Nerve In Arm Research Articles

Brachialis to Anterior Interosseous Nerve Transfer: Comprehensive Anatomic Rationale.

Distal nerve transfers for muscle reinnervation and restoration of function after upper and lower motor neuron lesions are a well-established surgical approach. The brachialis to anterior interosseous nerve (BrAIN) transfer is performed for prehension reanimation in lower brachial plexus and traumatic cervical spinal cord injuries. The aim of the study is to shed light on the inconsistent results observed in patients who undergo the BrAIN transfer. An anatomic dissection was conducted on 30 fresh upper limb specimens to examine the intraneural topography of the median nerve (MN) in the upper arm at the level of the BrAIN transfer and the presence of intraneural fascicular interconnections distally. Fascicular interconnections between the AIN and other MN branches were consistently found in the distal third of the upper arm. The first interconnection was at 3.85 ± 1.82 cm proximal to the interepicondylar line, and the second one, after further proximal neurolysis, was at 9.45 ± 1.16 cm from the interepicondylar line. Intraneural topography of the AIN at the transfer level varied, with dorsomedial, dorsolateral, and purely dorsal locations observed. Consistent fascicular interconnections between the AIN and MN branches and intraneural topography variability of the MN may lead to aberrant reinnervation.

Ultrasound-guided localization of the radial nerve along the humerus: providing reference points for safer upper arm surgery.

The close proximity of the radial nerve to the humerus poses a risk during upper arm surgery. Although the general course of the radial nerve is well-known, its exact position in relation to anatomical reference points remains poorly investigated. This study aimed to develop a standardized protocol for the sonographic and clinical identification of the radial nerve in the upper arm. The ultimate goal is to assist surgeons in avoiding iatrogenic radial nerve palsy. A total of 76 measurements were performed in 38 volunteers (both sides). Ultrasound measurements were performed using a linear transducer (10MHz) to identify the radial nerve at two key points: RD (where the radial nerve crosses the dorsal surface of the humerus) and RL (where the radial nerve crosses the lateral aspect of the humerus). Distances from specific reference points (acromion, lateral epicondyle, medial epicondyle, olecranon fossa) to RD and RL were measured, and the angle between the course of the nerve and the humeral axis was recorded. Humeral length was defined as the distance between the posterodorsal corner of the acromion and the lateral epicondyle. The distance from the lateral epicondyle to RD was on average 15.5cm ± 1.3, corresponding to 50% of the humeral length. The distance from the lateral epicondyle to RL was on average 6.7cm ± 0.8, corresponding to 21% of the humeral length. The course of the nerve between RD and RL showed an average angulation of 37° to the anatomical axis of the humerus. Gender, BMI, dominant hand, and arm thickness did not correlate with the distances to RD or RL. Measurements were consistent between the left and right side. The radial nerve can typically be identified by employing a 1/2 and 1/5 ratio on the dorsal and lateral aspects of the humerus. Due to slight variations in individual anatomy, the utilization of ultrasound-assisted visualization presents a valuable and straightforward approach to mitigate the risk of iatrogenic radial nerve palsy during upper arm surgery. This study introduces an easy and fast protocol for this purpose.

Outcomes of complete neurotomy and immediate repair of the musculocutaneous nerve for treatment of elbow spasticity.

Neurotomy interrupts the stretch reflex and can be used for the treatment of spasticity. We hypothesized that neurotomy with nerve repair reduces spasticity while preserving motor function due to the preferential recovery of efferent over afferent fibres. This study reports the 1-year outcomes of neurotomy and immediate repair of the musculocutaneous nerve in the proximal arm for treatment of elbow flexor spasticity, comparing these to outcomes in the literature for neurectomy without nerve repair. A total of 10 adult patients with spasticity of the elbow flexors from stroke or traumatic brain injury who had undergone neurotomy and immediate repair of the musculocutaneous nerve were prospectively studied. The results suggest that this procedure effectively reduces elbow flexor spasticity, improves elbow resting position, active elbow extension and is useful for achieving patient goals with effects lasting at least 12 months.Level of evidence: IV (therapeutic).

Nerve cross-sectional area in advanced uremic neuropathy: A nerve ultrasound pilot study.

