Connectivity Profile for Subthalamic Nucleus Deep Brain Stimulation in Early Stage Parkinson Disease.

OBJECTIVE: This study was undertaken to describe relationships between electrode localization and motor outcomes from the subthalamic nucleus (STN) deep brain stimulation (DBS) in early stage Parkinson disease (PD) pilot clinical trial. METHODS: To determine anatomical and network correlates associated with motor outcomes for subjects randomized to early DBS (n = 14), voxelwise sweet spot mapping and structural connectivity analyses were carried out using outcomes of motor progression (Unified Parkinson Disease Rating Scale Part III [UPDRS-III] 7-day OFF scores [∆baseline➔24 months, MedOFF/StimOFF]) and symptomatic motor improvement (UPDRS-III ON scores [%∆baseline➔24 months, MedON/StimON]). RESULTS: Sweet spot mapping revealed a location associated with slower motor progression in the dorsolateral STN (anterior/posterior commissure coordinates: 11.07 ± 0.82mm lateral, 1.83 ± 0.61mm posterior, 3.53 ± 0.38mm inferior to the midcommissural point; Montreal Neurological Institute coordinates: +11.25, -13.56, -7.44mm). Modulating fiber tracts from supplementary motor area (SMA) and primary motor cortex (M1) to the STN correlated with slower motor progression across STN DBS subjects, whereas fiber tracts originating from pre-SMA and cerebellum were negatively associated with motor progression. Robustness of the fiber tract model was demonstrated in leave-one-patient-out (R = 0.56, p = 0.02), 5-fold (R = 0.50, p = 0.03), and 10-fold (R = 0.53, p = 0.03) cross-validation paradigms. The sweet spot and fiber tracts associated with motor progression revealed strong similarities to symptomatic motor improvement sweet spot and connectivity in this early stage PD cohort. INTERPRETATION: These results suggest that stimulating the dorsolateral region of the STN receiving input from M1 and SMA (but not pre-SMA) is associated with slower motor progression across subjects receiving STN DBS in early stage PD. This finding is hypothesis-generating and must be prospectively tested in a larger study. ANN NEUROL 2023;94:271-284.

Intraoperative physiology augments atlas-based data in awake deep brain stimulation.

BACKGROUND: Deep brain stimulation (DBS) is commonly performed with patients awake to perform intraoperative microelectrode recordings and/or macrostimulation testing to guide final electrode placement. Supplemental information from atlas-based databases derived from prior patient data and visualised as efficacy heat maps transformed and overlaid onto preoperative MRIs can be used to guide preoperative target planning and intraoperative final positioning. Our quantitative analysis of intraoperative testing and corresponding changes made to final electrode positioning aims to highlight the value of intraoperative neurophysiological testing paired with image-based data to optimise final electrode positioning in a large patient cohort. METHODS: Data from 451 patients with movement disorders treated with 822 individual DBS leads at a single institution from 2011 to 2021 were included. Atlas-based data was used to guide surgical targeting. Intraoperative testing data and coordinate data were retrospectively obtained from a large patient database. Medical records were reviewed to obtain active contact usage and neurologist-defined outcomes at 1 year. RESULTS: Microelectrode recording firing profiles differ per track, per target and inform the locations where macrostimulation testing is performed. Macrostimulation performance correlates with the final electrode track chosen. Centroids of atlas-based efficacy heat maps per target were close in proximity to and may predict active contact usage at 1 year. Overall, patient outcomes at 1 year were improved for patients with better macrostimulation response. CONCLUSIONS: Atlas-based imaging data is beneficial for target planning and intraoperative guidance, and in conjunction with intraoperative neurophysiological testing during awake DBS can be used to individualize and optimise final electrode positioning, resulting in favourable outcomes.

Long-term outcomes of mesial temporal laser interstitial thermal therapy for drug-resistant epilepsy and subsequent surgery for seizure recurrence: a multi-centre cohort study.

