Theta-Alpha Connectivity in the Hippocampal-Entorhinal Circuit Predicts Working Memory Load.

Working memory (WM) maintenance relies on multiple brain regions and inter-regional communications. The hippocampus and entorhinal cortex (EC) are thought to support this operation. Besides, EC is the main gateway for information between the hippocampus and neocortex. However, the circuit-level mechanism of this interaction during WM maintenance remains unclear in humans. To address these questions, we recorded the intracranial electroencephalography from the hippocampus and EC while patients (N = 13, six females) performed WM tasks. We found that WM maintenance was accompanied by enhanced theta/alpha band (2-12 Hz) phase synchronization between the hippocampus to the EC. The Granger causality and phase slope index analyses consistently showed that WM maintenance was associated with theta/alpha band-coordinated unidirectional influence from the hippocampus to the EC. Besides, this unidirectional inter-regional communication increased with WM load and predicted WM load during memory maintenance. These findings demonstrate that WM maintenance in humans engages the hippocampal-entorhinal circuit, with the hippocampus influencing the EC in a load-dependent manner.

Predictable and unpredictable deviance detection in the human hippocampus and amygdala.

Our brains extract structure from the environment and form predictions given past experience. Predictive circuits have been identified in wide-spread cortical regions. However, the contribution of medial temporal structures in predictions remains under-explored. The hippocampus underlies sequence detection and is sensitive to novel stimuli, sufficient to gain access to memory, while the amygdala to novelty. Yet, their electrophysiological profiles in detecting predictable and unpredictable deviant auditory events remain unknown. Here, we hypothesized that the hippocampus would be sensitive to predictability, while the amygdala to unexpected deviance. We presented epileptic patients undergoing presurgical monitoring with standard and deviant sounds, in predictable or unpredictable contexts. Onsets of auditory responses and unpredictable deviance effects were detected earlier in the temporal cortex compared with the amygdala and hippocampus. Deviance effects in 1-20 Hz local field potentials were detected in the lateral temporal cortex, irrespective of predictability. The amygdala showed stronger deviance in the unpredictable context. Low-frequency deviance responses in the hippocampus (1-8 Hz) were observed in the predictable but not in the unpredictable context. Our results reveal a distributed network underlying the generation of auditory predictions and suggest that the neural basis of sensory predictions and prediction error signals needs to be extended.

Multiple craniotomies in patients with brain metastases: a two-center, propensity score-matched study.

The current study addresses the question of whether the resection of more than one BM by multiple craniotomies within the same operation is associated with more adverse events (AEs) and worse functional outcome compared to cases in which only one BM was resected. All patients who underwent more than one craniotomy for resection of multiple BM at two Swiss tertiary neurosurgical care centers were included. Any AEs, functional outcome, and overall survival (OS) were analyzed after 1:1 propensity score matching with patients who underwent removal of a single BM only. A total of 94 patients were included in the final study cohort (47 of whom underwent multiple craniotomies). There was no significant difference in the incidence of AEs between the single and the multiple craniotomy group (n = 2 (4.3%) vs. n = 4 (8.5%), p = .7). Change in modified Rankin Scale (mRS) and Karnofsky Performance Status (KPS) at discharge demonstrated that slightly more single craniotomy patients improved in mRS, while the proportion of patients who worsened in mRS (16.3 vs. 16.7%) and KPS (13.6 vs. 15.2%) was similar in both groups (p = .42 for mRS and p = .92 for KPS). Survival analysis showed no significant differences in OS between patients with single and multiple craniotomies (p = .18). Resection of multiple BM with more than one craniotomy may be considered a safe option without increased AEs or worse functional outcome.

Treatment outcomes and the role of the DES scheme in the appropriate treatment selection for high-grade dural arteriovenous fistulas.

