Optimal Frequency in Repetitive Transcranial Magnetic Stimulation for the Management of Chronic Pain: A Network Meta-Analysis of Randomized Controlled Trials

OBJECTIVE

Repetitive Transcranial Magnetic Stimulation (rTMS) has been shown to be effective for pain modulation in a variety of pathological conditions causing neuropathic pain. The purpose of this study is to conduct a network meta-analysis (NMA) of randomized control trials to identify the most optimal frequency required to achieve chronic pain modulation using rTMS.

METHODS

A comprehensive search was conducted in electronic databases to identify randomized controlled trials investigating the efficacy of rTMS for chronic pain management. A total of 24 studies met the inclusion criteria, and a NMA was conducted to identify the most effective rTMS frequency for chronic pain management.

RESULTS

Our analysis revealed that high frequency rTMS (20 Hz) was the most effective frequency for chronic pain modulation. Patients treated with 20 Hz had lower pain levels than those treated at 5 Hz (mean difference [MD] = -3.11 [95% confidence interval {CI}: -5.61 - -0.61], P = 0.032) and control (MD = -1.99 [95% CI: -3.11 - -0.88], P = 0.023). Similarly, treatment with 10 Hz had lower pain levels compared to 5 Hz (MD = -2.56 [95% CI: -5.05 - -0.07], P = 0.045) and control (MD = -1.44 [95% CI: -2.52 - -0.36], P = 0.031). 20 Hz and 10 Hz were not statistically different.

CONCLUSIONS

This NMA suggests that high frequency rTMS (20 Hz) is the most optimal frequency for chronic pain modulation. These findings have important clinical implications and can guide healthcare professionals in selecting the most effective frequency for rTMS treatment in patients with chronic pain.

Long-term outcomes of mesial temporal laser interstitial thermal therapy for drug-resistant epilepsy and subsequent surgery for seizure recurrence: a multi-centre cohort study

BACKGROUND

Magnetic resonance-guided laser interstitial thermal therapy (MRgLITT) is a minimally invasive alternative to surgical resection for drug-resistant mesial temporal lobe epilepsy (mTLE). Reported rates of seizure freedom are variable and long-term durability is largely unproven. Anterior temporal lobectomy (ATL) remains an option for patients with MRgLITT treatment failure. However, the safety and efficacy of this staged strategy is unknown.

METHODS

This multicentre, retrospective cohort study included 268 patients consecutively treated with mesial temporal MRgLITT at 11 centres between 2012 and 2018. Seizure outcomes and complications of MRgLITT and any subsequent surgery are reported. Predictive value of preoperative variables for seizure outcome was assessed.

RESULTS

Engel I seizure freedom was achieved in 55.8% (149/267) at 1 year, 52.5% (126/240) at 2 years and 49.3% (132/268) at the last follow-up ≥1 year (median 47 months). Engel I or II outcomes were achieved in 74.2% (198/267) at 1 year, 75.0% (180/240) at 2 years and 66.0% (177/268) at the last follow-up. Preoperative focal to bilateral tonic-clonic seizures were independently associated with seizure recurrence. Among patients with seizure recurrence, 14/21 (66.7%) became seizure-free after subsequent ATL and 5/10 (50%) after repeat MRgLITT at last follow-up≥1 year.

CONCLUSIONS

MRgLITT is a viable treatment with durable outcomes for patients with drug-resistant mTLE evaluated at a comprehensive epilepsy centre. Although seizure freedom rates were lower than reported with ATL, this series represents the early experience of each centre and a heterogeneous cohort. ATL remains a safe and effective treatment for well-selected patients who fail MRgLITT.

Responsive neurostimulation device therapy in pediatric patients with complex medically refractory epilepsy

OBJECTIVE

Pediatric epilepsy is characterized as drug resistant in 20%-30% of patients and defined as persistent seizures despite adequate treatment with two first-line antiepileptic medications. The American Academy of Neurology advocates surgical options earlier in the treatment of epilepsy to provide long-term seizure reduction. The new development of minimally invasive approaches has recently allowed for surgical options to patients not previously deemed surgical candidates. These may include patients with bilateral, deep, eloquent, or poorly localizing epileptogenic foci. To this end, responsive neurostimulation (RNS) is an FDA-approved closed-loop neuromodulation device for adjuvant treatment of adults with medically intractable epilepsy arising from one or multiple foci.

METHODS

In this study, the authors describe their initial institutional experience with the use of RNS in pediatric patients with drug-resistant epilepsy. An IRB-approved retrospective review was conducted of 8 pediatric patients who underwent RNS implantation at Cincinnati Children's Hospital Medical Center between 2019 and 2021.

RESULTS

Eight patients met the inclusion criteria for the study. The average age at the time of surgery was 14.7 years (range 8-18 years) with a mean follow-up of 16.5 months. All patients underwent invasive monitoring with stereo-EEG, subdural grid placement, or a combination of both. All patients had either bilateral or eloquent cortex targets. Trajectories were based on noninvasive (phase 1) and invasive (phase 2) seizure onset zone localization data. Four (50%) of the 8 patients underwent surgical intervention for epilepsy prior to RNS placement. RNS electrodes were placed with robot-assisted guidance in a hybrid operating room with intraoperative CT and electrocorticography. The authors demonstrated individualized RNS electrode trajectory and placement with targets in the amygdala/hippocampus, bilateral insula, bilateral parietal and occipital targets, and frontoparietal regions for a total of 14 implanted electrodes. One adverse event occurred, a wound infection requiring return to the operating room for removal of the RNS implant. All patients demonstrated a reduction in seizure frequency. All patients achieved > 50% reduction in seizure frequency at last follow-up.

CONCLUSIONS

RNS implantation in carefully selected pediatric patients appears safe and efficacious in reducing seizure burden with a low rate of operative complications.

