epilepsy evaluation and in cognitive neurosciences to localize neuronal sources of brain potentials recorded on EEG. This study evaluates the spatial accuracy of electrical source imaging for known sources, using electrical stimulation potentials recorded on simultaneous stereo-EEG and 37-electrode scalp EEG, and identifies factors determining the localization error. In 11 patients undergoing simultaneous stereo-EEG and 37-electrode scalp EEG recordings, sequential series of 99-110 biphasic pulses (2 ms pulse width) were applied by bipolar electrical stimulation on adjacent contacts of implanted stereo-EEG electrodes. The scalp EEG correlates of stimulation potentials were recorded with a sampling rate of 30 kHz. Electrical source imaging of averaged stimulation potentials was calculated utilizing a dipole source model of peak stimulation potentials based on individual four-compartment finite element method head models with various skull conductivities (range from 0.0413 to 0.001 S/m). Fitted dipoles with a goodness of fit of ≥80% were included in the analysis. The localization error was calculated using the Euclidean distance between the estimated dipoles and the centre point of adjacent stimulating contacts. A total of 3619 stimulation locations, respectively, dipole localizations, were included in the evaluation. Mean localization errors ranged from 10.3 to 26 mm, depending on source depth and selected skull conductivity. The mean localization error increased with an increase in source depth (r(3617) = [0.19], P = 0.000) and decreased with an increase in skull conductivity (r(3617) = [-0.26], P = 0.000). High skull conductivities (0.0413-0.0118 S/m) yielded significantly lower localization errors for all source depths. For superficial sources (<20 mm from the inner skull), all skull conductivities yielded insignificantly different localization errors. However, for deeper sources, in particular >40 mm, high skull conductivities of 0.0413 and 0.0206 S/m yielded significantly lower localization errors. In relation to stimulation locations, the majority of estimated dipoles moved outward-forward-downward to inward-forward-downward with a decrease in source depth and an increase in skull conductivity. Multivariate analysis revealed that an increase in source depth, number of skull holes and white matter volume, while a decrease in skull conductivity independently led to higher localization error. This evaluation of electrical source imaging accuracy using artificial patterns with a high signal-to-noise ratio supports its application in presurgical epilepsy evaluation and cognitive neurosciences. In our artificial potential model, optimizing the selected skull conductivity minimized the localization error. Future studies should examine if this accounts for true neural signals.

Validating EEG, MEG and Combined MEG and EEG Beamforming for an Estimation of the Epileptogenic Zone in Focal Cortical Dysplasia.

MEG and EEG source analysis is frequently used for the presurgical evaluation of pharmacoresistant epilepsy patients. The source localization of the epileptogenic zone depends, among other aspects, on the selected inverse and forward approaches and their respective parameter choices. In this validation study, we compare the standard dipole scanning method with two beamformer approaches for the inverse problem, and we investigate the influence of the covariance estimation method and the strength of regularization on the localization performance for EEG, MEG, and combined EEG and MEG. For forward modelling, we investigate the difference between calibrated six-compartment and standard three-compartment head modelling. In a retrospective study, two patients with focal epilepsy due to focal cortical dysplasia type IIb and seizure freedom following lesionectomy or radiofrequency-guided thermocoagulation (RFTC) used the distance of the localization of interictal epileptic spikes to the resection cavity resp. RFTC lesion as reference for good localization. We found that beamformer localization can be sensitive to the choice of the regularization parameter, which has to be individually optimized. Estimation of the covariance matrix with averaged spike data yielded more robust results across the modalities. MEG was the dominant modality and provided a good localization in one case, while it was EEG for the other. When combining the modalities, the good results of the dominant modality were mostly not spoiled by the weaker modality. For appropriate regularization parameter choices, the beamformer localized better than the standard dipole scan. Compared to the importance of an appropriate regularization, the sensitivity of the localization to the head modelling was smaller, due to similar skull conductivity modelling and the fixed source space without orientation constraint.

