"Mail-slot" technique for minimally-invasive placement of subdural grid electrodes: a single-institution experience.

BACKGROUND: In the management of multi-drug-resistant focal epilepsies, intracranial electrode implantation is employed for precise localization of the ictal onset zone. In select patients, subdural grid electrode implantation is utilized. Subdural grid placement traditionally requires large craniotomies to visualize the cortex prior to mapping. However, smaller craniotomies may enable shorter operations and reduced risks. We aimed to compare surgical outcomes between patients undergoing traditional large craniotomies with those undergoing tailored 'mini' craniotomies (the "Mail-Slot" technique) for subdural grid placement. METHODS: This retrospective cohort study included 23 patients who underwent subdural electrode implantation for epilepsy monitoring between 2014 and 2020. Patients were categorized into mini craniotomies (N=9) and traditional large craniotomies (N=14) groups. Demographics, operative details, and outcomes were reviewed. Craniotomy size and number of electrodes were determined via post-hoc radiographs. RESULTS: Of the 23 patients studied, the mini group had smaller craniotomy sizes (mean=22.71 cm2 vs. 65.17 cm2, p<0.001) and higher electrode-to-size ratios (mean=4.25 vs. 1.71, p<0.0001). The mini group had slightly fewer total electrodes (mean=88.67 vs. 107.43, p=0.047). No significant differences were found in operative duration, blood loss, invasive EEG duration, complications, or Engel scores between the groups. One patient per group required further invasive epilepsy monitoring for localization; all patients underwent therapeutic surgery. CONCLUSION: Our findings suggest that mini craniotomies for subdural grid placement in epilepsy monitoring offer significant advantages, including smaller craniotomy sizes and shorter operation durations, without compromising safety or efficacy. These results support the trend towards minimally invasive, patient-tailored surgical approaches in epilepsy treatment.

Theta mediated dynamics of human hippocampal-neocortical learning systems in memory formation and retrieval.

Episodic memory arises as a function of dynamic interactions between the hippocampus and the neocortex, yet the mechanisms have remained elusive. Here, using human intracranial recordings during a mnemonic discrimination task, we report that 4-5 Hz (theta) power is differentially recruited during discrimination vs. overgeneralization, and its phase supports hippocampal-neocortical when memories are being formed and correctly retrieved. Interactions were largely bidirectional, with small but significant net directional biases; a hippocampus-to-neocortex bias during acquisition of new information that was subsequently correctly discriminated, and a neocortex-to-hippocampus bias during accurate discrimination of new stimuli from similar previously learned stimuli. The 4-5 Hz rhythm may facilitate the initial stages of information acquisition by neocortex during learning and the recall of stored information from cortex during retrieval. Future work should further probe these dynamics across different types of tasks and stimuli and computational models may need to be expanded accordingly to accommodate these findings.

Theta mediated dynamics of human hippocampal-neocortical learning systems in memory formation and retrieval.

Episodic memory arises as a function of dynamic interactions between the hippocampus and the neocortex, yet the mechanisms have remained elusive. Here, using human intracranial recordings during a mnemonic discrimination task, we report that 4-5 Hz (theta) power is differentially recruited during discrimination vs. overgeneralization, and its phase supports hippocampal-neocortical when memories are being formed and correctly retrieved. Interactions were largely bidirectional, with small but significant net directional biases; a hippocampus-to-neocortex bias during acquisition of new information that was subsequently correctly discriminated, and a neocortex-to-hippocampus bias during accurate discrimination of new stimuli from similar previously learned stimuli. The 4-5 Hz rhythm may facilitate the initial stages of information acquisition by neocortex during learning and the recall of stored information from cortex during retrieval. Future work should further probe these dynamics across different types of tasks and stimuli and computational models may need to be expanded accordingly to accommodate these findings.

Utility of adding electrodes in patients undergoing invasive seizure localization: A case series.