BACKGROUND: Magnetic resonance-guided laser interstitial thermal therapy (MRgLITT) is a minimally invasive alternative to surgical resection for drug-resistant mesial temporal lobe epilepsy (mTLE). Reported rates of seizure freedom are variable and long-term durability is largely unproven. Anterior temporal lobectomy (ATL) remains an option for patients with MRgLITT treatment failure. However, the safety and efficacy of this staged strategy is unknown. METHODS: This multicentre, retrospective cohort study included 268 patients consecutively treated with mesial temporal MRgLITT at 11 centres between 2012 and 2018. Seizure outcomes and complications of MRgLITT and any subsequent surgery are reported. Predictive value of preoperative variables for seizure outcome was assessed. RESULTS: Engel I seizure freedom was achieved in 55.8% (149/267) at 1 year, 52.5% (126/240) at 2 years and 49.3% (132/268) at the last follow-up ≥1 year (median 47 months). Engel I or II outcomes were achieved in 74.2% (198/267) at 1 year, 75.0% (180/240) at 2 years and 66.0% (177/268) at the last follow-up. Preoperative focal to bilateral tonic-clonic seizures were independently associated with seizure recurrence. Among patients with seizure recurrence, 14/21 (66.7%) became seizure-free after subsequent ATL and 5/10 (50%) after repeat MRgLITT at last follow-up≥1 year. CONCLUSIONS: MRgLITT is a viable treatment with durable outcomes for patients with drug-resistant mTLE evaluated at a comprehensive epilepsy centre. Although seizure freedom rates were lower than reported with ATL, this series represents the early experience of each centre and a heterogeneous cohort. ATL remains a safe and effective treatment for well-selected patients who fail MRgLITT.

Eleven-Year Outcomes of Deep Brain Stimulation in Early-Stage Parkinson Disease.

OBJECTIVE: The deep brain stimulation (DBS) in early-stage Parkinson's disease (PD) pilot clinical trial randomized 30 patients (Hoehn & Yahr II off; medication duration 0.5-4 years; without dyskinesia/motor fluctuations) to optimal drug therapy (ODT) (early ODT) or bilateral subthalamic nucleus (STN) DBS plus ODT (early DBS+ODT). This study aims to report the 11-year outcomes of patients who completed the DBS in early-stage PD pilot clinical trial. MATERIALS AND METHODS: Attempts were made to contact all 29 subjects who completed the two-year trial to participate in an 11-year follow-up study. Mixed-effects models compared overall trend in outcomes for randomization groups (fixed-effects: assigned treatment, year, their interaction; random-effect: subject) to account for repeated measures. RESULTS: Twelve subjects participated in this 11-year follow-up study (n = 8 early ODT, n = 4 early DBS+ODT). Participating subjects were 70.0 ± 4.8 years old with a PD medication duration of 13.7 ± 1.7 years (early DBS duration 11.5 ± 1.3 years, n = 4). Three early ODT subjects received STN-DBS as standard of care (DBS duration 6.5 ± 2.0 years). Early ODT subjects had worse motor complications (Unified Parkinson's Disease Rating Scale [UPDRS]-IV) than early DBS+ODT subjects over the 11-year follow-up period (between-group difference = 3.5 points; pinteraction = 0.03). Early DBS+ODT was well-tolerated after 11 years and showed comparable outcomes to early ODT for other UPDRS domains, Parkinson Disease Questionnaire-39 (PDQ-39), and levodopa equivalent daily dose (LEDD). CONCLUSIONS: Eleven years after randomization, early DBS+ODT subjects had fewer motor complications than early ODT subjects. These results should be interpreted with caution because only 40% of pilot trial subjects participated in this 11-year follow-up study. The Food and Drug Administration has approved the conduct of a pivotal clinical trial evaluating DBS in early-stage PD (IDEG050016). CLINICAL TRIAL REGISTRATION: The Clinicaltrials.gov registration number for the study is NCT00282152.