A Multi-Modular System for the Visualization and Classification of MER Data During Neurostimulation Procedures.

This paper proposes an interactive analysis and visualization tool for the accuracy improvement of electrode placement during neurostimulation therapy surgery. During the procedure, the presented system assists the surgeon in the crucial tissue type detection by providing a fused visualization of the current electrode location and the microelectrode recordings (MER). The system processes the MER in real-time and utilizes a convolutional neural network (CNN) to classify the targeted tissue type. In addition to presenting the MER in its raw waveform, the system also offers the visualization of the frequency domain and the result of the neural network. To further assist the decision-making process, additional visualization methods are integrated into the system. Using the pre-operative taken CT and MRI scans, the system offers 3D visualization in the form of direct volume rendering (DVR) and axis-aligned slice views in 2D. Both domains are enriched by the MER readings and the result of the machine learning classifier.

SpikeDeep-classifier: a deep-learning based fully automatic offline spike sorting algorithm.

Objective.Advancements in electrode design have resulted in micro-electrode arrays with hundreds of channels for single cell recordings. In the resulting electrophysiological recordings, each implanted electrode can record spike activity (SA) of one or more neurons along with background activity (BA). The aim of this study is to isolate SA of each neural source. This process is called spike sorting or spike classification. Advanced spike sorting algorithms are time consuming because of the human intervention at various stages of the pipeline. Current approaches lack generalization because the values of hyperparameters are not fixed, even for multiple recording sessions of the same subject. In this study, a fully automatic spike sorting algorithm called 'SpikeDeep-Classifier' is proposed. The values of hyperparameters remain fixed for all the evaluation data.Approach.The proposed approach is based on our previous study (SpikeDeeptector) and a novel background activity rejector (BAR), which are both supervised learning algorithms and an unsupervised learning algorithm (K-means). SpikeDeeptector and BAR are used to extract meaningful channels and remove BA from the extracted meaningful channels, respectively. The process of clustering becomes straight-forward once the BA is completely removed from the data. Then, K-means with a predefined maximum number of clusters is applied on the remaining data originating from neural sources only. Lastly, a similarity-based criterion and a threshold are used to keep distinct clusters and merge similar looking clusters. The proposed approach is called cluster accept or merge (CAOM) and it has only two hyperparameters (maximum number of clusters and similarity threshold) which are kept fixed for all the evaluation data after tuning.Main results.We compared the results of our algorithm with ground-truth labels. The algorithm is evaluated on data of human patients and publicly available labeled non-human primates (NHPs) datasets. The average accuracy of BAR on datasets of human patients is 92.3% which is further reduced to 88.03% after (K-means + CAOM). In addition, the average accuracy of BAR on a publicly available labeled dataset of NHPs is 95.40% which reduces to 86.95% after (K-mean + CAOM). Lastly, we compared the performance of the SpikeDeep-Classifier with two human experts, where SpikeDeep-Classifier has produced comparable results.Significance.The SpikeDeep-Classifier is evaluated on the datasets of multiple recording sessions of different species, different brain areas and different electrode types without further retraining. The results demonstrate that 'SpikeDeep-Classifier' possesses the ability to generalize well on a versatile dataset and henceforth provides a generalized and fully automated solution to offline spike sorting.Clinical trial registration numberThe clinical trial registration number for patients implanted with the Utah array isNCT 01849822.For the epilepsy patients, approval from the local ethics committee at the Ruhr-University Bochum, Germany, was obtained prior to implantation. The Clinical trial registration number for the epilepsy patients implanted with microwires is16-5670.

Evaluation and discussion of handmade face-masks and commercial diving-equipment as personal protection in pandemic scenarios.

