Utility of the occipital nerve block in the emergency department: A case series.

INTRODUCTION: Tension headaches, as well as various scalp pathologies including lacerations and abscesses are commonly treated in the emergency department (ED). The occipital nerve block (ONB), previously described in anesthesia and neurology literature, offers analgesia of the posterior scalp on the side ipsilateral to the injection while maintaining a low adverse effect profile. CASE REPORT: We report three cases in which ONB was utilized for tension headache, scalp laceration repair, and incision and drainage of scalp abscess. These patients all reported significant pain improvement without any reported complications. CONCLUSION: The ONB is a landmark based technique that offers an opportunity to provide analgesia in the ED that is simple, effective, and without known significant risks that are associated with other modalities of treatment.

Scalp Nerve Block Alleviates Headaches Associated With Sonication During Transcranial Magnetic Resonance-Guided Focused Ultrasound.

BACKGROUND AND OBJECTIVES: In magnetic resonance-guided focused ultrasound (MRgFUS) procedures, headache is a frequent symptom and cause of treatment discontinuation. Herein, we assessed the efficacy of scalp nerve block (SNB) for alleviating headache during MRgFUS procedures. METHODS: The effect of SNB on intraprocedural headache was examined by retrospectively comparing 2 patient cohorts at a single institution. During the study period from April 2020 to February 2022, an SNB protocol for all patients with a skull density ratio ≤0.55 was instituted on October 6, 2021. The number of patients with a skull density ratio ≤0.55 was 34 before the protocol and 36 afterward. Headache intensity was evaluated using a numerical rating scale (NRS) after each sonication. To evaluate the effect of SNB on headache intensity, multiple regression analysis was performed per patient and per sonication. In the per-patient analysis, the effect of SNB was evaluated using the maximum NRS, mean NRS, and NRS at the first ultrasound exposure that reached 52.5°C. In the per-sonication analysis, the effect of SNB was evaluated not only for the entire sonication but also for sonications classified into ≤9999 J, 10 000 to 29 999 J, and ≥30 000 J energy doses. RESULTS: With SNB, headache alleviation was observed in the NRS after the first sonication that reached 52.5°C in each patient (ß = -2.40, 95% CI -4.05 to -0.758, P = .00499), in the NRS when all sonications were evaluated (ß = -0.647, 95% CI -1.19 to -0.106, P = .0201), and in the NRS when all sonications were classified into 10 000 to 29 999 J (ß = -1.83, 95% CI -3.17 to -0.485, P = .00889). CONCLUSION: SNB significantly reduced headache intensity during MRgFUS, especially that caused by sonication with a moderate-energy dose. These findings suggest that scalp nerves play a role in headache mechanisms during MRgFUS.

Nerve Blocks for Craniotomy.

PURPOSE OF REVIEW: Postcraniotomy headache (PCH) is a common adverse event and can lead to various complications and decreased quality of life. RECENT FINDINGS: To reduce postcraniotomy pain and associated complications, a multimodal pain therapy including analgesics, analgesic adjuncts, and regional anesthesia is essential. The use of opioids should be minimized to facilitate prompt postoperative neurosurgical assessment. Here, we provide an update on the latest evidence regarding the role of scalp nerve blocks in the pain management of patients undergoing craniotomy procedure. Nerve blocks are effective in alleviating postoperative pain after craniotomy. Scalp blocks contribute to lower pain levels and less opioid consumption in the first 48 h following surgery. Moreover, there is a significant decrease in patients suffering from PONV among patients who receive scalp block.

Surgical Treatment of Malignant Peripheral Nerve Sheath Tumor of the Scalp With Intracranial and Extracranial Extension: A Rare Case Report.