BDNF rs6265 Genotype Influences Outcomes of Pharmacotherapy and Subthalamic Nucleus Deep Brain Stimulation in Early-Stage Parkinson's Disease.

INTRODUCTION: The efficacy of pharmacotherapy and deep brain stimulation of the subthalamic nucleus in treating Parkinson's disease motor symptoms is highly variable and may be influenced by patient genotype. The relatively common (prevalence about one in three) and protein-altering rs6265 single nucleotide polymorphism (C > T) in the gene BDNF has been associated with different clinical outcomes with levodopa. OBJECTIVE: We sought to replicate this reported association in early-stage Parkinson's disease subjects and to examine whether a difference in clinical outcomes was present with subthalamic nucleus deep brain stimulation. MATERIALS AND METHODS: Fifteen deep brain stimulation and 13 medical therapy subjects were followed for 24 months as part of the Vanderbilt DBS in Early Stage PD clinical trial (NCT00282152, FDA IDE #G050016). Primary outcome measures were the Unified Parkinson's Disease Rating Scale (UPDRS) and Parkinson's Disease Questionnaire-39. RESULTS: Outcomes with drug therapy in subjects carrying the rs6265 T allele were significantly worse following 12 months of treatment compared to C/C subjects (UPDRS: +20 points, p = 0.019; PDQ-39: +16 points, p = 0.018). In contrast, rs6265 genotype had no effect on overall motor response to subthalamic nucleus deep brain stimulation at any time point; further, rs6265 C/C subjects treated with stimulation were associated with worse UPDRS part II scores at 24 months compared to medical therapy. CONCLUSIONS: Genotyping for the rs6265 polymorphism may be useful for predicting long-term response to drug therapy and counseling Parkinson's disease patients regarding whether to consider earlier subthalamic nucleus deep brain stimulation. Validation in a larger cohort of early-stage Parkinson's disease subjects is warranted.

Examining the Need to Standardize Implanted Stimulator Connectors: NANS Survey Results.

INTRODUCTION: Connectors between implanted stimulator electrodes and pulse generators allow revisions, including battery changes or generator upgrades, to proceed without disturbing uninvolved components, such as the electrode. As new devices are introduced, however, connector incompatibility, even with updated hardware from the same manufacturer, can lead to additional procedures, expense, and morbidity. MATERIALS AND METHODS: Following the example of the cardiac pacemaker/defibrillator industry, the Institute of Neuromodulation (IoN) met to explore the possibility of creating connector standards for implanted neurostimulation devices. At a subsequent meeting of the Association for the Advancement of Medical Instrumentation, which coordinates the development of such standards, industry representatives asked for data defining the need for a new standard. Accordingly, IoN prepared an online survey to be sent to the North American Neuromodulation Society mailing list regarding experience with the connectivity of spinal cord stimulation (SCS) generators and electrodes. RESULTS: The 87 respondents of 9657 surveyed included 77 clinicians, who reported a total of 42,572 SCS implants and revisions. More than a quarter of revisions (2741 of 9935) required the interconnection of devices made by separate manufacturers, in most cases (n = 1528) to take advantage of a new feature (e.g., rechargeability, new waveform) or because an original component could not be replaced (n = 642). Connector adapters provided by manufacturers were used in less than half (n = 1246) of these cases. Nearly all (94%) of the clinicians agreed that standardized connectors should be developed for SCS, and 86% opined that standardized connectors should be developed for other neurostimulation therapies. CONCLUSION: Those who responded to our survey support the development of standard connectors for implanted stimulators, with voluntary compliance by manufacturers, to mitigate the need for adapters and facilitate interchanging components when appropriate. Other advantages to patients and manufacturers might accrue from the adoption of standards, as technology evolves and diversifies.

Structural Correlates of the Sensorimotor Cerebellum in Parkinson's Disease and Essential Tremor.

