Publications by authors named "Efstathios Kondylis"

Background And Objectives: Deep brain stimulation (DBS) is an established neurosurgical treatment of a variety of neurological disorders. DBS is considered a safe and effective neurosurgical procedure; however, surgical complications are inevitable, and clinical outcomes may vary. The aim of this study was to describe DBS complications at a large clinical center in the United States and to investigate the relationship between patients' baseline characteristics, surgical technique, and operative complications.

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  • Hydrocephalus can happen after brain surgery for epilepsy, but how it occurs isn't fully understood.
  • A patient with this condition was treated with a special medication that helps reduce inflammation, and after 6 months, they showed improvements in their health and school performance.
  • More research is needed to learn how this inflammation treatment might help other patients after epilepsy surgery.
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Hemispherectomy is an effective procedure used in the treatment of drug-resistant hemispheric epilepsy, especially in the pediatric population. A number of resective and disconnective techniques are used, and selection of surgical strategy is paramount to achieving successful results. Notably, disconnective (or functional) hemispherotomy maximizes the benefits of safe, surgical disconnection while minimizing hemispheric tissue resection, thereby avoiding some of the perioperative factors contributing to morbidity in traditional anatomical hemispherectomy procedures.

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  • - The study focused on the safety and complication rates of pediatric stereoencephalography (SEEG) electrode placement in children under 12, noting that their thinner skulls pose challenges compared to adults.
  • - Out of 53 patients reviewed, the median skull thickness was 4.1 mm, and only 1.9% experienced hardware complications, with a small rate (9.4%) of asymptomatic hemorrhages.
  • - The findings suggest that despite potential risks, SEEG is generally safe for younger patients, and using sutures to secure electrodes may be beneficial for those with thinner skulls.
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  • The study looked at how surgery helps people with epilepsy who don’t get better with medication, focusing on long-term effects over many years.
  • They found that a lot of patients had fewer seizures and some even became seizure-free, with many feeling better after a while even if they weren’t better right away.
  • Overall, the results showed that even if someone still has seizures after surgery, they can still experience significant improvements over time.
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Background: Minimally invasive surgery (MIS) for intracranial pathology minimizes surgical morbidity but can come at the cost of operator ergonomics and technical surgical success. Here, the authors present a case series to report the first use of a novel 15-mm tubular retraction system with integrated lighting and visualization capabilities for MIS access to intracranial lesions.

Objective: To demonstrate feasibility and effectiveness of the 15-mm Aurora Surgiscope (Integra Lifesciences) for intracranial MIS approaches.

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Background: Rasmussen encephalitis (RE) is a rare inflammatory disease affecting one hemisphere, causing progressive neurological deficits and intractable seizures.

Objective: To report long-term seizure outcomes, reoperations, and functional outcomes in patients with RE who underwent hemispherectomy at our institution.

Methods: Retrospective review was performed for all patients with RE who had surgery between 1998 and 2020.

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Objective: Neuropsychological profiles are heterogeneous both across and within epilepsy syndromes, but especially in frontal lobe epilepsy (FLE), which has complex semiology and epileptogenicity. This study aimed to characterize the cognitive heterogeneity within FLE by identifying cognitive phenotypes and determining their demographic and clinical characteristics.

Method: One hundred and six patients (age 16-66; 44% female) with FLE completed comprehensive neuropsychological testing, including measures within five cognitive domains: language, attention, executive function, processing speed, and verbal/visual learning.

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Introduction: Non-motor DBS outcomes have received little attention in ET relative to PD. This study examines neuropsychological outcomes in ET following thalamic VIM DBS.

Methods: Fifty patients completed neuropsychological evaluations preoperatively and approximately seven months postoperatively.

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Objective: To assess and validate the performance of a new tool developed for segmenting and characterizing lacunas in postoperative MR images of epilepsy patients.

Methods: A MATLAB-based pipeline was implemented using SPM12 to produce the 3D mask of the surgical lacuna and estimate its volume. To validate its performance, we compared the manual and automatic lacuna segmentations obtained from 51 MRI scans of epilepsy patients who underwent temporal lobe resections.

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Invasive neuromonitoring is an important component of presurgical workup and seizure onset zone localization in patients with epilepsy being considered for surgical resection. In the United States, intraparenchymal stereoelectroencephalography (SEEG) electrodes have been replacing subdural grid electrodes for most cases, following a trend that has already matured in Europe. The use of robotic assistance has been shown to improve operative times and accuracy in SEEG electrode placement, as users benefit from the embedded planning software as well as the efficiency and accuracy of the robotic arm.

