Association of Do-Not-Resuscitate orders and in-hospital mortality among patients undergoing cranial neurosurgery.

BACKGROUND: Previous studies identified pre-existing DNR orders as a predictor of mortality after surgery. We sought to evaluate mortality of patients receiving cranial neurosurgery with DNR orders placed at the time of, or within 24 h of admission. METHODS: We performed a retrospective cohort study using the California State Inpatient Database, January 2018 to December 2020. We used International Classification of Diseases, 10th Revision (ICD-10) codes to identify emergent hospitalizations with principal diagnosis of brain injury, including traumatic brain injury [TBI], ischemic stroke [IS], intracerebral hemorrhage [ICH], subarachnoid hemorrhage [SAH], or malignant brain tumor [mBT]. We used procedure and Diagnosis Related Group codes to identify cranial neurosurgery. Patients with DNR were one-to-one matched to non-DNR controls based on diagnosis (exact matching), age, sex, Elixhauser comorbidity index, and organ failure (coarsened matching). The primary outcome was inpatient mortality. RESULTS: In California, 30,384 patients underwent cranial neurosurgery, 2018-2020 (n = 3,112, 10% DNR). DNR patients were older, more often female, more often White, with greater comorbidity and organ system dysfunction. There were 2,505 patients with DNR orders 1:1 matched to controls. Patients with DNR had greater inpatient mortality (56% vs. 23%, p < 0.001; Hazard Ratio 3.11, 95% CI 2.50-3.86), received tracheostomy (Odds Ratio [OR] 0.37, 95% CI 0.24-0.57) and gastrostomy less (OR 0.48, 95% CI 0.39-0.58) compared to controls. Multivariable analysis of the unmatched cohort demonstrated similar results. CONCLUSION: Patients undergoing cranial neurosurgery with early or pre-existing DNR have high inpatient mortality compared to clinically similar non-DNR patients; 1 in 2 died during their hospitalization.

Treatment of hydrocephalus in an ovine model with an intraparenchymal stent.

OBJECTIVE: While CSF diversion is highly effective at treating hydrocephalus, shunting is unfortunately associated with a very high revision rate. Studies have demonstrated that proximal catheter obstruction is a major cause of failure. A novel proximal access device was developed, and pilot testing was performed in a sheep model of hydrocephalus. METHODS: Hydrocephalus was induced in 8 sheep using a cisternal injection of 4 ml of 25% kaolin, and the sheep were randomized to either a standard ventricular catheter or a novel intraparenchymal stent (IPS). Both groups received identical valves and distal catheters. The novel device included a 3D-printed stainless steel port and a 6 × 40-mm covered peripheral vascular stent. Animals were euthanized for signs of hydrocephalus or at a time point of 2 months. MRI was performed to determine ventricular size. Time to failure and Evans indices were compared using the Wilcoxon rank-sum test. RESULTS: All 4 experimental devices were placed without difficulty into the right lateral ventricle. There was a trend toward longer survival in the experimental group (40 vs 26 days, p = 0.24). Within the IPS group, 3 of the 4 sheep did not experience clinical symptoms of shunt failure and had an average of 37% decrease in Evans index. While 3 of 4 traditional proximal catheters demonstrated debris within the inlet holes, there was no obstructive material found in the IPSs. CONCLUSIONS: An IPS was successfully used to treat hydrocephalus in a sheep model. While statistical significance was not achieved, there were clear benefits to using a stent, including a decreased clog rate and the ability to perform a percutaneous revision. Further testing is needed to ensure efficacy and safety prior to human application.

Novel Standalone Motion-Sparing Pelvic Fixation Prevents Short-Term Insufficiency Fractures After Midsacrectomies Without Sacrificing Normal, Mobile Lumbar Segments Traditionally Used for Stabilization.