BACKGROUND: Parkinson's disease (PD) and essential tremor (ET) are commonly encountered movement disorders. Pathophysiologic processes that localize to the cerebellum are described in both. There are limited studies investigating cerebellar structural changes in these conditions, largely because of inherent challenges in the efficiency of segmentation. METHODS: We applied a novel multiatlas cerebellar segmentation method to T1-weighted images in 282 PD and 111 essential tremor patients to define 26 cerebellar lobule volumes. The severity of postural and resting tremor in both populations and gait and postural instability in PD patients were defined using subscores of the UPDRS and Washington Heights-Inwood Genetic Study motor scales. These clinical measurements were related to lobule volume size. Multiple comparisons were controlled using a false discovery rate method. RESULTS: Group differences were identified between ET and PD patients, with reductions in deep cerebellar nucleus volume in ET versus reduced lobule VI volume in PD. In ET patients, lobule VIII was negatively correlated with the severity of postural tremor. In PD patients, lobule IV was positively correlated with resting tremor and total tremor severity. We observed differences in cerebellar structure that localized to sensorimotor lobules of the cerebellum. Lobule volumes appeared to differentially relate to clinical symptoms, suggesting important clinicopathologic distinctions between these conditions. These results emphasize the role of the cerebellum in tremor symptoms and should foster future clinical and pathologic investigations of the sensorimotor lobules of the cerebellum. © 2020 International Parkinson and Movement Disorder Society.

Long-term, single-center surveillance of non-invasive group A streptococcal (GAS) infections, emm types and emm clusters.

Group A streptococci (GAS) are among the most frequent pathogens in children. Many epidemiological studies focus on specific GAS infections (such as tonsillopharyngitis or invasive disease), on GAS carriers or on post-streptococcal sequelae. By comparison, reports on regional GAS characteristics, particularly circulating non-invasive GAS in Europe, are rare. In a monocentric study, all GAS isolated from pediatric patients at a tertiary care hospital over a 6-year period (2006-2012) were characterized. GAS emm types and clusters were determined. Associated patient data were analyzed. Five hundred sixty-six GAS strains were collected. GAS tonsillopharyngitis was most common (71.6%), followed by pyoderma (6.0%), otitis media (3.7%), perineal dermatitis (3.4%), and invasive infections (1.4%). Colonizing strains represented 13.6% of GAS. GAS emm12 was most prevalent among invasive and non-invasive isolates. Emm1, emm4, emm28, and emm89 were the most frequent non-invasive GAS strains. The emm E4 cluster was most common, followed by the A-C4, A-C3, and E1. Among the GAS infections, different emm types and clusters were identified, e.g., emm4 was more common among patients with scarlet fever. Three new emm subtypes were characterized: emm29.13, emm36.7, and emm75.5. This comprehensive review of a large, local GAS cohort points to the differences between and similarities among GAS genotypes and disease manifestations, while minimizing regional variations. Considerable deviation from previous epidemiological findings is described, especially regarding the frequent detection of emm1 and emm89 in non-invasive GAS infections. Periodic updates on molecular and epidemiological GAS characteristics are needed to track the multifaceted pathogenic potential of GAS.

Survival of Group A Streptococcus (GAS) is Enhanced Under Desiccated Culture Conditions.

