Assessment of postoperative pain, dysesthesia, and weather sensitivity after pterional and temporal neurosurgical approaches.

OBJECTIVE: Many neurosurgical approaches require incision of the temporal muscle (TM). Consequently, patients often report reduced opening of the mouth, facial asymmetry, numbness, and pain after lateral craniotomies. A systematic assessment of these postoperative subjective complaints is lacking in the literature. Therefore, in this study, the authors evaluate subjective complaints after pterional, frontolateral-extended pterional, or temporal craniotomy using a 6-item questionnaire. They examine the association of these subjective complaints with the extent of the mobilization of the TM. METHODS: The questionnaire assessed complaints about limited opening of the mouth, pain in the mastication muscles, facial asymmetry, sensory deficits in the temporal region, weather sensitivity, and headache. Eligible patients with benign intracranial processes operated on using lateral cranial approaches between 2016 and 2019 were included. The questionnaire was answered before surgery (baseline) and 3 and 15 months after surgery. Surgeons documented the extent of TM incision. RESULTS: Among the 55 patients in this study, all complaints apart from headache showed an increase at a statistically significant rate at 3 months postoperatively, that is, limited mouth opening (p < 0.0001), pain in the mastication muscles (p < 0.0001), an impression of asymmetry in the mastication muscles (p = 0.0002), sensory disturbances in the temporal region (p < 0.0001), and weather sensitivity (p < 0.001). Only pain in the mastication muscles showed a relevant decrease at 15 months postsurgery (p = 0.058). The extent of the mobilized TM was associated with pain in the mastication muscles at 3 months (p = 0.0193). CONCLUSIONS: Subjective complaints in patients following lateral craniotomy can be detected. As the extent of the mobilized TM relevantly influenced pain in the mastication muscles, the authors conclude that one should sparsely mobilize the TM. Furthermore, a neurosurgeon should be aware and warn the patient of subjective postoperative complaints and inform the patient about their natural course.

Development and first results of a national databank on care and treatment outcome after traumatic brain injury.

PURPOSE: In absence of comprehensive data collection on traumatic brain injury (TBI), the German Society for Neurosurgery (DGNC) and the German Society for Trauma Surgery (DGU) developed a TBI databank for German-speaking countries. METHODS: From 2016 to 2020, the TBI databank DGNC/DGU was implemented as a module of the TraumaRegister (TR) DGU and tested in a 15-month pilot phase. Since its official launch in 2021, patients from the TR-DGU (intermediate or intensive care unit admission via shock room) with TBI (AIS head ≥ 1) can be enrolled. A data set of > 300 clinical, imaging, and laboratory variables, harmonized with other international TBI data collection structures is documented, and the treatment outcome is evaluated after 6- and 12 months. RESULTS: For this analysis, 318 patients in the TBI databank could be included (median age 58 years; 71% men). Falls were the most common cause of injury (55%), and antithrombotic medication was frequent (28%). Severe or moderate TBI were only present in 55% of patients, while 45% suffered a mild injury. Nevertheless, intracranial pathologies were present in 95% of brain imaging with traumatic subarachnoid hemorrhages (76%) being the most common. Intracranial surgeries were performed in 42% of cases. In-hospital mortality after TBI was 21% and surviving patients could be discharged after a median hospital stay of 11 days. At the 6-and 12 months follow-up, a favorable outcome was achieved by 70% and 90% of the participating TBI patients, respectively. Compared to a European cohort of 2138 TBI patients treated in the ICU between 2014 and 2017, patients in the TBI databank were already older, frailer, fell more commonly at home. CONCLUSION: Within five years, the TBI databank DGNC/DGU of the TR-DGU could be established and is since then prospectively enrolling TBI patients in German-speaking countries. With its large and harmonized data set and a 12-month follow-up, the TBI databank is a unique project in Europe, already allowing comparisons to other data collection structures and indicating a demographic change towards older and frailer TBI patients in Germany.

Effect of transcutaneous auricular vagal nerve stimulation on the fatigue syndrome in patients with gastrointestinal cancers - FATIVA: a randomized, placebo-controlled pilot study protocol.