Uremic neuropathy (UN) is a disabling neuropathy in end-stage kidney disease (ESKD) affecting the majority of patients receiving long-term hemodialysis (HD). One previous nerve ultrasound study reported an increased cross-sectional area (CSA) of the median nerve in moderate UN, while another study found enlarged sural nerves in small-fiber polyneuropathy associated with ESKD. The present cohort study aims to analyze bilateral CSA of multiple nerves in UN. Ten nondiabetic ESKD patients with UN on HD for at least 2years and 10 healthy age-matched controls underwent bilateral ultrasound examinations with CSA measurements in 13 arm and leg nerve sites. Nerve conduction studies (NCS) and the total neuropathy score (TNS) were recorded. Pearson's coefficient and the Mann-Whitney U-test were used to analyze correlations and compare groups. ESKD patients presented advanced neuropathic symptoms (mean TNS 15.9). NCS showed significantly reduced motor and sensory amplitudes in the UN group compared to the control group, and a slightly reduced nerve CSA was observed in 5 of 13 nerve sites (p<.05); the other nerve sites were not enlarged. Sural nerve CSA (p<.05) and sensory amplitude (p<.01) were negatively correlated with the TNS. Nerve enlargement was not observed in the present study in advanced UN. A reduced nerve CSA observed in the sural nerve suggests an axonal loss associated with long-term HD in ESKD. During clinical workup of an acute disease of the peripheral nervous system in ESKD patients, nerve enlargement might be attributable to other causes than chronic UN.

Permanent Peripheral Nerve Stimulator for Complex Regional Pain Syndrome of the Forearm and Hand

Summary: A 51-year-old woman with diabetes and depression was referred to the anesthesia pain clinic with a 15-year history of complex regional pain syndrome type I of the right forearm and hand in the radial sensory nerve distribution. There was no recognized antecedent trauma and she had failed both medical treatment and radial sensory nerve decompression surgery. An ultrasound-guided local anesthetic block of the radial nerve in the upper arm resulted in partial and temporary improvement in pain. She subsequently underwent trial of a peripheral nerve stimulator (PNS) followed by permanent PNS implant placement over the radial nerve proper proximal to the elbow. Within the first month of use, she endorsed substantially improved pain and strength in her right hand. These improvements were sustained for more than 1 year. Applications of PNS technology for treatment of extremity complex regional pain syndrome and neuropathic extremity pain in general are reviewed.

Prosthetic Fitting Concepts after Major Amputation in the Upper Limb - an Overview of Current Possibilities

The upper extremity and particularly the hands are crucial for patients in interacting with their environment, therefore amputations or severe damage with loss of hand function significantly impact their quality of life. In cases where biological reconstruction is not feasible or does not lead to sufficient success, bionic reconstruction plays a key role in patient care. Classical myoelectric prostheses are controlled using two signals derived from surface electrodes in the area of the stump muscles. Prosthesis control, especially in high amputations, is then limited and cumbersome. The surgical technique of Targeted Muscle Reinnervation (TMR) offers an innovative solution: The major arm nerves that have lost their target organs due to amputation are rerouted to muscles in the stump area. This enables the establishment of cognitive control signals that allow significantly improved prosthesis control. A selective literature review on TMR and bionic reconstruction was conducted, incorporating relevant articles and discussing them considering the clinical experience of our research group. Additionally, a clinical case is presented. Bionic reconstruction combined with Targeted Muscle Reinnervation enables intuitive prosthetic control with simultaneous movement of various prosthetic degrees of freedom and the treatment of neuroma and phantom limb pain. Long-term success requires a high level of patient compliance and intensive signal training during the prosthetic rehabilitation phase. Despite technological advances, challenges persist, especially in enhancing signal transmission and integrating natural sensory feedback into bionic prostheses. TMR surgery represents a significant advancement in the bionic care of amputees. Employing selective nerve transfers for signal multiplication and amplification, opens up possibilities for improving myoelectric prosthesis function and thus enhancing patient care. Advances in the area of external prosthetic components, improvements in the skeletal connection due to osseointegration and more fluid signal transmission using wireless, fully implanted electrode systems will lead to significant progress in bionic reconstruction, both in terms of precision of movement and embodiment.