Streptococcus pyogenes or Group A Streptococcus (GAS) infections are the leading cause of bacterial tonsillopharyngitis. The bacterium can survive and persist within the human host for a long time as it is observed in up to 40% of the population who are considered as carriers. Recurrent tonsillopharyngitis is a particular problem in children which is caused either by relapses due to failed bacterial clearance or by reinfection. A prolonged survival in tonsillar crypts or on inanimate surfaces might be sources for reinfection. We therefore examined 64 clinical GAS isolates from children with tonsillopharyngitis for their long-term survival under either liquid or desiccated culture conditions. After 6 weeks, the overall GAS survival rate was 400-fold increased under desiccated culture conditions compared to liquid culture conditions, but varied depending on the emm-type between 20-fold (emm4) and 14000-fold (emm3). The survival rates of isolates from emm75 were significantly lower which is probably due to their production of hydrogen peroxide up to fatal doses. No hydrogen peroxide production could be detected for other emm-types. Furthermore, 11 isolates from patients with recurrent tonsillopharyngitis were compared to isolates of the same emm-type from patients with single episodes of tonsillopharyngitis. A significant elevated pH value and an increased survival rate for isolates from patients with recurrent infections were observed. In conclusion, significant differences in long-term survival of different GAS isolates as well as survival under desiccated culture conditions might contribute to both failed bacterial clearance and reinfection in patients with recurrent tonsillopharyngitis.

Intrathecal Baclofen for Severe Spasticity: Longitudinal Data From the Product Surveillance Registry.

OBJECTIVE: To assist in the assessment of intrathecal baclofen (ITB) therapy risks and benefits by providing surgical intervention rate, safety, and elective device replacement rate data. MATERIALS AND METHODS: An ongoing prospective, long-term, multicenter Product Surveillance Registry (PSR) (NCT01524276) enrolled consented patients implanted with the SynchroMed II infusion system. Pump and catheter performance data were collected, with patients followed prospectively for events related to the device, procedure, and therapy. Investigators provided event descriptions, patient symptoms, and patient outcomes. RESULTS: We analyzed registry data from 1743 patients (77% adult, 46.8% female) treated with ITB for severe spasticity at 53 registry sites between August 2003 and October 2017, for an accumulated 6481 patient-years. Discontinuation from the registry was largely (58.6% of discontinued patients) due to study site closure and patient relocation; exit due to an adverse event was limited to 0.3%. After 10 years, 87.2% of adult and 76.3% of pediatric patients continued with ITB. Overall, 99.1% of pumps reaching end of battery life were replaced at the time of explant. CONCLUSIONS: ITB therapy for the treatment of severe spasticity requires surgical implantation of a programmable infusion system for chronic drug delivery. If complications arise, many necessitate surgical intervention for correction. For spinal and cerebral spasticity in pediatric and adult patients, discontinuation rates due to an adverse event were low (0.3%), and there was high acceptance (99.1%) of surgical intervention for therapy continuation. Patient/caregiver willingness to accept surgical and other risks for therapy continuation was extremely high.

Effects of surgical targeting in laser interstitial thermal therapy for mesial temporal lobe epilepsy: A multicenter study of 234 patients.

OBJECTIVE: Laser interstitial thermal therapy (LITT) for mesial temporal lobe epilepsy (mTLE) has reported seizure freedom rates between 36% and 78% with at least 1 year of follow-up. Unfortunately, the lack of robust methods capable of incorporating the inherent variability of patient anatomy, the variability of the ablated volumes, and clinical outcomes have limited three-dimensional quantitative analysis of surgical targeting and its impact on seizure outcomes. We therefore aimed to leverage a novel image-based methodology for normalizing surgical therapies across a large multicenter cohort to quantify the effects of surgical targeting on seizure outcomes in LITT for mTLE. METHODS: This multicenter, retrospective cohort study included 234 patients from 11 centers who underwent LITT for mTLE. To investigate therapy location, all ablation cavities were manually traced on postoperative magnetic resonance imaging (MRI), which were subsequently nonlinearly normalized to a common atlas space. The association of clinical variables and ablation location to seizure outcome was calculated using multivariate regression and Bayesian models, respectively. RESULTS: Ablations including more anterior, medial, and inferior temporal lobe structures, which involved greater amygdalar volume, were more likely to be associated with Engel class I outcomes. At both 1 and 2 years after LITT, 58.0% achieved Engel I outcomes. A history of bilateral tonic-clonic seizures decreased chances of Engel I outcome. Radiographic hippocampal sclerosis was not associated with seizure outcome. SIGNIFICANCE: LITT is a viable treatment for mTLE in patients who have been properly evaluated at a comprehensive epilepsy center. Consideration of surgical factors is imperative to the complete assessment of LITT. Based on our model, ablations must prioritize the amygdala and also include the hippocampal head, parahippocampal gyrus, and rhinal cortices to maximize chances of seizure freedom. Extending the ablation posteriorly has diminishing returns. Further work is necessary to refine this analysis and define the minimal zone of ablation necessary for seizure control.

