Fusion between the median and musculocutaneous nerve: A case study.

The musculocutaneous nerve (C5-C7) is a terminal branch of the lateral cord of the brachial plexus and provides motor innervation to the anterior compartment of arm muscles. Both the musculocutaneous and median nerve may show numerous anatomical variations. Keeping in mind possible aberrations in the course of the upper limb nerves may increase the safety and success rate of surgical procedures. The presented report is a detailed anatomical study of the fusion between the median and musculocutaneous nerve, supplemented by intraneural fascicular dissection. In the presented case, the musculocutaneous nerve was not found in its typical location in the axillary cavity and upper arm during the preliminary assessment. However, a careful intraneural fascicular dissection revealed that musculocutaneous nerve was fused with the median nerve and with its lateral root; Those nerves were surrounded by a common epineurium, however they were separable. The muscular branch to the biceps brachii muscle arose from the trunk (fascicular bundle) dissected out from the median nerve and corresponding to the musculocutaneous nerve. Such variation may be of utmost clinical importance, especially during reconstructions of the brachial plexus or its branches.

Musculocutaneous neuropathy.

INTRODUCTION: Isolated musculocutaneous neuropathy is uncommon. In this study we aimed to determine its causes and clinical presentation and interpret the electrodiagnostic findings associated with this condition. METHODS: Our investigation was a retrospective review of patients diagnosed with musculocutaneous neuropathy at the Mayo Clinic (Rochester, Minnesota) electromyography (EMG) laboratory between 1997 and 2015. RESULTS: Thirty-two patients with musculocutaneous neuropathy and 5 patients with lateral antebrachial cutaneous neuropathy were identified. The most common cause was acute trauma or surgery (65%). Fourteen percent of the cases were idiopathic and 14% were inflammatory. Pain and sensory disturbance were more common presentations than weakness. Weakness from nerve injury was not noted in 2 patients, suggesting that other muscles may provide adequate elbow flexion/supination. The bilateral absence of lateral antebrachial cutaneous nerve sensory responses suggests an inflammatory cause. DISCUSSION: Musculocutaneous neuropathy usually results from trauma or iatrogenic injury. Nerve conduction studies alone are insufficient to confirm neuropathy, and needle EMG examination should be a routine part of the diagnostic evaluation. Muscle Nerve 58: 726-729, 2018.

Comparing Electrical Stimulation With and Without Ultrasound Guidance for Phenol Neurolysis to the Musculocutaneous Nerve.

BACKGROUND: Ultrasound guidance is increasingly being used for neurolytic procedures that have traditionally been done with electrical stimulation (e-stim) guidance alone. Ultrasound visualization with e-stim-guided neurolysis can potentially allow adjustments in injection protocols that will reduce the volume of neurolytic agent needed to achieve clinical improvement. OBJECTIVE: This study compared e-stim only to e-stim with ultrasound guidance in phenol neurolysis of the musculocutaneous nerve (MCN) for elbow flexor spasticity. We also evaluated the ultrasound appearance of the MCN in this population. DESIGN: Retrospective review. SETTING: University hospital outpatient clinic. PARTICIPANTS: Adults (N = 167) receiving phenol neurolysis to the MCN for treatment of elbow flexor spasticity between 1997 and 2014 and adult control subjects. METHODS: For each phenol injection of the MCN, the method of guidance, volume of phenol injected, technical success, improved range of motion at the elbow postinjection, adverse effects, reason for termination of injections, and details of concomitant botulinum toxin injection were recorded. The ultrasound appearance of the MCN, including nerve cross-sectional area and shape, were recorded and compared between groups. MAIN OUTCOME MEASURES: The volume of phenol injected and MCN cross-sectional area and shape as demonstrated by ultrasound. RESULTS: The addition of ultrasound to e-stim-guided phenol neurolysis was associated with lower doses of phenol when compared to e-stim guidance alone (2.31 mL versus 3.69 mL, P < .001). With subsequent injections, the dose of phenol increased with e-stim guidance (P < .001), but not with e-stim and ultrasound guidance (P = .95). Both methods of guidance had high technical success, improved ROM at elbow postinjection, and low rates of adverse events. In comparing the ultrasound appearance of the MCN in patients with spasticity to that of normal controls, there was no difference in the cross-sectional area of the nerve, but there was more variability in shape. CONCLUSIONS: Combined e-stim and ultrasound guidance during phenol neurolysis to the MCN allows a smaller volume of phenol to be used for equal effect, both at initial and repeat injection. The MCN shape was more variable in individuals with spasticity; this should be recognized so as to successfully locate the nerve to perform neurolysis. LEVEL OF EVIDENCE: IV.

