Individual Nerve Research Articles

Independent association of the Meckel’s cave with trigeminal neuralgia and development of a screening tool

PurposeTo 1) investigate the association of the properties of the Meckel’s cave (MC) with TN occurrence (i.e., affected vs. unaffected nerves) and whether such association was independent of neurovascular contact (NVC); and 2) develop an objective screening tool for TN. Materials and methodsTwo hundred and nineteen trigeminal nerves were included. (The severity of) NVC was identified for individual nerve, and a set of 107 radiomic features were extracted to characterize various properties of each MC. Both procedures were primarily based on magnetic resonance imaging sequences. A radiomic score (Rad-score) was constructed for each MC to integrate the features associated with TN occurrence. Independent t-test and logistic regression were conducted to assess the association and develop the screening tool mentioned above. ResultsTwelve features were selected to build the Rad-score, with the Inverse Difference Moment Normalized (IDMN) having the greatest weight. The Rad-score was significantly (p ≤ 0.05) higher in the affected compared to the unaffected nerves, irrespective of NVC. The Rad-score and NVC were incorporated in the regression model/screening tool, which demonstrated an acceptable discriminating ability (C-statistic = 0.84). ConclusionThis study has identified a potential association of the properties/features of the MC with TN occurrence, probably involving the demyelination and axonal injury of the trigeminal ganglion within the MC as suggested by the IDMN. Such association may be independent of NVC. This finding may provide new insight into the etiology and/or pathophysiology of TN. The screening tool, which demonstrated an acceptable discriminating ability, may contribute to an improvement in its diagnosis.

ANCA-Associated Vasculitic Neuropathy: A Case Report

Anti-neutrophil cytoplasmic antibodies (ANCA)-associated vasculitides (AAVs) are a group of autoimmune diseases that can affect many vital organs and tissues, as well as the nervous system. When peripheral nerves are affected, one of the clinical features of AAVs can be vasculitic neuropathies (VNs). This usually causes asymmetric weakness and numbness in the distal parts of extremities, frequently followed by pain. Nerve conduction study (NCS) reveals axonal loss in multiple individual nerves, whereas a length-dependent process may also be observed. As AAV is a rare diagnostic entity and can manifest with a vast variety of symptoms, it is seldom involved in the initial diagnostic work-up of polyneuropathy. Moreover, the only definitive diagnostic method for VN is peripheral nerve biopsy. Therefore, AAV represents one of the greatest difficulties in the differential diagnosis of neuropathies. In this article, we present a clinical case of a 73-year-old patient admitted to the hospital due to blurry vision, headache, and limb weakness. The findings of the neurological examination were consistent with polyneuropathy. A thorough examination was performed to determine the exact diagnosis. However, due to the lack of typical symptoms, VN was diagnosed only after acute renal failure evolved. This case demonstrates the many symptoms that AAV can present with and the importance of a thorough differential diagnosis for multiple mononeuropathies.

Regional Analgesia for Cesarean Delivery: A Narrative Review Toward Enhancing Outcomes in Parturients.

With the current surge on peripheral nerve blocks in post-cesarean pain management and the historical lack of unequivocal evidence supporting its universal use, this review intended to re-examine the extended scope of literature on regional anesthesia and postoperative analgesia in low-transverse cesarean section. A literature search was conducted up to April 2023 using PubMed to identify articles relevant to our search words "cesarean section", "neuraxial morphine", "post-cesarean analgesia", as well as the name of each individual nerve block. The literature search was ultimately narrowed to systematic reviews and randomized controlled trials published between 2012 and 2023. We define, describe, and discuss the evidence surrounding each individual regional anesthetic technique in the presence and absence of intrathecal morphine, which is used as the gold standard when appropriate. In the absence of neuraxial morphine, all regional anesthetic techniques have some level of analgesic benefit in the post-cesarean analgesia. Transversus Abdominis Plane blocks continue to have the most studies in their use. Newer fascia plane blocks including the anterior Quadratus Lumborum, and Erector Spinae Plane blocks provide significant analgesia. In addition, direct comparison among peripheral nerve blocks consistently favors the more proximal, centralized techniques. Conversely, in the presence of neuraxial morphine, no peripheral anesthetic technique has reliably and reproducibly demonstrated an added analgesic benefit regardless of the peripheral nerve block technique or location of local anesthetic injection in the post-cesarean population. Neuraxial morphine continues to be the gold standard for post-cesarean section analgesia, the benefit of additional single injection regional anesthetic is currently not evidence supported. In cases where neuraxial opioids have not or cannot be given, there is overwhelming evidence that regional anesthetic techniques improve post-cesarean section analgesia and decrease post-operative opioid consumption. Even though there is no consensus on the optimal peripheral nerve block, emerging evidence suggests more centralized abdominal fascia plane block trends towards better analgesia.