ABSTRACT: Malignant peripheral nerve sheath tumors of the scalp are rare neoplasms of the peripheral nervous system. Here, we describe an unusual malignant peripheral nerve sheath tumor of the scalp in an 84-year-old Asian man. The tumor was associated with bony destruction, intracranial, and extracranial extension. Trans-arterial embolization was done twice preoperatively. En block excision was performed and the dura and soft tissue defect were reconstructed by anterolateral thigh free fasciocutaneous flap. There is no recurrence and the wound healed well during follow-up.

Ultrasound-guided scalp nerve block in anesthesia of children receiving cranial suture reconstruction.

OBJECTIVE: Analgesia is very important for children with craniosynostosis who are undergoing cranial suture reconstruction. This study investigated the effectiveness and safety of an analgesic technique based on scalp nerve block combined with general anesthesia versus general anesthesia alone. METHODS: This was a single-center, prospective, randomized, controlled study. A total of 60 children aged 6-24 months who underwent cranial suture reconstruction were randomly divided into two groups: Group A (general anesthesia combined with scalp nerve block) and Group N (general anesthesia). The hemodynamics were recorded preoperatively, at 5 min after incision and at 1, 6 and 12 h after surgery; the pain was scored at 1, 6 and 12 h after surgery, and blood glucose was detected at 1 h after surgery. RESULTS: The mean arterial pressure and heart rate at 5 min after incision and 1 h after surgery in Group N were higher than those in Group A; the blood glucose and FLACC score in Group N were higher than those in Group A; and the number of postoperative analgesic pump presses were also significantly increased in Group N. CONCLUSION: Preoperative scalp nerve block can reduce hemodynamic fluctuation and postoperative pain in children undergoing cranial suture reconstruction for craniosynostosis. Thus, it can be safely and effectively applied in the anesthesia of these children.

The effectiveness of scalp nerve block on hemodynamic response in craniotomy: a systematic review and meta-analysis of randomized trials.

INTRODUCTION: Strategies that blunt noxious stimuli and stabilize hemodynamics may reduce perioperative cardiovascular complications and enhance recovery after craniotomy. EVIDENCE ACQUISITION: Our systematic literature review and meta-analysis investigated whether scalp nerve block (SNB) reduces the acute hemodynamic response compared with non-SNB (scalp infiltration or control) in adult patients undergoing elective craniotomy. We searched MEDLINE, EMBASE, CENTRAL, and two Chinese databases for randomized trials. Primary outcomes included mean arterial pressure and heart rate during skull pin insertion and surgical incision in craniotomy. Secondary outcomes included incidence of hypertension and dosage of intraoperative analgesic opioids used. Random-effects models were used for meta-analyses. EVIDENCE SYNTHESIS: SNB significantly reduced the mean arterial pressure (mean difference: -14.00 mmHg; 95% confidence interval [CI]: -19.71 to -8.28) and heart rate (mean difference: -11.55 beat/min; 95% CI: -19.31 to -3.80), when compared with non-SNB during skull pin insertion. A similar trend was observed during skin incisions (SNB vs. non-SNB, mean difference in mean arterial pressure: -9.46 mmHg; 95% CI: -14.53 to -4.38; mean difference in heart rate: -9.34 beat/min; 95% CI: -15.40 to -3.28). Subgroup analysis showed that, compared with scalp infiltration, SNB reduced mean arterial pressure and heart during pin insertion but not during skin incisions. SNB also reduced the incidence of intraoperative hypertension, but no difference was observed in intraoperative opioid consumption when compared with non-SNB. CONCLUSIONS: SNB alleviated the craniotomy-associated hemodynamic response. SNB may be superior to scalp infiltration in maintaining hemodynamic stability during pin insertion. However, high-quality trials are still needed to provide more conclusive evidence.

Ultrasound-Guided Scalp Blocks for an Awake Craniotomy: A Case Report.