Bifurcation of the Radial Nerve in the Arm as a Cause of Traumatic Partial Nerve Palsy: A Case Report

Purpose: To describe the case of a traumatic partial nerve palsy following an open crushing arm injury. The partial palsy was due to the presence of radial nerve bifurcation in the proximal arm. Methods: A 23-year-old male was involved in a motor vehicle accident, where his motorbike crushed against a steel road divider sustaining multiple injuries in the spine, thorax, and right arm. On clinical examination, the patient presented a deep, blunt trauma on the posterior aspect of the proximal arm and partial radial nerve palsy was diagnosed with preservation of the brachioradialis and the extensor radialis longus muscle function. Surgical exploration was carried out. Results: An extensible posterior approach to the arm was performed and two main radial nerve branches were found. The lateral, more sizeable nerve, had an epineural hematoma without any distal response during intraoperative stimulation. The medial, thinner nerve trunk was preserved and, when stimulated, elicited response from the brachioradialis. Conclusion: We describe an uncommon variation of the radial nerve which was associated with partial palsy following blunt force trauma. This anatomical variation should be kept in mind in cases like the one described.

The anatomical variations of median nerve in Shiraz, Iran.

The origin and distribution of median nerve varies among the different individuals. The median nerve variations in axillary region were reported by many authors previously. Understanding of these variations is especially necessary for clinicians to prevent iatrogenic nerve damage. The current work aimed to evaluate the possible anatomical variations of median nerve in the axillary region in a sample of the Iranian cadavers (Shiraz, Fars). We dissected 26 upper limbs from 13 male cadavers to investigate the different variations of median and musculocutaneous nerves according to Venieratos and Anagnostopoulou classification. In 23.07% of specimens (n=6), the medial root united with 2 lateral roots and formed the median nerve proximal to the coracobrachialis muscle. In one case, a communicating branch separated from the musculocutaneous nerve distal to the coracobrachialis and connected to the median nerve in upper arm. Our results suggest that there are anatomical variations of the median nerve in terms of its origin and its communication with the musculocutaneous nerve in the population of southern Iran. The anatomical knowledge of the median nerve variations is important for clinicians to improve patient health outcome. Theses variations of the median nerve should be considered during surgical procedures of the axillary region and nerve block of the infra clavicular part of the brachial plexus.

Reference Values of Shear Wave Elastography of Median and Tibial Nerve in Healthy Population: A Cross-sectional Study

Introduction: Peripheral nerves are rarely assessed using high- resolution Ultrasonography (USG). Computed Tomography (CT) and Magnetic Resonance Imaging (MRI) scans can be costly and occasionally inaccessible. In contrast, USG provides a dynamic, portable and cost-effective method for evaluating peripheral nerves. Shear Wave Elastography (SWE) is a relatively recent ultrasound-based technique that quantitatively measures tissue stiffness. Aim: To determine the reference values for SWE measurements of the median and tibial nerves in healthy individuals and to explore potential associations with age, gender, height, weight and Body Mass Index (BMI) of the subjects. Materials and Methods: The present cross-sectional study was conducted in the Radiodiagnosis and Imaging Unit, Sri Guru Ram Das Institute of Medical Sciences and Research, Sri Amritsar, Punjab, India, from October 2022 to April 2024, involved 100 subjects (45 males and 55 females). Subjects were deemed eligible for the study following evaluation by a general physician. The study was conducted over a period of one year. High-resolution real-time USG was utilised to assess the median and tibial nerves in both arms and legs bilaterally. SWE was conducted on the tibial and median nerves, and the velocities generated were subsequently evaluated to establish baseline levels for the peripheral nerves. Collected data were transformed, coded and entered into Microsoft Excel, then analysed using Statistical Package for Social Sciences (SPSS) software version 25.0 (SPSS-PC-25). Parametric data were expressed as mean±Standard Deviation (SD) or median and compared using the Mann-Whitney U test. Results: The mean age of healthy subjects was 41.18±12.34 years, while the weight and height were 72.59±7.44 kg and 172.74±6.75 cm, respectively. The average velocities generated in healthy subjects (45 males and 55 females) using SWE were found to be 3.606±0.133 m/s and 3.632±0.173 m/s for the left and right median nerves (p-value &gt;0.05), and 3.626±0.140 m/s and 3.623±0.138 m/s for the left and right tibial nerves (p-value&gt;0.05), respectively. The SWE measurements obtained from the bilateral median and tibial nerves showed no significant differences in their values, indicating no significant association (p-value&gt;0.05). No significant correlation was found between the SWE measurements and age, sex, height, weight, or BMI of the subjects (p-value&gt;0.05). Conclusion: The present study serves as an initial step in gathering tibial nerve stiffness values from healthy participants using SWE and exploring the factors affecting nerve stiffness.