Management of displaced supracondylar fractures in children and adherence to the BOAST guideline- experience in a District General Hospital, UK

BackgroundSupracondylar fracture is the most common elbow fracture in children. These fractures can be associated with significant complications, including nerve injury, vascular compromise, compartment syndrome and clinical deformity. The British Orthopaedic Association Standards for Trauma (BOAST) provide clear and comprehensive guidance for managing the supracondylar fracture. AimsWe reviewed the management of displaced (Gartland type 2 and 3) supracondylar fractures and adherence to BOAST guidelines between 1st audit and re-audit following the introduction of supracondylar assessment proforma. MethodsWe retrospectively analysed the adherence to BOAST guidelines for 103 patients operated between 2014 and 2020. Documentation of vascular status and individual nerve functions were assessed during presentation to the emergency department, immediately before surgery, and postoperatively before discharge from the hospital. We also reviewed the documentation of the K-wire's size utilised for fixation, the medial wire fixation technique, and post-fixation stability during the operation. A new supracondylar fracture assessment proforma was designed and implemented after the 1st audit as part of the quality improvement measure. During the second stage of the audit cycle, we reviewed 22 patients and used the same methodology as the first audit to analyse the data. ResultsResults: We found significant improvements in the documentation of capillary refill time from 65 % to 95.5 % (p = 0.0038), radial pulse from 59.2 % to 95.5 % (p = 0.0009), and documentation of individual nerve function from 37.9 % to 72.7 % (p = 0.0040) in the emergency department during 2nd stage of the audit cycle. Individual nerve function documentation by the operating team immediately before surgery changed from 42.7 % to 50 %. The use of 2 mm K-wires improved from 53.3 % to 89.5 % (p = 0.0037) Documentation of medial wire fixation technique and post-fixation stability increased to 100 % from 82.9 % to 89.5 % from 42.7 % (p = 0.0002), respectively. Postoperatively, we noted improvement in both radial pulse and capillary refill time documentation from 27.2 % to 54.2 % (p = 0.0216) and the individual nerve function from 9.7 % to 50 % (p = 0.00005). ConclusionPoor adherence in stage 1 of the audit cycle to BOAST standards was significantly improved in stage 2 (Re-audit) after introducing a simple supracondylar fracture assessment proforma and focussed educational sessions.

The Case for Conscious Experience Being in Individual Neurons

The idea that individual nerve cells might have conscious experiences has been around ever since cells were identified in the seventeenth century, but in the era of modern neuroscience the case for individual human neuronal experience has received little attention. A series of arguments will be presented suggesting that all the human conscious experiences that we talk about are events in individual neurons, not global to the brain or organism. We conclude that cellular consciousness is the only plausible way to explain ‘our’ experiences within current physics and biology, however implausible it might at first seem. This implies that our experiences are multiple in space as well as time, consistent with the neuroscience watchword that there is ‘no single place where everything comes together in the brain’. The central argument is that events of experience must involve rich integration of information and individual neurons are the only places in brains where integration of information occurs. Any more global ‘binding’ is neither required nor physically possible. The detailed nature of events of integration of signals in a neuron’s dendrites remains uncertain but recent developments provide some candidates.