Gender Equality in Neurosurgery and Strategic Goals Toward a More Balanced Workforce

The Women in Neurosurgery (WINS) and the American Association of Neurological Surgeons published a white paper in 2008 setting an ambitious goal for women to comprise 20% of neurosurgery residents by 2012 and 20% of practicing neurosurgeons by 2020. Although there has been steady progress, we have fallen short of these benchmarks. We take this opportunity to look back at the accomplishments made over the past decade and provide an update on our present status. We evaluate current barriers toward progress and propose new goals, highlighting the systemic changes necessary to accomplish them. We propose the following updated recommendations to recruit and retain diverse talent into the neurosurgical workforce. (1) Neurosurgical departments and societies should provide diverse, early formal mentorship opportunities for medical students, residents, and junior faculty members. (2) Parental leave policies must be delineated, promoted, and enforced for all neurosurgeons, with greater awareness of internal discrimination and normalization of the discussion surrounding this topic. (3) We need to strive for compensation equity, with transparency in compensation mechanisms and regular assessment of compensation metrics. (4) Departments and institutions must have a zero-tolerance policy for sexual harassment and discrimination and establish a safe reporting structure. Finally, we propose attainable benchmarks toward achieving gender balance in the neurosurgical workforce, with a goal for women to comprise 30% of the entering residency class by 2030 and to comprise 30% of practicing neurosurgeons by 2038. We hope that this will guide further progress toward our future of building a balanced workforce.

Acute thoracic disc heralded by change in spinal cord stimulation pattern: illustrative case

BACKGROUND

Spinal cord stimulation (SCS) uses unique electric stimulation parameters to selectively treat specific regions of chronic or refractory back pain. Changing these parameters can lead to spreading paresthesia and/or pain beyond the desired region.

OBSERVATIONS

A patient with a history of stable, successful SCS treatment presented with acute development of paresthesias that were relieved by reduction of stimulation parameters. The patient required paradoxically lower SCS settings for control of chronic back pain. This presentation prompted further investigation, which revealed a new disc protrusion and cord compression at the level of the paddle lead.

LESSONS

In patients with SCS, a new onset of back pain accompanied by acute paresthesia that is reversible by reducing the SCS amplitude warrants investigation for new spine pathology.

Developing a Professionalism and Harassment Policy for Organized Neurosurgery

Annual conferences, educational courses, and other meetings draw a diverse community of individuals, yet also create a unique environment without the traditional guard rails. Unlike events held at one's home institution, clear rules and jurisdiction have not been universally established. To promote the open exchange of ideas, as well as an environment conducive to professional growth of all participants, the leading neurosurgical professional organizations joined forces to delineate the expectations for anyone who participates in sponsored events. The One Neurosurgery Summit Taskforce on Professionalism and Harassment developed a foundational policy that establishes common expectations for behavior and a unified roadmap for the prompt response to untoward events. We hope that publishing this policy will inspire other medical organizations to establish their own meeting and conference policies. More importantly, we wish to bring greater attention to everyone's responsibility for ensuring a safe and respectful space for education, scientific debate, and networking during organized events.

Contemporary Analysis of Minimal Clinically Important Difference in the Neurosurgical Literature

BACKGROUND

Minimal clinically important difference (MCID) is determined when a patient or physician defines the minimal change that outweighs the costs and untoward effects of a treatment. These measurements are "anchored" to validated quality-of-life instruments or physician-rated, disease-activity indices. To capture the subjective clinical experience in a measurable way, there is an increasing use of MCID.

OBJECTIVE

To review the overall concept, method of calculation, strengths, and weaknesses of MCID and its application in the neurosurgical literature.

METHODS

Recent articles were reviewed based on PubMed query. To illustrate the strengths and limitations of MCID, studies regarding the measurement of pain are emphasized and their impact on subsequent publications queried.

RESULTS

MCID varies by population baseline characteristics and calculation method. In the context of pain, MCID varied based on the quality of pain, chronicity, and treatment options.

CONCLUSION

MCID evaluates outcomes relative to whether they provide a meaningful change to patients, incorporating the risks and benefits of a treatment. Using MCID in the process of evaluating outcomes helps to avoid the error of interpreting a small but statistically significant outcome difference as being clinically important.

Reducing Superfluous Opioid Prescribing Practices After Brain Surgery: It Is Time to Talk About Drugs

BACKGROUND

Opioids are prescribed routinely after cranial surgery despite a paucity of evidence regarding the optimal quantity needed. Overprescribing may adversely contribute to opioid abuse, chronic use, and diversion.

OBJECTIVE

To evaluate the effectiveness of a system-wide campaign to reduce opioid prescribing excess while maintaining adequate analgesia.

METHODS

A retrospective cohort study of patients undergoing a craniotomy for tumor resection with home disposition before and after a 2-mo educational intervention was completed. The educational initiative was composed of directed didactic seminars targeting senior staff, residents, and advanced practice providers. Opioid prescribing patterns were then assessed for patients discharged before and after the intervention period.

RESULTS

A total of 203 patients were discharged home following a craniotomy for tumor resection during the study period: 98 who underwent surgery prior to the educational interventions compared to 105 patients treated post-intervention. Following a 2-mo educational period, the quantity of opioids prescribed decreased by 52% (median morphine milligram equivalent per day [interquartile range], 32.1 [16.1, 64.3] vs 15.4 [0, 32.9], P < .001). Refill requests also decreased by 56% (17% vs 8%, P = .027) despite both groups having similar baseline characteristics. There was no increase in pain scores at outpatient follow-up (1.23 vs 0.85, P = .105).

CONCLUSION

A dramatic reduction in opioids prescribed was achieved without affecting refill requests, patient satisfaction, or perceived analgesia. The use of targeted didactic education to safely improve opioid prescribing following intracranial surgery uniquely highlights the ability of simple, evidence-based interventions to impact clinical decision making, lessen potential patient harm, and address national public health concerns.

Developing a professionalism and harassment policy for organized neurosurgery

Annual conferences, educational courses, and other meetings draw a diverse community of individuals, yet also create a unique environment without the traditional guard rails. Unlike events held at one's home institution, clear rules and jurisdiction have not been universally established. To promote the open exchange of ideas, as well as an environment conducive to professional growth of all participants, the leading neurosurgical professional organizations joined to delineate the expectations for anyone who participates in sponsored events. The One Neurosurgery Summit Taskforce on Professionalism and Harassment developed a foundational policy that establishes common expectations for behavior and a unified roadmap for the prompt response to untoward events. We hope that publishing this policy will inspire other medical organizations to establish their own meeting and conference policies. More importantly, we wish to bring greater attention to everyone's responsibility for ensuring a safe and respectful space for education, scientific debate, and networking during organized events.