Neural coordination of bilateral hand movements: evidence for an involvement of brainstem motor centres.

Bilateral hand movements are assumed to be coordinated by a neural coupling mechanism. Neural coupling is experimentally reflected in complex electromyographic (EMG) responses in the forearm muscles of both sides to unilateral electrical arm nerve stimulation (ES). The aim of this study was to examine a potential involvement of the reticulospinal system in neural coupling by the application of loud acoustic stimuli (LAS) known to activate neurons of this system. LAS, ES and combined LAS/ES were applied to healthy subjects during visually guided bilateral hand flexion-extension movements. Muscle responses to the different stimuli were evaluated by electrophysiological recordings. Unilateral electrical ulnar nerve stimulation resulted in neural coupling responses in the forearm extensors (FE) of both sides. Interestingly, LAS evoked bilateral EMG responses that were similar in their configuration to those induced by ES. The presence of startles was associated with a shift of the onset and enhanced amplitude of LAS-induced coupling-like responses. Upon combined LAS/ES application, ES facilitated ipsilateral startles and coupling-like responses. Modulation of coupling-like responses by startles, the similarity of the responses to ES and LAS, and their interaction following combined stimulation suggests that both responses are mediated by the reticulospinal system. Our findings provide novel indirect evidence that the reticulospinal system is involved in the neural coupling of hand movements. This becomes clinically relevant in subjects with a damaged corticospinal system where a dominant reticulospinal system leads to involuntary limb coupling, referred to as associated movements. KEY POINTS: Automatic coordination of hand movements is assumed to be mediated by a neural coupling mechanism reflected by bilateral reflex responses in forearm muscles to unilateral electrical arm nerve stimulation (ES). Loud acoustic stimuli (LAS) were applied to assess a potential involvement of the reticulospinal system in the neural coupling mechanism. LAS evoked a bilateral reflex response in the forearm extensors that was similar to the neural coupling response to ES, and which could be separated from the acoustic startle response. Combined application of LAS and ES resulted in a facilitation of startle and coupling-like responses ipsilateral to ES, thus indicating an interaction of afferences from both stimuli. These novel findings provide indirect evidence that the reticulospinal system is a key motor structure for the coupling of bilateral hand movements.

How a Robotic Visualization System Can Facilitate Targeted Muscle Reinnervation

Abstract Background Innovations in medical technologies have impacted surgery sustainably in the last decades. To enable and further improve microsurgical outcomes, different loupes and optic-based microscopes have been proposed in recent years. In amputation surgery continuous progress and prosthetic developments have provided amputees with an improved degree of function and quality of life.Herein, we present a 17-year-old patient who suffered a traumatic loss of the left upper limb and underwent target muscle reinnervation surgery facilitated by a three-dimensional (3D) robotic exoscope system. Methods The rerouting of the distal ends of the arm nerves (TMR) was performed in the upper limb of a traumatic transhumeral amputee patient using a 3D robotic exoscope system (RS, RoboticScope, BHS Technologies, Innsbruck, Austria). Perioperative data was collected and compared to standard. Users' perspective evaluation of the system during the surgical procedure was done using a 5-point Likert scale. Results Operation time was 311 minutes, the robotic system was used for 101 minutes. Overall users' evaluation revealed a 4.5 for the selected items on the Likert scale. The evaluation showed similar results in the evaluation of the system by the main and assistant surgeons. No special training was required beforehand. The bimanual control allowed for improved personal freedom in the surgical field at a comfortable position. The imaging of colors will need future improvements until an authentic representation of in situ structures is achieved. Conclusion Major advantages of a robotic scope 3D exoscope system are improved image quality, ergonomic position, and increased accessibility in a wider operating field due to system-implied features. Another benefit is digital documentation and simultaneous education through the possibility of capturing images and videos, as well as easy transportation in between operating rooms without risk to harm the vulnerable optic. Digital microscopes are still associated with high acquisition costs, and they are not yet implemented as standard of care due to limited experience.