OBJECTIVE: Endovascular and microsurgical treatment are viable options for the majority of Borden type III dural arteriovenous fistulas (dAVFs). The aim of this study was to examine treatment outcomes in a comparative analysis of endovascular and surgical treatment modalities for Borden type III fistulas and explore clinical implications of the DES scheme in selecting ideal candidates for surgical therapy. METHODS: Patients diagnosed with dAVFs with leptomeningeal venous drainage admitted to the Departments of Neurosurgery or Neuroradiology of the University Hospital Zurich between January 2014 and October 2021 were included in this study. Comprehensive patient data including demographics, clinical presentation, and dAVF characteristics, including established classifications, were collected. Treatment outcomes were assessed based on postinterventional angiography findings. In addition, treatment-related complications were assessed based on the Clavien-Dindo classification. RESULTS: Among all Borden type III dAVFs, 15 were initially treated endovascularly (60% complete occlusion rate) and 10 with microsurgical disconnection (90% complete occlusion rate) (p = 0.18). Subgroup analysis of dAVFs meeting the criteria for directness and exclusivity based on the DES scheme showed a 100% complete occlusion rate after microsurgical disconnection, whereas embolization achieved a complete occlusion rate of 60% (p = 0.06). There was no significant difference in the rate or severity of treatment-related complications between treatment modalities. CONCLUSIONS: This study suggests that microsurgical disconnection is a viable primary treatment modality for Borden type III dAVFs, particularly for dAVFs that meet the criteria of directness and exclusivity according to the DES scheme. The DES scheme demonstrates its relevance in selecting the most appropriate treatment strategy for affected patients.

Anterior-Posterior Hippocampal Dynamics Support Working Memory Processing.

The hippocampus is a locus of working memory (WM) with anterior and posterior subregions that differ in their transcriptional and external connectivity patterns. However, the involvement and functional connections between these subregions in WM processing are poorly understood. To address these issues, we recorded intracranial EEG from the anterior and the posterior hippocampi in humans (seven females and seven males) who maintained a set of letters in their WM. We found that WM maintenance was accompanied by elevated low-frequency activity in both the anterior and posterior hippocampus and by increased theta/alpha band (3-12 Hz) phase synchronization between anterior and posterior subregions. Cross-frequency and Granger prediction analyses consistently showed that the correct WM trials were associated with theta/alpha band-coordinated unidirectional influence from the posterior to the anterior hippocampus. In contrast, WM errors were associated with bidirectional interactions between the anterior and posterior hippocampus. These findings imply that theta/alpha band synchrony within the hippocampus may support successful WM via a posterior to anterior influence. A combination of intracranial recording and a fine-grained atlas may be of value in understanding the neural mechanisms of WM processing.SIGNIFICANCE STATEMENT Working memory (WM) is crucial to everyday functioning. The hippocampus has been proposed to be a subcortical node involved in WM processes. Previous studies have suggested that the anterior and posterior hippocampi differ in their external connectivity patterns and gene expression. However, it remains unknown whether and how human hippocampal subregions are recruited and coordinated during WM tasks. Here, by recording intracranial electroencephalography simultaneously from both hippocampal subregions, we found enhanced power in both areas and increased phase synchronization between them. Furthermore, correct WM trials were associated with a unidirectional influence from the posterior to the anterior hippocampus, whereas error trials were correlated with bidirectional interactions. These findings indicate a long-axis specialization in the human hippocampus during WM processing.

Passive and active markers of cortical excitability in epilepsy.

Electroencephalography (EEG) has been the primary diagnostic tool in clinical epilepsy for nearly a century. Its review is performed using qualitative clinical methods that have changed little over time. However, the intersection of higher resolution digital EEG and analytical tools developed in the past decade invites a re-exploration of relevant methodology. In addition to the established spatial and temporal markers of spikes and high-frequency oscillations, novel markers involving advanced postprocessing and active probing of the interictal EEG are gaining ground. This review provides an overview of the EEG-based passive and active markers of cortical excitability in epilepsy and of the techniques developed to facilitate their identification. Several different emerging tools are discussed in the context of specific EEG applications and the barriers we must overcome to translate these tools into clinical practice.

Safety of microneurosurgical interventions for superficial and deep-seated brain metastases: single-center cohort study of 637 consecutive cases.