BACKGROUND AND OBJECTIVES: Sacrectomy is often the treatment of choice to provide the greatest chance of progression-free and overall survival for patients with primary malignant bone tumors of the sacrum. After midsacrectomy, the stability of the sacropelvic interface is diminished, resulting in insufficiency fractures. Traditional stabilization involves lumbopelvic fixation but subjects normal mobile segments to fusion. The purpose of this study was to determine whether standalone intrapelvic fixation is a safe adjunct to midsacrectomy, avoiding both sacral insufficiency fractures and the morbidity of instrumenting into the mobile spine. METHODS: A retrospective study identified all patients who underwent resection of sacral tumors at 2 comprehensive cancer centers between June 2020 and July 2022. Demographic, tumor-specific, operative characteristics and outcome data were collected. The primary outcome was presence of sacral insufficiency fractures. A retrospective data set of patients undergoing midsacrectomy without hardware placement was collected as a control. RESULTS: Nine patients (5 male, 4 female), median age 59 years, underwent midsacrectomy with concomitant placement of standalone pelvic fixation. No patients developed insufficiency fractures during the 216 days of clinical and 207 days of radiographic follow-up. There were no adverse events attributable to the addition of standalone pelvic fixation. In our historical cohort of partial sacrectomies without stabilization, there were 4/25 patients (16%) with sacral insufficiency fractures. These fractures appeared between 0 and 5 months postoperatively. CONCLUSION: A novel standalone intrapelvic fixation after partial sacrectomy is a safe adjunct to prevent postoperative sacral insufficiency fractures in patients undergoing midsacrectomy for tumor. Such a technique may allow for long-term sacropelvic stability without sacrificing mobile lumbar segments.

Credentialing, Certification, and Peer Review Essentials for the Neurosurgeon.

Credentialing and certification are essential processes during hiring to ensure that the physician is competent and possesses the qualifications and skill sets claimed. Peer review ensures the continuing evolution of these skills to meet a standard of care. We have provided an overview and discussion of these processes in the United States. Credentialing is the process by which a physician is determined to be competent and able to practice, used to ensure that medical staff meets specific standards, and to grant operative privileges at an institution. Certification is a standardized affirmation of a physician's competence on a nationwide basis. Although not legally required to practice in the United States, many institutions emphasize certification for full privileges on an ongoing basis at a hospital. In the United States, peer review of adverse events is a mandatory prerequisite for accreditation. The initial lack of standardization led to the development of the Health Care Quality Improvement Act, which protects those involved in the peer review process from litigation, and the National Provider Databank, which was established as a national database to track misconduct. A focus on quality improvement in the peer review process can lead to improved performance and patient outcomes. A thorough understanding of the processes of credentialing, certification, and peer review in the United States will benefit neurosurgeons by allowing them to know what institutions are looking for as well and their rights and responsibilities in any given situation. It could also be useful to compare these policies and practices in the United States to those in other countries.

Sepsis and septic shock after craniotomy: Predicting a significant patient safety and quality outcome measure.

