The relationship of the musculocutaneous nerve to the brachial plexus evaluated by MRI.

Axillary plexus blocks (AXB) are widely used for upper limb operations. It is recommend that AXB should be performed using a multiple injection technique. Information about the course and position of the musculocutaneous nerve (MCN) is of relevance for AXB performance. The objective of this study was to examine the position of the MCN and its relationship to the axillary sheath using MRI. 54 patients underwent an AXB with 40 ml of local anaesthetic before MRI examination. The course of the MCN and the position where it left the axillary sheath and perforated the coracobrachial muscle (MCN exit point), in relation to the axillary artery and the block needle insertion point in the axillary fold, were recorded. The MCN was seen clearly in 23, partly in 26, and not identified in five patients at the MCN exit point. The mean distance from the insertion point of the block needle in the axillary fold to the MCN exit point was 36.8 mm (SD = 18.9, range: 0-90.5). In 37 patients the MCN exit point was positioned inside the Q1 quadrant (lateral anterior to the axillary artery) and in 11 patients inside the Q2 quadrant (medial anterior to the axillary artery). There is a wide variability as to where the musculocutaneous nerve (MCN) leaves the axillary sheath. Therefore multiple injection techniques, or the use of a proximally directed catheter, should be appropriate to block the MCN.

A novel classification of musculocutaneous nerve variations: The relationship between the communicating branch and transposed innervation of the brachial flexors to the median nerve.

The musculocutaneous nerve innervates the brachial flexors; i.e., the coracobrachialis, biceps brachii, and brachialis. The musculocutaneous and median nerve sometimes share a communicating branch and also muscular branches to brachial flexors are sometimes transposed to median nerve. Because these variations constitute a potentially important clinical and surgical issue, we evaluated 130 upper limbs of 65 cadavers and 184 cases of musculocutaneous and median nerve variations in the literature and devised a novel system of classification that covers each pattern of variation. Our proposed classification was applicable in all of our cases and those previously reported. In addition, transposed innervation of the brachial flexors from the musculocutaneous nerve to the communicating branches was observed in one limb in our case series. In this case and all previously reported cases of transposed innervation of the brachial flexors, communicating branches between the musculocutaneous and median nerve were found and no brachial flexor branch arose from the musculocutaneous nerve distal to the communicating branches. Consequently, we established that, as per our novel classification, all patterns of communicating branches could be classified into five types and the patterns of transposed innervation of the brachial flexors into three types.

Spinal nerve root compositions of musculocutaneous nerve: an anatomical study.

AIM: This study was aimed to investigate the variations in the spinal nerve root compositions of musculocutaneous nerve and to confirm which spinal nerve root is the main ingredient in participating amount. MATERIAL AND METHODS: A total of 20 fresh cadavers were dissected. Brachial plexus and its branches were extracted. Musculocutaneous nerve stump was traced back to the roots to identify its fascicular origin. The number of fascicles originating from a particular nerve root and their axial location with in the nerve were noted. RESULTS: The most frequent type of spinal nerve compositions of musculocutaneous nerve was C5, C6, and C7 with incidence of 60%. Musculocutaneous nerve had bundles from C5 root in all specimens, 90% of the specimens had contribution from C6 and only 70% of them had bundles from C7 root. There were a total of 46 (37.7%) bundles in C5 fascicles, 48 (39.3%) bundles in C6 fascicles, and 28 (22.9%) bundles in C7 fascicles. CONCLUSIONS: In electrophysiological studies it should be remembered that C7 or C6 lesions may not impair musculocutaneous nerve functions. The success of musculocutaneous nerve neurotization may be improved if care is taken to ensure whether or not C7 root is contributing to the musculocutaneous nerve.

Sonography of the lateral antebrachial cutaneous nerve with magnetic resonance imaging and anatomic correlation.

OBJECTIVES: Abnormalities of the lateral antebrachial cutaneous nerve (LABCN) are associated with antecubital elbow conditions, such as distal biceps brachii tendon tears and traumatic cephalic vein phlebotomy. These can lead to lateral forearm, elbow, and wrist symptoms that can mimic other disease processes. The purpose of this study was to characterize the sonographic appearance of the LABCN using cadaveric dissection and retrospective analysis of sonographic examinations of symptomatic patients with magnetic resonance imaging correlation. METHODS: For the first part of this study, a cadaveric elbow specimen was examined, and sonography was performed after dissection to identify the LABCN. Subsequently, 26 elbows in 13 patients with LABCN abnormalities were identified with sonography and retrospectively evaluated to characterize the appearance of the LABCN in both symptomatic and asymptomatic elbows. RESULTS: The symptomatic LABCNs showed fusiform enlargement, increased echogenicity, and loss of the normal fascicular echo texture. The mean cross-sectional area of the symptomatic nerves was 12.0 mm(2) (range, 6.1-17.2 mm(2)), with a maximum thickness of 3.5 mm (range, 2.3-5.9 mm), compared to 3.3 mm(2) (range, 1.9-5.2 mm(2)), with a maximum thickness of 1.3 mm (range, 0.9-2.2 mm), in the contralateral normal elbows. CONCLUSIONS: The close proximity of the LABCN to the distal biceps tendon and the cephalic vein makes it vulnerable to compression and injury in the setting of distal biceps tendon tears and traumatic phlebotomy, which may cause nerve enlargement and increased echogenicity. Awareness of the location and appearance of the LABCN on sonography is important for determining potential causes of lateral elbow and forearm pain.