PURPOSE: Microneurosurgical techniques have greatly improved over the past years due to the introduction of new technology and surgical concepts. To reevaluate the role of micro-neurosurgery in brain metastases (BM) resection in the era of new systemic and local treatment options, its safety profile needs to be reassessed. The aim of this study was to analyze the rate of adverse events (AEs) according to a systematic, comprehensive and reliably reproducible grading system after microneurosurgical BM resection in a large and modern microneurosurgical series with special emphasis on anatomical location. METHODS: Prospectively collected cases of BM resection between 2013 and 2022 were retrospectively analyzed. Number of AEs, defined as any deviations from the expected postoperative course according to Clavien-Dindo-Grade (CDG) were evaluated. Patient, surgical, and lesion characteristics, including exact anatomic tumor locations, were analyzed using uni- and multivariate logistic regression and survival analysis to identify predictive factors for AEs. RESULTS: We identified 664 eligible patients with lung cancer being the most common primary tumor (44%), followed by melanoma (25%) and breast cancer (11%). 29 patients (4%) underwent biopsy only whereas BM were resected in 637 (96%) of cases. The overall rate of AEs was 8% at discharge. However, severe AEs (≥ CDG 3a; requiring surgical intervention under local/general anesthesia or ICU treatment) occurred in only 1.9% (n = 12) of cases with a perioperative mortality of 0.6% (n = 4). Infratentorial tumor location (OR 5.46, 95% 2.31-13.8, p = .001), reoperation (OR 2.31, 95% 1.07-4.81, p = .033) and central region tumor location (OR 3.03, 95% 1.03-8.60) showed to be significant predictors in a multivariate analysis for major AEs (CDG ≥ 2 or new neurological deficits). Neither deep supratentorial nor central region tumors were associated with more major AEs compared to convexity lesions. CONCLUSIONS: Modern microneurosurgical resection can be considered an excellent option in the management of BM in terms of safety, as the overall rate of major AEs are very rare even in eloquent and deep-seated lesions.

The Architecture of Human Memory: Insights from Human Single-Neuron Recordings.

Deciphering the mechanisms of human memory is a central goal of neuroscience, both from the point of view of the fundamental biology of memory and for its translational relevance. Here, we review some contributions that recordings from neurons in humans implanted with electrodes for clinical purposes have made toward this goal. Recordings from the medial temporal lobe, including the hippocampus, reveal the existence of two classes of cells: those encoding highly selective and invariant representations of abstract concepts, and memory-selective cells whose activity is related to familiarity and episodic retrieval. Insights derived from observing these cells in behaving humans include that semantic representations are activated before episodic representations, that memory content and memory strength are segregated, and that the activity of both types of cells is related to subjective awareness as expected from a substrate for declarative memory. Visually selective cells can remain persistently active for several seconds, thereby revealing a cellular substrate for working memory in humans. An overarching insight is that the neural code of human memory is interpretable at the single-neuron level. Jointly, intracranial recording studies are starting to reveal aspects of the building blocks of human memory at the single-cell level. This work establishes a bridge to cellular-level work in animals on the one hand, and the extensive literature on noninvasive imaging in humans on the other hand. More broadly, this work is a step toward a detailed mechanistic understanding of human memory that is needed to develop therapies for human memory disorders.

Persistent neuronal firing in the medial temporal lobe supports performance and workload of visual working memory in humans.

The involvement of the medial temporal lobe (MTL) in working memory is controversially discussed. Recent findings suggest that persistent neural firing in the hippocampus during maintenance in verbal working memory is associated with workload. Here, we recorded single neuron firing in 13 epilepsy patients (7 male) while they performed a visual working memory task. The number of colored squares in the stimulus set determined the workload of the trial. Performance was almost perfect for low workload (1 and 2 squares) and dropped at high workload (4 and 6 squares), suggesting that high workload exceeded working memory capacity. We identified maintenance neurons in MTL neurons that showed persistent firing during the maintenance period. More maintenance neurons were found in the hippocampus for trials with correct compared to incorrect performance. Maintenance neurons increased and decreased firing in the hippocampus and increased firing in the entorhinal cortex for high compared to low workload. Population firing predicted workload particularly during the maintenance period. Prediction accuracy of workload based on single-trial activity during maintenance was strongest for neurons in the entorhinal cortex and hippocampus. The data suggest that persistent neural firing in the MTL reflects a domain-general process of maintenance supporting performance and workload of multiple items in working memory below and beyond working memory capacity. Persistent neural firing during maintenance in the entorhinal cortex may be associated with its preference to process visual-spatial arrays.

Validation of the Clavien-Dindo grading system of complications for microsurgical treatment of unruptured intracranial aneurysms.

