Sharan, Ashwini

BACKGROUND AND OBJECTIVES: The Congress of Neurological Surgeons (CNS) Leadership Institute developed the first structured leadership program designed specifically for neurosurgeons. Led by the experts in neurosurgery, health care administration, and business, the program provides formal leadership training and mentorship aimed at advancing neurosurgeons' professional development at local, regional, national, and international levels. METHODS: The CNS Leadership Institute offers 2 curricula tailored for junior and senior faculty. Training begins with assigned readings, webinars, and online lectures that establish essential leadership principles. Core learning occurs during 2 in-person courses featuring interactive lectures, feedback sessions, and a longitudinal leadership project guided by national mentors. Program outcomes were assessed through a 40-question survey of alumni evaluating training effectiveness, skill application, and career advancement. RESULTS: Since 2016, 195 neurosurgeons have completed the CNS Leadership Institute. Among the 77 survey respondents, 70.1% reported significant professional advancement (new leadership role or job transition), and 64.8% directly attributed their advancement in skills and insights acquired through the program. Overall program effectiveness was rated 4.4 of 5, and the mean likelihood-to-recommend was 8.95 (95% CI: 8.70-9.20), yielding a Net Promoter Score of +63 (95% CI: +49 to +77). Alumni have assumed prominent roles including 16 Residency Program Directors, 3 Department Chairs, 1 Vice Dean, 4 Service Line Leaders, 13 CNS Executive Committee members, and over 100 committee or editorial board appointments critical to the specialty. CONCLUSION: The CNS Leadership Institute equips neurosurgeons with structured leadership training, mentorship, and practical tools to enhance their effectiveness as leaders. Survey results confirm that the program has a measurable impact on participants' career trajectories and professional growth. This initiative provides a reproducible model for cultivating the next generation of neurosurgical leaders and advancing the specialty's capacity for strategic, transformational leadership.

Abstract The epileptic network hypothesis and epileptogenic zone hypothesis are two theories of ictogenesis. The network hypothesis posits that coordinated activity among interconnected nodes produces seizures. The epileptogenic zone hypothesis posits that distinct regions are necessary and sufficient for seizure generation. High-frequency oscillations, and particularly fast ripples, are thought to be biomarkers of the epileptogenic zone. We sought to test these theories by comparing high-frequency oscillation rates and networks in surgical responders and non-responders, with no appreciable change in seizure frequency or severity, within a retrospective cohort of 48 patients implanted with stereo-EEG electrodes. We recorded inter-ictal activity during non-rapid eye movement sleep and semi-automatically detected and quantified high-frequency oscillations. Each electrode contact was localized in normalized coordinates. We found that the accuracy of seizure onset zone electrode contact classification using high-frequency oscillation rates was not significantly different in surgical responders and non-responders, suggesting that in non-responders the epileptogenic zone partially encompassed the seizure onset zone(s) (P > 0.05). We also found that in the responders, fast ripple on oscillations exhibited a higher spectral content in the seizure onset zone compared with the non-seizure onset zone (P < 1 × 10−5). By contrast, in the non-responders, fast ripple had a lower spectral content in the seizure onset zone (P < 1 × 10−5). We constructed two different networks of fast ripple with a spectral content >350 Hz. The first was a rate–distance network that multiplied the Euclidian distance between fast ripple-generating contacts by the average rate of fast ripple in the two contacts. The radius of the rate–distance network, which excluded seizure onset zone nodes, discriminated non-responders, including patients not offered resection or responsive neurostimulation due to diffuse multifocal onsets, with an accuracy of 0.77 [95% confidence interval (CI) 0.56–0.98]. The second fast ripple network was constructed using the mutual information between the timing of the events to measure functional connectivity. For most non-responders, this network had a longer characteristic path length, lower mean local efficiency in the non-seizure onset zone, and a higher nodal strength among non-seizure onset zone nodes relative to seizure onset zone nodes. The graphical theoretical measures from the rate–distance and mutual information networks of 22 non- responsive neurostimulation treated patients was used to train a support vector machine, which when tested on 13 distinct patients classified non-responders with an accuracy of 0.92 (95% CI 0.75–1). These results indicate patients who do not respond to surgery or those not selected for resection or responsive neurostimulation can be explained by the epileptic network hypothesis that is a decentralized network consisting of widely distributed, hyperexcitable fast ripple-generating nodes.

Abstract Scientists debate where, when, and how different visual, orthographic, lexical, and semantic features are involved in visual word recognition. In this study, we investigate intracranial neurophysiology data from 151 patients engaged in reading single words. Using representational similarity analysis, we characterize the neural representation of a hierarchy of word features across the entire cerebral cortex. We find evidence of both feed-forward and feedback processing, with early representation of visual and lexical information in lingual gyrus followed by lexical representation in fusiform gyrus and semantic sensitivity in inferior frontal gyrus, with letter representation emerging later in fusiform gyrus. Furthermore, we observed a variety of anatomically heterogeneous temporal response shapes, and these functional populations had significant feature sensitivity. Taken together, our results demonstrate the early influence of lexical, phonological, and semantic features in visual word recognition and reveal feed-forward, feed-back, and anatomically distributed processing mechanisms that contribute to visual word recognition.