OBJECTIVES: Sepsis and septic shock are important quality and patient safety metrics. This study examines incidence of Sepsis and/or septic shock (S/SS) after craniotomy for tumor resection, one of the most common neurosurgical operations. METHODS: Multicenter, prospectively collected data from the American College of Surgeons National Surgical Quality Improvement Program (ACS NSQIP) database was used to identify patients undergoing craniotomy for tumor (CPT 61510, 61521, 61520, 61518, 61526, 61545, 61546, 61512, 61519, 61575) from 2012-2015. Univariate and multivariate logistic regression models were used to identify risk factors for S/SS. RESULTS: There were 18,642 patients that underwent craniotomy for tumor resection. The rate of sepsis was 1.35% with a mortality rate of 11.16% and the rate of septic shock was 0.65% with a 33.06% mortality rate versus an overall mortality rate of 2.46% in the craniotomy for tumor cohort. The 30-day readmission rate was 50.54% with S/SS vs 10.26% in those without S/SS. Multiple factors were identified as statistically significant (p <0.05) for S/SS including ascites (OR = 33.0), ventilator dependence (OR = 4.5), SIRS (OR = 2.8), functional status (OR = 2.3), bleeding disorders (OR = 1.7), severe COPD (OR = 1.6), steroid use (OR = 1.6), operative time >310 minutes (OR = 1.5), hypertension requiring medication (OR = 1.5), ASA class ≥ 3 (OR = 1.4), male sex (OR = 1.4), BMI >35 (OR = 1.4) and infratentorial location. CONCLUSIONS: The data indicate that sepsis and septic shock, although uncommon after craniotomy for tumor resection, carry a significant risk of 30-day unplanned reoperation (35.60%) and mortality (18.21%). The most significant risk factors are ventilator dependence, ascites, SIRS and poor functional status. By identifying the risk factors for S/SS, neurosurgeons can potentially improve outcomes. Further investigation should focus on the creation of a predictive score for S/SS with integration into the electronic health record for targeted protocol initiation in this unique neurosurgical patient population.

Descriptive Analysis of 1972 Cervical Corpectomy Patients and 30-Day Postoperative Outcomes.

BACKGROUND: There exists no large, multi-institutional analysis of patients undergoing cervical corpectomy for common degenerative spinal disease, including patient demographics and comorbidities as well as postoperative complications. METHODS: Using Current Procedural Terminology and International Classification of Diseases codes, 1972 patients who underwent a cervical corpectomy for degenerative spinal disease were identified from the American College of Surgeons National Surgical Quality Improvement Program data sets from 2012 to 2015. A descriptive analysis of the patients who underwent the procedure as well as 30-day outcomes and adverse events were collected. Multivariate logistic regression models were used to determine the effect of any preoperative factors identified from a univariate logistic regression analysis (variables with P < .10) of complications. RESULTS: The total complication rate, defined as major or minor adverse event, mortality, unplanned readmission, unplanned reoperation, or admission >30 days, was 13.28%. The percentage of patients who had ≥1 major or minor adverse events was 5.02%. Several factors commonly associated with an increased risk of perioperative complications, including smoking and diabetes, were found not to be independently associated with complications in this cohort. CONCLUSIONS: This study is the largest analysis of cervical corpectomies. The results of the multivariate analysis provide guidance on risk factors associated with perioperative complications. These data could help develop risk-appropriate strategies for minimizing the effects of certain preoperative factors on perioperative complications.

Lead Toxicity From Intradiscal Retained Bullet Fragment: Management Considerations and Recommendations.

BACKGROUND: Lead toxicity (plumbism) secondary to retained lead missiles in synovial joint spaces is a rare complication after gunshot injuries. Management of lead missiles in the intradiscal space regarding potential lead toxicity is less certain. CASE DESCRIPTION: We reviewed the literature regarding lead toxicity secondary to intradiscal bullets particularly concerning incidence, management, and outcomes. A lack of high-quality published data precludes a meta-analysis from taking place. Only four reports of lead toxicity secondary to missiles in the intradiscal space have been published. Including an additional case presented in this report, our review of the literature has led us to make several management recommendations, largely based on both the available literature and our current report. CONCLUSIONS: First, there is insufficient evidence for removing retained lead missiles solely to mitigate the risk of lead toxicity. Second, chelation therapy in addition to surgical removal of the lead source is a valuable adjunct in the perioperative period and should be undertaken with the assistance of medical toxicology. Third, a retained missile does not mandate a simultaneous stabilization procedure in lieu of other indications based on the data available at this time.

Comparative Analysis of Decompression Versus Decompression and Fusion for Surgical Management of Lumbar Spondylolisthesis.