OBJECTIVE: Pandemic scenarios like the current Corona outbreak show the vulnerability of both globalized markets and just-in-time production processes for urgent medical equipment. Even usually cheap personal protection equipment becomes excessively expensive or is not deliverable at all. To avoid dangerous situations especially to medical professionals, but also to affected patients, 3D-printer and maker-communities have teamed up to develop and print shields, masks and adapters to help the medical personnel. In this study, we investigate three home-made respiratory masks for filter and protection efficacy and discuss the results and legal aspects. MATERIALS AND METHODS: A home-printed respiratory mask with a commercial filter, a scuba-diving mask with a commercial filter and a mask sewn from a vacuum cleaner bag were investigated with 99mTc-labeled NaCl-aerosol, and the respective filter-efficacy was measured under a scintigraphic camera. RESULTS: The sewn mask from a vacuum cleaner bag had a filter efficacy of 69.76%, the 3D-printed mask of 39.27% and the scuba-diving mask of 85.07%. CONCLUSION: Home-printed personal protection equipment can be a-yet less efficient-alternative against aerosol in case professional masks are not available, but legal aspects of their use and distribution have to be kept in mind in order to avoid compensation claims.

Brainatomy: A Novel Way of Teaching Sphenoid Bone Anatomy With a Simplified 3-Dimensional Model.

BACKGROUND: The diagnosis and treatment of diseases at and around the sphenoid bone demands throughout understanding of its anatomy in 3-dimensional (3-D) space. However, despite the complex anatomic nature of the sphenoid bone, the current educational resources for its 3-D anatomy are insufficient for fast and long-term retention of the anatomic relationships. OBJECTIVE: To provide a simplified 3-D model of the sphenoid bone that anyone can easily learn and recall as an internal mental model. METHODS: Various studies on the anatomy of the sphenoid bone were analyzed. The collected data included the shape, foramina, canals, fissures, and minute details of the sphenoid bone. The gained detailed knowledge was subsequently used to create a 3-D model of the sphenoid bone with the help of 3-D computer software. A live lecture was given with this same software and simultaneously recorded with a microphone and a computer-screen recorder. A novel approach in lecturing, building the sphenoid bone from the scratch in a piecemeal fashion, was utilized. RESULTS: The sphenoid bone was recreated as an horizontally elongated box without a superior and posterior wall. All its foramina, canals, and fissures are visually easy to follow. Understanding its neuroanatomic terminologies based on their anatomic nature and relationships is enhanced. CONCLUSIONS: This simplified 3-D model, along with the video lecture, will enhance the efficiency of studying sphenoid bone anatomy. The educational resources of this study can be obtained by medical students, radiologists, neurologists, neurosurgeons, neuroscientists, or anyone else seeking for fundamental understanding of sphenoid bone anatomy.

SpikeDeeptector: a deep-learning based method for detection of neural spiking activity.

OBJECTIVE: In electrophysiology, microelectrodes are the primary source for recording neural data (single unit activity). These microelectrodes can be implanted individually or in the form of arrays containing dozens to hundreds of channels. Recordings of some channels contain neural activity, which are often contaminated with noise. Another fraction of channels does not record any neural data, but only noise. By noise, we mean physiological activities unrelated to spiking, including technical artifacts and neural activities of neurons that are too far away from the electrode to be usefully processed. For further analysis, an automatic identification and continuous tracking of channels containing neural data is of great significance for many applications, e.g. automated selection of neural channels during online and offline spike sorting. Automated spike detection and sorting is also critical for online decoding in brain-computer interface (BCI) applications, in which only simple threshold crossing events are often considered for feature extraction. To our knowledge, there is no method that can universally and automatically identify channels containing neural data. In this study, we aim to identify and track channels containing neural data from implanted electrodes, automatically and more importantly universally. By universally, we mean across different recording technologies, different subjects and different brain areas. APPROACH: We propose a novel algorithm based on a new way of feature vector extraction and a deep learning method, which we call SpikeDeeptector. SpikeDeeptector considers a batch of waveforms to construct a single feature vector and enables contextual learning. The feature vectors are then fed to a deep learning method, which learns contextualized, temporal and spatial patterns, and classifies them as channels containing neural spike data or only noise. MAIN RESULTS: We trained the model of SpikeDeeptector on data recorded from a single tetraplegic patient with two Utah arrays implanted in different areas of the brain. The trained model was then evaluated on data collected from six epileptic patients implanted with depth electrodes, unseen data from the tetraplegic patient and data from another tetraplegic patient implanted with two Utah arrays. The cumulative evaluation accuracy was 97.20% on 1.56 million hand labeled test inputs. SIGNIFICANCE: The results demonstrate that SpikeDeeptector generalizes not only to the new data, but also to different brain areas, subjects, and electrode types not used for training. CLINICAL TRIAL REGISTRATION NUMBER: The clinical trial registration number for patients implanted with the Utah array is NCT01849822. For the epilepsy patients, approval from the local ethics committee at the Ruhr-University Bochum, Germany, was obtained prior to implantation.