OBJECTIVE: Microsurgery plays an essential role in managing unruptured intracranial aneurysms (UIAs). The Clavien-Dindo classification is a therapy-oriented grading system that rates any deviation from the normal postoperative course in five grades. In this study, the authors aimed to test the applicability of the Clavien-Dindo grade (CDG) in patients who underwent microsurgical treatment of UIAs. METHODS: The records of patients who underwent microsurgery for UIAs (January 2013-November 2018) were retrieved from a prospective database. Complications at discharge and at short-term follow-up (3 months) were rated according to the Clavien-Dindo system. Patient outcomes were graded using the modified Rankin Scale (mRS) and the National Institutes of Health Stroke Scale (NIHSS). A descriptive statistic was used for data analysis. RESULTS: Overall, 156 patients underwent 157 surgeries for 201 UIAs (size range 4-42 mm). Thirty-nine patients (25%) had complex UIAs. An adverse event (CDG ≥ I) occurred in 21 patients (13.5%) by the time of discharge. Among these, 10 patients (6.4%) presented with a new neurological deficit. Significant correlations existed between a CDG ≥ I and an increase in mRS and NIHSS scores (p < 0.001). Patients treated for complex aneurysms had a significantly higher risk of developing new neurological deficits (20.5% vs 1.7%, p = 0.007). At the 3-month follow-up, a CDG ≥ I was registered in 16 patients (10.3%); none presented with a new neurological deficit. A CDG ≥ I was associated with a longer hospital length of stay (LOS) (no complication vs CDG ≥ I, 6.2 ± 3.5 days vs 9.3 ± 7.7 days, p = 0.02). CONCLUSIONS: The CDG was applicable to patients who received microsurgery of UIAs. A significant correlation existed between CDG and outcome scales, as well as LOS. The aneurysm complexity was significantly associated with a higher risk for new neurological deficit.

Preoperative risk factors associated with new focal neurological deficit and other major adverse events in first-time intracranial meningioma neurosurgery.

BACKGROUND: Neurosurgical resection is the mainstay of meningioma treatment. Adverse event (AE) rates of meningioma resections are significant, but preoperative risk factors for major AEs in patients undergoing first-time meningioma surgery are largely unknown. The aim of this study was to explore major AEs and identify preoperative risk factors in patients undergoing first-time meningioma surgery. METHODS: Data on all meningioma resections performed at the University Hospital Zurich from 1 January 2013 to 31 December 2018 were collected in a prospective registry. All AEs that occurred within 3 months of surgery were documented in detail and classified as "minor" or "major." Statistical analysis included initial individual bivariate analyses of all preoperative factors and the occurrence of major AEs. Statistically significant variables were then included in a logistic regression model to identify predictors. RESULTS: Three hundred forty-five patients were included in the study. Mean age was 58.1 years, and 77.1% of patients were female. The overall major AE rate was 20.6%; the most common of which was a new focal neurological deficit (12.8% of patients). Six preoperative factors showed a significant association with the occurrence of major AEs in bivariate analysis. All variables included in the logistic regression model showed increased odds of occurrence of major AE, but only tumor complexity as measured by the Milan Complexity Scale was a statistically significant predictor, with a score of 4 or more having twice the odds of major AEs (OR: 2.00, 95% CI: 1.15-3.48). CONCLUSION: High tumor complexity is an independent predictor of the occurrence of major AEs following meningioma resection. Preoperative assessment of tumor complexity using the Milan Complexity Scale is warranted and can aid communication with patients about AE rates and surgical decision-making.

The relation between neuronal firing, local field potentials and hemodynamic activity in the human amygdala in response to aversive dynamic visual stimuli.

The amygdala is a central part of networks of brain regions underlying perception and cognition, in particular related to processing of emotionally salient stimuli. Invasive electrophysiological and hemodynamic measurements are commonly used to evaluate functions of the human amygdala, but a comprehensive understanding of their relation is still lacking. Here, we aimed at investigating the link between fast and slow frequency amygdalar oscillations, neuronal firing and hemodynamic responses. To this aim, we recorded intracranial electroencephalography (iEEG), hemodynamic responses and single neuron activity from the amygdala of patients with epilepsy. Patients were presented with dynamic visual sequences of fearful faces (aversive condition), interleaved with sequences of neutral landscapes (neutral condition). Comparing responses to aversive versus neutral stimuli across participants, we observed enhanced high gamma power (HGP, >60 â€‹Hz) during the first 2 â€‹s of aversive sequence viewing, and reduced delta power (1-4 â€‹Hz) lasting up to 18 â€‹s. In 5 participants with implanted microwires, neuronal firing rates were enhanced following aversive stimuli, and exhibited positive correlation with HGP and hemodynamic responses. Our results show that high gamma power, neuronal firing and BOLD responses from the human amygdala are co-modulated. Our findings provide, for the first time, a comprehensive investigation of amygdalar responses to aversive stimuli, ranging from single-neuron spikes to local field potentials and hemodynamic responses.