Hydrogen Peroxide Production of Group A Streptococci (GAS) is emm-Type Dependent and Increased at Low Temperatures.

Group A streptococcus (GAS) is an important human pathogen whose clinical isolates differ in their ability to produce hydrogen peroxide (H2O2). H2O2 is primarily produced by the enzyme lactate oxidase (LctO), an in depth in silico research revealed that all genome-sequenced GAS possess the required gene lctO. The importance of lctO for GAS is underlined by its highly conserved catabolite control element (cre box) as well as its perfect promotor sequence in comparison to the known consensus sequences of the Gram-positive model organism Bacillus subtilis. In this study, we provide further insight in the function and regulation of lactate oxidase by analyzing a large group of clinical GAS isolates. We found that H2O2 production increased over time in the late stationary phase; after 4 days of incubation, 5.4% of the isolates showed a positive result at 37 °C, while the rate increased to 16.4% at 20 °C. This correlation between H2O2 production and low temperatures suggests additional regulatory mechanisms for lctO besides catabolite control protein A (CcpA) and indicates that lctO might play a role for GAS energy metabolism at sub-body temperatures. Furthermore, we could identify that H2O2 production was different among clinical isolates; we could correlate H2O2 production to emm-types, indicating that emm-types 6 and 75 had the highest rate of H2O2 production. The emm-type- and temperature-dependent H2O2 production of clinical GAS isolates might contribute to their different survival strategies.

Charting the road forward in psychiatric neurosurgery: proceedings of the 2016 American Society for Stereotactic and Functional Neurosurgery workshop on neuromodulation for psychiatric disorders.

OBJECTIVE: Refractory psychiatric disease is a major cause of morbidity and mortality worldwide, and there is a great need for new treatments. In the last decade, investigators piloted novel deep brain stimulation (DBS)-based therapies for depression and obsessive-compulsive disorder (OCD). Results from recent pivotal trials of these therapies, however, did not demonstrate the degree of efficacy expected from previous smaller trials. To discuss next steps, neurosurgeons, neurologists, psychiatrists and representatives from industry convened a workshop sponsored by the American Society for Stereotactic and Functional Neurosurgery in Chicago, Illinois, in June of 2016. DESIGN: Here we summarise the proceedings of the workshop. Participants discussed a number of issues of importance to the community. First, we discussed how to interpret results from the recent pivotal trials of DBS for OCD and depression. We then reviewed what can be learnt from lesions and closed-loop neurostimulation. Subsequently, representatives from the National Institutes of Health, the Food and Drug Administration and industry discussed their views on neuromodulation for psychiatric disorders. In particular, these third parties discussed their criteria for moving forward with new trials. Finally, we discussed the best way of confirming safety and efficacy of these therapies, including registries and clinical trial design. We close by discussing next steps in the journey to new neuromodulatory therapies for these devastating illnesses. CONCLUSION: Interest and motivation remain strong for deep brain stimulation for psychiatric disease. Progress will require coordinated efforts by all stakeholders.

Confined Thalamic Deep Brain Stimulation in Refractory Essential Tremor.