Gender diversity in United States neurosurgery training programs

OBJECTIVE

Neurosurgery continues to be one of the medical specialties with the lowest representation of females in both the resident and faculty workforce. Currently, there are limited available data on the gender distribution of faculty and residents in Accreditation Council for Graduate Medical Education (ACGME)-accredited neurosurgery training programs. This information is critical to accurately measure the results of any effort to improve both the recruitment and retention of women in neurosurgery. The objective of the current study was to define the current gender distribution of faculty and residents in ACGME-accredited neurosurgery training programs.

METHODS

Data publicly available through institutional and supplemental websites for neurosurgical faculty and residents at ACGME-accredited programs were analyzed for the 2017-2018 academic year. Data collected for faculty included gender, age, year of residency graduation, academic rank, h-index, American Board of Neurological Surgery certification status, and leadership positions. Resident data included gender and postgraduate year of training.

RESULTS

Among the 109 ACGME-accredited neurosurgical residency programs included in this study, there were 1350 residents in training, of whom 18.2% were female and 81.8% were male. There are 1320 faculty, of whom 8.7% were female and 91.3% were male. Fifty-eight programs (53.2%) had both female faculty and residents, 35 programs (32.1%) had female residents and no female faculty, 4 programs (3.7%) had female faculty and no female residents, and 6 programs (5.5%) lacked both female residents and faculty. Six programs (5.5%) had incomplete data. Female faculty were younger, had lower h-indices, and were less likely to be board certified and attain positions of higher academic rank and leadership.

CONCLUSIONS

This study serves to provide a current snapshot of gender diversity in ACGME-accredited neurosurgery training programs. While there are still fewer female neurosurgeons achieving positions of higher academic rank and serving in leadership positions than male neurosurgeons, the authors' findings suggest that this is likely due to the small number of women in the neurosurgical field who are the farthest away from residency graduation and serves to highlight the significant progress that has been made toward achieving greater gender diversity in the neurosurgical workforce.

Toward an understanding of sexual harassment in neurosurgery

OBJECTIVE

The goal of this study was the creation and administration of a survey to assess the depth and breadth of sexual harassment across neurosurgery.

METHODS

A survey was created to 1) assess perceived attitudes toward systemic issues that might be permissive of sexual harassment; 2) measure the reported prevalence and severity of sexual harassment; and 3) determine the populations at highest risk and those most likely to perpetrate sexual harassment. Demographic information was also included to facilitate further analysis. The SurveyMonkey platform was used, and a request to complete the survey was sent to all Society of Neurological Surgeons and Congress of Neurological Surgeons (CNS) active and resident members as well as CNS transitional, emeritus, and inactive members. Data were analyzed using RStudio version 1.2.5019.

RESULTS

Nearly two-thirds of responders indicated having witnessed sexual harassment in some form (62%, n = 382). Males were overwhelmingly identified as the offenders in allegations of sexual harassment (72%), with individuals in a "superior position" identified as offenders in 86%. Less than one-third of responders addressed the incidents of sexual harassment when they happened (yes 31%, no 62%, unsure 7%). Of those who did report, most felt there was either no impact or a negative one (negative: 34%, no impact: 38%). Almost all (85%) cited barriers to taking action about sexual harassment, including retaliation/retribution (87%), impact on future career (85%), reputation concerns (72%), and associated stress (50%). Female neurosurgeons were statistically more likely than male neurosurgeons to report witnessing or experiencing sexual harassment, as well as assessing it as a problem.

CONCLUSIONS

This study demonstrates that neurosurgeons report significant sexual harassment across all ages and practice settings. Sexual harassment impacts both men and women, with more than half personally subjected to this behavior and two-thirds having witnessed it. Male dominance, a hierarchical environment, and a permissive environment remain prevalent within the neurosurgical community. This is not just a historical problem, but it continues today. A change of culture will be required for neurosurgery to shed this mantle, which must include zero tolerance of this behavior, new policies, awareness of unconscious bias, and commitment to best practices to enhance diversity. Above all, it will require that all neurosurgeons and neurosurgical leaders develop an awareness of sexual harassment in the workplace and establish consistent mechanisms to mitigate against its highly deleterious effects in the specialty.

Prevalence of Alternative Diagnoses and Implications for Management in Idiopathic Normal Pressure Hydrocephalus Patients

BACKGROUND

Following Bayes theorem, ventriculomegaly and ataxia confer only a 30% chance of idiopathic Normal Pressure Hydrocephalus (NPH). When coupled with positive responses to best diagnostic testing (extended lumbar drainage), 70% of patients recommended for shunting will not actually have NPH. This is inadequate clinical care.

OBJECTIVE

To determine the proportion of alternative and treatable diagnoses in patients referred to a multidisciplinary NPH clinic.

METHODS

Patients without previously diagnosed NPH were queried from prospectively collected data. At least 1 neurosurgeon, cognitive neurologist, and neuropsychologist jointly formulated best treatment plans.

RESULTS

Of 328 total patients, 45% had an alternative diagnosis; 11% of all patients improved with treatment of an alternative diagnosis. Of 87 patients with treatable conditions, the highest frequency of pathologies included sleep disorders, and cervical stenosis, followed by Parkinson disease. Anti-cholinergic burden was a contributor for multiple patients. Of 142 patients undergoing lumbar puncture, 71% had positive responses and referred to surgery. Compared to NPH patients, mimickers were statistically significantly older with lower Montreal Cognitive Assessment (MoCA) score and worse gait parameters. Overall, 26% of the original patients underwent shunting. Pre-post testing revealed a statistically significant improved MoCA score and gait parameters in those patients who underwent surgery with follow-up.

CONCLUSION

Because the Multidisciplinary NPH Clinic selected only 26% for surgery (corroborating 30% in Bayes theorem), an overwhelming majority of patients with suspected NPH will harbor alternative diagnoses. Identification of contributing/confounding conditions will support the meticulous work-up necessary to appropriately manage patients without NPH while optimizing clinical responses to shunting in correctly diagnosed patients.

Adapting to Space Limitations During Prone Real-Time Magnetic Resonance Imaging-Guided Stereotaxic Laser Ablation: Technical Pearls

BACKGROUND

New techniques of intraoperative magnetic resonance imaging (MRI)-guided stereotaxy enable minimally invasive approaches to intracranial pathology. Laser interstitial thermal therapy (LITT), convection-enhanced drug delivery, and stereotactic biopsy can be performed with a real-time confirmation of location and the ability to adjust for intracranial shift during the procedure. However, these procedures are constrained by patient positioning and the need for trajectories that avoid collision between stereotactic elements and the small MRI bore. To our knowledge, this is the first report to outline the technical details of safe intraoperative MRI (iMRI)-guided stereotaxy, performed with prone positioning.

