Mutual oligosynaptic inhibition of group Ia afferents between the anterior and posterior parts of the deltoid in humans.

The anterior (DA) and posterior parts of the deltoid (DP) show alternating contraction during shoulder flexion and extension movements. It is expected that an inhibitory spinal reflex between the DA and DP exists. In this study, spinal reflexes between the DA and DP were examined in healthy human subjects using post-stimulus time histogram (PSTH) and electromyogram averaging (EMG-A). Electrical conditioning stimulation was delivered to the axillary nerve branch that innervates the DA (DA nerve) and DP (DP nerve) with the intensity below the motor threshold. In the PSTH study, the stimulation to the DA and DP nerves inhibited (decrease in the firing probability) 31 of 54 DA motor units and 31 of 51 DP motor units. The inhibition was not provoked by cutaneous stimulation. The central synaptic delay of the inhibition between the DA and DP nerves was 1.5 ± 0.5 ms and 1.4 ± 0.4 ms (mean ± SD) longer than those of the homonymous facilitation of the DA and DP, respectively. In the EMG-A study, conditioning stimulation to the DA and DP nerves inhibited the rectified and averaged EMG of the DP and DA, respectively. The inhibition diminished with tonic vibration stimulation to the DA and DP and recovered 20-30 min after vibration removal. These findings suggest that oligo(di or tri)-synaptic inhibition mediated by group Ia afferents between the DA and DP exists in humans.

Thickness of the Deltoid Muscle and Location of the Anterior Branch of the Axillary Nerve and the Posterior Circumflex Humeral Artery for Deltoid Injections.

This study investigated the thickness of the deltoid muscle and the location of the anterior branch of the axillary nerve (AAN) and posterior circumflex humeral artery (PCHA), with the goal of maximizing the effectiveness of deltoid injections. Forty specimens from 22 adult Korean cadavers were used. A reference line was identified, connecting the anterior point of the deltoid muscle (AP) and the posterior point of the deltoid muscle (PP) on the surface. The midpoint between the AP and PP was used as the origin point (OP). The line connecting the OP and the lowest point of the deltoid tuberosity (DP) was used as the y-axis. The mean distance of the reference line from the AP to PP was 4.7 ± 0.7 cm. The vertical mean length of the deltoid muscle from the OP and DP was 16.1 ± 1.0 cm. At the 3, 5, and 7 cm sites, the thickness of the deltoid muscle was 0.62 ± 0.9, 0.73 ± 0.7, and 1.3 ± 1.1 cm, respectively. Most of the branches of the axillary nerve were concentrated in the third section (4-6 cm, 51%), while the branches of the PCHA were predominantly found in the fourth section (6-8 cm, 69%). The peripheral branches of the AAN entering the muscle were distributed between 2.2 and 9.8 cm from the acromion. The mean number of the peripheral branches of the AAN was 9.6 ± 3.4. In the deltoid muscle, the mean number of peripheral branches of the PCHA was 8.2 ± 2.8. Administering deltoid injections 5-6 cm below the OP is recommended to avoid axillary nerve injury.

C6 and not C5 nerve fibers more commonly contribute most to deltoid muscle innervation: anatomical study with application to better diagnosing cervical nerve injuries.

Most anatomical textbooks list both the C5 and C6 spinal nerves as contributing to the deltoid muscle's innervation via the axillary nerve. To our knowledge, no previous study has detailed the exact spinal nerve components of the axillary nerve terminating in the deltoid via cadaveric dissection. Twenty formalin-fixed cadavers (40 sides) underwent dissection of the brachial plexus. The fascicles making up the axillary nerve branch that specifically terminated in the deltoid muscle were traced proximally. The axillary nerve branch to the deltoid muscle was most commonly (70%) made up of three spinal nerve segments and less commonly (30%) by two spinal nerve segments. For all axillary nerve branches to the deltoid muscle, C4 spinal nerves contributed 0-5%, C5 spinal nerves contributed 1-80%, C6 spinal nerve contributed 15-99%, C7 spinal nerves contributed 0-30%, and C8 and T1 spinal nerves were not found to contribute any fibers to any deltoid muscle branches. The nerve to the deltoid muscle was contributed to equally by C5 and C6 nerve fibers on 10% of sides. On 16% of sides, C5 contributed the most nerve fibers to this muscle. On 35% of sides, C6 contributed the majority fibers found in the axillary nerve branches to the deltoid. Based on our anatomical study, C6 is more often than not the main level of innervation. C5 was never the sole component of the axillary nerve branches to the deltoid muscle. Such anatomical data will now need to be reconciled with clinical studies.