Ultrasound-guided scalp blocks may revolutionize regional anesthesia for neurosurgery. In this report, we demonstrate that ultrasound-guided scalp blocks can be used effectively for a craniotomy. A 48-year-old patient with a brain tumor at the motor cortex was scheduled for an awake craniotomy. Ultrasound-guided scalp blocks targeting the bilateral supraorbital, supratrochlear, zygomaticotemporal, auriculotemporal, greater auricular, lesser occipital, greater occipital, and third occipital nerves were performed. A total of 29 mL of levobupivacaine 0.3% was used. No additional local anesthetic agent was given for skull pinning, skin incision, or the craniotomy. Postoperatively, the patient remained pain-free, and she was discharged without complications.

Influence of scalp block on oncological outcomes of high-grade glioma in adult patients with and without isocitrate dehydrogenase-1 mutation.

High-grade gliomas are notorious for a high recurrence rate even after curative resection surgery. Studies regarding the influence of scalp block on high-grade gliomas have been inconclusive, possibly because the condition's most important genetic mutation profile, namely the isocitrate dehydrogenase 1 (IDH1) mutation, had not been analyzed. Therefore, we conducted a single-center study including patients with high-grade glioma who underwent tumor resection between January 2014 and December 2019. Kaplan-Meier survival analysis revealed that scalp block was associated with longer progression-free survival (PFS; 15.17 vs. 10.77 months, p = 0.0018), as was the IDH1 mutation (37.37 vs. 10.90 months, p = 0.0149). Multivariate Cox regression analysis revealed that scalp block (hazard ratio: 0.436, 95% confidence interval: 0.236-0.807, p = 0.0082), gross total resection (hazard ratio: 0.405, 95% confidence interval: 0.227-0.721, p = 0.0021), and IDH1 mutation (hazard ratio: 0.304, 95% confidence interval: 0.118-0.784, p = 0.0138) were associated with better PFS. Our results demonstrate that application of scalp block, regardless of IDH1 profile, is an independent factor associated with longer PFS for patients with high-grade glioma.

Monitored Anesthetic Care Combined with Scalp Nerve Block in Awake Craniotomy: An Effective Attempt at Enhanced Recovery After Neurosurgery.

BACKGROUND: Enhanced recovery after surgery has been attempted in neurosurgery at a greater rate. However, concern exists regarding the feasibility of using enhanced recovery after neurosurgery (ERANS). How to manage available resources to safely perform ERANS and improve clinical outcomes has been the subject of much debate and discussion. METHODS: Owing to the paucity of data available on the use of ERANS protocols, we performed the present feasibility study. We studied the outcomes of the protocols used within a tertiary referral neurosurgery center. Data from patients who had undergone awake craniotomy within an ERANS protocol were prospectively recorded in our institution from September 2017 to December 2018. We also evaluated the safety and effectiveness of the novel ERANS protocol. RESULTS: A total of 20 patients (mean age, 49.5 ± 17.8 years) were included in the present study. Intraoperative hypertension, hypotension, and bradycardia were present in 4 (20%), 1 (5%), and 1 (5%) patient, respectively. The postoperative morbidities included epilepsy in 1 (5%), pain in 3 (15%), and nausea or vomiting in 2 (10%). No significant changes had occurred in the mean arterial pressure, heart rate, blood glucose, or lactic acid level throughout the procedure. The median length of intensive care unit stay and postoperative hospital stay were 1 and 9.5 days, respectively. No 30-day readmissions or reoperations occurred during the present study. CONCLUSIONS: Applying an ERANS protocol was feasible, associated with a low incidence of complications, and acceptable intensive care unit and postoperative hospital lengths of stay. The findings from the present study might provide a new approach for the further research of ERANS.

Influence of Levobupivacaine Regional Scalp Block on Hemodynamic Stability, Intra- and Postoperative Opioid Consumption in Supratentorial Craniotomies: A Randomized Controlled Trial.