Intracranial electroencephalography (iEEG) has been the mainstay of identifying the seizure onset zone (SOZ), a key diagnostic procedure in addition to neuroimaging when considering epilepsy surgery. In many patients, iEEG has been the basis for resective epilepsy surgery, to date still the most successful treatment for drug-resistant epilepsy. Intracranial EEG determines the location and resectability of the SOZ. Advances in recording and implantation of iEEG provide multiple options in the 21st century. This not only includes the choice between subdural electrodes (SDE) and stereoelectroencephalography (SEEG) but also includes the implantation and recordings from microelectrodes. Before iEEG implantation, especially in magnetic resonance imaging -negative epilepsy, a clear hypothesis for seizure generation and propagation should be based on noninvasive methods. Intracranial EEG implantation should be planned by a multidisciplinary team considering epileptic networks. Recordings from SDE and SEEG have both their advantages and disadvantages. Stereo-EEG seems to have a lower rate of complications that are clinically significant, but has limitations in spatial sampling of the cortical surface. Stereo-EEG can sample deeper areas of the brain including deep sulci and hard to reach areas such as the insula. To determine the epileptogenic zone, interictal and ictal information should be taken into consideration. Interictal spiking, low frequency slowing, as well as high frequency oscillations may inform about the epileptogenic zone. Ictally, high frequency onsets in the beta/gamma range are usually associated with the SOZ, but specialized recordings with combined macro and microelectrodes may in the future educate us about onset in higher frequency bands. Stimulation of intracranial electrodes triggering habitual seizures can assist in identifying the SOZ. Advanced computational methods such as determining the epileptogenicity index and similar measures may enhance standard clinical interpretation. Improved techniques to record and interpret iEEG may in the future lead to a greater proportion of patients being seizure free after epilepsy surgery.

SummaryObjectivesInterictal epileptiform discharges (IEDs) have been linked to memory impairment, but the spatial and temporal dynamics of this relationship remain elusive. In the present study, we aim to systematically characterize the brain areas and times at which IEDs affect memory.MethodsEighty epilepsy patients participated in a delayed free recall task while undergoing intracranial electroencephalography (EEG) monitoring. We analyzed the locations and timing of IEDs relative to the behavioral data in order to measure their effects on memory.ResultsOverall IED rates did not correlate with task performance across subjects (r = 0.03, p = 0.8). However, at a finer temporal scale, within‐subject memory was negatively affected by IEDs during the encoding and recall periods of the task but not during the rest and distractor periods (p < 0.01, p < 0.001, p = 0.3, and p = 0.8, respectively). The effects of IEDs during encoding and recall were stronger in the left hemisphere than in the right (p < 0.05). Of six brain areas analyzed, IEDs in the inferior‐temporal, medial‐temporal, and parietal areas significantly affected memory (false discovery rate < 0.05).SignificanceThese findings reveal a network of brain areas sensitive to IEDs with key nodes in temporal as well as parietal lobes. They also demonstrate the time‐dependent effects of IEDs in this network on memory.

Background Recent studies evaluated short-term efficacy and safety of peripheral nerve stimulation (PNS) of the occipital nerves for managing chronic migraine. We present 52-week safety and efficacy results from an open-label extension of a randomized, sham-controlled trial. Methods In this institutional review board-approved, randomized, multicenter, double-blinded study, patients were implanted with a neurostimulation system, randomized to an active or control group for 12 weeks, and received open-label treatment for an additional 40 weeks. Outcomes collected included number of headache days, pain intensity, migraine disability assessment (MIDAS), Zung Pain and Distress (PAD), direct patient reports of headache pain relief, quality of life, satisfaction and adverse events. Statistical tests assessed change from baseline to 52 weeks using paired t-tests. Intent-to-treat (ITT) analyses of all patients ( N = 157) and analyses of only patients who met criteria for intractable chronic migraine (ICM; N = 125) were performed. Results Headache days were significantly reduced by 6.7 (±8.4) days in the ITT population ( p < 0.001) and by 7.7 (±8.7) days in the ICM population ( p < 0.001). The percentages of patients who achieved a 30% and 50% reduction in headache days and/or pain intensity were 59.5% and 47.8%, respectively. MIDAS and Zung PAD scores were significantly reduced for both populations. Excellent or good headache relief was reported by 65.4% of the ITT population and 67.9% of the ICM population. More than half the patients in both cohorts were satisfied with the headache relief provided by the device. A total of 183 device/procedure-related adverse events occurred during the study, of which 18 (8.6%) required hospitalization and 85 (40.7%) required surgical intervention; 70% of patients experienced an adverse event. Conclusion Our results support the 12-month efficacy of PNS of the occipital nerves for headache pain and disability associated with chronic migraine. More emphasis on adverse event mitigation is needed in future research. Trial registration: Clinical trials.gov (NCT00615342).

Background: Chronic migraine (CM) is a debilitating neurological disorder with few treatment options. Peripheral nerve stimulation (PNS) of the occipital nerves is a potentially promising therapy for CM patients. Methods: In this randomized, controlled multicenter study, patients diagnosed with CM were implanted with a neurostimulation device near the occipital nerves and randomized 2:1 to active ( n = 105) or sham ( n = 52) stimulation. The primary endpoint was a difference in the percentage of responders (defined as patients that achieved a ≥50% reduction in mean daily visual analog scale scores) in each group at 12 weeks. Results: There was not a significant difference in the percentage of responders in the Active compared with the Control group (95% lower confidence bound (LCB) of −0.06; p = 0.55). However, there was a significant difference in the percentage of patients that achieved a 30% reduction ( p = 0.01). Importantly, compared with sham-treated patients, there were also significant differences in reduction of number of headache days (Active Group = 6.1, baseline = 22.4; Control Group = 3.0, baseline = 20.1; p = 0.008), migraine-related disability ( p = 0.001) and direct reports of pain relief ( p = 0.001). The most common adverse event was persistent implant site pain. Conclusion: Although this study failed to meet its primary endpoint, this is the first large-scale study of PNS of the occipital nerves in CM patients that showed significant reductions in pain, headache days, and migraine-related disability. Additional controlled studies using endpoints that have recently been identified and accepted as clinically meaningful are warranted in this highly disabled patient population with a large unmet medical need. Trial registration: Clinical trials.gov (NCT00615342).