OBJECTIVE

To present technical pearls to guide the safe conduction of iMRI-guided stereotaxy and LITT while in the prone position.

METHODS

The details of the positioning and trajectories for a series of patients who underwent Clearpoint® (MRI Interventions Inc) frameless real-time MRI-guided stereotaxis using a posterior approach were reviewed.

RESULTS

In this series, 5 patients underwent selective amygdalohippocampectomy, and 2 underwent tumor biopsy/ablation while in the prone position without any complications.

CONCLUSION

Prone iMRI procedures can be performed safely even in a 60-cm MRI bore.

Effects of surgical targeting in laser interstitial thermal therapy for mesial temporal lobe epilepsy: A multicenter study of 234 patients

OBJECTIVE

Laser interstitial thermal therapy (LITT) for mesial temporal lobe epilepsy (mTLE) has reported seizure freedom rates between 36% and 78% with at least 1 year of follow-up. Unfortunately, the lack of robust methods capable of incorporating the inherent variability of patient anatomy, the variability of the ablated volumes, and clinical outcomes have limited three-dimensional quantitative analysis of surgical targeting and its impact on seizure outcomes. We therefore aimed to leverage a novel image-based methodology for normalizing surgical therapies across a large multicenter cohort to quantify the effects of surgical targeting on seizure outcomes in LITT for mTLE.

METHODS

This multicenter, retrospective cohort study included 234 patients from 11 centers who underwent LITT for mTLE. To investigate therapy location, all ablation cavities were manually traced on postoperative magnetic resonance imaging (MRI), which were subsequently nonlinearly normalized to a common atlas space. The association of clinical variables and ablation location to seizure outcome was calculated using multivariate regression and Bayesian models, respectively.

RESULTS

Ablations including more anterior, medial, and inferior temporal lobe structures, which involved greater amygdalar volume, were more likely to be associated with Engel class I outcomes. At both 1 and 2 years after LITT, 58.0% achieved Engel I outcomes. A history of bilateral tonic-clonic seizures decreased chances of Engel I outcome. Radiographic hippocampal sclerosis was not associated with seizure outcome.

SIGNIFICANCE

LITT is a viable treatment for mTLE in patients who have been properly evaluated at a comprehensive epilepsy center. Consideration of surgical factors is imperative to the complete assessment of LITT. Based on our model, ablations must prioritize the amygdala and also include the hippocampal head, parahippocampal gyrus, and rhinal cortices to maximize chances of seizure freedom. Extending the ablation posteriorly has diminishing returns. Further work is necessary to refine this analysis and define the minimal zone of ablation necessary for seizure control.

Post-operative nonketotic hyperglycemic induced focal motor status epilepticus related to treatment with corticosteroids following standard anterior temporal lobectomy

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Complications from standard ATL are uncommon and the use of post-operative corticosteroids may reduce complications.

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Following standard ATL, FMSE was present after treatment with corticosteroids that resolved after blood sugar control.

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After epilepsy surgery, corticosteroids should be used cautiously in people with comorbid diabetes mellitus.

Racial disparities in the diagnosis and management of trigeminal neuralgia

OBJECTIVE A number of studies have documented inequalities in care and outcomes for a variety of clinical conditions. The authors sought to identify racial and socioeconomic disparities in the diagnosis and treatment of trigeminal neuralgia (TN), as well as the potential underlying reasons for those disparities, which could serve as areas of focus for future quality improvement initiatives. METHODS The medical records of patients with an ICD-9 code of 350.1, signifying a diagnosis of TN, at the Henry Ford Medical Group (HFMG) in the period from 2006 to 2012 were searched, and clinical and socioeconomic data were retrospectively reviewed. Analyses were conducted to assess potential racial differences in subspecialty referral patterns and the specific type of treatment modality undertaken for patients with TN. RESULTS The authors identified 652 patients eligible for analysis. Compared with white patients, black patients were less likely to undergo percutaneous ablative procedures, stereotactic radiosurgery, or microvascular decompression (p < 0.001). However, there was no difference in the likelihood of blacks and whites undergoing a procedure once they had seen a neurosurgeon (67% vs 70%, respectively; p = 0.712). Blacks and whites were equally likely to be seen by a neurologist or neurosurgeon if they were initially seen in either the emergency room (38% vs 37%, p = 0.879) or internal medicine (48% vs 50%, p = 0.806). Among patients diagnosed (268 patients) after the 2008 publication of the European Federation of Neurological Societies and the American Academy of Neurology guidelines for medical therapy for TN, fewer than 50% were on medications sanctioned by the guidelines, and there were no statistically significant racial disparities between white and black patients (p = 0.060). CONCLUSIONS According to data from a large database from one of the nation's largest comprehensive health care systems, there were significant racial disparities in the likelihood of a patient undergoing a procedure for TN. This appeared to stem from outside HFMG from a difference in referral patterns to the neurologists and neurosurgeons.

DTI-based response-driven modeling of mTLE laterality

Purpose

To develop lateralization models for distinguishing between unilateral and bilateral mesial temporal lobe epilepsy (mTLE) and determining laterality in cases of unilateral mTLE.

Background

mTLE is the most common form of medically refractory focal epilepsy. Many mTLE patients fail to demonstrate an unambiguous unilateral ictal onset. Intracranial EEG (icEEG) monitoring can be performed to establish whether the ictal origin is unilateral or truly bilateral with independent bitemporal ictal origin. However, because of the expense and risk of intracranial electrode placement, much research has been done to determine if the need for icEEG can be obviated with noninvasive neuroimaging methods, such as diffusion tensor imaging (DTI).

Methods

Fractional anisotropy (FA) was used to quantify microstructural changes reflected in the diffusivity properties of the corpus callosum, cingulum, and fornix, in a retrospective cohort of 31 patients confirmed to have unilateral (n = 24) or bilateral (n = 7) mTLE. All unilateral mTLE patients underwent resection with an Engel class I outcome. Eleven were reported to have hippocampal sclerosis on pathological analysis; nine had undergone prior icEEG. The bilateral mTLE patients had undergone icEEG demonstrating independent epileptiform activity in both right and left hemispheres. Twenty-three nonepileptic subjects were included as controls.