Visualization of axonal and volume currents in median nerve compound action potential using magnetoneurography

ObjectiveReconstruct compound median nerve action currents using magnetoneurography to clarify the physiological characteristics of axonal and volume currents and their relationship to potentials. MethodsThe median nerves of both upper arms of five healthy individuals were investigated. The propagating magnetic field of the action potential was recorded using magnetoneurography, reconstructed into a current, and analyzed. The currents were compared with the potentials recorded from multipolar surface electrodes. ResultsReconstructed currents could be clearly visualized. Axonal currents flowed forward or backward in the axon, arcing away from the depolarization zone, turning about the subcutaneous volume conductor, and returning to the depolarization zone. The zero-crossing latency of the axonal current was approximately the same as the peak of its volume current and the negative peak of the surface electrode potential. Volume current waveforms were proportional to the derivative of axonal ones. ConclusionsMagnetoneurography allows the visualization and quantitative evaluation of action currents. The currents in axons and in volume conductors could be clearly discriminated with good quality. Their properties were consistent with previous neurophysiological findings. SignificanceMagnetoneurography could be a novel tool for elucidating nerve physiology and pathophysiology.

Evaluation of Percutaneous Peritoneal Drainage Among Patients with High Risk Perforated Peritonitis in Tertiary Care Hospital

Objective: This study aimed to share our experience in treating various types of injection-induced peripheral nerve injuries and explore numerous problems that are related to this category of peripheral nerve injuries. Study Design: Retrospective study Place and Duration: Department of Neurosurgery, Gomal Medical College DI Khan in the duration from October, 2022 to March, 2023. Methods: Total 130 patients of both gender with age 8-70 years were included. Patients with post-operative peripheral nerve injuries were following intramuscular injections, brachial nerves block procedures, subclavian and jugular venous cannulation procedures for central line placements, and routine intravenous injections in the peripheral veins of the limbs. Frequency of peripheral nerve injuries and its management among all cases were assessed. SPSS 22.0 was used to analyze all data. Results: In all 130 patients, 82 (63.1%) cases were males and 48 (36.9%) patients were females. 45 (34.6%) patients had age 8-15 years, 30 (23.1%) cases had age 16-25 years, 33 (25.4%) cases had age 26-35 years and 22 (16.9%) patients had age &gt;35 years. Mean duration of peripheral nerve injury was 2.4±7.38 months. Most common reason was intramuscular injection found in 104 (80%) cases. Most common affected nerve was sciatic nerve in the gluteal region, the radial nerve in the arm and axillary nerve in the shoulder region. Non-functional status among all cases were found in 58 (44.6%) cases. Six (4.6%) of the patients in our series experienced neurological impairment following surgery in the form of motor weakness. The best outcomes, 115 (88.5%), were reported with the repair of the radial nerve after surgery. Conclusion: We came to the conclusion that a quick referral to a specialized peripheral nerve center, an early intervention, and early diagnosis are just a few crucial elements that can lead to a positive outcome and reduce the frequency of medicolegal lawsuits. By having in-depth anatomical understanding and providing patients with adequate counseling before to the treatment, the problem can be avoided in the vast majority of cases. Keywords: Peripheral nerve injury, Surgery, Improvement, Injection

Quantitative MR Neurography in Multifocal Motor Neuropathy and Amyotrophic Lateral Sclerosis

The aim of this study was to assess the phenotype of multifocal motor neuropathy (MMN) and amyotrophic lateral sclerosis (ALS) in quantitative MR neurography. In this prospective study, 22 patients with ALS, 8 patients with MMN, and 10 healthy volunteers were examined with 3T MR neurography, using a high-resolution fat-saturated T2-weighted sequence, diffusion-tensor imaging (DTI), and a multi-echo T2-relaxometry sequence. The quantitative biomarkers fractional anisotropy (FA), radial and axial diffusivity (RD, AD), mean diffusivity (MD), cross-sectional area (CSA), T2-relaxation time, and proton spin density (PSD) were measured in the tibial nerve at the thigh and calf, and in the median, radial, and ulnar nerves at the mid-upper arm. MMN showed a characteristic imaging pattern of decreased FA (p = 0.018), increased RD (p = 0.014), increased CSA (p < 0.001), increased T2-relaxation time (p < 0.001), and increased PSD (p = 0.025) in the upper arm nerves compared to ALS and controls. ALS patients did not differ from controls in any imaging marker, nor were there any group differences in the tibial nerve (p > 0.05). MMN shows a characteristic pattern of quantitative DTI and T2-relaxometry parameters in the upper-arm nerves, primarily indicating demyelination. Peripheral nerve changes in ALS seem to be below the detection level of current state-of-the-art quantitative MR neurography.