The Case for Conscious Experience Being in Individual Neurons

The idea that individual nerve cells might have conscious experiences has been around ever since cells were identified in the seventeenth century, but in the era of modern neuroscience the case for individual human neuronal experience has received little attention. A series of arguments will be presented suggesting that all the human conscious experiences that we talk about are events in individual neurons, not global to the brain or organism. We conclude that cellular consciousness is the only plausible way to explain ‘our’ experiences within current physics and biology, however implausible it might at first seem. This implies that our experiences are multiple in space as well as time, consistent with the neuroscience watchword that there is ‘no single place where everything comes together in the brain’. The central argument is that events of experience must involve rich integration of information and individual neurons are the only places in brains where integration of information occurs. Any more global ‘binding’ is neither required nor physically possible. The detailed nature of events of integration of signals in a neuron’s dendrites remains uncertain but recent developments provide some candidates.

Synovial Cyst in the Setting of an Interspinous Fusion Device

Synovial cysts of the spine are degenerative cystic lesions that can lead to severe symptoms secondary to compression of the spinal cord, individual nerve roots, and/or the cauda equina. Some believe the etiology of this entity is related to increased motion across the facet joint and instability. We report a case of a lumbar synovial cyst located at the same level as a previously inserted spinous process fusion device. This case illustrates that, unlike a transpedicular instrumented fusion where the risk of synovial cyst formation is zero, a spinal process fusion can still lead to synovial cyst formation likely due to persistent micromotion across that segment.

(Pre)diabetes and a higher level of glycaemic measures are continuously associated with corneal neurodegeneration assessed by corneal confocal microscopy: the Maastricht Study

Aims/hypothesisTo assess the associations between glucose metabolism status and a range of continuous measures of glycaemia with corneal nerve fibre measures, as assessed using corneal confocal microscopy.MethodsWe used population-based observational cross-sectional data from the Maastricht Study of N=3471 participants (mean age 59.4 years, 48.4% men, 14.7% with prediabetes, 21.0% with type 2 diabetes) to study the associations, after adjustment for demographic, cardiovascular risk and lifestyle factors, between glucose metabolism status (prediabetes and type 2 diabetes vs normal glucose metabolism) plus measures of glycaemia (fasting plasma glucose, 2 h post-load glucose, HbA1c, skin autofluorescence [SAF] and duration of diabetes) and composite Z-scores of corneal nerve fibre measures or individual corneal nerve fibre measures (corneal nerve bifurcation density, corneal nerve density, corneal nerve length and fractal dimension). We used linear regression analysis, and, for glucose metabolism status, performed a linear trend analysis.ResultsAfter full adjustment, a more adverse glucose metabolism status was associated with a lower composite Z-score for corneal nerve fibre measures (β coefficients [95% CI], prediabetes vs normal glucose metabolism −0.08 [−0.17, 0.03], type 2 diabetes vs normal glucose metabolism −0.14 [−0.25, −0.04]; linear trend analysis showed a p value of 0.001), and higher levels of measures of glycaemia (fasting plasma glucose, 2 h post-load glucose, HbA1c, SAF and duration of diabetes) were all significantly associated with a lower composite Z-score for corneal nerve fibre measures (per SD: −0.09 [−0.13, −0.05], −0.07 [−0.11, −0.03], −0.08 [−0.11, −0.04], −0.05 [−0.08, −0.01], −0.09 [−0.17, −0.001], respectively). In general, directionally similar associations were observed for individual corneal nerve fibre measures.Conclusions/interpretationTo our knowledge, this is the first population-based study to show that a more adverse glucose metabolism status and higher levels of glycaemic measures were all linearly associated with corneal neurodegeneration after adjustment for an extensive set of potential confounders. Our results indicate that glycaemia-associated corneal neurodegeneration is a continuous process that starts before the onset of type 2 diabetes. Further research is needed to investigate whether early reduction of hyperglycaemia can prevent corneal neurodegeneration.Graphical

Comparison Between a Modified Fast 3-Dimensional Turbo Spin-Echo and Diffusion-Weighted Imaging With Background Suppression in Evaluation of Lumbosacral Plexus and Its Branches.