BACKGROUND: Thalamic ventral intermediate nucleus (VIM) deep brain stimulation (DBS) is an effective therapy for medication-refractory essential tremor (ET). However, 13-40% of patients with an initially robust tremor efficacy lose this benefit over time despite reprogramming attempts. At our institution, a cohort of ET patients with VIM DBS underwent implantation of a second anterior (ventralis oralis anterior; VOA) DBS lead to permit "confined stimulation." We sought to assess whether confined stimulation conferred additional tremor capture compared to VIM or VOA stimulation alone. METHODS: Seven patients participated in a protocol-based programming session during which a video-recorded Fahn-Tolosa-Marin Part A (FTM-A) tremor rating scale was used in the following 4 DBS states: off stimulation, VIM stimulation alone, VOA stimulation alone, and dual lead (confined) stimulation. RESULTS: The average (SD) baseline FTM-A off score was 17.6 (4.0). VIM stimulation alone lowered the average FTM-A total score to 6.9 (4.0). Confined stimulation further attenuated the tremor, reducing the total score to 5.7 (2.8). CONCLUSIONS: Confined thalamic DBS can provide additional symptomatic benefits in patients with unsatisfactory tremor control from VIM or VOA stimulation alone.

Functional connectivity disturbances of the ascending reticular activating system in temporal lobe epilepsy.

OBJECTIVE: Seizures in temporal lobe epilepsy (TLE) disturb brain networks and lead to connectivity disturbances. We previously hypothesised that recurrent seizures in TLE may lead to abnormal connections involving subcortical activating structures including the ascending reticular activating system (ARAS), contributing to neocortical dysfunction and neurocognitive impairments. However, no studies of ARAS connectivity have been previously reported in patients with epilepsy. METHODS: We used resting-state functional MRI recordings in 27 patients with TLE (67% right sided) and 27 matched controls to examine functional connectivity (partial correlation) between eight brainstem ARAS structures and 105 cortical/subcortical regions. ARAS nuclei included: cuneiform/subcuneiform, dorsal raphe, locus coeruleus, median raphe, parabrachial complex, pontine oralis, pedunculopontine and ventral tegmental area. Connectivity patterns were related to disease and neuropsychological parameters. RESULTS: In control subjects, regions showing highest connectivity to ARAS structures included limbic structures, thalamus and certain neocortical areas, which is consistent with prior studies of ARAS projections. Overall, ARAS connectivity was significantly lower in patients with TLE than controls (p<0.05, paired t-test), particularly to neocortical regions including insular, lateral frontal, posterior temporal and opercular cortex. Diminished ARAS connectivity to these regions was related to increased frequency of consciousness-impairing seizures (p<0.01, Pearson's correlation) and was associated with impairments in verbal IQ, attention, executive function, language and visuospatial memory on neuropsychological evaluation (p<0.05, Spearman's rho or Kendell's tau-b). CONCLUSIONS: Recurrent seizures in TLE are associated with disturbances in ARAS connectivity, which are part of the widespread network dysfunction that may be related to neurocognitive problems in this devastating disorder.

The Effects of Dexmedetomidine on Microelectrode Recordings of the Subthalamic Nucleus during Deep Brain Stimulation Surgery: A Retrospective Analysis.

BACKGROUND: The placement of subthalamic nucleus (STN) deep brain stimulation (DBS) electrodes can be facilitated by intraoperative microelectrode recording (MER) of the STN. OBJECTIVES: Optimal anesthetic management during surgery remains unclear because of a lack of quantitative data of the effect of anesthetics on MER. Therefore, we measured the effects of dexmedetomidine (DEX) on MER measures of the STN commonly taken intraoperatively. METHODS: MER from 45 patients was retrospectively compared between patients treated with remifentanil (REMI) alone or both REMI and DEX, which are the 2 main standards of care at our center. The measures examined were population activity, such as root mean square, STN length, and number of passes yielding STN, and the single-neuron measures of firing rate and variability. RESULTS: The addition of DEX does not affect population measures (number of passes: DEX+REMI, n = 68, REMI only, n = 154), or neuronal firing rates (number of neurons: DEX+REMI, n = 64, REMI only, n = 72), but firing rate variability was reduced. CONCLUSIONS: In this cohort, population-based measures routinely used for electrode placement in the STN were unaffected by DEX when added to REMI. Neuronal firing rates were also unaffected, but their variability was reduced, even beyond 20 min after cessation.