C5 Palsy Following Cervical Spine Decompression.

BACKGROUND: Cervical spinal surgery is considered safe and effective. One of the few specific complications of this procedure is C5 nerve root palsy. Expressed primarily by deltoid muscle and biceps brachii weakness, it is rare and has been related to nerve root traction or to ischemic spinal cord damage. OBJECTIVES: To determine the clinical and epidemiological traits of C5 palsy. To determine whether C5 palsy occurs predominantly in one specific surgical approach compared to others. METHODS: A retrospective study of patients who underwent cervical spine surgery at our medical center during a consecutive 8-year period was conducted. The patient data were analyzed for demographics, diagnosis, and surgery type and approach, as well as for complications, with emphasis on the C5 nerve root palsy. RESULTS: The study group was comprised of 124 patients. Seven (5.6%) developed a C5 palsy following surgery. Interventions were either by anterior, by posterior or by a combined approach. Seven patients developed this complication. All of whom had myelopathy and were older males. A combined anteroposterior (5 patients) and posterior access (2 patients) were the only approaches that were associated with the C5 palsy. None of the patients who were operated via an anterior approach did develop this sequel. CONCLUSIONS: The incidence of the C5 root palsy in our cohort reached 5.6%. Interventions performed through a combined anterior-posterior access in older myelopathic males, may carry the highest risk for this complication.

Musculoskeletal ultrasound diagnosis of quadrilateral space syndrome: A case report.

INTRODUCTION: Quadrilateral space syndrome (QSS) is a peripheral nerve entrapment disease, which can be misdiagnosed in clinic. In the past, QSS was mainly diagnosed by clinical symptoms combined with magnetic resonance imaging (MRI), electromyography (EMG), and arterial angiography. There are few reports on the diagnosis of QSS by musculoskeletal ultrasound (MSKUS) combined with clinical symptoms. PATIENT CONCERNS: A middle-aged female patient had posterolateral pain and numbness in her right shoulder for 2 months. DIAGNOSES: At first, she was diagnosed as suprascapular nerve entrapment, while EMG of suprascapular nerve and axillary nerve indicated that nerve conduction was normal. Then, MRI was performed, showing the shoulder had no abnormalities, and EMG and arterial angiography of upper limb showed no abnormalities too. Finally, she was diagnosed as QSS according to MSKUS and lidocaine block test. INTERVENTIONS: Two sealing treatments of axillary nerve block in quadrilateral space under the guidance of MSKUS were performed. OUTCOMES: After 2 treatments, the pain and numbness in her shoulder disappeared, and her shoulder could move normally. There was no recurrence after 3 months of follow-up. CONCLUSION: MSKUS is an effective method to diagnose QSS. It is fast, convenient and inexpensive, and is worth popularizing in clinic.

Effect of surgical approaches on deltoid innervation and clinical outcomes in the treatment of proximal humeral fractures.