Introduction: Surgery can be an effective treatment for epilepsy if the seizure onset is adequately localized. Invasive monitoring is used if noninvasive methods are inconclusive. Initial invasive monitoring may fail if the pre-surgical hypothesis regarding location of epileptic foci is wrong. At this point, a decision must be made whether to remove all electrodes without a clearly defined location of onset or to implant additional electrodes with the aim of achieving localization by expanding coverage. Methods: Electrodes were placed according to a hypothesis derived from noninvasive monitoring techniques in adult patients with long term epilepsy. Seizure onset was not clearly localized at the end of the invasive monitoring period in ten patients, and additional electrodes were placed based on a new hypothesis that incorporated data from the invasive monitoring period. Results: Successful localization was achieved in nine patients. There were no complications with adding additional electrodes. At final follow up, four patients were seizure free while four others had at least a 50% reduction in seizures after undergoing surgical intervention. Conclusion: Seizure foci were localized safely in 90% of adult patients with long term epilepsy after implanting additional electrodes and expanding coverage. Patients undergoing invasive monitoring without clear localization should have additional electrodes placed to expand monitoring coverage as it is safe and effective.

Surgeon-Led Initiatives to Increase Access to Surgical Treatment of Epilepsy at an Academic Level 4 Epilepsy Center: An Observational Cohort Study.

BACKGROUND: Underutilization of surgical treatment for epilepsy is multifactorial, and the multidisciplinary nature of caring for these patients represents a significant hurdle in expanding surgical treatment of epilepsy. OBJECTIVE: To develop internal and external surgical referral relationships for patients with medically refractory epilepsy with the goal of improving access to care. METHODS: To expand access to surgical epilepsy treatment at University of California (UC)-Irvine, 4 broad approaches focused on developing referral relationships and process improvement of surgical evaluation were undertaken in 2015 and 2016. The authors performed a retrospective review of all surgical epilepsy case referrals of the senior author from 2014 through 2020. RESULTS: Epilepsy surgical volume at UC-Irvine increased from an average of 5.2 cases annually to 32 cases in the first year (2015) of implementation. There was continued case volume growth from 2015 through 2020 to 52 procedures in the most recent year (P = .03). Hospital payments for epilepsy procedures increased from $1.09M in 2015 to $2.02M and $1.8M in 2019 and 2020 (P < .01), respectively, while maintaining a diverse payer mix. 79.4% of these patients did not have a previously established option for surgical epilepsy care. CONCLUSION: We outline strategies that level 4 epilepsy centers may use to strengthen collaborations and improve patient access for surgical epilepsy treatment. Increased collaboration can both improve the number of patients with epilepsy with access to specialized surgical care and produce reimbursement benefits for the centers caring for these patients, regardless of insurance source.

Neurostimulation in people with drug-resistant epilepsy: Systematic review and meta-analysis from the ILAE Surgical Therapies Commission.

OBJECTIVE: Summarize the current evidence on efficacy and tolerability of vagus nerve stimulation (VNS), responsive neurostimulation (RNS), and deep brain stimulation (DBS) through a systematic review and meta-analysis. METHODS: We followed the Preferred Reporting Items of Systematic reviews and Meta-Analyses reporting standards and searched Ovid Medline, Ovid Embase, and the Cochrane Central Register of Controlled Trials. We included published randomized controlled trials (RCTs) and their corresponding open-label extension studies, as well as prospective case series, with ≥20 participants (excluding studies limited to children). Our primary outcome was the mean (or median, when unavailable) percentage decrease in frequency, as compared to baseline, of all epileptic seizures at last follow-up. Secondary outcomes included the proportion of treatment responders and proportion with seizure freedom. RESULTS: We identified 30 eligible studies, six of which were RCTs. At long-term follow-up (mean 1.3 years), five observational studies for VNS reported a pooled mean percentage decrease in seizure frequency of 34.7% (95% confidence interval [CI]: -5.1, 74.5). In the open-label extension studies for RNS, the median seizure reduction was 53%, 66%, and 75% at 2, 5, and 9 years of follow-up, respectively. For DBS, the median reduction was 56%, 65%, and 75% at 2, 5, and 7 years, respectively. The proportion of individuals with seizure freedom at last follow-up increased significantly over time for DBS and RNS, whereas a positive trend was observed for VNS. Quality of life was improved in all modalities. The most common complications included hoarseness, and cough and throat pain for VNS and implant site pain, headache, and dysesthesia for DBS and RNS. SIGNIFICANCE: Neurostimulation modalities are an effective treatment option for drug-resistant epilepsy, with improving outcomes over time and few major complications. Seizure-reduction rates among the three therapies were similar during the initial blinded phase. Recent long-term follow-up studies are encouraging for RNS and DBS but are lacking for VNS.