BACKGROUND: The anesthetic management of supratentorial craniotomy (CR) necessitates tight intraoperative hemodynamic control. This type of surgery may also be associated with substantial postoperative pain. We aimed at evaluating the influence of regional scalp block (SB) on hemodynamic stability during the noxious events of supratentorial craniotomies and total intravenous anesthesia, its influence on intraoperative anesthetic agents' consumption, and its effect on postoperative pain control. METHODS: Sixty patients scheduled for elective CR were prospectively enrolled. Patient, anesthesiologist, and neurosurgeon were blind to the random performance of SB with either levobupivacaine 0.33% (intervention group [group SB], n = 30) or the same volume of saline (control group [group CO], placebo group, n = 30). General anesthesia was induced and maintained using target-controlled infusions of remifentanil and propofol that were adjusted according to hemodynamic parameters and state entropy of the electroencephalogram (SE), respectively. Mean arterial blood pressure (MAP), heart rate (HR), SE, and propofol and remifentanil effect-site concentrations (Ce) were recorded at the time of scalp block performance (Baseline), and 0, 1, 3, and 5 minutes after skull-pin fixation (SP), skin incision (SI), CR, and dura-mater incision (DM). Morphine consumption and postoperative pain intensity (0-10 visual analog scale [VAS]) were recorded 1, 3, 6, 24, and 48 hours after surgery. Propofol and remifentanil overall infusion rates were also recorded. Data were analyzed using 2-tailed Student unpaired t tests, 2-way mixed-design analysis of variance (ANOVA), and Tukey's honestly significant difference (HSD) tests for post hoc comparisons as appropriate. RESULTS: Demographics and length of anesthetic procedure of group CO and SB were comparable. SP, SI, and CR were associated with a significantly higher MAP in group CO than in group SB, at least at one of the time points of recording surrounding those noxious events. This was not the case at DM. Similarly, HR was significantly higher in group CO than in group SB during SP and SI, at least at 1 of the points of recording, but not during CR and DM. Propofol and remifentanil Ce and overall infusion rates were significantly higher in group CO than in group SB, except for propofol Ce during SP. Postoperative pain VAS and cumulative morphine consumption were significantly higher in group CO than in group SB. CONCLUSIONS: In supratentorial craniotomies, SB improves hemodynamic control during noxious events and provides adequate and prolonged postoperative pain control as compared to placebo.

Postoperative analgesia of scalp nerve block with ropivacaine in pediatric craniotomy patients: a protocol for a prospective, randomized, placebo-controlled, double-blinded trial.

BACKGROUND: Moderate-to-severe postoperative pain following craniotomy has a high incidence in pediatric patients. Such pain may cause agitation, intracranial hypertension, epileptic seizures, and postoperative hematoma, which affect morbidity and mortality. Although scalp nerve block (SNB) achieves satisfactory pain relief except for suboccipital mid-craniotomy in adults and ropivacaine is widely used as a long-acting peripheral nerve block agent in children, there are few studies of SNB with ropivacaine in pediatric patients undergoing craniotomy. In addition, the neurosurgery operation time is relatively long, but the duration of action of SNB is limited. It is generally believed that postoperative SNB is better than preoperative SNB for postoperative analgesia. However, considering the concept of preemptive analgesia, we believe that preoperative SNB may achieve a longer postoperative analgesia effect than we expected. METHODS: This trial is a single-institution, prospective, randomized, controlled, double-blind study. A total of 180 children aged between 1 and 12 years who are undergoing elective craniotomy will be randomly allocated in a 1:1:1 ratio to three groups: group B (preoperative ropivacaine block group), group A (postoperative ropivacaine block group), and group N (nonblocking control group). This randomization will be stratified by age in two strata (1-6 years and 7-12 years). The primary outcome is the total consumption of sufentanil within 24 h after surgery. The secondary outcomes include assessment of pain scores, total consumption of sufentanil and emergency-remedy medicine consumption at observation points, the occurrence of postoperative complications, and the length of hospitalization after surgery. DISCUSSION: This study is designed to explore the effect and feasibility of SNB with ropivacaine for postoperative analgesia in pediatric patients undergoing craniotomy. Further aims are to compare the effects of preoperative and postoperative SNB on postoperative analgesia in order to identify whether there is a preemptive analgesic effect and determine the better time to implement SNB in pediatric patients during craniotomy. TRIAL REGISTRATION: Chinese Clinical Trial Registry ChiCTR1800017386. Registered on 27 July 2018.