Preoperative ultrasound for runoff-venous decompression of peripheral nerves for arteriovenous access-related pain in the upper limb.

INTRODUCTION: Arteriovenous access (AVA)-related pain treated successfully with runoff-venous decompression of the causative nerve, following ultrasound (US)-assisted preoperative evaluation, has never been reported. CASE PRESENTATION: A 57-year-old man suffering from constant exhausting pains along the outflow cephalic vein of the radiocephalic arteriovenous fistula at the wrist and the antecubital fossa, was treated surgically after the diagnosis of AVA-related pain derived from cephalic vein compression on two peripheral cutaneous nerves, the superficial radial nerve (SRN) and the lateral antebrachial cutaneous nerve (LACN). TECHNIQUE: The SRN and LACN, which ran along and/or provided sensory innervation to the painful regions in the upper limb, were traced using ultrasonography in the short axis and proved to be compressed by and in contact with veins where the pain existed, at the wrist and the antecubital fossa. Once diagnostic US-guided blocks of both were performed and pain disappeared, they were identified as the causative nerves. The cephalic venous decompression surgeries that separated and transposed the veins away from the SRN and the LACN were performed sequentially under pneumatic tourniquet inflation to improve nerve visualization. RESULTS: The pains disappeared after the operations. An adequate length of the runoff cephalic vein was maintained for needle cannulations during hemodialysis. CONCLUSIONS: Outflow venous compression to the peripheral nerves may be a cause of AVA-related pain. US-guided assessments of the nerves may improve the safety and efficiency of venous decompression surgeries to treat AVA-related pains.

Simultaneous acute shoulder arthritis and multiple mononeuropathy in a newly diagnosed type 2 diabetes patient - First case report.

Diabetes is a common disorder that leads to the musculoskeletal symptoms such as the shoulder arthritis. The involvement of peripheral nervous system is one of the troublesome for the patients as it provokes chronic sensory symptoms, lower motor neuron involvement and autonomic symptoms. In the course of the disease there has been several types of neuropathies described. A 41-year-old male patient was admitted to the internal medicine department because of the general weakness, malaise, polydypsia and polyuria since several days. The initial blood glucose level was 780mg/dl. During the first day the continuous insulin infusion was administered. On the next day when he woke up, the severe pain in the right shoulder with limited movement, right upper extremity weakness and burning pain in the radial aspect of this extremity appeared. On examination right shoulder joint movement limitation was found with the muscle weakness and sensory symptoms in the upper limbs. The clinical picture indicated on the right shoulder arthritis and the peripheral nervous system symptoms such as the right musculocutaneous, supraspinatus, right radial nerve and left radial nerve damage. We present a first case report of simultaneous, acute involvement of the shoulder joint and multiple neuropathy in a patient with newly diagnosed type 2 diabetes, presumably in the state of ketoacidosis.

Compression of lateral antebrachial cutaneous nerve in waitresses.

OBJECTIVE: In a retrospective survey of our electrophysiology laboratory, we encountered 3 cases of lateral antebrachial cutaneous nerve (LACN) compression in waitresses and propose direct compression of LACN by carrying heavy trays on the lateral bicipital tendon. LACN, a branch of musculocutaneous nerve, provides sensory innervations to lateral forearm. Causes of LACN involvement include venipuncture, elbow surgery, and trauma. METHODS: We encountered 6 cases of LACN neuropathy, 3 cases that were in slim waitresses carrying heavy trays. History and physical examination and forearm electrophysiologic studies (EPS) were performed in 3 waitresses at initial and follow-up visits. Antidromic stimulation of LACN was undertaken by Spindler and Felsenthals technique. Latency, amplitude, and conduction velocity were measured and compared with contralateral limb. RESULTS: All 3 patients were female waitresses aged 35-42 years, presented with few months of painful paresthesias of distal forearm, worse during working hours. Tinel sign at lateral cubital fossa was positive in all. EPS confirmed delayed latency, low amplitude, and slow conduction velocity of LACN on symptomatic side compared with normal. All 3 patients revealed electrophysiologic abnormalities consistent with LACN compression due to heavy trays in slim waitresses and considered occupational hazard. Treatment included nortriptyline or gabapentin and avoidance of heavy trays. Clinical and EPS findings improved over 8 months. CONCLUSIONS: We described 3 cases of LACN compression in waitresses from edges of heavy trays with typical symptoms and abnormal electrophysiological studies and improvement by avoiding compression and with analgesics. We propose inadequate fatty tissue in antecubital fossa contributed to compression of LACN.