OBJECTIVE: When lumbar stenosis involves spondylolisthesis, many surgeons include fixation. Two recent trials have shown no consensus to definitive treatment. We aimed to add to the discourse of fusion versus decompression in patients with lumbar spondylolisthesis by providing a large-scale generalizable study. METHODS: We used multicenter, prospectively collected data from the American College of Surgeons National Surgical Quality Improvement Program database to compare 30-day outcomes for decompression alone versus combination decompression and fusion in the treatment of lumbar spondylolisthesis. Logistic regression models were used to analyze the effect of surgical type on multiple characteristics. Univariate 2-tailed χ2 analyses were used to identify further outcome differences. RESULTS: In total, 9606 patients with treated lumbar spondylolisthesis were identified (907 decompression only, 8699 decompression and fusion). The fusion group tended to be younger (P < 0.001) and was more likely to be smokers (P = 0.01). Unplanned return to surgery was 3.02% in the fusion group, compared with 1.02% (P = 0.011). Minor adverse events occurred in 12.8% of the fusion group versus 4.9% (P < 0.001). Major adverse events occurred in 4.5% of the fusion group versus 3.1% (P = 0.0498). There was no significant difference in 30-day mortality, prolonged admission, or 30-day readmission. CONCLUSIONS: Unplanned return to the operating room and major and minor adverse events were greater for patients undergoing fusion. This could influence future decision-making in lumbar spondylolisthesis. This study indicates that further investigation is warranted but that decompression may be associated with less morbidity in the properly selected patient.

Trends in Interhospital Transfers and Mechanical Thrombectomy for United States Acute Ischemic Stroke Inpatients.

OBJECTIVE: Stroke care in the US is increasingly regionalized. Many patients undergo interhospital transfer to access specialized, time-sensitive interventions such as mechanical thrombectomy. METHODS: Using a stratified survey design of the US Nationwide Inpatient Sample (2009-2014) we examined trends in interhospital transfers for ischemic stroke resulting in mechanical thrombectomy. International Classification of Disease-Ninth Revision (ICD-9) codes were used to identify stroke admissions and inpatient procedures within endovascular-capable hospitals. Regression analysis was used to identify factors associated with patient outcomes. RESULTS: From 2009-2014, 772,437 ischemic stroke admissions were identified. Stroke admissions that arrived via interhospital transfer increased from 12.5% to 16.8%, 2009-2014 (P-trend < .001). Transfers receiving thrombectomy increased from 4.0% to 5.2%, 2009-2014 (P-trend = .016), while those receiving tissue plasminogen activator increased from 16.0% to 20.0%, 2009-2014 (P-trend < .001). One in 4 patients receiving thrombectomy were transferred from another acute care facility (n = 6,014 of 24,861). Compared to patients arriving via the hospital "front door" receiving mechanical thrombectomy, those arriving via transfer were more often from rural areas and received by teaching hospitals with greater frequency of thrombectomy. Those arriving via interhospital transfer undergoing thrombectomy had greater odds of symptomatic intracranial hemorrhage (adjusted odds ratio [AOR] 1.19, 95% CI: 1.01-1.42) versus "front door" arrivals. There were no differences in inpatient mortality (AOR 1.11, 95% CI: .93-1.33). CONCLUSIONS: From 2009 to 2014, interhospital stroke transfers to endovascular-capable hospitals increased by one-third. For every ∼15 additional transfers over the time period one additional patient received thrombectomy. Optimization of transfers presents an opportunity to increase access to thrombectomy.

Risk Factors and Associated Complications of Symptomatic Venous Thromboembolism in Patients with Craniotomy for Meningioma.

