A transient cortical state with sleep-like sensory responses precedes emergence from general anesthesia in humans

During awake consciousness, the brain intrinsically maintains a dynamical state in which it can coordinate complex responses to sensory input. How the brain reaches this state spontaneously is not known. General anesthesia provides a unique opportunity to examine how the human brain recovers its functional capabilities after profound unconsciousness. We used intracranial electrocorticography and scalp EEG in humans to track neural dynamics during emergence from propofol general anesthesia. We identify a distinct transient brain state that occurs immediately prior to recovery of behavioral responsiveness. This state is characterized by large, spatially distributed, slow sensory-evoked potentials that resemble the K-complexes that are hallmarks of stage two sleep. However, the ongoing spontaneous dynamics in this transitional state differ from sleep. These results identify an asymmetry in the neurophysiology of induction and emergence, as the emerging brain can enter a state with a sleep-like sensory blockade before regaining responsivity to arousing stimuli.National Institutes of Health (U.S.) (Grant K99-MH111748)National Institutes of Health (U.S.) (Grant R00-NS080911)National Institutes of Health (U.S.) (Grant DP2-OD006454)National Institutes of Health (U.S.) (Grant S10-RR023401)National Institutes of Health (U.S.) (Grant R01- NS062092)National Institutes of Health (U.S.) (Grant R01AG056015)National Institutes of Health (U.S.) (Grant P01GM118269)National Institutes of Health (U.S.) (Grant R01-EB009282

The endoscopic endonasal approach is not superior to the microscopic transcranial approach for anterior skull base meningiomas—a meta-analysis

Object In the past decade, the endonasal transsphenoidal approach (eTSA) has become an alternative to the microsurgical transcranial approach (mTCA) for tuberculum sellae meningiomas (TSMs) and olfactory groove meningiomas (OGMs). The aim of this meta-analysis was to evaluate which approach offered the best surgical outcomes. Methods: A systematic review of the literature from 2004 and meta-analysis were conducted in accordance with the PRISMA guidelines. Pooled incidence was calculated for gross total resection (GTR), visual improvement, cerebrospinal fluid (CSF) leak, intraoperative arterial injury, and mortality, comparing eTSA and mTCA, with p-interaction values. Results: Of 1684 studies, 64 case series were included in the meta-analysis. Using the fixed-effects model, the GTR rate was significantly higher among mTCA patients for OGM (eTSA: 70.9% vs. mTCA: 88.5%, p-interaction < 0.01), but not significantly higher for TSM (eTSA: 83.0% vs. mTCA: 85.8%, p-interaction = 0.34). Despite considerable heterogeneity, visual improvement was higher for eTSA than mTCA for TSM (p-interaction < 0.01), but not for OGM (p-interaction = 0.33). CSF leak was significantly higher among eTSA patients for both OGM (eTSA: 25.1% vs. mTCA: 10.5%, p-interaction < 0.01) and TSM (eTSA: 19.3%, vs. mTCA: 5.81%, p-interaction < 0.01). Intraoperative arterial injury was higher among eTSA (4.89%) than mTCA patients (1.86%) for TSM (p-interaction = 0.03), but not for OGM resection (p-interaction = 0.10). Mortality was not significantly different between eTSA and mTCA patients for both TSM (p-interaction = 0.14) and OGM resection (p-interaction = 0.88). Random-effect models yielded similar results. Conclusion: In this meta-analysis, eTSA was not shown to be superior to mTCA for resection of both OGMs and TSMs. Electronic supplementary material The online version of this article (10.1007/s00701-017-3390-y) contains supplementary material, which is available to authorized users

Implications of Mitochondrial Dysfunction for the Anesthetic and Perioperative Management:A Case Report of Spinal Fusion, Genetic Confusion, and a Patient's Perspective

We describe a patient's personal struggle with a symptom complex consisting of profound muscle weakness requiring pyridostigmine, and metabolic abnormalities suggestive of mitochondrial disease. This included a profound sensitivity to opioids, which in the past caused severe respiratory depression during a prior hospital admission. Interestingly, the patient herself is a professor of ethics in genomic sciences, and she and her medical team thus far have not been able to formally diagnose her with mitochondrial disease. The patient now presented for a multilevel lumbar spine fusion and her hospital course and perspective on her medical odyssey are described here

Evidence-based dexamethasone dosing in malignant brain tumors: what do we really know?