Early motor function after local treatment of brain metastases in the motor cortex region with stereotactic radiotherapy/radiosurgery or microsurgical resection: a retrospective study of two consecutive cohorts.

BACKGROUND: We compared the functional outcome and influential factors of two standard treatment modalities for central cerebral metastases: electrophysiological-controlled microsurgical resection (MSR) and stereotactic radiotherapy/stereotactic radiosurgery (SRT/SRS). METHODS: We performed a database search for central metastasis treatments during the period from January 2008 to September 2012 in two clinical registers: 1) register for intraoperative neuromonitoring (Department of Neurosurgery), and 2) prospective database for SRT/SRS (Department of Radiotherapy). Neurological status before and after treatment, Karnofsky performance index (KPI), histology, tumor localization and volume, and oncological status were standardized and pooled together for analysis. Muscle strength was graded on a scale of 0-5. RESULTS: We identified 27 MSR and 41 SRT/SRS cases from 68 treatments. The MSR-treated patients had significant less muscle strength in the upper and lower extremities before and after the treatment as compared to the patients receiving SRT/SRS. Muscle strength of the extremities did not change for patients receiving SRT/SRS, while MSR patients had significant improvement in lower extremity muscle strength (p = 0.05) and a non-significant improvement in the upper extremities. MSR showed significant improvement in hemiparesis as compared to radiotherapy, but this was accompanied with a significant deterioration of extremity muscle strength after surgery, as compared to SRT/SRS (improvement p = 0.04, deterioration p = 0.10). CONCLUSION: Electrophysiologically guided microsurgery of central metastases had a significantly better functional outcome regarding hemiparesis. However, there was also a trend for less secondary neurological deterioration after SRT/SRS. TRIAL REGISTRATION: ISRCTN81776764. Retrospectively Registered 27 July 2017.

[Deep brain stimulation in movement disorders: evidence and therapy standards]. / Tiefe Hirnstimulation bei Bewegungsstörungen: Evidenz und Therapiestandards.

The deep brain stimulation (DBS) in movement disorders is well established and in many aspects evidence-based procedure. The treatment indications are very heterogeneous and very specific in their course and therapy. The deep brain stimulation plays very important, but usually not the central role in this conditions. The success in the application of DBS is essentially associated with the correct, appropriate and timely indication of the therapy in the course of these diseases. Thanks to the good standardization of the DBS procedure and sufficient published data, the recommendations for indication, diagnosis and operative procedures can be generated. The following article attempts to summarize the most important decision-making criteria and current therapy standards in this fairly comprehensive subject and to present them in close proximity to practice.

Insular Cortex Surgery for the Treatment of Refractory Epilepsy.