OBJECTIVES: This study aims to investigate the effects of deltopectoral and anterolateral acromial approaches commonly used in open reduction-internal fixation of proximal humeral fractures on the clinical outcomes, and axillary nerve damage through electrophysiological assessment. PATIENTS AND METHODS: Forty-eight patients (22 males, 26 females; mean age 47.9±13.2 years; range, 22 to 73 years) diagnosed with Arbeitsgemeinschaft für Osteosynthesefragen (AO)/Orthopaedic Trauma Association (OTA) type 11 proximal humeral fractures who underwent osteosynthesis with anatomical locking plates in our hospital between January 2015 and June 2016 were prospectively examined. The patients were divided into two groups according to either the deltopectoral or anterolateral deltoid-split surgical approach used. Clinical outcomes were evaluated using the Disabilities of the Arm, Shoulder, and Hand (DASH) scores and Constant-Murley scores (CMS) obtained at three- and 12-month follow-up visits. Needle electromyography (EMG) was performed for the electrophysiological assessment of the deltoid muscle. RESULTS: There were no significant differences between the groups in terms of demographic data, follow-up times, and complications. DASH scores and CMS obtained postoperatively at three months (p=0.327 and p=0.531, respectively) and 12 months (p=0.324 and p=0.648, respectively) revealed no significant differences. In addition, the two groups did not significantly differ with respect to the presence of EMG abnormalities (p=0.792). Avascular necrosis of the humeral head was detected in only two patients from the deltopectoral group. CONCLUSION: Deltopectoral and anterolateral approaches do not differ regarding the presence of postoperative EMG abnormalities and functional outcomes. Surgeons can thus adopt either approach. However, dissection without damaging the soft tissue should be performed in both approaches.

Isolated Axillary Nerve Rupture due to Closed Nondislocating Injury of the Shoulder in Contact Sports: A Report of 2 Cases.

CASE: Axillary nerve rupture without shoulder joint fracture or dislocation in contact sports is very rare. To date, there has been no detailed report on such cases. We present 2 rare cases of axillary nerve rupture in contact sports who were successfully treated with free nerve grafting. CONCLUSION: In contact sports, the deltoid muscle is sometimes paralyzed temporarily after a collision. However, similar to our cases, the axillary nerve can be lacerated without fracture or dislocation. It is necessary to watch the course of paralysis carefully and consider nerve reconstruction if it does not recover.

Optimal reference electrode placement for accessory and axillary nerve conduction studies.

BACKGROUND: Various techniques are described for proximal motor nerve conduction studies (NCSs). We investigated alternative reference electrode (E2) locations for accessory and axillary NCSs. METHODS: Multi-channel recordings were made from trapezius or deltoid referred to different sites, and from those sites referred to a remote electrode. Responses were compared using grouped statistics, and correlation analysis. RESULTS: For accessory NCSs, all belly:E2 montages showed comparable responses but axillary NCSs were more variable. Low amplitude contamination was seen at the sternum and contralateral acromion but greater distortion using other potential E2 sites. In both accessory and axillary studies, the ipsilateral acromion showed moderate activity, which correlated with the belly:remote response. CONCLUSIONS: Variation in E2 electrode sites may significantly distort the measured compound muscle action potential (CMAP). For accessory and axillary NCS, a sternal reference has favorable characteristics. Other sites, such as ipsilateral acromion or deltoid insertion, may not yield a representative CMAP.

Effects of neuromuscular electrical stimulation in patients with pulmonary arterial hypertension: a randomized controlled pilot study.

BACKGROUND: Patients with pulmonary arterial hypertension (PAH) present impairments in muscle strength and exercise capacity. There is growing evidence about the benefits of neuromuscular electrical stimulation (NMES) in patients with respiratory diseases, except in patients with PAH. The aim of this study was to investigate the effects of NMES on muscle strength, and other physical and psychosocial variables in patients with PAH. METHODS: Patients with PAH were randomly divided into two groups as NMES and control. The NMES was applied to the bilateral deltoid and quadriceps femoris muscles with 50 Hz for 3 days/week, 8 weeks for the NMES group. Muscle strength, muscle cross-sectional area and thickness, arterial stiffness, exercise capacity, functional mobility and balance, balance confidence, fatigue, physical activity, and quality of life were assessed at baseline and after 8 weeks by blinded assessors. RESULTS: There was no significant difference in the demographic and clinical characteristics between the patient groups (p > 0.05). The improvements in muscle strength, muscle cross-sectional area and thickness, pulse wave velocity, exercise capacity, functional mobility and balance, balance confidence, fatigue, physical activity, and quality of life were significantly higher in the NMES group compared to the control group (p < 0.05). CONCLUSIONS: This study suggests that NMES intervention is safe and effective for patients with PAH.

Innervation of the clavicular part of the deltoid muscle by the lateral pectoral nerve.