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Background: Spinal subdural hematomas (SDHs) have been reported secondary to direct trauma or iatrogenic causes associated with coagulopathies. Spinal SDHs found after the development of acute intracranial SDHs, without any evidence of trauma to the spine, are extremely rare. In addition to this rare presentation, there is a lack of consensus regarding whether surgical decompression is the ideal treatment strategy.

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The subthalamic nucleus (STN) is proposed to participate in pausing, or alternately, in dynamic scaling of behavioral responses, roles that have conflicting implications for understanding STN function in the context of deep brain stimulation (DBS) therapy. To examine the nature of event-related STN activity and subthalamic-cortical dynamics, we performed primary motor and somatosensory electrocorticography while subjects (n = 10) performed a grip force task during DBS implantation surgery. Phase-locking analyses demonstrated periods of STN-cortical coherence that bracketed force transduction, in both beta and gamma ranges.

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Coupled oscillatory activity recorded between sensorimotor regions of the basal ganglia-thalamocortical loop is thought to reflect information transfer relevant to movement. A neuronal firing-rate model of basal ganglia-thalamocortical circuitry, however, has dominated thinking about basal ganglia function for the past three decades, without knowledge of the relationship between basal ganglia single neuron firing and cortical population activity during movement itself. We recorded activity from 34 subthalamic nucleus (STN) neurons, simultaneously with cortical local field potentials and motor output, in 11 subjects with Parkinson's disease (PD) undergoing awake deep brain stimulator lead placement.

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Individuals with pharmacoresistant epilepsy remain a large and under-treated patient population. Continued technologic advancements in implantable neurostimulators have spurred considerable research efforts directed towards the development of novel antiepileptic stimulation therapies. However, the lack of adequate preclinical experimental platforms has precluded a detailed understanding of the differential effects of stimulation parameters on neuronal activity within seizure networks.

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  • Recent research shows that excessive coupling of low-frequency phase to high-frequency gamma amplitude occurs in both Parkinson's disease and essential tremor, impacting motor control.
  • The study involved recording brain activity during a handgrip task, revealing shared features of abnormal phase-amplitude coupling across movement disorders, even when movement kinematics were similar.
  • Findings suggest that individuals with Parkinson's and essential tremor can achieve similar movement performance to healthy individuals by reducing the excessive sensorimotor phase-amplitude coupling typical of their conditions.
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  • Movement-related synchronization of high frequency activity (HFA, 76-100 Hz) occurs in a specific area of the sensorimotor cortex during movement, helping researchers validate electrode placement in studies on deep brain stimulation.
  • The study involved recording electrocorticography (ECoG) signals from 8 subjects during a hand grip task to examine movement-related changes in HFA compared to a pre-movement baseline.
  • Results showed that significant HFA changes were localized both in time and space, limited to specific electrodes in the pre- and post-central gyri, indicating the importance of HFA in accurately mapping motor functions on the cortical surface.
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  • Researchers use subdural electrocorticography (ECoG) electrodes during deep brain stimulation (DBS) surgeries to study cortical activity, but accurately locating these electrodes is challenging with two-dimensional fluoroscopic images.
  • A new method helps project the position of ECoG electrodes onto a cortical surface by aligning CT and MRI images with fluoroscopy, overcoming issues like parallax distortion and variable skull shapes.
  • Validation shows this approach is precise, with an average error of just 1.65 mm across multiple patients, improving the reliability of ECoG recordings for research.
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  • Deep brain stimulation (DBS) marks a significant breakthrough in treating brain functions, especially for movement disorders where it’s considered the best option when medication fails.
  • While DBS is effective, the exact mechanisms behind its therapeutic effects remain unclear, which limits improvements in treatment efficiency and reduction of side effects.
  • A new area of research focusing on the network effects of DBS is developing, utilizing techniques like imaging and electrophysiology to better understand brain disorders and enhance treatment strategies.
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High-frequency oscillations (HFOs) have been proposed as a novel marker for epileptogenic tissue, spurring tremendous research interest into the characterization of these transient events. A wealth of continuously recorded intracranial electroencephalographic (iEEG) data is currently available from patients undergoing invasive monitoring for the surgical treatment of epilepsy. In contrast to data recorded on research-customized recording systems, data from clinical acquisition systems remain an underutilized resource for HFO detection in most centers.

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