Results

In cases of right mTLE, FA showed significant differences from control in all callosal subregions, in both left and right superior cingulate subregions, and in forniceal crura. Comparison of right and left mTLE cases showed significant differences in FA of callosal genu, rostral body, and splenium and the right posteroinferior and superior cingulate subregions. In cases of left mTLE, FA showed significant differences from control only in the callosal isthmus. Significant differences in FA were identified when cases of right mTLE were compared with bilateral mTLE cases in the rostral and midbody callosal subregions and isthmus. Based on 11 FA measurements in the cingulate, callosal and forniceal subregions, a response-driven lateralization model successfully differentiated all cases (n = 54) into groups of unilateral right (n = 12), unilateral left (n = 12), and bilateral mTLE (n = 7), and nonepileptic control (23).

Conclusion

The proposed response-driven DTI biomarker is intended to lessen diagnostic ambiguity of laterality in cases of mTLE and help optimize selection of surgical candidates. Application of this model shows promise in reducing the need for invasive icEEG in prospective cases.

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Develop response-driven lateralization model using diffusion tensor imaging

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Distinguish between unilateral and bilateral mesial temporal lobe epilepsy (mTLE)

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Determine or lessen diagnostic ambiguity of laterality in cases of unilateral mTLE

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Optimize selection of surgical candidates

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Reduction of the need for intracranial EEG

Atypical meningiomas: is postoperative radiotherapy indicated?

Object

The role of postoperative radiation therapy after surgery for atypical meningiomas remains controversial. In this retrospective cohort study, the authors examine the recurrence rates for atypical meningiomas after resection (with or without adjuvant radiotherapy) and identify which factors were associated with recurrence.

Methods

Of 90 patients with atypical meningiomas who underwent surgery between 1999 and 2009, 71 (79%) underwent gross-total resection (GTR) and 19 (21%) underwent subtotal resection (STR); 31 patients received adjuvant radiotherapy. All tumors were pathology-confirmed WHO Grade II atypical meningiomas. Univariate and multivariate analyses were performed to identify factors associated with recurrence-free survival.

Results

Among 90 patients, 17 developed tumor recurrence (81% recurrence-free survival at 5 years). In the overall group, adjuvant radiotherapy reduced the recurrence rate to 9% from 19% at 5 years (p = 0.048). After STR, adjuvant radiotherapy significantly reduced recurrence from 91% to 20% (p = 0.0016). However, after GTR, adjuvant radiotherapy did not significantly reduce the recurrence rate (16.7% without radiation therapy vs 11.8% with radiation therapy) (p = 1.00). Five factors independently predictive of tumor recurrence included mitotic index, sheeting, necrosis, nonuse of radiation therapy, and STR. Further recursive partitioning analysis showed significant increases in risk for patients older than 55 years with mitoses and sheeting.

Conclusions

Adjuvant radiotherapy was effective at lowering recurrence rates in patients after STR but delivered no significant improvement in patients after GTR. Given that rates after GTR were similar with or without adjuvant radiotherapy, close observation without postoperative radiation therapy may be a viable option for these patients. Patients older than 55 years and those with mitoses noted during pathological examination had a significant risk of recurrence after GTR; for these patients, postoperative radiotherapy is recommended.

DTI values in key white matter tracts from infancy through adolescence

BACKGROUND AND PURPOSE

DTI is an advanced neuroimaging technique that allows in vivo quantification of water diffusion properties as surrogate markers of the integrity of WM microstructure. In our study, we investigated normative data from a large number of pediatric and adolescent participants to examine the developmental trends in DTI during this conspicuous WM maturation period.

MATERIALS AND METHODS

DTI data in 202 healthy pediatric and adolescent participants were analyzed retrospectively. Fractional anisotropy and mean diffusivity values in the corpus callosum and internal capsule were fitted to an exponential regression model to delineate age-dependent maturational changes across the WM structures.

RESULTS

The DTI metrics demonstrated characteristic exponential patterns of progression during development and conspicuous age-dependent changes in the first 36 months, with rostral WM tracts experiencing the highest slope of the exponential function. In contrast, the highest final FA and lowest MD values were detected in the splenium of the corpus callosum and the posterior limb of the internal capsule.

CONCLUSIONS

Our analysis shows that the more caudal portions of the corpus callosum and internal capsule begin the maturation process earlier than the rostral regions, but the rostral regions develop at a more accelerated pace, which may suggest that rostral regions rely on development of more caudal brain regions to instigate their development. Our normative DTI can be used as a reference to study normal spatiotemporal developmental profiles in the WM and help identify abnormal WM structures in patient populations.

Management strategies after nondiagnostic results with frameless stereotactic needle biopsy: Retrospective review of 28 patients

Background:

Although frameless stereotactic needle biopsy is an accepted procedure for the diagnosis of intracranial lesions, findings are nondiagnostic in 2–15% of patients and no recommendations yet exist to guide subsequent care. After reviewing the postoperative course after nondiagnostic biopsy of 28 patients, we developed a paradigm to guide management in the future.

Methods:

In reviewing the medical records of 284 frameless stereotactic needle biopsies (January 2000 to December 2006), we identified a subset of 28 patients who underwent 29 (10.2%) biopsies that did not yield a definitive diagnosis based on permanent pathologic samples. Postoperative treatment plans and clinical courses were further examined in 21 patients; 7 without follow-up were excluded.

Results:

Of the 21 patients, lesion location and characteristics guided the surgeon's decision to recommend further surgery or initiate empiric treatment. Soon after initial biopsy, five patients underwent a second procedure (biopsy or resection) that yielded diagnostic pathologic tissue. Of 16 patients who had empiric treatment, 7 (43.7%) subsequently had their treatment plan changed because of a lack of improvement and 5 underwent a second biopsy (4 diagnostic). Evolving clinical information precipitated treatment change in two patients. Of 10 patients who had a second surgery for better diagnostic information, the diagnostic yield was 90%.

Conclusions:

Considering the 90% diagnostic yield, we now recommend repeat surgery for most patients with nondiagnostic biopsies, especially for lesions considered potentially neoplastic or infectious. Empiric management, for lesions likely to be neurodegenerative, is an option but requires close follow-up examination.