BACKGROUND: Cancer-related fatigue (CRF) is defined as a "distressing, persistent, subjective sense of physical, emotional, and/or cognitive tiredness or exhaustion related to cancer or cancer treatment that is not proportional to recent activity and interferes with usual functioning." CRF is frequently observed in cancer patients even before the initiation of tumor therapy. Its cause is not clear, but in addition to primary effects of therapy, a tumor-induced elevated level of inflammatory cytokines may play a role. Transcutaneous auricular vagal nerve stimulation (taVNS) is a noninvasive way to activate central nervous pathways and modulate pain perception and the immune system. It has positive effects on autoimmune conditions and can also improve fatigue associated with Sjogren's syndrome. It is the main purpose of this feasibility study to investigate the feasibility of daily taVNS against CRF. Therefore, the stimulation protocol of the newly introduced smartphone app of the manufacturer is evaluated. Additionally, the effect taVNS on CRF and quality of life (QoL) shall be evaluated. METHODS: Thirty adult patients with gastrointestinal tumors during or after treatment, relevant CRF (Hornheide questionnaire) and life expectancy > 1 year, are enrolled. Patients are randomized to treatment or sham arm and be informed that they will either feel the stimulation or not. Treatment group will receive left-sided tragus above-threshold stimulation with 25 Hz, 250 µs pulse width, and 28-s/32-s on/off paradigm for 4 h throughout the day for 4 weeks. Sham group will receive no stimulation via a nonfunctional electrode. A daily stimulation protocol with time and average intensity is automatically created by a smartphone app connected to the stimulator via Bluetooth®. Multidimensional Fatigue Inventory-20, Short-Form 36 and Beck Depression Inventory questionnaires will be filled out before and after 4 weeks of stimulation. DISCUSSION: Primarily, the patients' daily stimulation time and intensity will be evaluated through the electronic protocol after 4 weeks. Secondarily, the effect of taVNS on cancer-related fatigue and QoL will be measured through the questionnaires. As taVNS seems to modulate inflammatory cytokines, this noninvasive method may - if accepted by the patients - be a promising adjunct in the treatment of cancer-related fatigue. TRIAL REGISTRATION: The study was approved by local ethics committee (21-7395) and registered at the DRKS database (DRKS00027481).

Brainatomy-Demystifying the Temporal Bone, Rule of 3-2-1.

BACKGROUND: The temporal bone is difficult to comprehend in three-dimensional (3D) space. We provide a novel 3D mental model of the temporal bone which helps clinicians and surgeons dealing with it in teaching, diagnosing, conservative managements, and preoperative and intraoperative orientation. This study is part of the scientific project Brainatomy. OBJECTIVE: To analyze and simplify the temporal bone anatomy to enhance its comprehension and long-term retention. METHODS: The study was conducted at the Neurosurgical Department of the University Hospital of Bochum, Germany. We retrospectively analyzed data sets of 221 adult patients who underwent computed tomography (CT) of the skull (n = 167) and magnetic resonance imaging (MRI) of the brain (n = 54). A total of 142 patients with their respective imaging scans remained in our pool of interest after excluding 79 scans. The raw digital imaging and communications in medicine scans were transformed into 3D objects. Spatial analyses were then conducted, and all collected data were used to create our own 3D model of the temporal bone. RESULTS: We define the temporal bone as a prism-shaped model and divide it into 6 compartments: apex, neurovascular, mastoid, blank, tympanic, and temporomandibular compartments. The division into compartments has been achieved with the "Rule of 3-2-1." Finally, the 3D model has been used to record a video (Video), using a novel and "easy-to-follow" didactic approach. CONCLUSION: This simplified 3D model along with the corresponding video (Video) potentially enhances the efficiency of studying temporal none anatomy with a novel "easy-to-follow" approach.

Mastication after craniotomy: pilot assessment of postoperative oral health-related quality of life.