OBJECTIVE: Patients undergoing surgical resection of meningioma are at increased risk for developing venous thromboembolism (VTE). The aim of this study was to assess occurrence of VTE in patients who underwent surgical resection of meningioma to determine risk factors and associated complications of VTE. METHODS: The American College of Surgeons National Surgical Quality Improvement Project database from 2012 to 2015 was reviewed for patients who had undergone meningioma resection according to primary Current Procedural Terminology codes and International Classification of Diseases, Ninth Revision. RESULTS: The study included 5036 patients with meningioma. Rate of VTE was 3.38%, with pulmonary embolism rate of 1.47% and deep venous thrombosis rate of 2.42%. During the first 30 days after surgery, patients with VTE had a mortality rate of 5.88% compared with 1.15% for patients without VTE. Multivariate binary logistic regression analysis determined 5 risk factors for VTE,: age ≥60 years, American Society of Anesthesiologists classification III, operative time ≥310 minutes, ventilator dependence, and preoperative transfusions. Univariate analysis revealed a number of complications significantly associated with VTE occurrence, including unplanned intubation, ventilator use for >48 hours, stroke, sepsis, septic shock, pneumonia, urinary tract infection, and transfusions. CONCLUSIONS: Risk factors of VTE and associated complications were identified. Understanding these risk factors provides physicians with further insight in managing this subgroup of patients in a personalized fashion in the perioperative period to minimize the incidence and morbidity of VTE.

Category specific spatial dissociations of parallel processes underlying visual naming.

The constituent elements and dynamics of the networks responsible for word production are a central issue to understanding human language. Of particular interest is their dependency on lexical category, particularly the possible segregation of nouns and verbs into separate processing streams. We applied a novel mixed-effects, multilevel analysis to electrocorticographic data collected from 19 patients (1942 electrodes) to examine the activity of broadly disseminated cortical networks during the retrieval of distinct lexical categories. This approach was designed to overcome the issues of sparse sampling and individual variability inherent to invasive electrophysiology. Both noun and verb generation evoked overlapping, yet distinct nonhierarchical processes favoring ventral and dorsal visual streams, respectively. Notable differences in activity patterns were noted in Broca's area and superior lateral temporo-occipital regions (verb > noun) and in parahippocampal and fusiform cortices (noun > verb). Comparisons with functional magnetic resonance imaging (fMRI) results yielded a strong correlation of blood oxygen level-dependent signal and gamma power and an independent estimate of group size needed for fMRI studies of cognition. Our findings imply parallel, lexical category-specific processes and reconcile discrepancies between lesional and functional imaging studies.

Recursive grid partitioning on a cortical surface model: an optimized technique for the localization of implanted subdural electrodes.

OBJECT: Precise localization of subdural electrodes (SDEs) is essential for the interpretation of data from intracranial electrocorticography recordings. Blood and fluid accumulation underneath the craniotomy flap leads to a nonlinear deformation of the brain surface and of the SDE array on postoperative CT scans and adversely impacts the accurate localization of electrodes located underneath the craniotomy. Older methods that localize electrodes based on their identification on a postimplantation CT scan with coregistration to a preimplantation MR image can result in significant problems with accuracy of the electrode localization. The authors report 3 novel methods that rely on the creation of a set of 3D mesh models to depict the pial surface and a smoothed pial envelope. Two of these new methods are designed to localize electrodes, and they are compared with 6 methods currently in use to determine their relative accuracy and reliability. METHODS: The first method involves manually localizing each electrode using digital photographs obtained at surgery. This is highly accurate, but requires time intensive, operator-dependent input. The second uses 4 electrodes localized manually in conjunction with an automated, recursive partitioning technique to localize the entire electrode array. The authors evaluated the accuracy of previously published methods by applying the methods to their data and comparing them against the photograph-based localization. Finally, the authors further enhanced the usability of these methods by using automatic parcellation techniques to assign anatomical labels to individual electrodes as well as by generating an inflated cortical surface model while still preserving electrode locations relative to the cortical anatomy. RESULTS: The recursive grid partitioning had the least error compared with older methods (672 electrodes, 6.4-mm maximum electrode error, 2.0-mm mean error, p < 10(-18)). The maximum errors derived using prior methods of localization ranged from 8.2 to 11.7 mm for an individual electrode, with mean errors ranging between 2.9 and 4.1 mm depending on the method used. The authors also noted a larger error in all methods that used CT scans alone to localize electrodes compared with those that used both postoperative CT and postoperative MRI. The large mean errors reported with these methods are liable to affect intermodal data comparisons (for example, with functional mapping techniques) and may impact surgical decision making. CONCLUSIONS: The authors have presented several aspects of using new techniques to visualize electrodes implanted for localizing epilepsy. The ability to use automated labeling schemas to denote which gyrus a particular electrode overlies is potentially of great utility in planning resections and in corroborating the results of extraoperative stimulation mapping. Dilation of the pial mesh model provides, for the first time, a sense of the cortical surface not sampled by the electrode, and the potential roles this "electrophysiologically hidden" cortex may play in both eloquent function and seizure onset.