Application of Responsive Neurostimulation as both a Diagnostic Tool for Seizure Localization and a Supplementary Tool for Surgical Management in Patients with Multiple Epileptogenic Foci: A Case Series.

AIM: To present a series of medically refractory focal epilepsy patients with multiple or eloquent epileptogenic zones (EZs) in whom a responsive neurostimulation (RNS) system was used as a complementary modality to surgical resection. RNS was also used as a diagnostic tool to monitor long-term epileptogenic activity for enhanced localization, especially in patients with bilateral temporal seizures. MATERIAL AND METHODS: Ten consecutive patients who underwent RNS system placement and surgical resection at a single institution were assessed. RESULTS: The RNS system, with its capacity for chronic ambulatory electrocorticography (ECoG), provided important diagnostic information that helped to modify the plan of surgical resection in one patient with bitemporal epilepsy in order to improve seizure outcomes. In addition, the RNS facilitated the surgical management of patients with multiple or eloquent EZs. CONCLUSION: The authors report a population of 10 patients in which the RNS system was used as a diagnostic tool for improved localization of EZs over a long interval or as a complementary therapeutic tool in patients with multiple or eloquent EZs.

Elective versus nonelective brain tumor resections: a 5-year propensity score matching cost comparison analysis.

OBJECTIVE: Elective surgical cases generally have lower costs, higher profit margins, and better outcomes than nonelective cases. Investigating the differences in cost and profit between elective and nonelective cases would help hospitals in planning strategies to withstand financial losses due to potential pandemics. The authors sought to evaluate the exact cost and profit margin differences between elective and nonelective supratentorial tumor resections at a single institution. METHODS: The authors collected economic analysis data in all patients who underwent supratentorial tumor resection at their institution between January 2014 and December 2018. The patients were grouped into elective and nonelective cases. Propensity score matching was used to adjust for heterogeneity of baseline characteristics between the two groups. RESULTS: There were 143 elective cases and 232 nonelective cases over the 5 years. Patients in the majority of elective cases had private insurance and in the majority of nonelective cases the patients had Medicare/Medicaid (p < 0.01). The total charges were significantly lower for elective cases ($168,800.12) compared to nonelective cases ($254,839.30, p < 0.01). The profit margins were almost 6 times higher for elective than for nonelective cases ($13,025.28 vs $2,128.01, p = 0.04). After propensity score matching, there was still a significant difference between total charges and total cost. CONCLUSIONS: Elective supratentorial tumor resections were associated with significantly lower costs with shorter lengths of stay while also being roughly 6 times more profitable than nonelective cases. These findings may help future planning for hospital strategies to survive financial losses during future pandemics that require widespread cancellation of elective cases.

Enhancing Safety in Epilepsy Surgery (EASINESS): Study Protocol for a Retrospective, Multicenter, Open Registry.

Introduction: Optimizing patient safety and quality improvement is increasingly important in surgery. Benchmarks and clinical quality registries are being developed to assess the best achievable results for several surgical procedures and reduce unwarranted variation between different centers. However, there is no clinical database from international centers for establishing standardized reference values of patients undergoing surgery for mesial temporal lobe epilepsy. Design: The Enhancing Safety in Epilepsy Surgery (EASINESS) study is a retrospectively conducted, multicenter, open registry. All patients undergoing mesial temporal lobe epilepsy surgery in participating centers between January 2015 and December 2019 are included in this study. The patient characteristics, preoperative diagnostic tools, surgical data, postoperative complications, and long-term seizure outcomes are recorded. Outcomes: The collected data will be used for establishing standardized reference values ("benchmarks") for this type of surgical procedure. The primary endpoints include seizure outcomes according to the International League Against Epilepsy (ILAE) classification and defined postoperative complications. Discussion: The EASINESS will define robust and standardized outcome references after amygdalohippocampectomy for temporal lobe epilepsy. After the successful definition of benchmarks from an international cohort of renowned centers, these data will serve as reference values for the evaluation of novel surgical techniques and comparisons among centers for future clinical trials. Clinical trial registration: This study is indexed at clinicaltrials.gov (NT 04952298).