BACKGROUND: Neurosurgical approaches to the brain often require the mobilization of the temporal muscle. Many patients complain of postoperative pain, atrophy, reduced mouth opening, and masticatory problems. Although the pterional, frontolateral-extended-pterional, and temporal craniotomies are the most frequently used approaches in neurosurgery, a systematic assessment of the postoperative oral health-related quality of life has never been performed so far. This study evaluates the oral health-related quality of life of patients after pterional, frontolateral-extended-pterional, or temporal craniotomy using a validated and standardized dental questionnaire, compares the results with the normal values of the general population, and investigates whether this questionnaire is sensitive to changes caused by surgical manipulation of the temporal muscle. METHODS: The "Oral Health Impact Profile" (OHIP14) is a validated questionnaire to assess the oral health-related quality of life. It asks the patients to assess their oral health situation within the past 7 days in 14 questions. Possible answers range from 0 (never) to 4 (very often). Sixty patients with benign intracranial processes operated through a lateral cranial approach were included. The questionnaire was answered before surgery (baseline) and 3 months and 15 months after surgery. RESULTS: Overall, postoperative OHIP scores increase significantly after 3 months and decrease after 15 months, but not to preoperative values. No factors can be identified which show a considerable relationship with the postoperative OHIP score. CONCLUSIONS: Postoperative impairment of mouth opening and pain during mastication can be observed 3 to 15 months after surgery and sometimes cause feedback from patients and their dentists. However, in line with existing literature, these complaints decrease with time. The study shows that the OHIP questionnaire is sensitive to changes caused by surgical manipulation of the temporal muscle and can therefore be used to investigate the influence of surgical techniques on postoperative complaints. Postoperatively, patients show worse OHIP scores than the general population, demonstrating that neurosurgical cranial approaches negatively influence the patient's oral health-related wellbeing. Larger studies using the OHIP questionnaire should evaluate if postoperative physical therapy, speech therapy, or specialized rehabilitation devices can improve the masticatory impairment after craniotomy. TRIAL REGISTRATION: Clinical trial register: DRKS00011096.

Evaluation and discussion of handmade face-masks and commercial diving-equipment as personal protection in pandemic scenarios.

OBJECTIVE: Pandemic scenarios like the current Corona outbreak show the vulnerability of both globalized markets and just-in-time production processes for urgent medical equipment. Even usually cheap personal protection equipment becomes excessively expensive or is not deliverable at all. To avoid dangerous situations especially to medical professionals, but also to affected patients, 3D-printer and maker-communities have teamed up to develop and print shields, masks and adapters to help the medical personnel. In this study, we investigate three home-made respiratory masks for filter and protection efficacy and discuss the results and legal aspects. MATERIALS AND METHODS: A home-printed respiratory mask with a commercial filter, a scuba-diving mask with a commercial filter and a mask sewn from a vacuum cleaner bag were investigated with 99mTc-labeled NaCl-aerosol, and the respective filter-efficacy was measured under a scintigraphic camera. RESULTS: The sewn mask from a vacuum cleaner bag had a filter efficacy of 69.76%, the 3D-printed mask of 39.27% and the scuba-diving mask of 85.07%. CONCLUSION: Home-printed personal protection equipment can be a-yet less efficient-alternative against aerosol in case professional masks are not available, but legal aspects of their use and distribution have to be kept in mind in order to avoid compensation claims.

Facial pain ­ an interdisciplinary challenge / Neuropathische Gesichtsschmerzen ­ eine interdisziplinäre Herausforderung

Acute pain has a warning function and is necessary to survive. Conversely, chronic or recurrent pain is a pathological entity itself and has tremendous impact on the quality of life of the patients . Facial pain is very common and can have various causes. The trigeminal nerve innervates the face, and tumours along its intracranial way as well as peripheral injury can lead to facial pain. Also, infections and systemic diseases, like multiple sclerosis, may cause pain in the face, so can vascular compressions of the trigeminal or glossopharyngeal nerve. Detailed pain history is crucial in order to rule out other than dental reasons for facial pain before invasive dental therapy is initiated. A multidisciplinary approach and additional imaging modalities might be necessary to find the optimal treatment for the patient.

Implant-Mediated Therapy of Arterial Hypertension.