Purpose: The present study aims to conduct a systematic review of literature reporting on the dose and dosing schedule of dexamethasone (DXM) in relation to clinical outcomes in malignant brain tumor patients, with particular attention to evidence-based practice. Methods: A systematic search was performed in PubMed, Embase, Web of Science, Cochrane, Academic Search Premier, and PsycINFO to identify studies that reported edema volume reduction, symptomatic relief, adverse events and survival in relation to dexamethasone dose in glioma or brain metastasis (BM) patients. Results: After screening 1812 studies, fifteen articles were included for qualitative review. Most studies reported a dose of 16 mg, mostly in a schedule of 4 mg four times a day. Due to heterogeneity of studies, it was not possible to perform quantitative meta-analysis. For BMs, best available evidence suggests that higher doses of DXM may give more adverse events, but may not necessarily result in better clinical condition. Some studies suggest that higher DXM doses are associated with shorter survival in the palliative setting. For glioma, DXM may lead to symptomatic improvement, yet no studies directly compare different doses. Results regarding edema reduction and survival in glioma patients are conflicting. Conclusions: Evidence on the safety and efficacy of different DXM doses in malignant brain tumor patients is scarce and conflicting. Best available evidence suggests that low DXM doses may be noninferior to higher doses in certain circumstances, but more comparative research in this area is direly needed, especially in light of the increasing importance of immunotherapy for brain tumors

Perioperative Use of Transcranial Magnetic Stimulation

A practical means of noninvasively stimulating the cortex was developed in the mid-1980s. Both electrical and magnetic stimulating pulses applied transcranially were shown to be capable of exciting motor cortex. Transcranial magnetic stimulation (TCMS), compared with transcranial electrical stimulation, produced relatively painfree cortical excitation. This generated interest in developing clinical applications making use of TCMS. This article reviews the basic principles of perioperative TCMS. Two clinical applications that require TCMS are then discussed. The first involves the use of TCMS for monitoring the functional integrity of the spinal cord descending motor paths during surgery. Spinal cord motor path monitoring may have utility because several case reports have suggested that somatosensory evoked potentials may not always predict new postoperative motor deficits. The second application involves the use of discrete TCMS for localizing eloquent cortex in the preoperative period. The ability to define cortical areas functionally as they relate to surgical pathology is an invaluable aid for planning a surgical approach to their cure. A method under development at the authors’ institution for correlating TCMS-derived functional data with anatomical data acquired from magnetic resonance imaging is described, and the use of this method for locating motor and visual association cortices is reviewed

Perioperative Use of Transcranial Magnetic Stimulation

A practical means of noninvasively stimulating the cortex was developed in the mid-1980s. Both electrical and magnetic stimulating pulses applied transcranially were shown to be capable of exciting motor cortex. Transcranial magnetic stimulation (TCMS), compared with transcranial electrical stimulation, produced relatively painfree cortical excitation. This generated interest in developing clinical applications making use of TCMS. This article reviews the basic principles of perioperative TCMS. Two clinical applications that require TCMS are then discussed. The first involves the use of TCMS for monitoring the functional integrity of the spinal cord descending motor paths during surgery. Spinal cord motor path monitoring may have utility because several case reports have suggested that somatosensory evoked potentials may not always predict new postoperative motor deficits. The second application involves the use of discrete TCMS for localizing eloquent cortex in the preoperative period. The ability to define cortical areas functionally as they relate to surgical pathology is an invaluable aid for planning a surgical approach to their cure. A method under development at the authors’ institution for correlating TCMS-derived functional data with anatomical data acquired from magnetic resonance imaging is described, and the use of this method for locating motor and visual association cortices is reviewed

Characterizing brain dynamics during ketamine-induced dissociation and subsequent interactions with propofol using human intracranial neurophysiology

The neural mechanisms underpinning ketamine’s dissociative and antidepressant effects remain poorly understood. Here, the authors analyzed ketamine-induced brain dynamics with intracranial recordings in humans and found that ketamine engages different brain areas in distinct frequency-dependent patterns that may relate to its dissociative and antidepressant effects