INTRODUCTION: The innervation pattern of the clavicular head of the deltoid muscle and its corresponding topography was investigated via cadaveric dissection in the present study, focusing on the lateral pectoral nerve. MATERIALS AND METHODS: Fifty-eight upper extremities were dissected and the nerve supplies to the deltoid muscle and the variability of the lateral pectoral and axillary nerves, including their topographical patterns, were noted. RESULTS: The clavicular portion of the deltoid muscle received a deltoid branch from the lateral pectoral nerve in 86.2% of cases. Two topographical patterns of the lateral pectoral nerve were observed, depending on the branching level from the brachial plexus: a proximal variant, where the nerve entered the pectoral region under the clavicle, and a distal variant, where the nerve entered the pectoral region from the axillary fossa around the caudal border of the pectoralis minor. These dissection findings were supported by histological confirmation of peripheral nerve tissue entering the clavicular part of the deltoid muscle. CONCLUSIONS: The topographical variations of the lateral pectoral nerve are relevant for orthopedic and trauma surgeons and neurologists. These new data could revise the interpretation of deltoid muscle atrophy and of thoracic outlet and pectoralis minor compression syndromes. They could also explain the residual anteversion function of the arm after axillary nerve injury and deficiency, which is often thought to be related to biceps brachii muscle function.

Examination of the human motor endplate after brachial plexus injury with two-photon microscopy.

INTRODUCTION: After traumatic nerve injury, neuromuscular junction remodeling plays a key role in determining functional outcomes. Immunohistochemical analyses of denervated muscle biopsies may provide valuable prognostic data regarding clinical outcomes to supplement electrodiagnostic studies. METHODS: We performed biopsies on nonfunctioning deltoid muscles in two patients after gunshot wounds and visualized the neuromuscular junctions using two-photon microscopy with immunohistochemistry. RESULTS: Although the nerves in both patients showed evidence of acute Wallerian degeneration, some of the motor endplates were intact but exhibited significantly decreased surface area and volume. Both patients exhibited substantial recovery of motor function over several weeks postinjury. DISCUSSION: Two-photon microscopic assessment of neuromuscular junction integrity and motor endplate morphometry in muscle biopsies provided evidence of partial sparing of muscle innervation. This finding supported the clinical judgment that eventual recovery would occur. With further study, this technique may help to guide operative decisionmaking after traumatic nerve injuries.

What Is the Survival and Function of Modular Reverse Total Shoulder Prostheses in Patients Undergoing Tumor Resections in Whom an Innervated Deltoid Muscle Can Be Preserved?