Focal epilepsy originating from the insular cortex is rare. One reason is the small amount of cortical tissue compared with other lobes of the brain. However, the incidence of insular epilepsy might be underestimated because of diagnostic difficulties. The semiology and the surface EEG are often not meaningful or even misleading, and elaborated imaging might be necessary. The close connections of the insular cortex with other potentially epileptogenic areas, such as the temporal lobe or frontal/central cortex, is increasingly recognized as possible reason for failure of epilepsy surgery for temporal or extratemporal seizures. Therefore, some centers consider invasive EEG recording of the insular cortex not only in case of insular epilepsy but also in other focal epilepsies with nonconclusive results from the presurgical work-up. The surgical approach to and resection of insular cortex is challenging because of its deep location and proximity to highly eloquent brain structures. Over the last decades, technical adjuncts like navigation tools, electrophysiological monitoring and intraoperative imaging have improved the outcome after surgery. Nevertheless, there is still a considerable rate of postoperative transient or permanent deficits, in some cases as unavoidable and calculated deficits. In most of the recent series, seizure outcome was favorable and comparable with extratemporal epilepsy surgery or even better. Up to now, the data volume concerning long-term follow-up is limited. This review focusses on the surgical challenges of resections to treat insular epilepsy, on prognostic factors concerning seizure outcome, on postoperative deficits and complications. Moreover, less invasive surgical techniques to treat epilepsy in this highly eloquent area are summarized.

Postoperative neuroimaging analysis of DRT deep brain stimulation revision surgery for complicated essential tremor.

BACKGROUND: We report a patient who received conventional bilateral deep brain stimulation of the ventral intermediate nucleus of thalamus (Vim) for the treatment of medication refractory essential tremor (ET). After initial beneficial effects, therapeutic efficacy was lost due to a loss of control of his proximal trunkal and extremity tremor. The patient received successful diffusion tensor magnetic resonance imaging fiber tractographic (DTI FT)-assisted DBS revision surgery targeting the dentato-rubro-thalamic tract (DRT) in the subthalamic region (STR). OBJECTIVE: To report the concept of DTI FT-assisted DRT DBS revision surgery for ET and to show sophisticated postoperative neuroimaging analysis explaining improved symptom control. METHODS: Analysis was based on preoperative DTI sequences and postoperative helical computed tomography (hCT). Leads, stimulation fields, and fibers were reconstructed using commercial software systems (Elements, Brainlab AG, Feldkirchen, Germany; GUIDE XT, Boston Scientific Corp., Boston, MA, USA). RESULTS: The patient showed immediate and sustained tremor improvement after DTI FT-assisted revision surgery. Analysis of the two implantations (electrode positions in both instances) revealed a lateral and posterior shift in the pattern of modulation of the cortical fiber pathway projection after revision surgery as compared to initial implantation, explaining a more efficacious stimulation. CONCLUSIONS: Our work underpins a possible superiority of direct targeting approaches using advanced neuroimaging technologies to perform personalized DBS surgery. The evaluation of DBS electrode positions with the herein-described neuroimaging simulation technologies will likely improve targeting and revision strategies. Direct targeting with DTI FT-assisted approaches in a variety of indications is the focus of our ongoing research.

Lesion guided radiofrequency thermocoagulation (L-RFTC) for hypothalamic hamartomas, nodular heterotopias and cortical dysplasias: Review and perspective.

Lesion guided radiofrequency thermocoagulation (L-RFTC) via stereotactically inserted coagulation probes is a further development of stereotactic thermocoagulation thalamotomy and stereo-EEG guided RFTC. In this method epileptogenic lesions detected via magnetic resonance imaging (MRI) move to the center of coagulation planning. Two surgical strategies can be applied: lesion disconnection and lesion destruction. This focused review collects all data published until January 2016 on L-RFTC for the indications hypothalamic hamartoma, periventricular nodular heterotopia and focal cortical dysplasia and describes technical issues, surgical objectives and outcomes. Special attention is given to the aspect of presurgical MRI requirements.

Lesion guided stereotactic radiofrequency thermocoagulation for palliative, in selected cases curative epilepsy surgery.