Shorter Disease Duration Correlates With Improved Long-term Deep Brain Stimulation Outcomes in Young-Onset DYT1 Dystonia

BACKGROUND:

Treatment with deep brain stimulation (DBS) of the globus pallidus internus in children with DYT1 primary torsion dystonia is highly effective; however, individual response to stimulation is variable, and a greater understanding of predictors of long-term outcome is needed.

OBJECTIVE:

To report the long-term outcomes of subjects with young-onset DYT1 primary torsion dystonia treated with bilateral globus pallidus DBS.

METHODS:

Fourteen subjects (7 male, 7 female) treated consecutively from 2000 to 2010 at our center were included in this retrospective study. The Burke-Fahn-Marsden Dystonia Rating Scale was performed at baseline and at 1, 2, and up to 6 years postoperatively.

RESULTS:

Pallidal DBS was well tolerated and highly effective, with mean Burke-Fahn-Marsden Dystonia Rating Scale movement scores improving from baseline by 61.5% (P &lt; .001) at 1 year, 64.4% (P &lt; .001) at 2 years, and 70.3% (P &lt; .001) at the final follow-up visit (mean, 32 months; range, 7–77 months). Disability scores also improved significantly. Multiple linear regression analysis revealed a significant influence of duration of disease as a predictor of percent improvement in Burke-Fahn-Marsden Dystonia Rating Scale movement score at long-term follow-up (duration of disease, P &lt; .05). Subjects with fixed orthopedic deformities (4) had less improvement in these regions. Location of the active DBS electrode used at final follow-up visit was not predictive of clinical outcome.

CONCLUSION:

Our findings highlight the sustained benefit from DBS and the importance of early referral for DBS in children with medically refractory DYT1 primary torsion dystonia, which can lead to improved long-term benefits.

Acute effects of thalamic deep brain stimulation and thalamotomy on sensorimotor cortex local field potentials in essential tremor

OBJECTIVE

Essential tremor (ET) is characterized by an action tremor believed to be due to excessive theta-alpha activity in the cerebello-thalamo-cortical system. This study aimed to test the hypothesis that therapeutic thalamic stimulation in patients with ET decreases theta-alpha oscillatory activity in primary motor (M1) and sensory (S1) cortices.

METHODS

During surgical treatment of ET in 10 patients, an electrocorticography (ECoG) strip electrode was placed temporarily over the arm region of M1 and S1. Local field potentials (LFP) were recorded at rest, during a tremor-inducing posture, during acute therapeutic thalamic stimulation, and following therapeutic thalamotomy (three patients). Power spectral density (PSD) was calculated using the Fast Fourier Transform.

RESULTS

At rest, alpha activity (8-13Hz) in M1 was significantly decreased during high-frequency stimulation, while theta activity (4-8Hz) decreased in S1. Following thalamotomy, theta and beta (13-30Hz) was increased in M1. Induction of postural tremor reduced M1 theta, alpha and beta activity compared to the resting state.

CONCLUSIONS

High-frequency thalamic deep brain stimulation (DBS) significantly reduces alpha oscillatory activity in the primary motor cortex of patients with ET, though this change is probably not critical for therapeutic efficacy.

SIGNIFICANCE

We demonstrate that ECoG can be effectively used to study the effect of subcortical stimulation on cortical oscillations.

Deep brain stimulation in children: experience and technical pearls

OBJECT

Deep brain stimulation (DBS) is an established technique for the treatment of several movement disorders in adults. However, the technical approach, complications, and results of DBS in children have not been well documented.

METHODS

A database of DBS implantations performed at a single institution, prospectively established in 1998, was reviewed for patients who received DBS prior to the age of 18. Diagnoses, surgical technique, and complications were noted. Outcomes were assessed using standard rating scales of neurological function.

RESULTS

Of 815 patients undergoing DBS implantation over a 12-year period, 31 were children (mean age at surgery 13.2 years old, range 4-17 years old). Diagnoses included the following: DYT1 primary dystonia (autosomal dominant, Tor1AΔGAG mutation, 10 cases), non-DYT1 primary dystonia (3 cases), secondary dystonia (11 cases), neurodegeneration with brain iron accumulation (NBIA, 3 cases), levodopa-responsive parkinsonism (2 cases), Lesch-Nyhan disease (1 case), and glutaric aciduria Type 1 (1 case). Six children ages 15-17 years old underwent awake microelectrode-guided surgery. For 25 children operated under general anesthesia, the surgical technique evolved from microelectrode-guided surgery to image-guided surgeries using real-time intraoperative MR imaging or CT for lead location confirmation. Complications included 5 hardware infections, all in children younger than 10 years old. At 1 year after implantation, patients with DYT1 dystonia had a mean improvement in the Burke-Fahn-Marsden Dystonia Rating Scale movement subscore of 75%, while those with secondary dystonia had only small improvements. Outcomes in the 3 children with NBIA were disappointing.

CONCLUSIONS

Results of DBS in children with primary and secondary dystonias were similar to those in adults, with excellent results for DYT1 dystonia in children without fixed orthopedic deformity and much more modest results in secondary dystonia. In contrast to reported experience in adults with NBIA, these results in children with NBIA were poor. Infection risk was highest in the youngest patients.

Isolated cerebellar mucormycosis, slowly progressive over 1 year in an immunocompetent patient

Background:

Mucormycosis is a rare, aggressive fungal disease with high mortality, typically presenting as rhinosinusitis in immunocompromised patients.

Case Description:

A 43-year-old man with a history of intravenous drug use, Hepatitis C, and no evidence of immunocompromise presented with worsening balance problems. He had received intravenous antibiotics 2.5 years earlier for local infection after injecting heroin into a neck vein. Imaging studies revealed a lesion, likely of neoplastic origin. At resection, purulent fluid sampled by neuropathology revealed right-angled, branching hyphae, suggesting mucormycosis. No further resection was performed, no other disease sites were found, and HIV findings were negative. Two weeks postoperatively, he developed renal failure; intravenous antifungal treatment and hemodialysis were discontinued. When kidney function recovered 2 weeks later, he declined additional treatment.

Conclusion:

In our immunocompetent patient, both the location of the infection in the posterior fossa and its slowly progressive characteristic were unique variations of this typically aggressive disease.