Comparative Effectiveness of Stereotactic Electroencephalography Versus Subdural Grids in Epilepsy Surgery.

OBJECTIVE: The aim was to compare the outcomes of subdural electrode (SDE) implantations versus stereotactic electroencephalography (SEEG), the 2 predominant methods of intracranial electroencephalography (iEEG) performed in difficult-to-localize drug-resistant focal epilepsy. METHODS: The Surgical Therapies Commission of the International League Against Epilepsy created an international registry of iEEG patients implanted between 2005 and 2019 with ≥1 year of follow-up. We used propensity score matching to control exposure selection bias and generate comparable cohorts. Study endpoints were: (1) likelihood of resection after iEEG; (2) seizure freedom at last follow-up; and (3) complications (composite of postoperative infection, symptomatic intracranial hemorrhage, or permanent neurological deficit). RESULTS: Ten study sites from 7 countries and 3 continents contributed 2,012 patients, including 1,468 (73%) eligible for analysis (526 SDE and 942 SEEG), of whom 988 (67%) underwent subsequent resection. Propensity score matching improved covariate balance between exposure groups for all analyses. Propensity-matched patients who underwent SDE had higher odds of subsequent resective surgery (odds ratio [OR] = 1.4, 95% confidence interval [CI] 1.05, 1.84) and higher odds of complications (OR = 2.24, 95% CI 1.34, 3.74; unadjusted: 9.6% after SDE vs 3.3% after SEEG). Odds of seizure freedom in propensity-matched resected patients were 1.66 times higher (95% CI 1.21, 2.26) for SEEG compared with SDE (unadjusted: 55% seizure free after SEEG-guided resections vs 41% after SDE). INTERPRETATION: In comparison to SEEG, SDE evaluations are more likely to lead to brain surgery in patients with drug-resistant epilepsy but have more surgical complications and lower probability of seizure freedom. This comparative-effectiveness study provides the highest feasible evidence level to guide decisions on iEEG. ANN NEUROL 2021;90:927-939.

Use of Automated Irrigating Drainage System in Six Patients With Chronic Subdural Hematoma: A Single-Center Experience.

Background Chronic subdural hematoma (cSDH) is predicted to become the most common intracranial neurosurgical condition by 2030. Recurrence is estimated between 5-15%, and the use of a surgical drain is associated with lower recurrence rates. The authors present their experience with six patients undergoing cSDH evacuation with an irrigating drainage system, comprising the largest single-institution group in the United States (US). Methods IRB-approved, retrospective chart review was performed for six patients who underwent irrigating surgical drain placement during cSDH evacuation. Outcome measures included device settings and duration of the irrigating drain, postoperative length of stay, neurological status at follow-up, and hematoma recurrence. Results There were no recurrences noted within this group at last follow-up, with an average follow-up length over three months. The average postoperative length of stay was 2.67 ± 0.51 days. Patients were drained on average for 1.41 ± 0.49 days at 0cm water, irrigating at 55.25 ± 46.44cc/hr. On postoperative day one, average hematoma size and midline shift (MLS) reduction were respectively 13.43 ± 3.31mm and 5.71 ± 1.33mm. No device-related complications were noted. Conclusion The authors' early experience with this irrigating drainage device demonstrates that it is safe and effective for this population. Although this is a preliminary study on a small sample size, the excellent results warrant further investigation and establishment of a standard protocol to compare against current treatment regimens.

Coupling between slow waves and sharp-wave ripples engages distributed neural activity during sleep in humans.