PURPOSE OF REVIEW: To give an overview on recent developments in permanent implant-based therapy of resistant hypertension. RECENT FINDINGS: The American Heart Association (AHA) recently updated their guidelines to treat high blood pressure (BP). As elevated BP now is defined as a systolic BP above 120 mmHg, the prevalence of hypertension in the USA has increased from 32% (old definition of hypertension) to 46%. In the past years, device- and implant-mediated therapies have evolved and extensively studied in various patient populations. Despite an initial drawback in a randomized controlled trial (RCT) of bilateral carotid sinus stimulation (CSS), new and less invasive and unilateral systems for baroreflex activation therapy (BAT) with the BAROSTIM NEO® have been developed which show promising results in small non-randomized controlled (RCT) studies. Selective vagal nerve stimulation (VNS) has been successfully evaluated in rodents, but has not yet been tested in humans. A new endovascular approach to reshape the carotid sinus to lower BP (MobiusHD™) has been introduced (baroreflex amplification therapy) with favorable results in non-RCT trials. However, long-term results are not yet available for this treatment option. A specific subgroup of patients, those with indication for a 2-chamber cardiac pacemaker, may benefit from a new stimulation paradigm which reduces the AV latency and therefore limits the filling time of the left ventricle. The most invasive approach for resistant hypertension still is the neuromodulation by deep brain stimulation (DBS), which has been shown to significantly lower BP in single cases. Implant-mediated therapy remains a promising approach for the treatment of resistant hypertension. Due to their invasiveness, such treatment options must prove superiority over conventional therapies with regard to safety and efficacy before they can be generally offered to a wider patient population. Overall, BAROSTIM NEO® and MobiusHD™, for which large RCTs will soon be available, are likely to meet those criteria and may represent the first implant-mediated therapeutical options for hypertension, while the use of DBS probably will be reserved for individual cases. The utility of VNS awaits appropriate assessment.

Brainatomy: A Novel Way of Teaching Sphenoid Bone Anatomy With a Simplified 3-Dimensional Model.

BACKGROUND: The diagnosis and treatment of diseases at and around the sphenoid bone demands throughout understanding of its anatomy in 3-dimensional (3-D) space. However, despite the complex anatomic nature of the sphenoid bone, the current educational resources for its 3-D anatomy are insufficient for fast and long-term retention of the anatomic relationships. OBJECTIVE: To provide a simplified 3-D model of the sphenoid bone that anyone can easily learn and recall as an internal mental model. METHODS: Various studies on the anatomy of the sphenoid bone were analyzed. The collected data included the shape, foramina, canals, fissures, and minute details of the sphenoid bone. The gained detailed knowledge was subsequently used to create a 3-D model of the sphenoid bone with the help of 3-D computer software. A live lecture was given with this same software and simultaneously recorded with a microphone and a computer-screen recorder. A novel approach in lecturing, building the sphenoid bone from the scratch in a piecemeal fashion, was utilized. RESULTS: The sphenoid bone was recreated as an horizontally elongated box without a superior and posterior wall. All its foramina, canals, and fissures are visually easy to follow. Understanding its neuroanatomic terminologies based on their anatomic nature and relationships is enhanced. CONCLUSIONS: This simplified 3-D model, along with the video lecture, will enhance the efficiency of studying sphenoid bone anatomy. The educational resources of this study can be obtained by medical students, radiologists, neurologists, neurosurgeons, neuroscientists, or anyone else seeking for fundamental understanding of sphenoid bone anatomy.

Origin of Syrinx Fluid in Syringomyelia: A Physiological Study.

BACKGROUND: The origin of syrinx fluid is controversial. OBJECTIVE: To elucidate the mechanisms of syringomyelia associated with cerebrospinal fluid pathway obstruction and with intramedullary tumors, contrast transport from the spinal subarachnoid space (SAS) to syrinx was evaluated in syringomyelia patients. METHODS: We prospectively studied patients with syringomyelia: 22 with Chiari I malformation and 16 with SAS obstruction-related syringomyelia before and 1 wk after surgery, and 9 with tumor-related syringomyelia before surgery only. Computed tomography-myelography quantified dye transport into the syrinx before and 0.5, 2, 4, 6, 8, 10, and 22 h after contrast injection by measuring contrast density in Hounsfield units (HU). RESULTS: Before surgery, more contrast passed into the syrinx in Chiari I malformation-related syringomyelia and spinal obstruction-related syringomyelia than in tumor-related syringomyelia, as measured by (1) maximum syrinx HU, (2) area under the syrinx concentration-time curve (HU AUC), (3) ratio of syrinx HU to subarachnoid cerebrospinal fluid (CSF; SAS) HU, and (4) AUC syrinx/AUC SAS. More contrast (AUC) accumulated in the syrinx and subarachnoid space before than after surgery. CONCLUSION: Transparenchymal bulk flow of CSF from the subarachnoid space to syrinx occurs in Chiari I malformation-related syringomyelia and spinal obstruction-related syringomyelia. Before surgery, more subarachnoid contrast entered syringes associated with CSF pathway obstruction than with tumor, consistent with syrinx fluid originating from the subarachnoid space in Chiari I malformation and spinal obstruction-related syringomyelia and not from the subarachnoid space in tumor-related syringomyelia. Decompressive surgery opened subarachnoid CSF pathways and reduced contrast entry into syringes associated with CSF pathway obstruction.