Intracranial electroencephalography reveals different temporal profiles for dorsal- and ventro-lateral prefrontal cortex in preparing to stop action.

Preparing to stop an inappropriate action requires keeping in mind the task goal and using this to influence the action control system. We tested the hypothesis that different subregions of prefrontal cortex show different temporal profiles consistent with dissociable contributions to preparing-to-stop, with dorsolateral prefrontal cortex (DLPFC) representing the task goal and ventrolateral prefrontal cortex (VLPFC) implementing action control. Five human subjects were studied using electrocorticography recorded from subdural grids over right lateral frontal cortex. On each trial, a task cue instructed the subject whether stopping might be needed or not (Maybe Stop [MS] or No Stop [NS]), followed by a go cue, and on some MS trials, a subsequent stop signal. We focused on go trials, comparing MS with NS. In the DLPFC, most subjects had an increase in high gamma activity following the task cue and the go cue. In contrast, in the VLPFC, all subjects had activity after the go cue near the time of the motor response on MS trials, related to behavioral slowing, and significantly later than the DLPFC activity. These different temporal profiles suggest that DLPFC and VLPFC could have dissociable roles, with DLPFC representing task goals and VLPFC implementing action control.

Roles for the pre-supplementary motor area and the right inferior frontal gyrus in stopping action: electrophysiological responses and functional and structural connectivity.

Both the pre-supplementary motor area (preSMA) and the right inferior frontal gyrus (rIFG) are important for stopping action outright. These regions are also engaged when preparing to stop. We aimed to elucidate the roles of these regions by harnessing the high spatio-temporal resolution of electrocorticography (ECoG), and by using a task that engages both preparing to stop and stopping outright. First, we validated the task using fMRI in 16 healthy control participants to confirm that both the preSMA and the rIFG were active. Next, we studied a rare patient with intracranial grid coverage of both these regions, using macrostimulation, diffusion tractography, cortico-cortical evoked potentials (CCEPs) and task-based ECoG. Macrostimulation of the preSMA induced behavioral motor arrest. Diffusion tractography revealed a structural connection between the preSMA and rIFG. CCEP analysis showed that stimulation of the preSMA evoked strong local field potentials within 30 ms in rIFG. During the task, when preparing to stop, there was increased high gamma amplitude (~70-250 Hz) in both regions, with preSMA preceding rIFG by ~750 ms. For outright stopping there was also a high gamma amplitude increase in both regions, again with preSMA preceding rIFG. Further, at the time of stopping, there was an increase in beta band activity (~16 Hz) in both regions, with significantly stronger inter-regional coherence for successful vs. unsuccessful stop trials. The results complement earlier reports of a structural/functional action control network between the preSMA and rIFG. They go further by revealing between-region timing differences in the high gamma band when preparing to stop and stopping outright. They also reveal strong between-region coherence in the beta band when stopping is successful. Implications for theories of action control are discussed.

Variability of the relationship between electrophysiology and BOLD-fMRI across cortical regions in humans.