To compare the fast 3-dimensional NerveVIEW (3D NerveVIEW) with diffusion-weighted imaging with background suppression (DWIBS) in imaging of lumbosacral plexus and its branches. A prospective study was performed on 30 healthy volunteers and patients who had undergone compressed sensing 3D NerveVIEW and DWIBS scans. There were 11 healthy subjects, 15 patients with lumbar disc herniation, and 4 patients with chronic inflammatory demyelinating polyradiculoneuropathy. Image quality was rated using a 4-point subjective scale. Quantitative evaluation of the nerves was done by measuring signal-to-noise ratio, contrast-to-noise ratio, and signal-to-background ratio, and the consistency in the measurements of nerve root cross-sectional areas was also assessed. The differences of signal-to-noise ratio, contrast-to-noise ratio, signal-to-background ratio, and the scores of image quality between 2 sequences were compared. The overall average image quality score of 3D NerveVIEW was significantly higher than that of DWIBS (2.72 ± 0.45 and 2.45 ± 0.81, respectively; P < 0.01). In terms of individual nerves, there was no significant difference between the 2 sequences in the display of the nerves from L2 to S1; however, 3D NerveVIEW was significantly better than DWIBS in demonstration of the S2-S3 nerves, as well as the nerve details. Regarding quantitative measurements, these sequences achieved comparable results with excellent interobserver agreements. Fast 3D NerveVIEW was superior to DWIBS with improved conspicuity of small distal nerves of S2-S3 and nerve details.

7T for clinical imaging of benign peripheral nerve tumors: preliminary results.

MRI has become an essential diagnostic imaging modality for peripheral nerve pathology. Early MR imaging for peripheral nerve depended on inferred nerve involvement by visualizing downstream effects such as denervation muscular atrophy; improvements in MRI technology have made possible direct visualization of the nerves. In this paper, we share our early clinical experience with 7T for benign neurogenic tumors. Patients with benign neurogenic tumors and 7T MRI examinations available were reviewed. Cases of individual benign peripheral nerve tumors were included to demonstrate 7T MRI imaging characteristics. All exams were performed on a 7T MRI MAGNETOM Terra using a 28-channel receive, single-channel transmit knee coil. Five cases of four pathologies were selected from 38 patients to depict characteristic imaging features in different benign nerve tumors and lesions using 7T MRI. The primary advantage of 7T over 3T is an increase in signal-to-noise ratio which allows higher in plane resolution so that the smallest neural structures can be seen and characterized. This improvement in MR imaging provides the opportunity for more accurate diagnosis and surgical planning in selected cases. As this technology continues to evolve for clinical purposes, we anticipate increasing applications and improved patient care using 7T MRI for the diagnosis of peripheral nerve masses.

Mimosa-Inspired Stimuli-Responsive Curling Bioadhesive Tape Promotes Peripheral Nerve Regeneration.

Trauma often results in peripheral nerve injuries (PNIs). These injuries are particularly challenging therapeutically because of variable nerve diameters, slow axonal regeneration, infection of severed ends, fragility of the nerve tissue, and the intricacy of surgical intervention. Surgical suturing is likely to cause additional damage to peripheral nerves. Therefore, an ideal nerve scaffold should possess good biocompatibility, diameter adaptability, and a stable biological interface for seamless biointegration with tissues. Inspired by the curl of Mimosa pudica, this study aimed to design and develop a diameter-adaptable, suture-free, stimulated curling bioadhesive tape (SCT) hydrogel for repairing PNI. The hydrogel is fabricated from chitosan and acrylic acid-N-hydroxysuccinimide lipid via gradient crosslinking using glutaraldehyde. It closely matches the nerves of different individuals and regions, thereby providing a bionic scaffold for axonal regeneration. In addition, this hydrogel rapidly absorbs tissue fluid from the nerve surface achieving durable wet-interface adhesion. Furthermore, the chitosan-based SCT hydrogel loaded with insulin-like growth factor-I effectively promotes peripheral nerve regeneration with excellent bioactivity. This procedure for peripheral nerve injury repair using the SCT hydrogel is simple and reduces the difficulty and duration of surgery, thereby advancing adaptive biointerfaces and reliable materials for nerve repair.

