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.

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.

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.

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.

Cross-neurotization of the caudal brachial plexus with the contralateral C-8 ventral nerve branch in the cat. Potential surgical applications, effects of graft collection on the healthy donor limb and results.

Contralateral transfer of the right, eighth ventral nerve branch (C8) (C8 cross-transfer - C8CT) was performed in 6 adult cats, in which the caudal part of the left brachial plexus (C8 and T1) had been severed, in order to mimic nerve root avulsion. Clinical and electrophysiological parameters, muscle contraction force measurements and histology were used to evaluate the effects of the surgery in a 14- to 36-month follow-up. The right forelimb (donor side) was clinically normal (no lameness) in all the cats at the end of the study. Electromyography performed 14 days after surgery revealed denervation fibrillation potentials in both forelimbs. Fibrillation potentials disappeared in all the cats at the end of the study. Direct stimulation of the right C8 ventral branch induced motor and sensory evoked potentials in the left limb muscles in all the cats. The left to right contraction ratio of the extensor carpi radialis muscle was approximately 1. This experimental study demonstrates that C8CT enables re-innervation of the contralateral brachial plexus and allows the establishment of new functional neuromuscular units. This can in turn enable the restoration of function, and could potentially lead to partial recovery after caudal brachial plexus avulsion in the cat.

Restoration of elbow flexion by performing contralateral lateral thoracic and thoracodorsal nerve transfers after experimental musculocutaneous nerve transection.

OBJECT: The immediate transfer of the right lateral thoracic nerve (LTN) and the thoracodorsal nerve (TDN) to the transected left musculocutaneous nerve (MCN), leading to nerve cross-neurotization, was performed in cats to evaluate reinnervation of the biceps brachii muscle (BBM). METHODS: Surgery to produce cross-neurotization of the MCN was performed in 12 cats (treatment group). Transection of the MCN was performed without attempts at neurotization in three cats (control group). Reinnervation of the BBM was assessed by performing electromyography (EMG) 6 months (14 cats) and 26 months (one cat) postsurgery. True Blue retrograde axonal tracing studies, tensile force measurements (muscle extensometry), and histopathological analyses were performed. All cats in the treatment group recovered voluntary contraction of the BBM and regained elbow flexion. Electromyography revealed no abnormal spontaneous activity in the BBM. Muscle evoked potentials were recorded in that muscle after right C-8 ventral branch stimulation. The muscle contraction strength in the left BBM varied from 108 to 557 g. The BBMs regained their normal appearances. The region of the MCN distal to the anastomosis displayed a normal histological appearance. Fluorescence was detected in the ventral horn of the spinal cord in the right C-8 and T-1 segments. In contrast, in all cats in the control group there was atrophy of the BBM, no EMG signal, and no clinical sign of recovery. There was no contraction of the BBM, no labeled neuron in the spinal cord, and the MCN displayed major degenerative changes. CONCLUSIONS: These findings demonstrate that the LTN and TDN can be used to neurotize injured contralateral brachial plexus nerves and obtain successful reinnervation in cats.

Contralateral motor rootlets and ipsilateral nerve transfers in brachial plexus reconstruction.

OBJECT: The goal of this study was to evaluate outcomes in patients with brachial plexus avulsion injuries who underwent contralateral motor rootlet and ipsilateral nerve transfers to reconstruct shoulder abduction/external rotation and elbow flexion. METHODS: Within 6 months after the injury, 24 patients with a mean age of 21 years underwent surgery in which the contralateral C-7 motor rootlet was transferred to the suprascapular nerve by using sural nerve grafts. The biceps motor branch or the musculocutaneous nerve was repaired either by an ulnar nerve fascicular transfer or by transfer of the 11th cranial nerve or the phrenic nerve. The mean recovery in abduction was 90 degrees and 92 degrees in external rotation. In cases of total palsy, only two patients recovered external rotation and in those cases mean external rotation was 70 degrees. Elbow flexion was achieved in all cases. In cases of ulnar nerve transfer, the muscle scores were M5 in one patient, M4 in six patients, and M3+ in five patients. Elbow flexion repair involving the use of the 11th cranial nerve resulted in a score of M3+ in five patients and M4 in two patients. After surgery involving the phrenic nerve, two patients received a score of M3 + and two a score of M4. Results were clearly better in patients with partial lesions and in those who were shorter than 170 cm (p < 0.01). The length of the graft used in motor rootlet transfers affected only the recovery of external rotation. There was no permanent injury at the donor sites. CONCLUSIONS: Motor rootlet transfer represents a reliable and potent neurotizer that allows the reconstruction of abduction and external rotation in partial injuries.

Functional magnetic resonance imaging and control over the biceps muscle after intercostal-musculocutaneous nerve transfer.