A portable, programmable, multichannel stimulator with high compliance voltage for noninvasive neural stimulation of motor and sensory nerves in humans

Most neural stimulators do not have a high enough compliance voltage to pass current through the skin. The few stimulators that meet the high compliance voltage necessary for transcutaneous stimulation are typically large benchtop units that are not portable, and the stimulation waveforms cannot be readily customized. To address this, we present the design and validation of a portable, programmable, multichannel, noninvasive neural stimulator that can generate three custom bipolar waveforms at ± 150 V with microsecond temporal resolution. The design is low-cost, open-source, and validated on the benchtop and with a healthy population to demonstrate its functionality for sensory and motor stimulation. Sensory stimulation included electrocutaneous stimulation targeting cutaneous mechanoreceptors at the surface of the skin and transcutaneous nerve stimulation targeting the median nerve at the wrist. Both electrocutaneous stimulation on the hand and transcutaneous stimulation at the wrist can elicit isolated tactile percepts on the hand but changes in pulse frequency are more discriminable for electrocutaneous stimulation. Also, neuromuscular electrical stimulation of the flexor digiti profundus is evoked by applying electrical stimulation directly above the muscle in the forearm and to the median and ulnar nerves in the upper arm. Muscle and nerve stimulation evoked similar grip forces and force rise times, but nerve stimulation had a significantly slower fatigue rate. The development and validation of this noninvasive stimulator and direct comparison of common sensory and motor stimulation targets in a human population constitute an important step towards more widespread use and accessibility of neural stimulation for education and research.

Unilateral Absence and Contralateral Communication Between Musculocutaneous and Median Nerve and Its Clinical Significance

Variations and Communications between the branches of different cords is not uncommon. Martin Gruber anastomosis, Berretini anastomosis and Cannieu and Riché anastomosis are few examples of such nerve communications. During routine anatomy dissection of axilla, in a 65 years old female cadaver, we found absence of musculocutaneous nerve in left upper limb. It was found that all the muscles of front of arm were supplied by median nerve on this side. When compared on the right side, there was one communication between musculocutaneous nerve and median nerve. This communicating branch was 75 mm long. All the muscles of anterior compartment of arm were supplied by MCN and the nerve continued afterwards as lateral cutaneous nerve of arm. The knowledge of such variations helps us in neurosurgeries like surgery for Neurofibromatosis. Orthopedic, general surgeons and neurosurgeons must consider the possibility of such variations in the surgery of arm and elbow. Surgeons who perform neurotization procedures of the musculocutaneous nerve to restore elbow flexion should be aware of these anatomical variations Cutting of such communicating branch can lead to altered mobility of limb.

Unilateral Absence and Contralateral Communication Between Musculocutaneous and Median Nerve and Its Clinical Significance

Variations and Communications between the branches of different cords is not uncommon. Martin Gruber anastomosis, Berretini anastomosis and Cannieu and Riché anastomosis are few examples of such nerve communications. During routine anatomy dissection of axilla, in a 65 years old female cadaver, we found absence of musculocutaneous nerve in left upper limb. It was found that all the muscles of front of arm were supplied by median nerve on this side. When compared on the right side, there was one communication between musculocutaneous nerve and median nerve. This communicating branch was 75 mm long. All the muscles of anterior compartment of arm were supplied by MCN and the nerve continued afterwards as lateral cutaneous nerve of arm. The knowledge of such variations helps us in neurosurgeries like surgery for Neurofibromatosis. Orthopedic, general surgeons and neurosurgeons must consider the possibility of such variations in the surgery of arm and elbow. Surgeons who perform neurotization procedures of the musculocutaneous nerve to restore elbow flexion should be aware of these anatomical variations Cutting of such communicating branch can lead to altered mobility of limb.