0494 Early Feasibility Study on Use of Noninvasive Temporal Interference Stimulation of the Hypoglossal Nerve in the Treatment of OSA

Abstract Introduction Hypoglossal nerve stimulation has proven effective as an alternative to Positive Airway Pressure (PAP) machines in treating obstructive sleep apnea (OSA). The only currently FDA-approved hypoglossal nerve stimulator requires surgical implantation. Somnial Inc. is developing a noninvasive nerve stimulator based on temporal interference (TI), such that multiple supra-kHz-modulating electrical fields overlap to create a hyper-localized field modulating at a lower, nerve-stimulating frequency equal to the offset between the original fields. Bilateral stimulation reduces lateral movement of the tongue and requires less energy applied to the individual nerves. In early studies, transcutaneous, bilateral TI stimulation showed strong forward and central tongue movement with long-term tolerability. Methods To determine the clinical impact of TI on the treatment of OSA, 11 patients recently diagnosed with moderate to severe OSA (AHI 15-50/hour) based on in-lab polysomnography (PSG) and BMI &amp;lt; 35 were subjected to bilateral TI stimulation of the hypoglossal nerves during another PSG. Two pairs of electrodes were placed on either side, medial to the inferior aspect of the mandible overlying the genioglossus muscle. The frequencies were modulated in a 4-second-on, 2-second-off pattern. Initial power settings were determined as sufficient to move the tongue without discomfort and were increased throughout the night in an approach similar to a CPAP titration study. Results 5 of the 11 patients analyzed in the study, including 4 out of 4 women, responded to the therapy (AHI reduction from baseline by &amp;gt;50% and an AHI of &amp;lt; 20/hour). Patient questionnaires indicate the treatment was well tolerated throughout the night. Conclusion These promising proof of concept results after a single night indicate the potential for the use of TI in the treatment of OSA. Transcutaneous application of stimulation energy via TI energy could be used to determine the efficacious does required to reduce AHI events in the at-home healthcare setting. This justifies future research in long-term, chronic-treatment studies with TI stimulation and the advancement of a home-based device. Support (if any)

Modern possibilities of upper extremity regional anesthesia

Today, regional anesthesia is widely used during surgical interventions in orthopedic surgery. Blockades of individual nerves and plexuses are used. Objective. To introduce readers: surgeons, orthopedists-traumatologists with the possibilities of regional anesthesia like an adequate method of analgesia during upper limb interventions. Methods. Relevant literature from PubMed, Scopus, Google Scholar databases and own experience of regional anesthesia were analyzed. The results. The work describes the effect of regional anesthesia on the nervous, respiratory, cardiovascular and coagulation systems. Information about blocks of peripheral nerves of the upper extremities: interscalene, supraclavicular, subclavian, axillary. Their advantages and disadvantages were analyzed. Interscalene block is not recommended for patients with severe lung disease due to the risk of respiratory failure. Complications of this analgesia include: phrenic nerve block (up to 100 %), sympathetic chain block and Horner's syndrome. Also, possible accidental injection into the vertebral artery. Indications for the supraclavicular block are operations on the hand, forearm, elbow and shoulder. Complications — phrenic nerve block (17‒50 %), recurrent laryngeal blockade (22 %), pneumothorax (0.6‒6.1 %). When planning anesthesia, the accompanying pathology of the patient and his general condition should be taken into account. Particular care is required when the patient is taking anticoagulants. Risk of bleeding and thrombosis should be carefully assessed. Special attention should be paid to the toxicity of local anesthetics and ways to eliminate it. Conclusions. Regional anesthesia can be used in the pre-, intra- and postoperative periods. Sometimes it’s the only method that permit surgical intervention. It is necessary to understand all the advantages and limitations to ensure high quality of patient care.