INTRODUCTION: Resective epilepsy surgery is an established treatment option in patients with pharmacoresistant, lesion related epilepsy. Yet, if the presurgical work-up proves multi-focal organization of the epileptogenic zone, or the area of intended resection is close to eloquent brain areas, patients may decide against resections because of an unfavorable risk-benefit-ratio. We assess if lesion guided cortical stereotactic radiofrequency thermocoagulation (L-RFTC) is a potential surgical alternative in these patients. METHODS: We performed seven procedures of L-RFTC. Three patients had monofocal epilepsy arising close to eloquent structures; in four, invasive pre-surgical workup documented monofocal seizure onset but strong interictal epileptic activity also independent and distant from the seizure onset zone. L-RFTC was restricted to the lesional area (=seizure onset site). RESULTS: 12 to 37 months after RFTC worthwhile seizure improvement was achieved in 6 patients. One patient became seizure free following complete coagulation of a focal cortical dysplasia, two had had 1-2 auras under tapered but not under continued medication. In one patient only subclinical seizures persisted. In one patient hypermotor seizures were transformed into milder short tonic seizures and another one had a seizure reduction by 50%. Only one patient did not profit at all. One patient developed a persisting neurological deficit. SIGNIFICANCE: In patients with complex epileptogenic zones L-RFTC can lead to worthwhile seizure reduction. This qualifies this procedure as a palliative surgical technique with potential good risk-benefit ratio. In patients with small focal cortical dysplasias L-RFTC may even allow minimal-invasive surgery with curative intention.

Role of Subdural Interhemispheric Electrodes in Presurgical Evaluation of Epilepsy Patients.

OBJECTIVE: Surgery is a well-established and safe treatment option for focal drug resistant epilepsy. However, difficulties are often encountered in diagnosing mesial cortical lesions. The aim of this study was to evaluate the usefulness and overall complication rate of subdural interhemispheric electrodes (IHEs) as part of an invasive presurgical evaluation of epilepsy patients. METHODS: A total of 100 patients who underwent implantation of subdural IHE were included in the study. Data on surgical complications, subdural electrodes and contacts, benefits of invasive electroencephalography recording, and final seizure outcome were collected and analyzed. RESULTS: A total of 343 subdural strip electrodes with a total of 1470 contacts were implanted. There were 6 perioperative/postoperative complications, none of them leading to a permanent neurologic deficit. An increased number of IHE (P = 0.005) and IHE-contacts (P = 0.03) also increased the rate of focus detection, while not significantly changing complication rate (P = 0.26). Two benefits of IHE (focus detection of interhemispheric lesions and mapping) in extratemporal resections were significantly associated with excellent seizure outcome (ILEA1) (P = 0.03, respectively P < 0.001). Other features associated with excellent seizure outcome are pure resections (w/o multiple subpial transection, P = 0.006), specific histology (P < 0.001), and a visible magnetic resonance imaging lesion (P = 0.002). CONCLUSION: Implantation of IHE for the preoperative evaluation of epilepsy patients is an established surgical procedure with an acceptable complication profile. The benefits delivered from IHE can positively influence final seizure outcome in the challenging group of extratemporal resections due to interhemispheric lesions. Thus IHEs demonstrate a useful diagnostic utility for the presurgical evaluation of selected epilepsy patients.

Pseudohypoxic brain swelling (postoperative intracranial hypotension-associated venous congestion) after spinal surgery: report of 2 cases.

BACKGROUND AND IMPORTANCE: Pseudohypoxic brain swelling is a rare event that may occur after uneventful brain surgery when subgaleal vacuum drainage is used. To date, such cases of unexpected postoperative disturbances of consciousness associated with radiological signs of basal ganglia, thalamic, brainstem, and cerebellum damage without any signs of vessel occlusion have not been known to occur after spinal surgery. CLINICAL PRESENTATION: We report for the first time on 2 patients presenting with a clinical and radiological picture of pseudohypoxic brain swelling after spinal surgery. In the first patient, bilateral basal ganglia damage occurred after thoracic spondylodiscitis surgery, manifested by epileptic seizures and coma lasting 1 week postoperatively with subsequent recovery. The second patient suffered basal ganglia and cerebellar and brainstem infarction after lumbar spondylodiscitis surgery, resulting in death. Because intraoperative cerebrospinal fluid leakage and use of postoperative epidural suction drainage with cerebrospinal fluid loss occurred in both cases, they are highly suspected to have potentially caused the complications. CONCLUSION: Pseudohypoxic brain swelling should be considered in patients with unexpected neurological deterioration after spinal surgery. It might be a form of postoperative intracranial hypotension-associated venous congestion, which should be distinguished from common postoperative cerebral ischemic events caused by arterial or venous occlusions.