Longitudinal comparison of pre- and postoperative diffusion tensor imaging parameters in young children with hydrocephalus

OBJECT

The goal in this study was to compare the integrity of white matter before and after ventriculoperitoneal (VP) shunt insertion by evaluating the anisotropic diffusion properties with the aid of diffusion tensor (DT) imaging in young children with hydrocephalus.

METHODS

The authors retrospectively identified 10 children with hydrocephalus who underwent both pre- and postoperative DT imaging studies. The DT imaging parameters (fractional anisotropy [FA], mean diffusivity, axial diffusivity, and radial diffusivity) were computed and compared longitudinally in the splenium and genu of the corpus callosum (gCC) and in the anterior and posterior limbs of the internal capsule (PLIC). The patients' values on DT imaging at the pre- and postshunt stages were compared with the corresponding age-matched controls as well as with a large cohort of healthy children in the database.

RESULTS

In the gCC, 7 of 10 children had abnormally low preoperative FA values, 6 of which normalized postoperatively. All 3 of the 10 children who had normal preoperative FA values had normal FA values postoperatively as well. In the PLIC, 7 of 10 children had abnormally high FA values, 6 of which normalized postoperatively, whereas the other one had abnormally low postoperative FA. Of the remaining 3 children, 2 had abnormally low preoperative FA values in the PLIC; this normalized in 1 patient after surgery. The other child had a normal preoperative FA value that became abnormally low postoperatively. When comparing the presurgery frequency of abnormally low, normal, and abnormally high FA values to those postsurgery, there was a statistically significant longitudinal difference in both gCC (p = 0.02) and PLIC (p = 0.002).

CONCLUSIONS

In this first longitudinal DT imaging study of young children with hydrocephalus, DT imaging anisotropy yielded abnormal results in several white matter regions of the brain, and trended toward normalization following VP shunt placement.

Comparing the risks of frameless stereotactic biopsy in eloquent and noneloquent regions of the brain: a retrospective review of 284 cases

Object

Frameless stereotactic biopsy has been shown in multiple studies to be a safe and effective tool for the diagnosis of brain lesions. However, no study has directly evaluated its safety in lesions located in eloquent regions in comparison with noneloquent locations. In this study, the authors determine whether an increased risk of neurological decline is associated with biopsy of lesions in eloquent regions of the brain.

Methods

Medical records, including imaging studies, were reviewed for 284 cases in which frameless stereotactic biopsy procedures were performed by 19 neurosurgeons at 7 institutions between January 2000 and December 2006. Lesion location was classified as eloquent or noneloquent in each patient. The incidence of neurological decline was calculated for each group.

Results

During the study period, 160 of the 284 biopsies predominately involved eloquent regions of the brain. In evaluation of the complication rate with respect to biopsy site, neurological decline occurred in 9 (5.6%) of 160 biopsies in eloquent brain areas and 10 (8.1%) of 124 biopsies in noneloquent regions; this difference was not statistically significant (p = 0.416). A higher number of needle passes was associated with the presence of a postoperative hemorrhage at the biopsy site, although not with a change in the result of neurological examination.

Conclusions

Frameless stereotactic biopsy of lesions located in eloquent brain regions is as safe and effective as biopsy of lesions in noneloquent regions. Therefore, with careful planning, frameless stereotactic biopsy remains a valuable and safe tool for diagnosis of brain lesions, independent of lesion location.

Anisotropic diffusion properties in infants with hydrocephalus: a diffusion tensor imaging study

BACKGROUND AND PURPOSE

Diffusion tensor imaging (DTI) can noninvasively detect in vivo white matter (WM) abnormalities on the basis of anisotropic diffusion properties. We analyzed DTI data retrospectively to quantify the abnormalities in different WM regions in children with hydrocephalus during early infancy.

MATERIALS AND METHODS

Seventeen infants diagnosed with hydrocephalus (age range, 0.13-16.14 months) were evaluated with DTI and compared with 17 closely age-matched healthy children (age range, 0.20-16.11 months). Fractional anisotropy (FA), mean diffusivity (MD), axial diffusivity, and radial diffusivity values in 5 regions of interest (ROIs) in the corpus callosum and internal capsule were measured and compared. The correlation between FA and age was also studied and compared by ROI between the 2 study groups.

RESULTS

Infants with hydrocephalus had significantly lower FA, higher MD, and higher radial diffusivity values for all 3 ROIs in the corpus callosum, but not for the 2 ROIs in the internal capsule. In infants with hydrocephalus, the increase of FA with age during normal development was absent in the corpus callosum but was still preserved in the internal capsule. There was also a significant difference in the frequency of occurrence of abnormal FA values in the corpus callosum and internal capsule.

CONCLUSIONS

This retrospective DTI study demonstrated significant WM abnormalities in infants with hydrocephalus in both the corpus callosum and internal capsule. The results also showed evidence that the impact of hydrocephalus on WM was different in the corpus callosum and internal capsule.

Management of vagal nerve stimulator infections: do they need to be removed?

OBJECT

Vagal nerve stimulators (VNSs) have been used successfully to treat medically refractory epilepsy. Although their efficacy is well established, appropriate management of infections is less clearly defined. In the authors' experience, patients who have gained a benefit from VNS implantation have been reluctant to have the device removed. The authors therefore sought conservative management options to salvage infected VNS systems.

METHODS

The authors performed a retrospective review of 191 (93 female and 98 male) consecutive patients in whom VNS systems were placed between 2000 and 2007.

RESULTS

They identified 10 infections (5.2%). In 9 of 10 patients the cultured organism was Staphylococcus aureus. Three (30%) of 10 patients underwent early removal (within 1 month) of the VNS as the initial treatment. The remaining 7 patients were initially treated with antibiotics. Two (28.6%) of these patients were successfully treated using antibiotics without VNS removal. Patients in whom conservative treatment failed were given cephalexin as first-line antibiotic treatment. All patients recovered completely regardless of treatment regimen.

CONCLUSIONS

This study confirms the low rate of infection associated with VNS placement and suggests that, in the case of infection, treatment without removal is a viable option. However, the authors' data suggest that oral antibiotics are not the best first-line therapy.

Validity of a retrospective National Institutes of Health Stroke Scale scoring methodology in patients with severe stroke

OBJECTIVE

Quantifying stroke severity is essential for interpreting outcomes in stroke studies; severity impacts outcomes. Because outcome studies often enroll patients some time after stroke and there is little standardization of the history and physical examination, objective measurement of stroke severity is limited. A method for retrospectively scoring the National Institutes of Health Stroke Scale (NIHSS) based on history and physical examination has been proposed, but has yet to be validated in patients with higher NIHSS score. We evaluate the validity of this scoring method across the spectrum of the NIHSS scores.