Effect of Scalp Nerve Block with Ropivacaine on Postoperative Pain in Patients Undergoing Craniotomy: A Randomized, Double Blinded Study.

Scalp nerve block with ropivacaine has been shown to provide perioperative analgesia. However, the best concentration of ropivacaine is still unknown for optimal analgesic effects. We performed a prospective study to evaluate the effects of scalp nerve block with varied concentration of ropivacaine on postoperative pain and intraoperative hemodynamic variables in patients undergoing craniotomy under general anesthesia. Eighty-five patients were randomly assigned to receive scalp block with either 0.2% ropivacaine, 0.33% ropivacaine, 0.5% ropivacaine, or normal saline. Intraoperative hemodynamics and post-operative pain scores at 2, 4, 6, 24 hours postoperatively were recorded. We found that scalp blockage with 0.2% and 0.33% ropivacaine provided adequate postoperative pain relief up to 2 h, while administration of 0.5% ropivacaine had a longer duration of action (up to 4 hour after craniotomy). Scalp nerve block with varied concentration of ropivacaine blunted the increase of mean arterial pressure in response to noxious stimuli during incision, drilling, and sawing skull bone. 0.2% and 0.5% ropivacaine decreased heart rate response to incision and drilling. We concluded that scalp block using 0.5% ropivacaine obtain preferable postoperative analgesia compared to lower concentrations. And scalp block with ropivacaine also reduced hemodynamic fluctuations in craniotomy operations.

DTI of great occipital nerve neuropathy: an initial study in patients with cervicogenic headache.

AIM: To assess differences in bilateral great occipital nerves (GONs) in patients with unilateral cervicogenic headache (CEH) using diffusion tensor imaging (DTI). MATERIALS AND METHODS: Twenty-three patients with unilateral CEH underwent GON magnetic resonance imaging (MRI). The clinical characteristics and fractional anisotropy (FA) and the apparent diffusion coefficient (ADC) values in bilateral GONs were determined by two observers with 7 and 3 years of experience in MRI. Three segments of GON were defined based on anatomy. The correlation of DTI measurements to the clinical characteristics and inter-/intra-observer performance were also evaluated. RESULTS: The mean GON FA for the symptomatic side was significantly lower (0.198±0.056) than that on the other side (0.311±0.04; p=0.000). The mean GON ADC for the symptomatic side was significantly higher (0.682±0.174) than that on the other side (0.465±0.138; p=0.000). Among the three defined segments of GON, statistically significant differences of ADC values were not found at segment S3 (0.692±0.257 versus 0.557±0.230; p=0.068). There were statistically significant differences of FA and ADC values in bilateral GON of segments S1 and S2. The intraclass correlation coefficient (ICC) of intra-/interobserver statistical analysis showed excellent inter/intra-observer agreement for FA and ADC. Significant correlation was only found between the duration and ADC. CONCLUSION: In patients with unilateral CEH, quantitative evaluation of the GON using DTI demonstrated FA decreases and ADC increases of the symptomatic side. Larger population and other occipital nerve neuropathy can be included in future research.

A comparison of effects of scalp nerve block and local anesthetic infiltration on inflammatory response, hemodynamic response, and postoperative pain in patients undergoing craniotomy for cerebral aneurysms: a randomized controlled trial.