Hippocampal-dependent memory consolidation during sleep is hypothesized to depend on the synchronization of distributed neuronal ensembles, organized by the hippocampal sharp-wave ripples (SWRs, 80 to 150 Hz), subcortical/cortical slow-wave activity (SWA, 0.5 to 4 Hz), and sleep spindles (SP, 7 to 15 Hz). However, the precise role of these interactions in synchronizing subcortical/cortical neuronal activity is unclear. Here, we leverage intracranial electrophysiological recordings from the human hippocampus, amygdala, and temporal and frontal cortices to examine activity modulation and cross-regional coordination during SWRs. Hippocampal SWRs are associated with widespread modulation of high-frequency activity (HFA, 70 to 200 Hz), a measure of local neuronal activation. This peri-SWR HFA modulation is predicted by the coupling between hippocampal SWRs and local subcortical/cortical SWA or SP. Finally, local cortical SWA phase offsets and SWR amplitudes predicted functional connectivity between the frontal and temporal cortex during individual SWRs. These findings suggest a selection mechanism wherein hippocampal SWR and cortical slow-wave synchronization governs the transient engagement of distributed neuronal populations supporting hippocampal-dependent memory consolidation.

Net Drainage as a Novel Metric for Irrigating Drainage Systems in Chronic Subdural Hematoma Management: A Case Report.

BACKGROUND AND IMPORTANCE: Chronic subdural hematoma (cSDH) is a common neurosurgical pathology with a projected increase in prevalence as the elderly population grows. Traditional treatment for cSDH involves burr hole drainage or craniotomy with or without a subdural drain. This case describes a novel irrigation and drainage protocol using IRRAflow dual-lumen catheter system that utilizes early irrigation and measurement of the net fluid output to improve postoperative outcomes. CLINICAL PRESENTATION: A 75-yr-old male presented to the emergency department with 2 wk of progressive dizziness, headache, confusion, and left-sided weakness over the past week. Computed tomography (CT) of the head showed 25-mm-thick, right-sided cSDH with 7 mm of right-to-left midline shift. The patient was taken to the operating room for right-sided craniotomy for subdural hematoma evacuation with placement of IRRAflow irrigating drain in the subdural space. The IRRAflow drain irrigated at 100 cc/h for 23 h with net output consistently greater than irrigation rate. Head CT the following day showed a progressive decrease in subdural collection. The patient was discharged on postoperative day 2 and had complete resolution of his neurological symptoms by postoperative day 11. CONCLUSION: As cSDHs become more prevalent in the aging population, development of improved management strategies is imperative. This report describes the use of an IRRAflow dual-lumen catheter with a novel protocol consisting of a high rate of irrigation but net fluid output, which led to rapid recovery and resolution of neurological deficits in a patient with a cSDH.

Surgical Robot-Enhanced Implantation of Intracranial Depth Electrodes for Single Neuron Recording Studies in Patients with Medically Refractory Epilepsy: A Technical Note.

OBJECTIVE: Single neuron or unit recording enables researchers to measure the electrophysiologic responses of single neurons using a microelectrode system. This approach is widely used in cognitive science and has become more widespread in humans with the use of hybrid (micro-within-macrowire) depth electrodes that enable the implantation of microwires into the brain parenchyma. METHODS: The authors describe their surgical technique in a total of 7 patients with intractable epilepsy who underwent robot-enhanced stereoencephalography in which both standard (nonhybrid) and hybrid depth electrodes were used for invasive chronic monitoring. RESULTS: The technique and accuracy of the procedure were evaluated with a total of 84 depth electrodes (46 hybrid, 38 standard) in 7 patients. No major complications, such as intracranial hemorrhage, infection or cerebrospinal fluid leakage, occurred regardless of the type of electrode used. CONCLUSIONS: The addition of hybrid depth electrodes for the purpose of in vivo single neuron recording in robot-enhanced stereoencephalography procedures is safe and does not impact the accuracy of targeting or patient safety.

Treatment of Multi-Focal Epilepsy With Resective Surgery Plus Responsive Neurostimulation (RNS): One Institution's Experience.