Intercostal nerve transfer to neurotize the musculocutaneous nerve after traumatic brachial plexus avulsion: a comparison of two, three, and four nerve transfers.

The purpose of this study was to compare the outcomes of different numbers of intercostal nerve (ICN) transfers for elbow flexion and to determine whether age, body mass index (BMI), type of injury, and preoperative delay influence the outcomes. From 2004 to 2010, 32 (30 included) consecutive patients underwent ICN transfer to the musculocutaneous nerve following brachial plexus injury. Elbow flexion strength was evaluated according to the British Medical Research Council (BMRC) grading system. Of nine patients who received two ICN transfers, six (66.7%) recovered with useful elbow flexion compared with 14 of 17 (82.4%) patients who received three ICN transfers. Of the four patients with four ICN transfers, three (75%) achieved useful recovery. Statistical analysis showed no significant difference. There is no significant difference among the outcomes of two, three, and four ICN transfers to the musculocutaneous nerve. Two ICN transfers are sufficient for useful recovery of elbow flexion. Younger patients achieve better results.

Dual reinnervation of biceps muscle after side-to-side anastomosis of an intact median nerve and a damaged musculocutaneous nerve.

Traumatic peripheral nerve injury can lead to significant long-term disability for previously healthy persons. Damaged nerve trunks have been traditionally repaired using cable grafts, but nerve transfer or neurotization procedures have become increasingly popular because the axonal regrowth distances are much shorter. These techniques sacrifice the existing nerve pathway, so muscle reinnervation depends entirely on the success of the repair. Providing a supplemental source of axons from an adjacent intact nerve by using side-to-side anastomosis might reinnervate the target muscle without compromising the function of the donor nerve. The authors report a case of biceps muscle reinnervation after side-to-side anastomosis of an intact median nerve to a damaged musculocutaneous nerve. The patient was a 34-year-old man who had sustained traumatic injury primarily to the right upper and middle trunks of the brachial plexus. At 9 months after the injury, because of persistent weakness, the severely damaged upper trunk of the brachial plexus was repaired with an end-to-end graft. When 8 months later biceps function had not recovered, the patient underwent side-to-side anastomosis of the intact median nerve to the adjacent distal musculocutaneous nerve via epineural windows. By 9 months after the second surgery, biceps muscle function had returned clinically and electrodiagnostically. Postoperative electromyographic and nerve conduction studies confirmed that the biceps muscle was being reinnervated partly by donor axons from the healthy median nerve and partly by the recovering musculocutaneous nerve. This case demonstrates that side-to-side anastomosis of an intact median to an injured musculocutaneous nerve can provide dual reinnervation of the biceps muscle while minimizing injury to both donor and recipient nerves.

Ultrasound guided alcohol neurolysis of musculocutaneous nerve to relieve elbow spasticity in hemiparetic stroke patients.

Proper management of elbow spasticity is important in stroke rehabilitation. We investigated the effect and safety of ultrasound guided alcohol neurolysis of the MC nerve for controlling elbow flexor spasticity in hemiparetic stroke patients. Ten hemiparetic stroke patients with severe elbow spasticity were recruited for this study. We identified the MC nerve using ultrasound and performed neurolysis with 35% ethyl alcohol. The severity of spasticity was assessed using the modified Ashworth scale (MAS) score and associated reaction (AR) of elbow flexor. During the 2 months follow-up period, both MAS score and AR were reduced in all 10 patients. Before treatment, the mean MAS score was 3.4 ± 0.5, and this improved to 0.1 ± 0.3 immediately post-neurolysis, 1.8 ± 1.0 at one month and 1.9 ± 0.8 at two months (p < 0.001). The mean change of AR of the affected elbow was significantly decreased, from 75.2 ± 30.0° before neurolysis to 24.8 ± 21.3° immediately post-neurolysis, 35.5 ± 24.7° at 1 month and 40.8 ± 25.1° at 2 months (p < 0.001). Ultrasound guided MC nerve block is an effective and safe procedure for relieving localized spasticity of the elbow flexor.

The effects of denervation, reinnervation, and muscle imbalance on functional muscle length and elbow flexion contracture following neonatal brachial plexus injury.