METHODS

The retrospective scoring algorithm was applied to history and physical examinations documented for 58 patients with ischemic stroke presenting to any of 17 regional acute care facilities who had a NIHSS score recorded by a stroke team physician. The retrospective NIHSS score was obtained by standardized chart review. Linear regression was used to estimate scale-dependent and scale-independent bias. Limits of agreement quantify deviation of the retrospective NIHSS score from the prospective NIHSS score.

RESULTS

Mean (SD) age at stroke was 66 (14) years; 27 (46.6%) patients were men, and 38 (65.5%) were white. The mean (SD) prospective NIHSS score was 13.6 (7.8); the mean (SD) retrospective NIHSS score was 13.7 (7.8). There were 23 (40%) prospective NIHSS scores above 15, and 13 scores (22%) above 20. The linear regression constant was 0.290 (95% confidence interval -0.107, 0.687); the slope was 0.987 (95% confidence interval 0.962, 1.013). The R(2) for the model was 0.991. Limits of agreement were -1.35 and 1.59.

CONCLUSION

The retrospective NIHSS appears valid across the entire spectrum of scores.

Two novel paradigms for the simultaneous assessment of conditioned taste aversion and food intake effects of anorexic agents

The conditioned taste aversion (CTA) is routinely used to assess the aversive consequences of anorexic agents, including potential pharmacological therapies for obesity. In a typical CTA paradigm, rats briefly sampling a novel tastant (e.g., saccharin) are acutely administered with toxin (e.g., lithium chloride, LiCl). After as few as one taste-toxin pairing, rats will reliably avoid the novel tastant. This paradigm is frequently used for the assessment of possible aversive consequences of drugs that are candidates for pharmacological therapies. The degree to which the drug supports development of a CTA is interpreted as an index of its aversive properties. Difficulties with previous work include the inability to assess affects on food intake and CTA simultaneously, particularly during chronic drug administration. We report here two novel CTA paradigms for the assessment of appetitive and aversive consequences of anorexic agents, simultaneously. In the first experiment, animals receive an intraoral infusion of a novel and highly palatable tastant immediately prior to administration of increasing doses of LiCl. In the second experiment, rats were implanted intraperitoneally with osmotic minipumps that chronically delivered a low dose of LiCl for 7 days. LiCl did not affect short or long term food intake in either experiment. However, LiCl did support the development of a CTA in both paradigms. These results suggest that both the appetitive and aversive consequences of anorexic agents can be assessed simultaneously during either acute or chronic drug administration.

Increased dietary fat attenuates the anorexic effects of intracerebroventricular injections of MTII

The hypothalamic melanocortin (MC) system provides a critical inhibitory control on food intake and body weight. Because access to high-fat (HF) diets is associated with the development of obesity, we hypothesized that increased dietary fat attenuates signaling through the MC system. To evaluate this hypothesis, we compared the efficacy of the MC3/4 receptor agonist, MTII, to reduce food intake in rats fed carefully matched HF or low-fat (LF) diets for 12 wk. Rats given the HF diet ad libitum were significantly more obese than rats given the LF diet, and had significantly higher plasma insulin and leptin levels. MTII given into the third cerebral ventricle in doses of 0.1, 0.3, and 1.0 nmol was less effective at reducing food intake in HF rats than in LF rats. Whole-hypothalamic expression of the MC agonist precursor gene, proopiomelanocortin, the MC antagonist agouti-related protein, and the MC4 receptor, were not different between the HF and LF groups. These results indicate that consumption of a HF diet decreases signaling through the melanocortin system, an abnormality that could contribute to diet-induced obesity.

Assessment of the aversive consequences of acute and chronic administration of the melanocortin agonist, MTII

BACKGROUND

The synthetic melanocortin (MC) agonist, melanotan-II (MTII), reduces food intake and body weight for hours to days after administration. One early report on the effect of MTII suggested that part of its anorexic action may be mediated by aversive consequences. In that experiment, MTII was found to support a mild conditioned taste aversion (CTA).

OBJECTIVE

The present experiments replicate and extend those findings in two additional CTA paradigms to further characterize the aversive effects of MTII in rats.

METHODS

Experiment 1 simultaneously assessed the ability of MTII to support CTA and reduce food intake, using a small oral infusion of a novel taste as the conditioned stimulus. Experiment 2 assessed the aversive consequences of chronic MTII administration. To accomplish this, we paired implantation of lithium chloride (LiCl)-, MTII- or saline-containing osmotic minipumps with a constantly available novel flavor. After 7 days, rats received a choice test between the minipump-paired flavor and a previously available neutral flavor.

RESULTS

Rats with saline minipumps exhibited no preference for either flavor. By contrast, rats in both the LiCl and MTII minipump groups significantly preferred the neutral flavor, indicating the development of a CTA. Additionally, CTA produced by administration of MTII was found to be more resistant to extinction than that produced by LiCl.

CONCLUSIONS

The reduction in food intake caused by MTII is accompanied by aversive consequences regardless of route of administration. These results present difficulties for the development of MCs-based therapies for obesity.

Intraventricular melanin-concentrating hormone stimulates water intake independent of food intake

The lateral hypothalamus (LH) has a critical role in the control of feeding and drinking. Melanin-concentrating hormone (MCH) is an orexigenic peptidergic neurotransmitter produced primarily in the LH, and agouti-related protein (AgRP) is an orexigenic peptidergic neurotransmitter produced exclusively in the arcuate (ARC), an area that innervates the LH. We assessed drinking and eating after third ventricular (i3vt) administration of MCH and AgRP. MCH (2.5, 5, and 10 micro g i3vt) significantly increased food as well as water intake over 4 h when administered during either the light or the dark portion of the day-night cycle. When MCH (5 micro g) was administered to rats with access to water but no food, they drank significantly more water than when given the vehicle. AgRP (7 micro g i3vt), on the other hand, increased water intake but only in proportion to food intake during the dark and the light, and water intake was not increased after i3vt AgRP in the absence of food. Hence, in contrast to AgRP, MCH elicits increased water intake independent of food intake. These results are consistent with historical data linking activity of the LH with water as well as food intake.