Sonographic-Assisted Catheter-Positioning in Intracerebral Hemorrhage.

Introduction: Intracerebral structures and pathologies such as intracerebral hemorrhages (ICH) can be displayed sufficiently by transcranial sonography (TCS). In some patients with ICH clot evacuation via surgery or catheter drainage to reduce secondary parenchymal injuries may be necessary. We hypothesized that bedside-placement of drainage-catheters, which is a minimal invasive evacuation-technique complicated by a higher rate of catheter misplacement can be optimized via TCS. Methods: Eleven consecutive ICH-patients diagnosed via computertomography (CT) were included in this prospective observational pilot study. All patients were examined via TCS, firstly in order to illustrate the hematoma, secondly to optimize catheter placement. Catheter placement was primarily validated via CT. Results: The TCS-depiction of ICH-extension was optimal in 10 patients; one patient showed a partially insufficient transtemporal bone window. Catheter positioning could be traced and adapted correctly via TCS-examination in all patients. Follow-up CT-scans confirmed TCS-description of catheter-positioning in all patients without any complications. Reduction of symptoms and ICH-volumes confirmed effectiveness of treatment. Conclusions: The illustration of ICH and the drainage-placement is possible via TCS in a cost- and time-efficient way.

Mapping the fine structure of cortical activity with different micro-ECoG electrode array geometries.

OBJECTIVE: Innovations in micro-electrocorticography (µECoG) electrode array manufacturing now allow for intricate designs with smaller contact diameters and/or pitch (i.e. inter-contact distance) down to the sub-mm range. The aims of the present study were: (i) to investigate whether frequency ranges up to 400 Hz can be reproducibly observed in µECoG recordings and (ii) to examine how differences in topographical substructure between these frequency bands and electrode array geometries can be quantified. We also investigated, for the first time, the influence of blood vessels on signal properties and assessed the influence of cortical vasculature on topographic mapping. APPROACH: The present study employed two µECoG electrode arrays with different contact diameters and inter-contact distances, which were used to characterize neural activity from the somatosensory cortex of minipigs in a broad frequency range up to 400 Hz. The analysed neural data were recorded in acute experiments under anaesthesia during peripheral electrical stimulation. MAIN RESULTS: We observed that µECoG recordings reliably revealed multi-focal cortical somatosensory response patterns, in which response peaks were often less than 1 cm apart and would thus not have been resolvable with conventional ECoG. The response patterns differed by stimulation site and intensity, they were distinct for different frequency bands, and the results of functional mapping proved independent of cortical vascular. Our analysis of different frequency bands exhibited differences in the number of activation peaks in topographical substructures. Notably, signal strength and signal-to-noise ratios differed between the two electrode arrays, possibly due to their different sensitivity for variations in spatial patterns and signal strengths. SIGNIFICANCE: Our findings that the geometry of µECoG electrode arrays can strongly influence their recording performance can help to make informed decisions that maybe important in number of clinical contexts, including high-resolution brain mapping, advanced epilepsy diagnostics or brain-machine interfacing.

Influence of Clonidine on Antihypertensive Selective Afferent Vagal Nerve Stimulation in Rats.

OBJECTIVE: Selective-afferent vagal nerve stimulation (sVNS) may be a treatment option for therapy-resistant hypertension, as it lowers blood pressure (BP) in rats without causing significant side effects. Alpha-2-agonists are widely used for the treatment of withdrawal, chronic pain and other disorders, and even if sVNS becomes a treatment option for therapy resistant hypertension, in some patients it might be necessary to combine sVNS with an alpha-2-agonist like clonidine. Alpha-2-agonists exhibit a central and peripheral mechanism of action. This study investigated the influence of the commonly used alpha-2-agonist clonidine on sVNS. MATERIALS AND METHODS: A polyimide multichannel-cuff-electrode was placed around the left vagal nerve bundle including the aortic depressor nerve (ADN) in eight male Wistar rats for the focused stimulation of baroreceptive fibers of the ADN. Stimulation parameters were adapted to the thresholds of the individual animals and ranged from frequencies between 30 and 50 Hz, amplitudes of 0.5-0.9 mA and pulse widths between 0.4 and 0.8 ms. BP was recorded using a microtip transducer in the left carotid artery, and electrocardiography was registered using subcutaneous needle electrodes. RESULTS: Before clonidine, we found a frequency-dependent drop of BP with maximum at 40 Hz. The animals' mean arterial blood pressures and respiration rate dropped after intravenous clonidine administration (10 µg/kg bodyweight), and sVNS still decreased in BP, but they did so to a lesser extent. Unwanted bradycardia, which was expected by the superimposition of sVNS and clonidine, did not occur. Left-sided vagotomy abolished the respiratory depressant effect of clonidine and blunted the BP reducing effect of sVNS while sVNS hardly affected heart rate anymore. CONCLUSIONS: The effect of sVNS on BP is dampened by clonidine, but sVNS can still lower the BP in clonidine treated rats without causing significant bradycardia.