The pathophysiology of paradoxical elbow flexion contractures following neonatal brachial plexus injury (NBPI) is incompletely understood. The current study tests the hypothesis that this contracture occurs by denervation-induced impairment of elbow flexor muscle growth. Unilateral forelimb paralysis was created in mice in four neonatal (5-day-old) BPI groups (C5-6 excision, C5-6 neurotomy, C5-6 neurotomy/repair, and C5-T1 global excision), one non-neonatal BPI group (28-day-old C5-6 excision), and two neonatal muscle imbalance groups (triceps tenotomy ± C5-6 excision). Four weeks post-operatively, motor function, elbow range of motion, and biceps/brachialis functional lengths were assessed. Musculocutaneous nerve (MCN) denervation and reinnervation were assessed immunohistochemically. Elbow flexion motor recovery and elbow flexion contractures varied inversely among the neonatal BPI groups. Contracture severity correlated with biceps/brachialis shortening and MCN denervation (relative axon loss), with no contractures occurring in mice with MCN reinnervation (presence of growth cones). No contractures or biceps/brachialis shortening occurred following non-neonatal BPI, regardless of denervation or reinnervation. Neonatal triceps tenotomy did not cause contractures or biceps/brachialis shortening, nor did it worsen those following neonatal C5-6 excision. Denervation-induced functional shortening of elbow flexor muscles leads to variable elbow flexion contractures depending on the degree, permanence, and timing of denervation, independent of muscle imbalance.

Primary restoration of elbow flexion in adult post-traumatic plexopathy patients.

Restoration of elbow flexion is one of the priorities in brachial plexus palsy, as this function brings the hand to the mouth. This study analyses the results of musculocutaneous nerve reconstruction in 194 patients with devastating paralysis. Results were analyzed in relation to denervation time, severity score, length of nerve grafts, and donor nerves used. Between 1978 and 2006, 194 post-traumatic plexopathy patients underwent musculocutaneous nerve reconstruction. 298 motor donors were used in 175 patients while 19 patients had microneurolysis. There were 104 intraplexus motor donors; 124 intercostal nerves were transferred in 39 patients; direct coaptation was performed in 31 patients and three or more intercostals were transferred in 33 patients; 16 patients underwent musculocutaneous to musculocutaneous repair. 144 patients had interposition nerve grafts. The mean follow-up was 4.48 ± 2.78 years. Results were good or excellent (≥M3+) in 52.53% of patients with more than 70° of elbow flexion. Patients, who were operated on less than 4 months from injury, with high severity score, attained significant better results than late cases with multiple root avulsions. Intraplexus donors have direct influence on biceps recovery, achieving significant better results than extraplexus donors. Intercostal nerves are an alternative source in avulsion injuries. The use of 3 intercostals with direct coaptation yielded optimal elbow flexion. Musculocutaneous nerve reconstruction is one of the priorities in upper limb reanimation. Functional outcomes are influenced by the age of the patient, severity of plexus lesion, denervation time, and type of reconstruction. Early surgery is recommended.

Results of intercostal nerve transfer to the musculocutaneous nerve in brachial plexus birth palsy.

BACKGROUND: Intercostal nerve (ICN) transfer has been one of the main extraplexal nerve transfers in treating brachial plexus root avulsion. This retrospective study evaluated results of ICN transfer for reconstruction of the musculocutaneous nerve (MCN) in brachial plexus birth palsy (BPBP). METHODS: Eighteen boys and 6 girls with BPBP, who had avulsion of at least 2 spinal nerves of the plexus, underwent ICN transfer for reconstruction of MCN, from March 2003 to October 2005. The brachial plexus lesion was diagnosed by clinical assessment, surgical exploration, and intraoperative neurophysiological investigations. The age at surgery ranged from 3 to 11 months of life, with a mean of 5 months. Two intercostals were used for one, 3 intercostals for 9, and 4 intercostals for 14 patients. The intercostals were transferred to MCN in 12 and to the anterior division of the upper trunk in the other 12 cases. RESULTS: Twenty-four children were followed up for 24 to 79 months, with an average of 53 months. No complications were found in the respiratory system. Of 14 transfers with 4 intercostals, biceps gained M4 strength in 8, M3 in 4, and M2 in 2. Of 9 transfers with 3 intercostals, biceps obtained M4 strength in 8 and M3 in 1. One transfer with 2 intercostals got M4 strength of biceps. Twelve patients whose intercostals were transferred to MCN, gained M4 strength of biceps in 11 and M3 in 1, whereas the other 12 patients with intercostals transferred to anterior division of the upper trunk, obtained M4 strength of biceps in 6, M3 in 4, and M2 in 2. The rate of M3 strength or more was 92% and that of M4 was 71%. CONCLUSIONS: ICN transfer is a safe and reliable procedure for reconstruction of the MCN in BPBP. There seems to be no difference of effects between transfers with 3 and those with 4 intercostals. The transferred nerves should be coapted to MCN, rather than a more proximal portion of the plexus. LEVEL OF EVIDENCE: Level III: retrospective comparative study.