Tractographic analysis of historical lesion surgery for depression.

Various surgical brain ablation procedures for the treatment of refractory depression were developed in the twentieth century. Most notably, key target sites were (i) the anterior cingulum, (ii) the anterior limb of the internal capsule, and (iii) the subcaudate white matter, which were regarded as effective targets. Long-term symptom remissions were better following lesions of the anterior internal capsule and subcaudate white matter than of the cingulum. It is possible that the observed clinical improvements of these various surgical procedures may reflect shared influences on presently unspecified brain affect-regulating networks. Such possibilities can now be analyzed using modern brain connectivity procedures such as diffusion tensor imaging (DTI) tractography. We determined whether the shared connectivities of the above lesion sites in healthy volunteers might explain the therapeutic effects of the various surgical approaches. Accordingly, modestly sized historical lesions, especially of the anatomical overlap areas, were 'implanted' in brain-MRI scans of 53 healthy subjects. These were entered as seed regions for probabilistic DTI connectivity reconstructions. We analyzed for the shared connectivities of bilateral anterior capsulotomy, anterior cingulotomy, subcaudate tractotomy, and stereotactic limbic leucotomy (a combination of the last two lesion sites). Shared connectivities between the four surgical approaches mapped onto the most mediobasal aspects of bilateral frontal lobe fibers, including the forceps minor and the anterior thalamic radiations that contacted subgenual cingulate regions. Anatomically, convergence of these shared connectivities may derive from the superolateral branch of the medial forebrain bundle (MFB), a structure that connects these frontal areas to the origin of the mesolimbic dopaminergic 'reward' system in the midbrain ventral tegmental area. Thus, all four surgical anti-depressant approaches may be promoting positive affect by converging influences onto the MFB.

Integrating magnetic resonance imaging postprocessing results into neuronavigation for electrode implantation and resection of subtle focal cortical dysplasia in previously cryptogenic epilepsy.

OBJECTIVE: Focal cortical dysplasias (FCDs) are highly epileptogenic lesions. Surgical removal is frequently the best treatment option for pharmacoresistant epilepsy. However, subtle FCDs may remain undetected even after high-resolution magnetic resonance imaging (MRI). Morphometric MRI analysis, which compares the individual brain with a normal database, can facilitate the detection of FCDs. We describe how the results of normal database-based MRI postprocessing can be used to guide stereotactic electrode implantation and subsequent resection of lesions that are suspected to be FCDs. METHODS: A presurgical evaluation was conducted on a 19-year-old woman with pharmacoresistant hypermotor seizures. Conventional high-resolution MRI was classified as negative for epileptogenic lesions. However, morphometric analysis of the spatially normalized MRI revealed abnormal gyration and blurring of the gray-white matter junction, which was suggestive of a small and deeply seated FCD in the left frontal lobe. RESULTS: The brain region highlighted by morphometric analysis was marked as a region of interest, transferred back to the original dimension of the individual MRI, and imported into a neuronavigation system. This allowed the region of interest-targeted stereotactic implantation of 2 depth electrodes, by which seizure onset was confirmed in the lesion. The electrodes also guided the final resection, which rendered the patient seizure-free. The lesion was histologically classified as FCD Palmini and Lüders IIB. CONCLUSION: Transferring normal database-based MRI postprocessing results into a neuronavigation system is a new and worthwhile extension of multimodal neuronavigation. The combination of resulting regions of interest with functional and anatomic data may facilitate planning of electrode implantation for invasive electroencephalographic recordings and the final resection of small or deeply seated FCDs.