Role of ultrasonography for evaluation of nerve recovery in repaired median nerve lacerations.

This study aimed to investigate whether ultrasonographic inspection of the repair site of median nerve lacerations may provide useful evidence about the functional outcome in the affected hand. Forty-three patients with complete transection of the median nerve at the distal forearm were examined at a median of 40.9 months after operation by detailed ultrasonographic imaging and clinical assessment of the affected hand by the Michigan Hand Questionnaire and Rosén-Lundborg Protocol to investigate the quality of nerve healing. The continuity of individual nerve fascicles was assessed and the cross-sectional area of the enlarged nerve at the repair site was measured and compared with the contralateral median nerve at the same level. An enlargement ratio for the repair site of each nerve was calculated and compared with the numeric results obtained from the two clinical tests. A statistically significant reverse correlation was observed between nerve enlargement and the functional results of the repaired nerve.Level of evidence: IV.

Электронно-микроскопическое исследование зрительного нерва с токсическим невритом в эксперименте

Рurpose. To identify ultrastructural changes of the optic nerve in the area of the trellis plate in rabbits after exposure to methyl alcohol. Material and methods. A model of experimental optic neuritis with the introduction of methyl alcohol into the retrobulbar space was reproduced on 8 rabbits. The animals were removed from the experiment on the 14th, 30th, 90th and 180th days after the administration of methanol. Pieces of the optic nerve (1–2 mm) were isolated from the enucleated eyeballs in the area of the lattice plate and examined using a transmission electron microscope. Results. On the 14th day after the administration of methanol, signs of pronounced cytoplasmic edema and destruction of intracellular organelles were detected in the ganglion neurons of the rabbit retina in the area of the lattice plate. In individual nerve fibers of the optic nerve, myelin sheaths were stratified and unfolded, axons swelled. Structural changes were detected in astrocytes, especially in the processes around blood vessels. Macrophages of nervous tissue — microgliocytes — became active. Morphological changes indicated a violation of microcirculation and permeability of the hematoneural barrier. The basal membranes around the walls of blood vessels were compacted. Intracellular organelles were destroyed in the cytoplasm of endothelial cells, hemostasis was determined inside the vessels. Subsequently, on the 30–90th day of the experiment, dystrophic and destructive changes in the cytoplasm of ganglion cells and their processes forming the optic nerve, as well as surrounding gliocytes progressed. There were signs of gliofibrosis. Destructive processes and gliofibrosis of the retina and nerve fibers of the optic nerve in the area of the lattice plate increased in degree of expression up to 180th days of the experiment. Conclusion. The results of electron microscopic studies of the intrabulbar part of the optic nerve in experimental animals in dynamics after the introduction of methyl alcohol indicate that the main trigger for the development of visual neuritis may be a violation of microcirculation processes in the retina and optic nerve, which leads to an increase in the permeability of the hematoneural barrier. These events entail dystrophic and destructive changes in the nervous tissue, the progression of which naturally leads, with the assistance of glial cells to gliofibrosis of the optic nerve. Keywords: toxic optic neuritis, methanol, hematoneural barrier, axon demyelination, gliofibrosis

How Tactile Afferents in the Human Fingerpad Encode Tangential Torques Associated with Manipulation: Are Monkeys Better than Us?