Objective: Patients with medically refractory focal epilepsy can be difficult to treat surgically, especially if invasive monitoring reveals multiple ictal onset zones. Possible therapeutic options may include resection, neurostimulation, laser ablation, or a combination of these surgical modalities. To date, no study has examined outcomes associated with resection plus responsive neurostimulation (RNS, Neuropace, Inc., Mountain View, CA) implantation and we describe our initial experience in patients with multifocal epilepsy undergoing this combination therapy. Methods: A total of 43 responsive neurostimulation (RNS) devices were implanted at UCI from 2015 to 2019. We retrospectively reviewed charts of patients from the same time period who underwent both resection and RNS implantation. Patients were required to have independent or multifocal onset, undergo resection and RNS implantation, and have a minimum of six-months for follow-up to be included in the study. Demographics, location of ictal onset, location of surgery, complications, and seizure outcome were collected. Results: Ten patients met inclusion criteria for the study, and seven underwent both procedures in the same setting. The average age was 36. All patients had multifocal ictal onset on video electroencephalogram or invasive EEG with four patients undergoing subdural grid placement and four patients undergoing bilateral sEEG prior to the definitive surgery. Five patients underwent resection plus ipsilateral RNS placement and the remainder underwent resection with contralateral RNS placement. Two minor complications were encountered in this group. At six months follow up, there was an average of 81% ± 9 reduction in seizures, while four patients experienced complete seizure freedom at 1 year. Conclusion: Patients with multifocal epilepsy can be treated with partial resection plus RNS. The complication rates are low with potential for worthwhile seizure reduction.

Two-year clinical outcomes associated with robotic-assisted subthalamic lead implantation in patients with Parkinson's disease.

Few centers have routinely implemented robotic stereotactic systems for deep brain stimulator (DBS) placement. The present study compares clinical outcomes associated with robotic-assisted subthalamic nucleus (STN)-targeted DBS surgery in patients with Parkinson's disease (PD) to those of the traditional frame-based method. A retrospective chart review was performed (February 2013-June 2017). Thirty-three patients were implanted using the Cosman-Roberts-Wells (CRW) frame and 27 patients were implanted using the ROSA robot. Movement Disorder Society-Unified Parkinson's Disease Rating Scale (MDS-UPDRS) or UPDRS part III motor scores and levodopa equivalent daily doses (LEDD) were examined preoperatively and at 6, 12, and 24 months of follow-up. Operative times and complication rates were recorded. For the frame-based group, the reduction in the mean MDS-UPDRS part III motor score compared to baseline was 27% both at 6 and 12 months, and 36.7% at 24 months. For the robotic-assisted group, the reduction in the mean motor score from baseline was 17.6% at 6 months, 19% at 12 months and 21.4% at 24 months. The mean LEDD for the frame-based group decreased by 48.7% at 6 months, 56.7% at 12 months, and 29.7% at 24 months. For the robotic-assisted group, the mean LEDD decreased by 42% at 6 months, 45% at 12 months and 50% at 24 months. There were no significant differences in the mean motor scores and the LEDD reduction between the two groups. Operative times tended to be longer for robotic-assisted DBS surgery. Clinical outcomes associated with robotic-assisted surgery are comparable to those with frame-based surgery.

A Novel Robotic-Assisted Technique to Implant the Responsive Neurostimulation System.

BACKGROUND: The responsive neurostimulation system (RNS) (NeuroPace Inc, Mountain View, California) was approved as an adjunctive therapy for medically refractory focal epilepsy. RNS detects epileptiform patterns and delivers electrical stimulation to abort seizures. OBJECTIVE: To describe a novel technique of RNS lead implantation using robotic-assisted targeting of ictal-onset zones based on stereoelectroencephalography (sEEG) localization. Secondary objectives are to report the accuracy of robotic-assisted lead implantation using the ROSA robot as well as to report the clinical outcome achieved after RNS implantation by this method. METHODS: A total of 16 patients with medically refractory focal epilepsy underwent sEEG implantation for ictal-onset localization followed by robotic RNS implantation. The electrode most correlative with ictal onset on sEEG was chosen as the target for the RNS electrode. Seizure control was measured at 6-mo and 1-yr follow-up. Ictal-onset electrocorticography (ECoG) data from RNS were compared with ictal onset from sEEG leads based on calculations of lead target to actual lead location from the ROSA robot. RESULTS: At 6-mo follow-up, the average percent seizure reduction was 82% based upon self-reported seizure diaries. At 1-yr follow-up, 8 patients had an average of 90% seizure reduction. The location of seizure onset from ECoG data show similar onset from sEEG leads within 0.165-mm discrepancy. CONCLUSION: The ROSA robot provides an ideal method for targeting subcortical ictal-onset zones. This method of RNS lead implantation achieves high accuracy and is associated with favorable clinical outcomes.