OBJECT: Recent progress in the understanding of cerebral plastic changes that occur after an intercostal nerve (ICN)-musculocutaneous nerve (MCN) transfer motivated a study with functional magnetic resonance (fMR) imaging to map reorganization in the primary motor cortex. METHODS: Eleven patients with traumatic root avulsions of the brachial plexus were studied. Nine patients underwent ICN-MCN transfer to restore biceps function and two patients were studied prior to surgery. The biceps muscle recovered well in seven patients who had undergone surgery and remained paralytic in the other two patients. Maps of neural activity within the motor cortex were generated for both arms in each patient by using fMR imaging, and the active pixels were counted. The motor task consisted of biceps muscle contraction. Patients with a paralytic biceps were asked to contract this muscle virtually. The location and intensity of motor activation of the seven surgically treated arms that required good biceps muscle function were compared with those of the four arms with a paralytic biceps and with activity obtained in the contralateral hemisphere regulating the control arms. Activity could be induced in the seven surgically treated patients whose biceps muscles had regained function and was localized within the primary motor area. In contrast, activity could not be induced in the four patients whose biceps muscles were paralytic. Neither the number of active pixels nor the mean value of their activations differed between the seven arms with good biceps function and control arms. The weighted center of gravity of the distribution of activity also did not appear to differ. CONCLUSIONS: Reactivation of the neural input activity for volitional biceps control after ICN-MCN transfer, as reflected on fMR images, is induced by successful biceps muscle reinnervation. In addition, the restored input activity does not differ from the normal activity regulating biceps contraction and, therefore, has MCN acceptor qualities. After ICN-MCN transfer, cerebral activity cannot reach the biceps muscle following the normal nervous system pathway. The presence of a common input response between corticospinal neurons of the ICN donor and the MCN acceptor seems crucial to obtain a functional result after transfer. It may even be the case that a common input response between donor and acceptor needs to be present in all types of nerve transfer to become functionally effective.

Brachial plexus injury: factors affecting functional outcome in spinal accessory nerve transfer for the restoration of elbow flexion.

OBJECT: Between 1994 and 1998, 44 nerve transfers were performed using a graft between a branch of the accessory nerve and musculocutaneous nerve to restore the flexion of the arm in patients with traumatic brachial plexus injuries. A retrospective study was conducted, including statistical evaluation of the following pre- and intraoperative parameters in 39 patients: 1) time interval between injury and surgery; and 2) length of the nerve graft used to connect the accessory and musculocutaneous nerves. METHODS: The postoperative follow-up interval ranged from 23 to 84 months, with a mean +/- standard deviation of 36 +/- 13 months. Reinnervation of the biceps muscle was achieved in 72% of the patients. Reinnervation of the musculocutaneous nerve was demonstrated in 86% of the patients who had undergone surgery within the first 6 months after injury, in 65% of the patients who had undergone surgery between 7 and 12 months after injury, and in only 50% of the patients who had undergone surgery 12 months after injury. A statistical comparison of the different preoperative time intervals (0-6 months compared with 7-12 months) showed a significantly better outcome in patients treated with early surgery (p < 0.05). An analysis of the impact of the length of the interposed nerve grafts revealed a statistically significant better outcome in patients with grafts 12 cm or shorter compared with that in patients with grafts longer than 12 cm (p < 0.005). CONCLUSIONS: Together, these results demonstrated that outcome in patients who undergo accessory to musculocutaneous nerve neurotization for restoration of elbow flexion following brachial plexus injury is greatly dependent on the time interval between trauma and surgery and on the length of the nerve graft used.

Nerve transfers to the biceps and brachialis branches to improve elbow flexion strength after brachial plexus injuries.

OBJECT: In this study the authors evaluated the outcome in patients with brachial plexus injuries who underwent nerve transfers to the biceps and the brachialis branches of the musculocutaneous nerve. METHODS: The charts of eight patients who underwent an ulnar nerve fascicle transfer to the biceps branch of the musculocutaneous nerve and a separate transfer to the brachialis branch were retrospectively reviewed. Outcome was assessed using the Medical Research Council (MRC) grade to classify elbow flexion strength in conjunction with electromyography (EMG). The mean patient age was 26.4 years (range 16-45 years) and the mean time from injury to surgery was 3.8 months (range 2.5-7.5 months). Recovery of elbow flexion was MRC Grade 4 in five patients, and Grade 4+ in three. Reinnervation of both the biceps and brachialis muscles was confirmed on EMG studies. Ulnar nerve function was not downgraded in any patient. CONCLUSIONS: The use of nerve transfers to reinnervate the biceps and brachialis muscle provides excellent elbow flexion strength in patients with brachial plexus nerve injuries.