BACKGROUND: The purpose of this study was to compare the effects of scalp nerve block (SNB) and local anesthetic infiltration (LA) with 0.75% ropivacaine on postoperative inflammatory response, intraoperative hemodynamic response, and postoperative pain control in patients undergoing craniotomy. METHODS: Fifty-seven patients were admitted for elective craniotomy for surgical clipping of a cerebral aneurysm. They were randomly divided into three groups: Group S (SNB with 15 mL of 0.75% ropivacaine), group I (LA with 15 mL of 0.75% ropivacaine) and group C (that only received routine intravenous analgesia). Pro-inflammatory cytokine levels in plasma for 72 h postoperatively, hemodynamic response to skin incision, and postoperative pain intensity were measured. RESULTS: The SNB with 0.75% ropivacaine not only decreased IL-6 levels in plasma 6 h after craniotomy but also decreased plasma CRP levels and increased plasma IL-10 levels 12 and 24 h after surgery compared to LA and routine analgesia. There were significant increases in mean arterial pressure 2 and 5 mins after the incision and during dura opening in Groups I and C compared with Group S. Group S had lower postoperative pain intensity, longer duration before the first dose of oxycodone, less consumption of oxycodone and lower incidence of PONV through 48 h postoperatively than Groups I and C. CONCLUSION: Preoperative SNB attenuated inflammatory response to craniotomy for cerebral aneurysms, blunted the hemodynamic response to scalp incision, and controlled postoperative pain better than LA or routine analgesia. TRIAL REGISTRATION: Clinicaltrials.gov NCT03073889 (PI:Xi Yang; date of registration:08/03/2017).

Scalp acupuncture treatment for children's autism spectrum disorders: A systematic review and meta-analysis.

BACKGROUND: Autism spectrum disorder (ASD) is a neurodevelopment disorder without definitive cure. Previous studies have provided evidences for efficacy and safety of scalp acupuncture in children with ASD. However, the efficacy of scalp acupuncture treatment (SAT) in children with ASD has not been evaluated systematically. The objective of this study is to evaluate the efficacy of SAT in children with ASD. METHODS: Information from 6 databases, including MEDLINE, EMBASE, Cochrane database, AMED, China National Knowledge Infrastructure, and Wanfang Data, were retrieved from the inception of each database from 1980 through September 2018. Randomized controlled trials evaluating the efficacy of SAT for patients with ASD were included. The primary outcome measures were the Childhood Autism Rating Scale (CARS) and Autism Behavior Checklist (ABC). The secondary outcome measures were Psychoeducational Profile (Third Edition) (PEP-3) scores. Risk of bias assessment and data synthesis were conducted with Review Manager 5.3 software. Methodological quality was assessed with the Cochrane risk of bias tool. RESULTS: Fourteen trials with 968 participants were conducted and 11 of the trials were suitable for meta-analysis. Compared with behavioral and educational interventions, SAT significantly decreased the overall CARS scores for children under 3 years old (mean difference (MD) = 3.08, 95% confidence interval (CI) [-3.96, -2.19], P < .001) and above 3 years old (MD = 5.29, 95% CI [-8.53, -2.06], P < .001), ABC scores (MD = 4.70, 95% CI [-6.94, -2.79], P < .001). Furthermore, SAT significantly improved PEP-3 scores in communication (MD = 3.61, 95% CI [2.85, 4.37], P < .001), physical ability (MD = 2.00, 95% CI [1.16, 2.84], P < .001), and behavior (MD = 2.76, 95% CI [1.80, 2.71], P < .001). CONCLUSION: SAT may be an effective treatment for children with ASD. Given the heterogeneity and number of participants, randomized controlled trials of high quality and design are required before widespread application of this therapy.

Safety and efficacy of addition of hyaluronidase to a mixture of lidocaine and bupivacaine in scalp nerves block in elective craniotomy operations; comparative study.