Robotic Orthogonal Implantation of Responsive Neurostimulation (RNS) Depth Electrodes in the Mesial Temporal Lobe: Case Series.

BACKGROUND: Responsive neurostimulation (RNS) is a closed-loop neurostimulation modality for treating intractable epilepsy in patients who are not candidates for resection. In the past, implantation of depth electrodes was done through a transoccipital approach that transverses the hippocampus. There have been no descriptions of orthogonal approaches to RNS electrode placement. OBJECTIVE: To describe our initial experience with placing RNS depth electrodes using an orthogonal approach to target the short axis of the mesial temporal lobe. METHODS: Presurgical work-up included magnetic resonance imaging, video electroencephalography, and neuropsychological testing. During the procedure, patients were placed with their heads in a neutral position. Electrodes were placed via stereotactic robotic assistance using a unilateral orthogonal approach targeting the amygdala or hippocampus. Patients who underwent RNS electrode implantation via orthogonal approach were identified. Multiple variables were collected, including age, disease onset, complications, follow-up, semiology, and seizure reduction. RESULTS: There were 8 patients who underwent RNS electrode placement with orthogonal approach. The mean age and follow-up were 44.8 and 1.2 yr, respectively. There were 4 patients with at least 1-yr follow-up. Of them, 1 was seizure free and 2 experienced over 50% reduction in seizures. There were no complications associated with electrode implantation. CONCLUSION: The initial experience using an orthogonal approach for depth electrode placement for RNS implantation was described. The potential advantages may include better safety, accuracy, and positioning in comparison to a transoccipital approach.

Novel Use of Dual-Lumen Catheter for Irrigation and Drainage After Evacuation of Chronic Subdural Hematoma.

BACKGROUND: Chronic subdural hematoma (cSDH) is an intracranial pathology most commonly affecting elderly patients. Patients may present with worsening headache, seizures, weakness, balance and gait problems, and memory deficits. Even in patients undergoing hematoma evacuation, there is a substantial risk for recurrence. The authors present the first use of an irrigating external ventricular drain in the United States in the perioperative management of a patient with cSDH treated with craniotomy (IRRAS, Stockholm, Sweden). CASE DESCRIPTION: An 82-year-old male presented with right-sided weakness, confusion, and right-sided neglect with expressive aphasia. He was found to have a large 2.5-cm cSDH with a 9-mm left-to-right midline shift. The patient was treated with a minicraniotomy to evacuate the hematoma and placement of an irrigating drain in the subdural space. The patient was discharged home on postoperative day 3 without complication. He was at neurologic baseline 2 weeks later on follow-up. CONCLUSIONS: The use of an irrigating drain for perioperative management of cSDH is a novel means to prevent recurrence and warrants further exploration.

Bidirectional prefrontal-hippocampal dynamics organize information transfer during sleep in humans.

How are memories transferred from short-term to long-term storage? Systems-level memory consolidation is thought to be dependent on the coordinated interplay of cortical slow waves, thalamo-cortical sleep spindles and hippocampal ripple oscillations. However, it is currently unclear how the selective interaction of these cardinal sleep oscillations is organized to support information reactivation and transfer. Here, using human intracranial recordings, we demonstrate that the prefrontal cortex plays a key role in organizing the ripple-mediated information transfer during non-rapid eye movement (NREM) sleep. We reveal a temporally precise form of coupling between prefrontal slow-wave and spindle oscillations, which actively dictates the hippocampal-neocortical dialogue and information transfer. Our results suggest a model of the human sleeping brain in which rapid bidirectional interactions, triggered by the prefrontal cortex, mediate hippocampal activation to optimally time subsequent information transfer to the neocortex during NREM sleep.