Subthalamic Nucleus Deep Brain Stimulation Alters Prefrontal Correlates of Emotion Induction.

OBJECTIVES: Deep brain stimulation (DBS) of the subthalamic nucleus (STN) improves motor symptoms in advanced Parkinson's disease. STN DBS may also affect emotion, possibly by impacting a parallel limbic cortico-striatal circuit. The objective of this study was to investigate changes in prefrontal cortical activity related to DBS during an emotion induction task. MATERIALS AND METHODS: We used near infrared spectroscopy to monitor prefrontal cortex hemodynamic changes during an emotion induction task. Seven DBS patients were tested sequentially in the stimulation-on and stimulation-off states while on dopaminergic medication. Patients watched a series of positive, negative, and neutral videos. The general linear model was used to compare prefrontal oxygenated hemoglobin concentration between DBS states. RESULTS: Deep brain stimulation was correlated with prefrontal oxygenated hemoglobin changes relative to the stimulation off state in response to both positive and negative videos. These changes were specific to emotional stimuli and were not seen during neutral stimuli. CONCLUSIONS: These results suggest that STN stimulation influences the prefrontal cortical representation of positive and negative emotion induction.

Regional and global connectivity disturbances in focal epilepsy, related neurocognitive sequelae, and potential mechanistic underpinnings.

Epilepsy is among the most common brain network disorders, and it is associated with substantial morbidity and increased mortality. Although focal epilepsy was traditionally considered a regional brain disorder, growing evidence has demonstrated widespread network alterations in this disorder that extend beyond the epileptogenic zone from which seizures originate. The goal of this review is to summarize recent investigations examining functional and structural connectivity alterations in focal epilepsy, including neuroimaging and electrophysiologic studies utilizing model-based or data-driven analytic methods. A significant subset of studies in both mesial temporal lobe epilepsy and focal neocortical epilepsy have demonstrated patterns of increased connectivity related to the epileptogenic zone, coupled with decreased connectivity in widespread distal networks. Connectivity patterns appear to be related to the duration and severity of disease, suggesting progressive connectivity reorganization in the setting of recurrent seizures over time. Global resting-state connectivity disturbances in focal epilepsy have been linked to neurocognitive problems, including memory and language disturbances. Although it is possible that increased connectivity in a particular brain region may enhance the propensity for seizure generation, it is not clear if global reductions in connectivity represent the damaging consequences of recurrent seizures, or an adaptive mechanism to prevent seizure propagation away from the epileptogenic zone. Overall, studying the connectome in focal epilepsy is a critical endeavor that may lead to improved strategies for epileptogenic-zone localization, surgical outcome prediction, and a better understanding of the neuropsychological implications of recurrent seizures.

Deep brain stimulation of the subthalamic nucleus alters frontal activity during spatial working memory maintenance of patients with Parkinson's disease.

Deep brain stimulation (DBS) of the subthalamic nucleus (STN) improves the motor symptoms of Parkinson's disease (PD). The STN may represent an important relay station not only in the motor but also the associative cortico-striato-thalamocortical pathway. Therefore, STN stimulation may alter cognitive functions, such as working memory (WM). We examined cortical effects of STN-DBS on WM in early PD patients using functional near-infrared spectroscopy. The effects of dopaminergic medication on WM were also examined. Lateral frontal activity during WM maintenance was greater when patients were taking dopaminergic medication. STN-DBS led to a trend-level worsening of WM performance, accompanied by increased lateral frontal activity during WM maintenance. These findings suggest that STN-DBS in PD might lead to functional modifications of the basal ganglia-thalamocortical pathway during WM maintenance.