BACKGROUND: Patients undergoing craniotomy operations are prone to various noxious stimuli, many strategies are commenced to provide state of analgesia, for better control of the stress response and to overcome its undesired effects on the haemodynamics and post-operative pain. Scalp nerves block are considered one of these strategies. This study was conceived to evaluate the effect of addition of hyaluronidase to the local anaesthetic mixture used in the scalp nerves block in patients undergoing elective craniotomy operations. METHODS: 64 patients undergoing elective craniotomy operations were enrolled in this prospective randomized, double-blind comparative study. Patients were randomly assigned to two groups. Group LA, patients subjected to scalp nerves block with 15 ml bupivacaine 0.5%, 15 ml lidocaine 2%, in 1:400000 epinephrine. Group H as Group LA with15 IU /ml Hyaluronidase. RESULTS: Patients in the H group showed lower VAS values for 8 h postoperative, compared to the LA group. The haemodynamic response showed lower values in the H group, compared to the LA group. Those effects were shown in the intraoperative period and for 6 h post-operative. No difference was detected regarding the incidence of complications nor the safety profile. CONCLUSION: Our data supports the idea that addition of hyaluronidase to the local anesthetic mixture improves the success rates of the scalp nerves block and its efficacy especially during stressful intraoperative periods and in the early postoperative period. No evident undesirable effects in relation to the addition of hyaluronidase. TRIAL REGISTRATION: Clinical Trial registry on ClinicalTrials.gov , NCT 03411330 , 25-1-2018.

A hybrid auricular control system: direct, simultaneous, and proportional myoelectric control of two degrees of freedom in prosthetic hands.

OBJECTIVE: The conventional myoelectric control scheme of hand prostheses provides a high level of robustness during continuous use. Typically, the electrical activity of an agonist/antagonist muscle pair in the forearm is detected and used to control either opening/closing or rotation of the prosthetic hand. The translation of more sophisticated control approaches (e.g. regression-based classifiers) to clinical practice is limited mainly because of their lack of robustness in real-world conditions (e.g. due to different arm positions). We therefore explore a new hybrid approach, in which a second degree of freedom (DOF) controlled by the myoelectric activity of the posterior auricular muscles is added to the conventional forearm control. With this, an independent, simultaneous and proportional control of rotation and opening/closing of the hand is possible. APPROACH: In this study, we compared the hybrid auricular control system (hACS) to the two most commonly used control techniques for two DOF. Ten able-bodied subjects and one person with transradial amputation performed two standardizes tests in three different arm positions. MAIN RESULTS: Subjects controlled a hand prosthesis significantly more rapidly and more accurately using the hACS. Moreover, the robustness of the system was not influenced by different arm positions. SIGNIFICANCE: The hACS therefore offers an alternative solution for simultaneous and proportional myoelectric control of two degrees of freedom that avoids several robustness issues related to machine learning based approaches.

The greater occipital nerve and its spinal and brainstem afferent projections: A stereological and tract-tracing study in the rat.

The neuromodulation of the greater occipital nerve (GON) has proved effective to treat chronic refractory neurovascular headaches, in particular migraine and cluster headache. Moreover, animal studies have shown convergence of cervical and trigeminal afferents on the same territories of the upper cervical and lower medullary dorsal horn (DH), the so-called trigeminocervical complex (TCC), and recent studies in rat models of migraine and craniofacial neuropathy have shown that GON block or stimulation alter nociceptive processing in TCC. The present study examines in detail the anatomy of GON and its central projections in the rat applying different tracers to the nerve and quantifying its ultrastructure, the ganglion neurons subserving GON, and their innervation territories in the spinal cord and brainstem. With considerable intersubject variability in size, GON contains on average 900 myelinated and 3,300 unmyelinated axons, more than 90% of which emerge from C2 ganglion neurons. Unmyelinated afferents from GON innervates exclusively laminae I-II of the lateral DH, mostly extending along segments C2-3 . Myelinated fibers distribute mainly in laminae I and III-V of the lateral DH between C1 and C6 and, with different terminal patterns, in medial parts of the DH at upper cervical segments, and ventrolateral rostral cuneate, paratrigeminal, and marginal part of the spinal caudal and interpolar nuclei. Sparse projections also appear in other locations nearby. These findings will help to better understand the bases of sensory convergence on spinomedullary systems, a critical pathophysiological factor for pain referral and spread in severe painful craniofacial disorders.