BACKGROUND: After proximal humerus resection for bone tumors, restoring anatomy and shoulder function remains demanding because muscles and bone are removed to obtain tumor-free surgical margins. Current modes of reconstruction such as anatomic modular prostheses, osteoarticular allografts, or allograft-prosthetic composites and arthrodeses are associated with relatively poor shoulder function related to loss of the deltoid and rotator cuff muscles. Newer prosthetic designs like the reverse total shoulder arthroplasty (RTSA) are felt to be useful in other reconstructions where rotator cuff function is compromised, so it seemed logical that it might help in tumor reconstructions as well in patients where the deltoid muscle and its innervation can be preserved. QUESTIONS/PURPOSES: In patients with a tumor of the proximal humerus that can be resected with preservation of the deltoid muscle, (1) What complications are associated with tumor resection and reconstruction with a modular RTSA? (2) What are the functional results of modular RTSA in these patients? METHODS: From January 2011 to January 2018, we treated 52 patients for bone tumors of the proximal humerus. Of these, three patients were treated with forequarter amputation, 14 were treated with standard modular proximal humerus implants, seven were treated with allograft-prosthetic composites (RTSA-APC), and 28 were treated with a modular RTSA. Generally, we used anatomic modular prosthetic reconstruction if during the tumor resection none of the abductor mechanism could be spared. Conversely, we preferred reconstruction with RTSA if an innervated deltoid muscle could be spared, but the rotator cuff and capsule could not, using RTSA-APC or modular RTSA if humeral osteotomy was distal or proximal to deltoid insertion, respectively. In this study, we retrospectively analyzed only patients treated with modular RTSA after proximal humerus resection. We excluded three patients treated with modular RTSA as revision procedures after mechanical failure of previous biological reconstructions and three patients treated after December 2016 to obtain an expected minimum follow-up of 2 years. There were nine men and 13 women, with a mean (range) age of 55 years (18 to 71). Reconstruction was performed in all patients using silver-coated modular RTSA protheses. Patients were clinically checked according to oncologic protocol. Complications and function were evaluated at final follow-up by the treating surgeon (PR) and shoulder surgeon (AC). Complications were evaluated according to Henderson classification. Functional results were assessed with the Musculoskeletal Tumor Society score (range 0 points to 30 points), Constant-Murley score (range 0 to 100), and American Shoulder and Elbow Surgeons score (range 0 to 100). The statistical analysis was performed using Kaplan-Meier curves. RESULTS: Complications occurred in five of 22 patients; there was a shoulder dislocation (Type I) in four patients and aseptic loosening (Type II) in one. Function in these patients on the outcomes scales we used was generally satisfactory; the mean Musculoskeletal Tumor Society score was 29, the mean Constant score was 61, and the mean American Shoulder and Elbow Surgeons score was 81. CONCLUSIONS: Although this was a small series of patients with heterogeneous diagnoses and resection types, and we were not able to directly compare the results of this procedure with those of other available reconstructions, we found patients treated with RTSA achieved reasonable shoulder function after resection and reconstruction of a proximal humerus tumor. It may not be valuable in all tumor resections, but in patients in whom the deltoid can be partly spared, this procedure appears to reasonably restore short-term shoulder function. However, future larger studies with longer follow-up are needed to confirm these findings. LEVEL OF EVIDENCE: Level IV, therapeutic study.

A new risk to the axillary nerve during percutaneous proximal humeral plate fixation using the Synthes PHILOS aiming system.

BACKGROUND: Percutaneous aiming arms have been developed to minimize injury during placement of submuscular proximal humerus plates. The purpose of this study was to determine the risk of axillary nerve injury during percutaneous proximal humeral plate fixation using the Synthes PHILOS aiming system. METHODS: By use of 10 fresh-frozen cadavers (20 shoulders), a 3.5-mm locking compression proximal humeral plate was fixated percutaneously to the humerus through a lateral deltoid-splitting approach using the PHILOS aiming guide. Dissection of the axillary nerve was then carried out, and measurements of its relation to the screw holes in row A through row G of the plate were taken. The lateral acromion-to-axillary nerve distance was also measured. RESULTS: The axillary nerve traversed row D in every shoulder, whereas it crossed over row C in 11 shoulders and both holes in row E in 16 shoulders. The closest distance to the axillary nerve achieved was 4.5 mm, corresponding to the distal (left) screw in row B. A significant negative correlation was found for the distance from the nerve to the closest proximal and distal screws (row B and row G, respectively) in both right shoulders (ρ = -0.797; 95% confidence interval, -0.916 to -0.548) and left shoulders (ρ = -0.615; 95% confidence interval, -0.831 to -0.237). CONCLUSION: The axillary nerve traverses rows C, D, and E of the proximal humeral plate using the PHILOS aiming system. Importantly, our study is the first to demonstrate that the axillary nerve crosses over row C. Left-sided plate screws also came in closer proximity to the axillary nerve than right-sided plate screws.

Clinical Anatomy for the Innervated Pattern and Boundary of the Subdeltoid Bursa.