Physiologic and morphologic aspects of nerve regeneration after end-to-end or end-to-side coaptation in a rat model of brachial plexus injury.

The results of repairing a transected rat musculocutaneous nerve by suturing the distal stump, end to side or end to end, to the ipsilateral ulnar nerve were assessed at 3 months by retrograde labeling and morphologic and physiologic analysis. Unlike most other models of end-to-side repair in which the injured recipient and donor reinnervating nerves have overlapping neuron pools in the spinal cord, in this model the neurons of the injured musculocutaneous and the reinnervating ulnar nerves are located in mutually exclusive segments of the spinal cord. Using retrograde labeling we show that the reinnervating fibers are derived solely from the ulnar nerve pool. Both end-to-side and end-to-end coaptation resulted in reinnervation of the distal musculocutaneous nerve and significant functional reinnervation of its dependent biceps brachii muscle. Although end-to-end coaptation resulted in better axon morphology and muscle function, it resulted in total loss of donor nerve function. By contrast, end-to-side coaptation resulted in good recovery with only minimal donor nerve deficit. These results show that significant functional reinnervation of biceps brachii muscle can occur solely on the basis of collateral sprouting of intact axons from the adjacent ulnar nerve.

Isolated musculocutaneous neuropathy caused by a proximal humeral exostosis.

We report an isolated musculocutaneous neuropathy caused by a proximal humeral osteochondroma that became symptomatic after the patient played recreational basketball. Lesion resection resulted in complete deficit resolution. Mass lesions involving the musculocutaneous nerve should be considered in patients with atraumatic, isolated musculocutaneous neuropathies that are recurrent or fail to recover, even in the setting of strenuous exercise.

Evidence for end-to-side sensory nerve regeneration in a human. Case report.

Division of a peripheral nerve produces an axotomy leading to neurite outgrowth from the proximal stump and wallerian degeneration in the distal stump. Because there is no longer a connection between the distal stump and neuronal cell bodies in the anterior spinal cord or dorsal root ganglion, it is assumed that no neurites should exist in the distal stump. The authors present the case of a patient who unexpectedly had a neuroma on the proximal end of the distal segment of a previously severed nerve. The lateral antebrachial cutaneous nerve had been surgically severed. Innervated by the radial nerve, a neuroma subsequently formed in the distal segment. Our hypothesis is that the proximal end of the distal portion of a severed nerve may be innervated by collateral sprouts of axons that branch at points of more distal plexus formation. This invokes a similar pathophysiology to the controversial notion of end-to-side nerve sprouting. Neuromas that develop on the "wrong side" of a nerve become an additional potential source of pain in patients with injured nerves.

[Should biopsy be done on the sensory branch of the radial nerve in leprosy patients? Apropos of 112 cases]. / Doit-on pratiquer des biopsies de la branche sensitive du nerf radial chez les malades lépreux? A propos de 112 cas.

Biopsies of the superficial sensory branch of the radial nerve are contested. Some authors mention it to be simple and without harm, but others are formally against this procedure. At ILAD, 274 biopsies were made between 1986 to 1992. We present a review of 112 leprosy patients for whom biopsy was done. On 112 reexamined patients, we observed 2 benign neuroma, hence 2%. The comparison of nerve function before biopsy and after, of 63 of the 112 patients, reexamination shows no significant modification of the functional score. Given even the occurrence of benign neuroma in only 2% of the cases, the authors do not recommend the biopsy of the superficial sensory branch of the radial nerve. For research purposes on neuritis in leprosy, as well as to assure diagnosis in primary neuritic leprosy, we propose the biopsy of the sensory branch of the musculo cutaneous nerve at elbow level.

Motor nerve biopsy in severe Guillain-Barré syndrome.

We undertook a biopsy of a terminal branch of the musculocutaneous nerve in a man with severe Guillain-Barré syndrome and very small distally evoked action potentials. The biopsy showed pronounced subperineurial edema, macrophage infiltration, and many axons that had been completely demyelinated, some associated with intratubal macrophages. The biopsy unequivocally identified the pathological process as primary demyelination, not axonal degeneration, and was more informative than previous reports of sural nerve biopsies in patients with Guillain-Barré syndrome.

A neuromuscular transmission disorder: combined myasthenia gravis and Lambert Eaton syndrome in one patient.

The distinction between myasthenia gravis and Lambert Eaton myasthenic syndrome can usually be made by the clinical and neurophysiological features. A patient was observed with features which suggested a combination of both disorders. This has been described in few patients before. The importance of electromyography in both distal and proximal limb muscles for a correct diagnosis is demonstrated. Only in proximal nerve stimulation tests was proof found of the existence of both syndromes.