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365 result(s) for "Warren, Aaron"
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A human brain network linked to restoration of consciousness after deep brain stimulation
Disorders of consciousness are characterized by severe impairments in arousal and awareness. Deep brain stimulation is a potential treatment, but outcomes vary—possibly due to differences in patient characteristics, electrode placement, or the specific brain network engaged. We describe 40 patients with disorders of consciousness undergoing deep brain stimulation targeting the thalamic centromedian-parafascicular complex. Improvements in consciousness are associated with better-preserved gray matter, particularly in the striatum. Electric field modeling reveals that stimulation is most effective when it extends below the centromedian nucleus, engaging the inferior parafascicular nucleus and the adjacent ventral tegmental tract—a pathway that connects the brainstem and hypothalamus and runs along the midbrain-thalamus border. External validation analyses show that effective stimulation engages a brain network overlapping with disrupted patterns of brain activity observed in two independent cohorts with impaired consciousness: one with arousal-impairing stroke lesions and the other with awareness-impairing seizures. Together, these findings advance the field by informing patient selection, refining stimulation targets, and identifying a brain network linked to recovery that may have broader therapeutic relevance across consciousness-impairing conditions. In people with severe brain injuries, stimulation restored consciousness by engaging a deep brain circuit for wakefulness—revealing a target that may also guide treatment in stroke and epilepsy.
Targeting the centromedian thalamic nucleus for deep brain stimulation
ObjectivesDeep brain stimulation (DBS) of the centromedian thalamic nucleus (CM) is an emerging treatment for multiple brain diseases, including the drug-resistant epilepsy Lennox-Gastaut syndrome (LGS). We aimed to improve neurosurgical targeting of the CM by: (1) developing a structural MRI approach for CM visualisation, (2) identifying the CM’s neurophysiological characteristics using microelectrode recordings (MERs) and (3) mapping connectivity from CM-DBS sites using functional MRI (fMRI).Methods19 patients with LGS (mean age=28 years) underwent presurgical 3T MRI using magnetisation-prepared 2 rapid acquisition gradient-echoes (MP2RAGE) and fMRI sequences; 16 patients proceeded to bilateral CM-DBS implantation and intraoperative thalamic MERs. CM visualisation was achieved by highlighting intrathalamic borders on MP2RAGE using Sobel edge detection. Mixed-effects analysis compared two MER features (spike firing rate and background noise) between ventrolateral, CM and parafasicular nuclei. Resting-state fMRI connectivity was assessed using implanted CM-DBS electrode positions as regions of interest.ResultsThe CM appeared as a hyperintense region bordering the comparatively hypointense pulvinar, mediodorsal and parafasicular nuclei. At the group level, reduced spike firing and background noise distinguished CM from the ventrolateral nucleus; however, these trends were not found in 20%–25% of individual MER trajectories. Areas of fMRI connectivity included basal ganglia, brainstem, cerebellum, sensorimotor/premotor and limbic cortex.ConclusionsIn the largest clinical trial of DBS undertaken in patients with LGS to date, we show that accurate targeting of the CM is achievable using 3T MP2RAGE MRI. Intraoperative MERs may provide additional localising features in some cases; however, their utility is limited by interpatient variability. Therapeutic effects of CM-DBS may be mediated via connectivity with brain networks that support diverse arousal, cognitive and sensorimotor processes.
Clinical trials for Lennox–Gastaut syndrome: Challenges and priorities
Objective: Lennox‐Gastaut syndrome (LGS) is a severe, childhood‐onset epilepsy that is typically refractory to treatment. We surveyed the current landscape of LGS treatment, aiming to identify challenges to the development of efficacious therapies, and to articulate corresponding priorities toward clinical trials that improve outcomes. Methods: The LGS Special Interest Group of the Pediatric Epilepsy Research Consortium integrated evidence from the literature and expert opinion, into a narrative review. Results: We provide an overview of approved and emerging medical, dietary, surgical and neuromodulation approaches for LGS. We note that quality of care could be improved by standardizing LGS treatment based on expert consensus and empirical data. Whereas LGS natural history is incompletely understood, prospective studies and use of large retrospective datasets to understand LGS across the lifespan would enable clinical trials that address these dynamics. Recent discoveries related to LGS pathophysiology should enable development of disease‐modifying therapies, which are currently lacking. Finally, clinical trials have focused chiefly on seizures involving “drops,” but should incorporate additional patient‐centered outcomes, using emerging measures adapted to people with LGS. Interpretation: Clinicians and researchers should enact these priorities, with the goal of patient‐centered clinical trials that are tailored to LGS pathophysiology and natural history.