Smoking status and perioperative adverse events in patients undergoing cranial tumor surgery.

INTRODUCTION: Smoking is agreed to be a major health risk factor, but it is debated whether it has an influence on perioperative adverse events (AEs) in elective cranial tumor surgery. METHODS: We analyzed the 2013-2016 data from our prospective institutional patient registry. Consecutive patients undergoing elective microsurgical tumor surgery of a glioma or a meningioma were included. Patients were categorized as active smokers, former smokers, and non-smokers. AE were graded by the therapy-oriented Clavien-Dindo scale. Possible predictors of postoperative AE were identified with the help of a binomial logistic regression model. RESULTS: We identified 798 patients, out of which 480 were non-smokers, 193 active smokers, and 125 former smokers. The rate of AEs for active smokers (30%, 95% CI [23-37%]) was indistinguishable from the AE rate of non-smokers (32%, 95% CI [28-37%]). No difference between smoking status was found looking at all AE individually, the odds ratio of suffering from local AE and systemic AE respectively were the same between all smoking groups. The modified Rankin scale at hospital admission was a strong and significant predictor of postoperative AE (P = 0.013). CONCLUSIONS: Active smoking was not associated with an increased risk for postoperative AE, neither looking at the total number of AE nor looking at individual AE. Smoking status should therefore not be a major factor in preoperative decision making. Although not based on data of this study, doctors should always encourage patients to stop smoking due to its well-known detrimental health effect.

Repeated craniotomies for intracranial tumors: is the risk increased? Pooled analysis of two prospective, institutional registries of complications and outcomes.

PURPOSE: Deciding whether to re-operate patients with intracranial tumor recurrence or remnant is challenging, as the data on safety of repeated procedures is limited. This study set out to evaluate the risks for morbidity, mortality, and complications after repeated operations, and to compare those to primary operations. METHODS: Retrospective observational two-center study on consecutive patients undergoing microsurgical tumor resection. The data derived from independent, prospective institutional registries. The primary endpoint was morbidity at 3 months (M3), defined as significant decrease on the Karnofsky Performance Scale (KPS). Secondary endpoints were mortality, rate and severity of complications according to the Clavien-Dindo Grade (CDG). RESULTS: 463/2403 (19.3%) were repeated procedures. Morbidity at M3 occurred in n = 290 patients (12.1%). In univariable analysis, patients undergoing repeated surgery were 98% as likely as patients undergoing primary surgery to experience morbidity (OR 0.98, 95% CI 0.72-1.34, p = 0.889). In multivariable analysis adjusted for age, sex, tumor size, histology and posterior fossa location, the relationship remained stable (aOR 1.25, 95% CI 0.90-1.73, p = 0.186). Mortality was n = 10 (0.4%) at discharge and n = 95 (4.0%) at M3, without group differences. At least one complication occurred in n = 855, and the rate (35.5% vs. 35.9%, p = 0.892) and severity (CDG; p = 0.520) was similar after primary and repeated procedures. Results were reproduced in subgroup analyses for meningiomas, gliomas and cerebral metastases. CONCLUSIONS: Repeated surgery for intracranial tumors does not increase the risk of morbidity. Mortality, and both the rate and severity of complications are comparable to primary operations. This information is of value for patient counseling and the informed consent process.

Incidence, depth, and severity of surgical site infections after neurosurgical interventions.