Effect of Cardiac-Cycle-Synchronized Selective Vagal Stimulation on Heart Rate and Blood Pressure in Rats.

INTRODUCTION: Activation of the baroreflex system through the selective vagal nerve stimulation (sVNS) may become a treatment option for therapy-resistant hypertension, which is a frequently observed problem in the antihypertensive therapy. In previous studies, we used continuous sVNS to lower blood pressure (BP) without major side effects in a rat model. As continuous stimulation is energy consuming and sVNS could be implemented in an antihypertensive stimulator, it was the aim of this study to investigate the efficacy of pulsatile, cardiac-cycle-synchronized sVNS (cssVNS) on the reduction of BP. METHODS: A multichannel cuff electrode was wrapped around the left vagal nerve in six male Wistar rats under Isoflurane anesthesia. BP was recorded in the left carotid artery. An electrocardiogram (ECG) was obtained via subcutaneous needle electrodes. The aortic depressor nerve fibers in the vagal nerve bundle were selectively stimulated with 18 parameter settings within a window of 15-30 ms after the R-peak in the ECG. The stimulation paradigm included every heartbeat, every second heart beat, and every third heart beat. BP and heart rate were initially recorded over 10 min. RESULTS: Using cssVNS, BP could be significantly reduced over 30 min and maintained at this level. While the highest BP reduction was seen during cssVNS at every heartbeat with minimal bradycardia, less-yet significant-BP reduction was seen during cssVNS at every second or third heartbeat without causing detectable bradycardia. CONCLUSION: cssVNS can chronically reduce BP in rats avoiding measurable bradycardic side effects. This energy-efficient technique might allow the implementation of sVNS using an implantable device to permanently lower BP in patients. FUNDING: The study was funded by Bundesministerium fur Bildung und Forschung/German Federal Ministry of Education and Research among the call "Individualisierte Medizintechnik" under the grant number FKZ 13GW0120B.

Haemodynamic Responses to Selective Vagal Nerve Stimulation under Enalapril Medication in Rats.

Selective vagal nerve stimulation (sVNS) has been demonstrated to lower blood pressure (BP) in rats without causing major side effects. This method might be adapted for the treatment of therapy-resistant hypertension in patients. Converting enzyme inhibitors (CEIs) are among the first drugs that are administered for arterial hypertension and prominently reduce BP primarily by interacting with the renin-angiotensin system of the kidneys. Beyond the reduction of BP, CEI have a positive effect on the survival rate after myocardial infarction; they reduce the rates of stroke and improve the neurohormonal status in heart-failure patients. If sVNS might be introduced as a therapy against resistant hypertension, patients will at least partially stay on their CEI medication. It is therefore the aim of this study to investigate the influence of the CEI enalapril on the haemodynamic and respiratory effects of sVNS. In 10 male Wistar rats, a polyimide-based multichannel-cuff-electrode was placed around the vagal nerve bundle to selectively stimulate the aortic depressor nerve fibres. Stimulation parameters were adapted to the thresholds of the individual animals and included repetition frequencies between 30 and 50 Hz, amplitudes of 0.5 to 1.5 mA and pulse widths between 0.4 ms and 1.0 ms. BP responses were detected with a microtip transducer in the left carotid artery, and electrocardiography was recorded with subcutaneous electrodes. After intravenous administration of enalapril (2 mg/kg bodyweight), the animals' mean arterial blood pressures (MAPs) decreased significantly, while the heart rates (HRs) were not significantly influenced. The effects of sVNS on BP and HR were attenuated by enalapril but were still present. We conclude that sVNS can lower the MAP during enalapril treatment without relevant side effects.