Understanding Cognitive Aging Through White Matter: A Fixel‐Based Analysis
Diffusion‐weighted imaging (DWI) has been frequently used to examine age‐related deterioration of white matter microstructure and its relationship to cognitive decline. However, typical tensor‐based analytical approaches are often difficult to interpret due to the challenge of decomposing and (mis)interpreting the impact of crossing fibers within a voxel. We hypothesized that a novel analytical approach capable of resolving fiber‐specific changes within each voxel (i.e., fixel‐based analysis [FBA])—would show greater sensitivity relative to the traditional tensor‐based approach for assessing relationships between white matter microstructure, age, and cognitive performance. To test our hypothesis, we studied 636 cognitively normal adults aged 65–80 years (mean age = 69.8 years; 71% female) using diffusion‐weighted MRI. We analyzed fixels (i.e., fiber‐bundle elements) to test our hypotheses. A fixel provides insight into the structural integrity of individual fiber populations in each voxel in the presence of multiple crossing fiber pathways, allowing for potentially increased specificity over other diffusion measures. Linear regression was used to investigate associations between each of three fixel metrics (fiber density, cross‐section, and density × cross‐section) with age and cognitive performance. We then compared and contrasted the FBA results to a traditional tensor‐based approach examining voxel‐wise fractional anisotropy. In a whole‐brain analysis, significant associations were found between fixel‐based metrics and age after adjustments for sex, education, total brain volume, site, and race. We found that increasing age was associated with decreased fiber density and cross‐section, namely in the fornix, striatal, and thalamic pathways. Further analysis revealed that lower fiber density and cross‐section were associated with poorer performance in measuring processing speed and attentional control. In contrast, the tensor‐based analysis failed to detect any white matter tracts significantly associated with age or cognition. Taken together, these results suggest that FBAs of DWI data may be more sensitive for detecting age‐related white matter changes in an older adult population and can uncover potentially clinically important associations with cognitive performance. We assessed the sensitivity and utility of a fixel‐based white matter analysis to detect age‐related white matter degeneration. Results revealed that fixel‐based analyses were more sensitive than tensor‐based analyses and that age‐related white matter decline was related to cognitive decline.
Methodologies to detect cortico-cortical evoked potentials: a systematic review
Cortico-cortical evoked potentials (CCEPs) are electrophysiological responses elicited by direct electrical stimulation of one cortical region and recorded from another, providing insights into functional connectivity and communication pathways between brain areas. However, no consistent standard for defining and measuring CCEPs currently exists. We conducted a systematic review of the CCEP literature on detection methods to evaluate commonalities and gaps in methodology. Extracted data included demographics, disease, recording type, montage, recording system, stimulation amplitude and frequency, time window used for epoching around stimulus onset, open access availability, and detection approach. Of 187 studies undergoing full-text review, over half lacked a description of the CCEP detection method. Specifically, 9.1% utilized visual identification, whereas 49.74% did not explicitly state the method. The remaining 72 studies represented 3,424 patients, of whom 58.3% had sEEG electrodes and most had epilepsy. The most common detection method was threshold-based (68.1%), followed by statistical testing (16.7%) to determine whether CCEPs differed significantly from baseline, data-driven methods (4.1%) that quantify responses after learning from data, and frequency-based approaches (4.1%). Bipolar (48.6%) and single-electrode referential montages (18.1%) were most frequently employed. Current CCEP detection methods lack consensus, with many studies omitting methodological details and relying heavily on threshold-based techniques that assume fixed response shapes. Future research should encourage the use of data-driven approaches, which learn directly from data, offer more robust alternatives, and improve quantification in both clinical and research contexts. https://www.crd.york.ac.uk/PROSPERO/view/CRD42024568261, identifier CRD42024568261.