Ciliary neurotrophic factor promotes motor reinnervation of the musculocutaneous nerve in an experimental model of end-to-side neurorrhaphy.

BACKGROUND: It is difficult to repair nerve if proximal stump is unavailable or autogenous nerve grafts are insufficient for reconstructing extensive nerve damage. Therefore, alternative methods have been developed, including lateral anastomosis based on axons' ability to send out collateral sprouts into denervated nerve. The different capacity of a sensory or motor axon to send a sprout is controversial and may be controlled by cytokines and/or neurotrophic factors like ciliary neurotrophic factor (CNTF). The aim of the present study was to quantitatively assess collateral sprouts sent out by intact motor and sensory axons in the end-to-side neurorrhaphy model following intrathecal administration of CNTF in comparison with phosphate buffered saline (vehiculum) and Cerebrolysin. The distal stump of rat transected musculocutaneous nerve (MCN) was attached in an end-to-side fashion with ulnar nerve. CNTF, Cerebrolysin and vehiculum were administered intrathecally for 2 weeks, and all animals were allowed to survive for 2 months from operation. Numbers of spinal motor and dorsal root ganglia neurons were estimated following their retrograde labeling by Fluoro-Ruby and Fluoro-Emerald applied to ulnar and musculocutaneous nerve, respectively. Reinnervation of biceps brachii muscles was assessed by electromyography, behavioral test, and diameter and myelin sheath thickness of regenerated axons. RESULTS: Vehiculum or Cerebrolysin administration resulted in significantly higher numbers of myelinated axons regenerated into the MCN stumps compared with CNTF treatment. By contrast, the mean diameter of the myelinated axons and their myelin sheath thickness in the cases of Cerebrolysin- or CNTF-treated animals were larger than were those for rats treated with vehiculum. CNTF treatment significantly increased the percentage of motoneurons contributing to reinnervation of the MCN stumps (to 17.1%) when compared with vehiculum or Cerebrolysin treatments (at 9.9 or 9.6%, respectively). Reduced numbers of myelinated axons and simultaneously increased numbers of motoneurons contributing to reinnervation of the MCN improved functional reinnervation of the biceps brachii muscle after CNTF treatment. CONCLUSION: The present experimental study confirms end-to-side neurorrhaphy as an alternative method for reconstructing severed peripheral nerves. CNTF promotes motor reinnervation of the MCN stump after its end-to-side neurorrhaphy with ulnar nerve and improves functional recovery of the biceps brachii muscle.

Isolated musculocutaneous neuropathy in an adolescent baseball pitcher.

Injury of the musculocutaneous nerve very rarely occurs in the absence of concomitant injury to other components of the brachial plexus. Until now, the few cases of isolated musculocutaneous nerve palsies have been reported only in adults. We report a case of isolated musculocutaneous neuropathy in a uniquely talented adolescent baseball pitcher. The biomechanics underlying this adolescent's ability to throw with high velocity likely contributed to the musculocutaneous nerve injury in this case.

The experimental research of nerve fibers compensation amplification innervation of ulnar nerve and musculocutaneous nerve in rhesus monkeys.

This experiment intended to authenticate the compensation and amplification effect of regenerated nerve fibers after nerve injury in primate. The Rhesus Monkeys right ulnar nerves and musculocutaneous nerves were chosed. The proximal impaired ulnar nerve as the proximal end and the distal impaired ulnar nerve musculocutaneous nerve as the distal ends. The ulnar nerve proximal stump fibers can grow into both the ulnar nerve distal stump and the musculocutaneus nerve at the same time and established two different electrophysiological conduction passageway. There exist nerve fibers compensation amplification effect after peripheral nerve injury on Rhesus Monkeys.

Origination of the brachialis branch of the musculocutaneous nerve: an electrophysiological study.

OBJECTIVE: To test an innovative method to study the origin of a specific nerve or of the nerve fibers innervating a given muscle on the healthy upper limb of a human being and to find the rationale for the brachialis branch of musculocutaneous nerve transfer. METHODS: An intraoperative electrophysiological study was conducted comprising 27 cases of contralateral C7 transfer. The goal of the study was to record compound muscle action potential of the brachialis muscle while various nerve roots of the brachial plexus were stimulated. RESULTS: Analysis of compound muscle action potential suggested that the brachialis branch of the musculocutaneous nerve is composed of fibers from the C5, C6, and C7 nerve roots and that the C5 and C6 nerve roots are the major origin for the brachialis branch of musculocutaneous nerve fibers. CONCLUSION: The technique proposed here was a more direct and functional method of tracing the origin of a specific nerve or of the nerve fibers innervating a given muscle on the healthy upper limb of a live patient.