The aim of this study was to accurately identify the distribution of sensory nerve branches running to bursa with mesoscopic dissection and boundaries following the injection of gelatin into the bursa. Eighteen shoulders of 11 Korean soft cadavers (average age, 65 years; age range, 43 - 88 years) were dissected. The most prominent point of greater tubercle of the humerus (GT) was used as a reference point. The horizontal line passing through GT was used as the x-axis while the vertical line passing through the GT was used as the y-axis. Average distances of the anterior, posterior, superior, and inferior from the GT were 1.9±0.6, 2.4±1.3, 2.1±0.7, and 3.2±1.5 cm, respectively. In 15 cases of 18 shoulders, the anterior branch of the axillary nerve was distributed to the subdeltoid bursa that was running posteriorly. The muscular branch of the anterior and middle parts of the deltoid was distributed to the branch of nerve that was running into the subdeltoid bursa. A branch of the posterior cord of brachial plexus was distributed to the subdeltoid bursa that was running anteriorly in three cases. Most of the branches of the axillary nerve were distributed into the posterolateral area. The branches of the posterior cord of brachial plexus were distributed in the anterolateral area. These results might be useful for preventing residual pain on the anterior shoulder region following an injection for the relief of shoulder pain.

Cadaveric Dissection of the Axillary Nerve: An Investigation of Extra-Muscular and Intra-Muscular Branching Patterns.

BACKGROUND: Variations in the axillary nerve branching patterns have been reported. The aim of the study is to investigate the extra- and intra-muscular course of the axillary nerve and quantify the regional innervation of the deltoid. METHODS: In fresh frozen specimens, the origin of the axillary nerve from the posterior cord of the brachial plexus and its extra- and intra-muscular course were identified. Muscle dimensions, branching patterns and the distance from the axillary nerve origin to major branches were measured. The weights of muscle segments supplied by major branches of the axillary nerve were recorded. RESULTS: Twenty-three cadaveric dissections were completed. The axillary nerve bifurcated within the quadrangular space in all cases. The mean distance from the origin to bifurcation of the axillary nerve was 39 ± 13 mm; from axillary nerve bifurcation to the teres minor branch was 13 ± 6 mm; and from axillary nerve bifurcation to the middle branch of anterior division was 26 ± 11 mm. The nerve to teres minor and superior lateral brachial cutaneous nerve originated from the posterior division or common trunk in all cases. No fibrous raphe were identified separating anterior, middle and posterior deltoid segments. The anterior division of axillary nerve supplied 85 ± 4% of the deltoid muscle (by weight). The posterior division supplied 15 ± 4% of the deltoid muscle (by weight). The posterior deltoid was supplied by both anterior and posterior divisions in 91.3% of cases. CONCLUSIONS: This study demonstrates a consistent branching pattern of the axillary nerve. The anterior division of the axillary nerve innervates all three deltoid segments in most instances (85% of the deltoid by weight). This study supports the concept of re-innervation of the anterior division alone in isolated axillary nerve injuries.

Diagnostic Utility of Repetitive Nerve Stimulation in a Large Cohort of Patients With Myasthenia Gravis.

PURPOSE: Optimizing the diagnostic utility of repetitive nerve stimulation in myasthenia gravis (MG) may include tailoring the examination to clinical phenotype. Therefore, we analyzed all available repetitive nerve stimulation parameters in a large cohort of patients with confirmed MG diagnosis. METHODS: All repetitive nerve stimulation examinations at the Uppsala University Hospital rendering an MG diagnosis during 1996 to 2014 were analyzed. The deltoid, trapezius, anconeus, nasalis, abductor digiti quinti, and frontalis muscles were examined. RESULTS: Two hundred one patients with MG were diagnosed. Abnormal amplitude decrement was found in 54% of patients with ocular MG, 77% of patients with predominantly bulbar fatigue, and in 83% of patients with predominantly limb fatigue. The deltoid muscle had the highest sensitivity in all MG subtypes, with a mean of 77% sensitivity in all clinical subtypes, and the most pronounced decrement for amplitude (P = 0.0002) and area (P < 0.0001). Technical issues were rare. CONCLUSIONS: These data contribute to further optimization of repetitive nerve stimulation strategies regarding muscle selection and technical performance in the electrodiagnostic workup of MG.

Interhemispheric interactions between trunk muscle representations of the primary motor cortex.