Current practices and trends in surgical decision‐making for children with Lennox–Gastaut syndrome: A cross‐sectional survey by the Pediatric Epilepsy Research Consortium
Objective The objective of this study is to characterize contemporary surgical management practices and factors influencing surgical decision‐making in the management of Lennox–Gastaut Syndrome (LGS) across pediatric epilepsy centers in the United States. Methods A 45‐item cross‐sectional survey was developed and distributed to Pediatric Epilepsy Research Consortium centers. Domains included institutional demographics, surgical evaluation timing and goals, presurgical workup, procedural utilization and outcomes, and barriers to surgery. Descriptive statistics and thematic analysis were performed. Results Thirty‐two pediatric epilepsy centers participated (38% response), the majority comprising pediatric epileptologists at Level 4 National Association of Epilepsy Centers. Most centers (66%) considered surgery after failure of 3–4 antiseizure medications. Presurgical workup typically included brain magnetic resonance imaging (MRI), long‐term electroencephalography (EEG) monitoring, and neuropsychological assessment, while use of functional imaging, magnetoencephalography, and intracranial EEG varied considerably. All centers offered vagus nerve stimulation and corpus callosotomy; 80%–90% offered resection, hemispherectomy, responsive neurostimulation (RNS); 60%–65% offered deep brain stimulation (DBS) and laser ablation. Among centers offering RNS, half targeted thalamic structures exclusively, and the remainder targeted cortical or combined cortical‐thalamic structures; the centromedian nucleus was the preferred thalamic target for RNS and DBS. Surgical decision‐making was influenced by patient characteristics, procedural considerations, and systemic factors. Seizure frequency, family preference, and multidisciplinary input were highly rated across all interventions. Etiology was critical for resection and hemispherectomy, while financial constraints, insurance barriers, and the need for future neuroimaging impacted neuromodulation selection. Scenario‐specific trends included less frequent consideration of DBS and RNS in children under five years, less use of hemispherectomy in older children, preference for corpus callosotomy in children with predominantly drop seizures, and procedural selection based on MRI findings. Significance Substantial variability exists in the surgical management of LGS. These findings highlight critical opportunities to harmonize practices, reduce disparities, and guide comparative effectiveness research to optimize outcomes. Plain Language Summary Lennox–Gastaut Syndrome (LGS) is a severe form of epilepsy that may require surgery when medications are not effective. This study found that surgical care for LGS varies widely across pediatric epilepsy centers in the United States, including when surgery is recommended, how patients are evaluated, and which procedures are available. Newer approaches such as brain stimulation are being used more often, although access remains inconsistent. These findings highlight the need for clearer treatment pathways to ensure that children with LGS have equitable access to the best possible care.
Surgical management of status epilepticus: A systematic review
Status Epilepticus (SE), unresponsive to medical management, is associated with high morbidity and mortality. Surgical management is typically considered in these refractory cases. The best surgical approach for affected patients remains unclear; however, given the lack of controlled trials exploring the role of surgery. We performed a systematic review according to PRIMSA guidelines, including case reports and series describing surgical interventions for patients in SE. Cases (157 patients, median age 12.9 years) were followed for a median of 12 months. Patients were in SE for a median of 21 days before undergoing procedures including: focal resection (36.9%), functional hemispherectomy (21%), lobar resection (12.7%), vagus nerve stimulation (VNS) (12.7%), deep brain stimulation (DBS) (6.4%), multiple subpial transection (MST) (3.8%), responsive neurostimulation (RNS) (1.9%), and cortical stimulator placement (1.27%), with 24 patients undergoing multiple procedures. Multiple SE semiologies were identified. 47.8% of patients had focal seizures, and 65% of patients had focal structural abnormalities on MRI. SE persisted for 36.8 ± 47.7 days prior to surgical intervention. SE terminated following surgery in 81.5%, terminated with additional adjuncts in 10.2%, continued in 1.9%, and was not specified in 6.4% of patients. Long‐term seizure outcomes were favorable, with the majority improved and 51% seizure‐free. Eight patients passed away in follow‐up, of which three were in SE. Seizures emerging from one hemisphere were both more likely to immediately terminate (OR 4.7) and lead to long‐term seizure‐free status (OR 3.9) compared to nonunilateral seizures. No other predictors, including seizure focality, SE duration, or choice of surgical procedure, were predictors of SE termination. Surgical treatment of SE can be effective in terminating SE and leading to sustained seizure freedom, with many different procedures showing efficacy if matched appropriately with SE semiology and etiology. Plain Language Summary Patients with persistent seizures (Status Epilepticus) that do not stop following medications can be treated effectively with surgery. Here, we systematically review the entirety of existing literature on surgery for treating status epilepticus to better identify how and when surgery is used and what patients do after surgery.
Mitochondrial Sirt3 contributes to the bone loss caused by aging or estrogen deficiency
Altered mitochondria activity in osteoblasts and osteoclasts has been implicated in the loss of bone mass associated with aging and estrogen deficiency - the 2 most common causes of osteoporosis. However, the mechanisms that control mitochondrial metabolism in bone cells during health or disease remain unknown. The mitochondrial deacetylase sirtuin-3 (Sirt3) has been earlier implicated in age-related diseases. Here, we show that deletion of Sirt3 had no effect on the skeleton of young mice but attenuated the age-related loss of bone mass in both sexes. This effect was associated with impaired bone resorption. Osteoclast progenitors from aged Sirt3-null mice were able to differentiate into osteoclasts, though the differentiated cells exhibited impaired polykaryon formation and resorptive activity, as well as decreased oxidative phosphorylation and mitophagy. The Sirt3 inhibitor LC-0296 recapitulated the effects of Sirt3 deletion in osteoclast formation and mitochondrial function, and its administration to aging mice increased bone mass. Deletion of Sirt3 also attenuated the increase in bone resorption and loss of bone mass caused by estrogen deficiency. These findings suggest that Sirt3 inhibition and the resulting impairment of osteoclast mitochondrial function could be a novel therapeutic intervention for the 2 most important causes of osteoporosis.