BACKGROUND: Today, there are only few reports on the incidence of surgical site infections (SSIs) in neurosurgery. The objective of this work was to determine the rate of SSI at a tertiary neurosurgical department for benchmarking purpose. METHODS: Data of consecutive patients undergoing neurosurgical treatment between January 2013 and December 2016 were prospectively entered into a registry. SSIs were diagnosed according to the 2017 Centers for Disease Control and Prevention criteria, with severity graded according to the Clavien-Dindo grade (CDG). We analyzed type and length of surgery (LOS), time to SSI, responsible microorganisms, and its association with the functional status (Karnofsky Performance Status = KPS). RESULTS: Of n = 5463 procedures, a SSI occurred in n = 106 (1.94%). The highest rates of SSI occurred after vascular (3.4%) and cerebrospinal fluid (CSF) diversion procedures (3%), as well as after procedures performed to treat a previous complication (2.9%). There was no difference in LOS across procedures with and without SSI. The median time between the index procedure and SSI was 15.5 days. SSIs were most frequently diagnosed after hospital discharge (55%). The most common microorganisms were coagulase-negative staphylococci, Staphylococcus aureus, and Escherichia coli. In 62.3% of cases, SSI required invasive treatment (surgical revision). Patients with SSI in the in- and out-patient setting (SSI occurring after hospital discharge) presented both with a median KPS of 80. CONCLUSIONS: The current report provides an overview on SSI in a contemporary, unselected, large series of patients undergoing modern neurosurgical care for benchmarking purposes. The overall rate of SSI was about 2%, but subpopulations with higher risks were identified where additional measures could be taken to prevent SSI and monitor patients at risk more closely for SSI.

Standardized assessment of outcome and complications in chronic subdural hematoma: results from a large case series.

INTRODUCTION: Chronic subdural hematomas (cSDH) are commonly deemed to have a benign prognosis. However, detailed and standardized data describing outcome and complications in a large prospective patient cohort is lacking. METHODS: Retrospective analysis of prospectively collected data in our institutional patient registry on consecutive patients undergoing surgery for cSDH from 2013 to 2017. Complications were assessed according to the Clavien-Dindo grading system (CDG). The outcome was measured with respect to two endpoints: occurrence of a complication with CDG 3-5 and lack of improvement in Karnofsky Performance Status (KPS) at the last follow-up. RESULTS: Out of 435 operations, 166 (38.3%) presented a complication until 3 months postoperative (CDG 1, 23 (5.3%); CDG 2, 62 (14.3%); CDG 3a, 7 (1.6%); CDG 3b, 64 (14.7%); CDG 4a, 2 (0.5%); and CDG 5, 8 (1.8%)). Higher CDG correlated with a lower KPS (rs = - 0.27, p < 0.001). A lack of improvement in KPS was associated with a Charlson Comorbidity Index (CCI) > 1 and the iso- or hypodense appearance of the cSDH. CONCLUSIONS: This study provides a reliable estimate of the rate of medical and surgical complications in cSDH surgery. Complications that required a surgical intervention turned out to be rare. Recording complications in a standardized and prospective fashion can therefore serve as a basis for assessing patient outcome and quality control within the department.

The influence of preoperative dependency on mortality, functional recovery and complications after microsurgical resection of intracranial tumors.

INTRODUCTION: The decision whether to operate on patients with intracranial tumors is complex and influenced by patient-specific factors, including the preoperative functional status. This work assesses the risks for mortality and complications, and post-operative recovery in functionally dependent patients undergoing microsurgical resection of intracranial tumors. METHODS: Observational two-center study, analyzing institutional registry data. Dependency was defined as admission Karnofsky Performance Scale (KPS) of ≤ 50. The primary endpoint was in-hospital mortality. Secondary endpoints were rate and type [Clavien-Dindo grade (CDG)] of complications, as well as postoperative change in KPS until the 3-month follow-up (M3). RESULTS: Of n = 1951 patients, n = 98 (5.0%) were dependent. Mortality rates were 2.0% for dependent and 0.4% for independent patients (p = 0.018). In univariable analysis, dependent patients were more likely than independent patients to die in hospital (OR 5.49, 95% CI 1.12-26.8, p = 0.035). In a multivariable model, the effect was slightly attenuated (OR 4.75, 95% CI 0.91-24.7, p = 0.064). Dependent patients tended to experience more postoperative complications. They were more likely to suffer from a severe complication (CDG 4 and 5; OR 3.55, 95% CI 1.49-8.46, p = 0.004). In 40.8 and 52.4% of cases, dependent patients regained functional independence at discharge and M3, respectively. CONCLUSIONS: In operated patients with intracranial tumors presenting functionally dependent at admission, the risk for in-hospital mortality and complications is elevated. However, if conducted successfully, surgery may lead to regain of independence in every second patient within 3 months.

Burr hole trepanation for chronic subdural hematomas: is surgical education safe?