Unilateral arm movements require trunk stabilization through bilateral contraction of axial muscles. Interhemispheric interactions between primary motor cortices (M1) could enable such coordinated contractions, but these mechanisms are largely unknown. Using transcranial magnetic stimulation (TMS), we characterized interhemispheric interactions between M1 representations of the trunk-stabilizing muscles erector spinae at the first lumbar vertebra (ES L1) during a right isometric shoulder flexion. These interactions were compared with those of the anterior deltoid (AD), the main agonist in this task, and the first dorsal interosseous (FDI). TMS over the right M1 elicited ipsilateral silent periods (iSP) in all three muscles on the right side. In ES L1, but not in AD or FDI, ipsilateral motor evoked potential (iMEP) could precede the iSP or replace it. iMEP amplitude was not significantly different whether ES L1 was used to stabilize the trunk or was voluntarily contracted. TMS at the cervicomedullary junction showed that the size of cervicomedullary evoked potential was unchanged during the iSP but increased during iMEP, suggesting that the iSP, but not the iMEP, is due to intracortical mechanisms. Using a dual-coil paradigm with two coils over the left and right M1, interhemispheric inhibition could be evoked at interstimulus intervals of 6 ms in ES L1 and 8 ms in AD and FDI. Together, these results suggest that interhemispheric inhibition is dominant when axial muscles are involved in a stabilizing task. The ipsilateral facilitation could be evoked by ipsilateral or subcortical pathways and could be used depending on the role axial muscles play in the task.NEW & NOTEWORTHY The mechanisms involved in the bilateral coordination of axial muscles during unilateral arm movement are poorly understood. We thus investigated the nature of interhemispheric interactions in axial muscles during arm motor tasks in healthy subjects. By combining different methodologies, we showed that trunk muscles receive both inhibitory and facilitatory cortical outputs during activation of arm muscles. We propose that inhibition may be conveyed mainly through interhemispheric mechanisms and facilitation by subcortical mechanisms or ipsilateral pathways.

Utility of repetitive nerve stimulation test for ALS diagnosis.

OBJECTIVE: Decremental responses in the repetitive nerve stimulation (RNS) test in amyotrophic lateral sclerosis (ALS) patients have been reported, although their possible diagnostic role has received little investigation. We investigated their diagnostic role in differentiation between ALS and cervical spondylotic amyotrophy (CSA), an important ALS mimic especially in Japan. METHODS: Patients were prospectively enrolled and the diagnosis was confirmed by follow-up. RNS was performed on the abductor pollicis brevis (APB), upper trapezius (trapezius) and deltoid muscles. RESULTS: Enrolled subjects consisted of 53 ALS and 37 CSA patients. Abnormal decremental responses (>5%) were observed in 32%, 51% and 75% of ALS patients and 3%, 0% and 20% of CSA patients for the APB, trapezius and deltoid muscles, respectively. The sensitivity for 23 ALS patients with upper-limb onset was 78% for the trapezius and 100% for the deltoid muscles. CONCLUSIONS: An abnormal decremental response in the trapezius muscle was 100% specific to ALS in comparison with CSA: abnormal decrement in this muscle would strongly suggest ALS. No decrement in the deltoid muscle might exclude ALS in patients having symptoms with upper-limb onset. SIGNIFICANCE: RNS is useful in differentiation between ALS and CSA.

Outcomes Following Closed Axillary Nerve Injury: A Case Report and Review of the Literature.

We report a case of a 43-year-old male who sustained an axillary nerve injury secondary to a glenohumeral joint dislocation at a young age, and who has served over 20 years in the military with near normal shoulder function. In addition, we review the literature for the natural history of axillary nerve injury. A 43-year-old male sustained a left anterior glenohumeral dislocation in a motor vehicle accident as an 18-year-old. Following prompt manual reduction and subsequent physical therapy, the patient developed a permanent axillary nerve palsy. Despite the development of complete atrophy of his deltoid musculature and persistent sensory loss in the axillary nerve distribution, he experienced restoration of function with minimal to no deficit. Ultimately, he enlisted in the military 4 years after the injury and has served 22 years, which includes combat deployments with normal shoulder function and absence of pain. Axillary nerve injury is a relatively common injury after anterior glenohumeral joint dislocation. There is little known about the long-term outcome of patient's with permanent axillary nerve injury. This case suggests that it is possible for a young athletic individual to function at a high level of activity after permanent loss of axillary nerve function.