Effect of selective vagal nerve stimulation on blood pressure, heart rate and respiratory rate in rats under metoprolol medication.

Selective vagal nerve stimulation (sVNS) has been shown to reduce blood pressure without major side effects in rats. This technology might be the key to non-medical antihypertensive treatment in patients with therapy-resistant hypertension. ß-blockers are the first-line therapy of hypertension and have in general a bradycardic effect. As VNS itself can also promote bradycardia, it was the aim of this study to investigate the influence of the ß1-selective blocker Metoprolol on the effect of sVNS especially with respect to the heart rate. In 10 male Wistar rats, a polyimide multichannel-cuff electrode was placed around the vagal nerve bundle to selectively stimulate the aortic depressor nerve fibers. The stimulation parameters were adapted to the thresholds of individual animals and were in the following ranges: frequency 30-50 Hz, amplitude 0.3-1.8 mA and pulse width 0.3-1.3 ms. Blood pressure responses were detected with a microtip transducer in the carotid artery, and electrocardiography was recorded with s.c. chest electrodes. After IV administration of Metoprolol (2 mg kg(-1) body weight), the animals' mean arterial blood pressure (MAP) and heart rate (HR) decreased significantly. Although the selective electrical stimulation of the baroreceptive fibers reduced MAP and HR, both effects were significantly alleviated by Metoprolol. As a side effect, the rate of stimulation-induced apnea significantly increased after Metoprolol administration. sVNS can lower the MAP under Metoprolol without causing severe bradycardia.

Mapping of sheep sensory cortex with a novel microelectrocorticography grid.

Microelectrocorticography (µECoG) provides insights into the cortical organization with high temporal and spatial resolution desirable for better understanding of neural information processing. Here we evaluated the use of µECoG for detailed cortical recording of somatosensory evoked potentials (SEPs) in an ovine model. The approach to the cortex was planned using an MRI-based 3D model of the sheep's brain. We describe a minimally extended surgical procedure allowing placement of two different µECoG grids on the somatosensory cortex. With this small craniotomy, the frontal sinus was kept intact, thus keeping the surgical site sterile and making this approach suitable for chronic implantations. We evaluated the procedure for chronic implantation of an encapsulated µECoG recording system. During acute and chronic recordings, significant SEP responses in the triangle between the ansate, diagonal, and coronal sulcus were identified in all animals. Stimulation of the nose, upper lip, lower lip, and chin caused a somatotopic lateral-to-medial, ipsilateral response pattern. With repetitive recordings of SEPs, this somatotopic pattern was reliably recorded for up to 16 weeks. The findings of this study confirm the previously postulated ipsilateral, somatotopic organization of the sheep's sensory cortex. High gamma band activity was spatially most specific in the comparison of different frequency components of the somatosensory evoked response. This study provides a basis for further acute and chronic investigations of the sheep's sensory cortex by characterizing its exact position, its functional properties, and the surgical approach with respect to macroanatomical landmarks.

Blood pressure control with selective vagal nerve stimulation and minimal side effects.

OBJECTIVE: Hypertension is the largest threat to patient health and a burden to health care systems. Despite various options, 30% of patients do not respond sufficiently to medical treatment. Mechanoreceptors in the aortic arch relay blood pressure (BP) levels through vagal nerve (VN) fibers to the brainstem and trigger the baroreflex, lowering the BP. Selective electrical stimulation of these nerve fibers reduced BP in rats. However, there is no technique described to localize and stimulate these fibers inside the VN without inadvertent stimulation of non-baroreceptive fibers causing side effects like bradycardia and bradypnea. APPROACH: We present a novel method for selective VN stimulation to reduce BP without the aforementioned side effects. Baroreceptor compound activity of rat VN (n = 5) was localized using a multichannel cuff electrode, true tripolar recording and a coherent averaging algorithm triggered by BP or electrocardiogram. MAIN RESULTS: Tripolar stimulation over electrodes near the barofibers reduced the BP without triggering significant bradycardia and bradypnea. The BP drop was adjusted to 60% of the initial value by varying the stimulation pulse width and duration, and lasted up to five times longer than the stimulation. SIGNIFICANCE: The presented method is robust to impedance changes, independent of the electrode's relative position, does not compromise the nerve and can run on implantable, ultra-low power signal processors.