BACKGROUND: There is a paucity of data concerning the safety and efficacy of surgical education for neurosurgical residents in the evacuation of chronic subdural hematomas (cSDH) by burr hole trepanation. METHODS: This is a retrospective analysis of prospectively collected data on consecutive patients receiving burr hole trepanation for uni- or bilateral cSDH. Patients operated by a supervised neurosurgery resident (teaching cases) were compared to patients operated by a board-certified faculty neurosurgeon (BCFN; non-teaching cases). The primary endpoint was surgical revision for any reason until the last follow-up. The secondary endpoint was occurrence of any complication until the last follow-up. Clinical status, type of complications, mortality, length of surgery (LOS), and hospitalization (LOH) were tertiary endpoints. RESULTS: A total of n = 253 cases were analyzed, of which n = 217 (85.8%) were teaching and n = 36 (14.2%) non-teaching cases. The study groups were balanced in terms of age, sex, surgical risk (ASA score), and preoperative status (Karnofsky Performance Scale (KPS), modified Rankin Scale (mRS), National Institute of Health Stroke Scale (NIHSS)). The cohort was followed for a mean of 242 days (standard deviation 302). In multivariate analysis, teaching cases were as likely as non-teaching cases to require revision surgery (OR 0.65, 95% CI 0.27-1.59; p = 0.348) as well as to experience any complication until the last follow-up (OR 0.79, 95% CI 0.37-1.67; p = 0.532). Mean LOS was about 10 min longer in teaching cases (53.0 ± 26.1 min vs. 43.5 ± 17.8 min; p = 0.036), but LOH was similar. There were no group differences in clinical status, mortality and type of complication at discharge, and the last follow-up. CONCLUSIONS: Burr hole trepanation for cSDH can be safely performed by supervised neurosurgical residents enrolled in a structured training program, without increasing the risk for revision surgery, perioperative complications, or worse outcome.

Brainstem cavernoma surgery with the support of pre- and postoperative diffusion tensor imaging: initial experiences and clinical course of 23 patients.

The spatial complexity of highly vulnerable structures makes surgical resection of brainstem cavernomas (BSC) a challenging procedure. Diffusion tensor imaging (DTI) allows for the visualization of white matter tracts and enables a better understanding of the anatomical location of corticospinal and sensory tracts before and after surgery.We investigated the feasibility and clinical usefulness of DTI-based fiber tractography in patients with BSC.Pre- and postoperative DTI visualization of corticospinal and sensory tracts were retrospectively analyzed in 23 individuals with BSC. Preoperative and postoperative DTI-fiber accuracy were associated to the neurological findings. Preoperatively, the corticospinal tracts were visualized in 90 % of the cases and the sensory tracts were visualized in 74 % of the cases. Postoperatively, the corticospinal tracts were visualized in 97 % of the cases and the sensory tracts could be visualized in 80 % of the cases. In all cases, the BSC had caused displacement, thinning, or interruption of the fiber tracts to various degrees. Tract visualization was associated with pre- and postoperative neurological findings. Postoperative damage of the corticospinal tracts was observed in two patients. On follow-up, the Patzold Rating (PR) improved in 19 out of 23 patients (83 %, p = 0.0002).This study confirms that DTI tractography allows accurate and detailed white matter tract visualization in the brainstem, even when an intraaxial lesion affects this structure. Furthermore, visualizing the tracts adjacent to the lesion adds to our understanding of the distorted intrinsic brainstem anatomy and it may assists in planning the surgical approach in specific cases.

A profile on the WISE cortical strip for intraoperative neurophysiological monitoring.

INTRODUCTION: During intraoperative neurophysiological monitoring in neurosurgery, brain electrodes are placed to record electrocorticography or to inject current for direct cortical stimulation. A low impedance electrode may improve signal quality. AREAS COVERED: We review here a brain electrode (WISE Cortical Strip, WCS®), where a thin polymer strip embeds platinum nanoparticles to create conductive electrode contacts. The low impedance contacts enable a high signal-to-noise ratio, allowing for better detection of small signals such as high-frequency oscillations (HFO). The softness of the WCS may hinder sliding the electrode under the dura or advancing it to deeper structures as the hippocampus but assures conformability with the cortex even in the resection cavity. We provide an extensive review on WCS including a market overview, an introduction to the device (mechanistics, cost aspects, performance standards, safety and contraindications) and an overview of the available pre- and post-approval data. EXPERT OPINION: The WCS improves signal detection by lower impedance and better conformability to the cortex. The higher signal-to-noise ratio improves the detection of challenging signals. The softness of the electrode may be a disadvantage in some applications and an advantage in others.