The relationship between blood oxygenation level-dependent (BOLD) functional MRI (fMRI) signal and the underlying neural electrical activity in humans is a topic of intense interest to systems neuroscience. This relationship has generally been assumed to be invariant regardless of the brain region and the cognitive task being studied. We critically evaluated these assumptions by comparing the BOLD-fMRI response with local field potential (LFP) measurements during visually cued common noun and verb generation in 11 humans in whom 1210 subdural electrodes were implanted. As expected, power in the mid-gamma band (60-120 Hz) correlated positively (r(2) = 0.16, p < 10(-16)) and power in the beta band (13-30 Hz) correlated negatively (r(2) = 0.09, p < 10(-16)) with the BOLD signal change. Beta and mid-gamma band activity independently explain different components of the observed BOLD signal. Importantly, we found that the location (i.e., lobe) of the recording site modulates the relationship between the electrocorticographic (ECoG) signal and the observed fMRI response (p < 10(-16), F(21,1830) = 52.7), while the type of language task does not. Across all brain regions, ECoG activity in the gamma and beta bands explains 22% of the fMRI response, but if the lobar location is considered, 28% of the variance can be explained. Further evaluation of this relationship at the level of individual gyri provides additional evidence of differences in the BOLD-LFP relationship by cortical locus. This spatial variability in the relationship between the fMRI signal and neural activity carries implications for modeling of the hemodynamic response function, an essential step for interregional fMRI comparisons.

Anatomic and electro-physiologic connectivity of the language system: a combined DTI-CCEP study.

Here we present a novel multimodal analysis of network connectivity in the language system. We assessed connectivity of Broca's area using tractography with diffusion tensor imaging (DTI), and with cortico-cortical evoked potentials (CCEPs) to measure the spread of artificial currents applied directly to human cortex. We found that both the amplitude and latency of CCEP currents significantly correlates (r(2)=0.41, p<10(-16)) with the number of DTI pathways connecting the stimulation and recording loci. This strategy of relating electrical information flow with the neural architecture will likely yield new insights into cognitive processes.

Frequency-specific electrocorticographic correlates of working memory delay period fMRI activity.

Electrocorticography (ECoG) and functional MRI (BOLD-fMRI) have been used previously to measure brain activity during working memory delay periods. These studies have separately reported oscillation changes in the theta (4-8 Hz) band and BOLD-fMRI increases during delay periods when information is maintained in memory. However, it is not known how intracranial cortical field potential (CFP) changes relate to BOLD-fMRI responses during delay periods. To answer this question, fMRI was obtained from six epilepsy patients during a visual working memory task. Then, following subdural macroelectrode implant, continuous ECoG was used to record CFPs during the same task. Time-frequency analyses showed delay period gamma band oscillation amplitude increases on electrodes located near fMRI activity, while in the theta band changes were higher for electrodes located away from fMRI activation. The amplitude of the ECoG gamma band response was significantly positively correlated with the fMRI response, while a negative correlation was found for the theta band. The findings are consistent with previous reports of local field potential (LFP) coupling in the gamma band with BOLD-fMRI responses during visual stimulation in monkeys, but are novel in that the relationship reported here persists after the disappearance of visual stimuli while information is being maintained in memory. We conclude that there is a relationship between BOLD-fMRI increases and human working memory delay period gamma oscillation increases and theta decreases. The spectral profile change provides a basis for comparison of working memory delay period BOLD-fMRI with field potential recordings in animals and other human intracranial EEG studies.

Dissociation between diffusion MR tractography density and strength in epilepsy patients with hippocampal sclerosis.

Mesial temporal lobe epilepsy (MTLE) is hypothesized to involve derangement of long-range limbic connectivity, but in vivo evidence is lacking. We used diffusion tractography to investigate the relationship between hippocampal atrophy and connectivity in MTLE patients with hippocampal sclerosis (HS). Atrophy was correlated with relatively decreased connectivity density but increased connectivity strength, suggesting that HS is accompanied by relatively sparse but strong connections as measured by diffusion anisotropy.