Detection and discrimination of electrical stimuli from an upper limb cuff electrode in M. Mulatta

Objective. Peripheral nerve interfaces seek to restore nervous system function through electrical stimulation of peripheral nerves. In clinical use, these devices should function reliably for years or decades. In this study, we assessed evoked sensations from multi-channel cuff electrode stimulation in macaque monkeys up to 711 d post-implantation. Approach. Three trained macaque monkeys received multi-channel cuff electrode implants at the median or ulnar nerves in the upper arm. Electrical stimuli from the cuff interfaces evoked sensations, which we measured via standard psychophysical tasks. We adjusted pulse amplitude or pulse width for each block with various electrode channel configurations to examine the effects of stimulus parameterization on sensation. We measured detection thresholds and just-noticeable differences (JNDs) at irregular, near-daily intervals for several months using Bayesian inferencing from trial data. We examined data trends using classical models such as Weber’s Law and the strength-duration relationship using linear regression. Main results. Detection thresholds were similar between blocks with pulse width modulation and blocks with pulse amplitude modulation when represented as charge per pulse, the product of the amplitude and the pulse width. Conversely, Weber fractions—calculated as the slope of the regression between JND charge values and reference stimulus charge—were significantly different between pulse width and pulse amplitude modulation blocks for the discrimination task. Significance. Weber fractions were lower in blocks with amplitude modulation than in blocks with pulse width modulation, suggesting that pulse amplitude modulation allows finer resolution of sensory encoding above threshold. Consequently, amplitude modulation may enable a greater dynamic range for sensory perception with neuroprosthetic devices.

STUDY OF ORIGIN OF BRANCHES OF THE RADIAL NERVE IN THE AXILLA, A CADAVERIC STUDY

Background: Radial nerve is the continuation of the posterior cord of the brachial plexus in the axilla. To know the mode of origin of Objectives: branches of the radial nerve in the axilla. Dissection was done on 44 upper li Methods: mbs from embalmed adult cadavers and 6 upper limbs from embalmed dead fetuses in the Department of Anatomy, J J M Medical College, Davangere. Dissection of Radial nerve and its branches in the axilla was carried out according to Cunningham's manual of practical anatomy. Results: The order of origin of the branches of the radial nerve in the axilla was posterior cutaneous nerve of arm(PCNA), nerve to long head of tricep( NLHT) and ulnar collateral nerve (UCN). Two types of common trunks were observed. Common trunk 1 (CT1) dividing to give nerve to long head of tricep(NLHT) and ulnar collateral nerve(UCN) in 2 specimens (4%). Common trunk 2 (CT2) dividing to give nerve to long head of tricep(NLHT), ulnar collateral nerve(UCN) and posterior cutaneous nerve of arm (PCNA) in 1 specimens (2%). The origin of Nerve to long head of triceps (NLHT) was directly from the radial nerve (RN) in 47 specimens (94%) , through common trunk 1 (CT1) in 2 specimens (4%) and through common trunk 2 (CT2) in 1 specimens (2%). The origin of ulnar collateral nerve (UCN) was directly from the radial nerve (RN) in 47 specimens (94%) , through common trunk 1 (CT1) in 2 specimens (4%) and through common trunk 2 (CT2) in 1 specimens (2%). The origin of Posterior cutaneous nerve of arm(PCNA) was directly from the radial nerve (RN) in 49 specimens (98%) and through common trunk 2 (CT2) in 1 specimens (2%). The present Interpretation and Conclusion: study is important for Surgeons, Orthopedicians, and Neurophysicians as it provides the knowledge of mode of origin of branches of radial nerve in the axilla.

Rare Branching Pattern of Brachial Plexus- A Case Series

Introduction: The musculocutaneous nerve is one of the branches from the lateral cord of brachial plexus. This nerve is solely devoted to the flexor compartment of arm hence it is called as nerve of arm. Numerous studies have been reported about the variations of this nerve but the real prevalence is still unknown, whereas, it may be hypothetical. Case report: This study shows a rare branching pattern where a thin nerve takes origin from the medial fasciculus of brachial plexus which then pierces the coracobrachialis and lies between the biceps brachii and brachialis. The nerve then pierces the biceps to supply the skin over the lateral surface of forearm. The median nerve took over the muscular branches of musculocutaneous nerve by giving off the branches to both biceps and brachialis.