Dexterous object manipulation depends critically on information about forces normal and tangential to the fingerpads, and also on torque associated with object orientation at grip surfaces. We investigated how torque information is encoded by human tactile afferents in the fingerpads and compared them to 97 afferents recorded in monkeys (n = 3; 2 females) in our previous study. Human data included slowly-adapting Type-II (SA-II) afferents, which are absent in the glabrous skin of monkeys. Torques of different magnitudes (3.5-7.5 mNm) were applied in clockwise and anticlockwise directions to a standard central site on the fingerpads of 34 human subjects (19 females). Torques were superimposed on a 2, 3, or 4 N background normal force. Unitary recordings were made from fast-adapting Type-I (FA-I, n = 39), and slowly-adapting Type-I (SA-I, n = 31) and Type-II (SA-II, n = 13) afferents supplying the fingerpads via microelectrodes inserted into the median nerve. All three afferent types encoded torque magnitude and direction, with torque sensitivity being higher with smaller normal forces. SA-I afferent responses to static torque were inferior to dynamic stimuli in humans, while in monkeys the opposite was true. In humans this might be compensated by the addition of sustained SA-II afferent input, and their capacity to increase or decrease firing rates with direction of rotation. We conclude that the discrimination capacity of individual afferents of each type was inferior in humans than monkeys which could be because of differences in fingertip tissue compliance and skin friction.SIGNIFICANCE STATEMENT We investigated how individual human tactile nerve fibers encode rotational forces (torques) and compared them to their monkey counterparts. Human hands, but not monkey hands, are innervated by a tactile neuron type (SA-II afferents) specialized to encode directional skin strain yet, so far, torque encoding has only been studied in monkeys. We find that human SA-I afferents were generally less sensitive and less able to discriminate torque magnitude and direction than their monkey counterparts, especially during the static phase of torque loading. However, this shortfall in humans could be compensated by SA-II afferent input. This indicates that variation in afferent types might complement each other signaling different stimulus features possibly providing computational advantage to discriminate stimuli.

Safety and Feasibility of Noninvasive Electromagnetic Stimulation of the Phrenic Nerves.

Mechanical ventilation is widely used in ICU patients as a lifesaving intervention. Diaphragmatic atrophy and thinning occur from lack of contractions of the diaphragm during mechanical ventilation. It may prolong weaning and increase the risk of respiratory complications. Noninvasive electromagnetic stimulation of the phrenic nerves may ameliorate the atrophy seen with ventilation. The objective of this study was to show that noninvasive repetitive electromagnetic stimulation is safe, feasible, and effective to stimulate the phrenic nerves in both awake individuals and anesthetized patients. A single-center study with 10 subjects overall, 5 awake volunteers and 5 anesthetized subjects. We used a prototype electromagnetic, noninvasive, simultaneous bilateral phrenic nerve stimulation device in both groups. In the awake volunteers, we assessed time-to-first capture of the phrenic nerves and safety measures, such as pain, discomfort, dental paresthesia, and skin irritation. In the anesthetized subjects, time-to-first capture as well as tidal volumes and airway pressures at 20%, 30%, and 40% stimulation intensity were assessed. Diaphragmatic capture was achieved in all the subjects within a median (range) of 1 min (1 min to 9 min 21 s) for the awake subjects and 30 s (20 s to 1 min 15 s) for the anesthetized subjects. There were no adverse or severe adverse events in either group, nor any dental paresthesia, skin irritation, or subjective pain in the stimulated area. Tidal volumes increased in all the subjects in response to simultaneous bilateral phrenic nerve stimulation and increased gradually with increasing stimulation intensity. Airway pressures corresponded to spontaneous breathing of ∼2 cm H2O. Noninvasive phrenic nerve stimulation can be safely performed in awake and anesthetized individuals. It was feasible and effective in stimulating the diaphragm by induction of physiologic and scalable tidal volumes with minimum positive airway pressures.

Donor Nerve Selection in Free Gracilis Muscle Transfer; Systematic Review and Meta-Analysis

Introduction: One of the crucial factors in facial reanimation surgery is the donor nerve selection. There have been several neurotizers to reinnervate the free gracilis muscle flap (FGMT). Currently the cross-face nerve graft (CFNG) and motor nerve to masseter are the most favored options. The “dual innervation” is described as potential way to combine the advantages of individual donor nerves and has shown successful results. Materials and Methods: Two databases were searched for the CFNG, masseteric nerve and dual innervation of FGMT. Defined primary measures were applied to the results to compare the extent of commissure excursion, facial symmetry at rest and smile, spontaneity, time to flap contraction for each neurotizer. Meta-analysis was conducted for studies including quantitative data for commissure excursion and facial symmetry. We included all study types except the animal studies. Only articles written in English language from 2001 were taken into consideration. We followed PRISMA guidelines. ROBINS-I and Newcastle-Ottawa tools were used to assess the risk of bias and quality for each study included in the meta-analysis. Results: 147 articles on FGMT were systematically reviewed and 13 studies were evaluated in the meta-analysis. All studies were high in quality. Heterogeneity was high among the studies, limiting the efficiency of our meta-analysis. Conclusion: CFNG is the most frequently utilized reinnervation technique. Masseteric nerve is very reliable and has the potential to provide more commissural excursion and higher success rate. Dual innervation is an effective alternative leading to effective clinical outcomes. A globalized and quantitative measurement method will contribute to the future of facial reanimation surgery.

Intraneural vascularity of the median, ulnar and common peroneal nerve: Microvascular ultrasound and pathophysiological implications.

Changes in the microvascular environment are considered crucial in the pathogenesis of compression neuropathies. Several studies have demonstrated elevated intraneural vascularity in severe neuropathy compared with healthy subjects, where intraneural vascularity is considered predominantly undetectable. The aim of this study was to assess and quantify intraneural vasculature by superb microvascular imaging (SMI) in healthy volunteers in the median, ulnar and common peroneal nerve. Intraneural vascularity was quantified in 26 healthy volunteers (312 segments overall) by SMI sonography using a 22-MHz linear transducer. Individual nerve segment vascularity was compared with the mean vascularity using one-way ANOVA and Kruskal-Wallis tests, respectively. Vendor-provided quantification and manual vessel count were compared by linear regression analysis. Intraneural vascularity was detectable in all nerve segments (100.0%). Vessel density was highest in the median nerve at the wrist (1.54 ± 0.44/mm2, P < 0.0001) and lowest in the sulcal ulnar nerve (0.90 ± 0.34/mm2, P < 0.0001). Vendor-provided automated quantification severely overestimated vascular content compared with manual quantification. Superb microvascular imaging can facilitate the visualisation of nerve vascularity and even detect local variations in vessel density. The pathophysiological implications for peripheral neuropathies, especially compression neuropathies, warrant further investigation, but the absence of visible intraneural vasculature as a negative finding in the diagnostic of compression neuropathies should be interpretedwith caution, as the intraneural vascularity may lie beyond the 18 MHz resolution power of a transducer.

Microanatomical study of arachnoid granulations and meningeal architecture around Meckel’s cave

Although the microanatomy of Meckel’s cave (MC) has been well studied, there are still controversies regarding the meningeal architecture of the space. Moreover, there are only general mentions of the arachnoid granulations near MC in just a few sources. This study is aimed at determining the frequency, location, and anatomical variability of the main clusters of arachnoid granulations around MC. The dissection involved 26 isolated specimens of MC fixed in formalin (neutral buffered, 10%). This number included five freshly harvested specimens examined histologically. Additional paraffin block with MC horizontal section was taken from our neuroanatomical collection. Carefully selected anatomical and histological techniques were applied to assess the complex relationships between the arachnoid granulations and adjacent structures. Arachnoid granulations were found around MC in all specimens with different anatomical variations. The main clusters of arachnoid granulations were close to the trigeminal ganglion and its divisions. The dorsolateral wall of MC was a thick layer formed by interweaving bundles of collagen fibers arranged in various directions. The entire MC was surrounded by a dural sleeve (envelope). This sleeve separated MC from the lateral sellar compartment. At its anterior (rostral) end, it formed a cribriform area pierced by individual fascicles of the trigeminal nerve’s primary divisions. The connective tissue forming the sleeve was not only continuous with the epineurium but also shifted to the perineuria surrounding individual nerve fascicles. The meningeal architecture around MC has a complex and multilayer arrangement with a collagenous sleeve closely related to the trigeminal ganglion. Arachnoid granulations are typically found around MC.