Enhancement of musculocutaneous nerve reinnervation after vascular endothelial growth factor (VEGF) gene therapy.

BACKGROUND: Vascular endothelial growth factor (VEGF) is not only a potent angiogenic factor but it also promotes axonal outgrowth and proliferation of Schwann cells. The aim of the present study was to quantitatively assess reinnervation of musculocutaneous nerve (MCN) stumps using motor and primary sensory neurons after plasmid phVEGF transfection and end-to-end (ETE) or end-to-side (ETS) neurorrhaphy. The distal stump of rat transected MCN, was transfected with plasmid phVEGF, plasmid alone or treated with vehiculum and reinnervated following ETE or ETS neurorrhaphy for 2 months. The number of motor and dorsal root ganglia neurons reinnervating the MCN stump was estimated following their retrograde labeling with Fluoro-Ruby and Fluoro-Emerald. Reinnervation of the MCN stumps was assessed based on density, diameter and myelin sheath thickness of regenerated axons, grooming test and the wet weight index of the biceps brachii muscles. RESULTS: Immunohistochemical detection under the same conditions revealed increased VEGF in the Schwann cells of the MCN stumps transfected with the plasmid phVEGF, as opposed to control stumps transfected with only the plasmid or treated with vehiculum. The MCN stumps transfected with the plasmid phVEGF were reinnervated by moderately higher numbers of motor and sensory neurons after ETE neurorrhaphy compared with control stumps. However, morphometric quality of myelinated axons, grooming test and the wet weight index were significantly better in the MCN plasmid phVEGF transfected stumps. The ETS neurorrhaphy of the MCN plasmid phVEGF transfected stumps in comparison with control stumps resulted in significant elevation of motor and sensory neurons that reinnervated the MCN. Especially noteworthy was the increased numbers of neurons that sent out collateral sprouts into the MCN stumps. Similarly to ETE neurorrhaphy, phVEGF transfection resulted in significantly higher morphometric quality of myelinated axons, behavioral test and the wet weight index of the biceps brachii muscles. CONCLUSION: Our results showed that plasmid phVEGF transfection of MCN stumps could induce an increase in VEGF protein in Schwann cells, which resulted in higher quality axon reinnervation after both ETE and ETS neurorrhaphy. This was also associated with a better wet weight biceps brachii muscle index and functional tests than in control rats.

Effect of low-dose FK506 after contralateral C7 transfer to the musculocutaneous nerve: a study in rats.

The purpose of this study in rats was to identify whether a minimal dose of FK506 could enhance nerve regeneration along a 4-cm cross-chest saphenous nerve graft. Our center established a cross-chest nerve regeneration model previously using the contralateral C7 root transfer to the musculocutaneous nerve. Using this model, 10 adult male Sprague-Dawley rats were divided into two groups: group 1 (N = 5) consisted of animals that did not receive any further treatment, and group 2 (N = 5) consisted of animals that received a daily subcutaneous dose of 0.7 mg/kg FK506 for a period of 4 weeks. Evaluation methods of the study groups consisted of behavioral assessment, needle electromyography studies, and qualitative and quantitative morphometry. In the FK506 group, the middle of the graft and the musculocutaneous nerve contained larger axons and thicker myelin, bicep muscle weight recovered to an average of 68% of the normal (right) side, and overall behavioral results were better (P = 0.03175) than for untreated controls. Although the FK506 group achieved higher average myelinated fiber counts in all histologic sections, higher amplitude, and shorter latency results, there was no statistically significant difference between the two groups. Contralateral C7 transfer in the rat brachial plexus is a good experimental model to assess nerve regeneration and test treatments designed to enhance recovery in lesions with long nerve gaps (40 mm). FK506-treated animals demonstrated more advanced axonal regeneration, myelinated fiber maturation, and bicep muscle reinnervation. These results suggest a potential clinical use of low-dose FK506 in patients with severe nerve injuries.

[The main tunnel syndromes]. / Les principaux syndromes canalaires.

Several tunnel syndromes are responsible for substantial functional impairment. The diagnosis has to be made and treatment is most often very simple--nerve decompression--with excellent results. Of these syndromes, the most common are median and ulnar tunnel syndromes of the wrist and ulnar tunnel syndrome of the elbow, but other syndromes must be identified at the risk of therapy failure due to poorly adapted treatment. Finally, good knowledge of this pathology must lead to prevention of the iatrogenic forms (sequelae of inguinal hernia treatment, ileac crest graft harvesting) by educating all surgeons interested in peripheral nerve surgery.

Unusual high-origin of the pronator teres muscle from a Struthers' ligament coexisting with a variation of the musculocutaneous nerve.

During routine anatomical dissection of the right upper extremity of a 53-year-old woman cadaver, an unusual high-origin of the pronator teres muscle was discovered. The fibers of the aberrant muscle arose from two bone origins--the medial epicondyle and a small supracondylar process of the humerus, and from a tendinous arch (Struthers' ligament) extending between them. In addition, there was a variation of the musculocutaneous nerve--in the axilary fossa the musculocutaneous was fused to the median nerve and its usual branches arose consecutively from the median nerve stem. The last of these branches--the lateral antebrachial cutaneous arose in the lower part of the arm from the median nerve and companion to it and to the brachial artery passed under the Struthers' ligament. Our findings indicate that in some rare cases of combined muscular-nerve variations, the lateral antebrachial cutaneous nerve can be added to the neurovascular structures possibly entrapped by the Struthers' ligament.

Clinico-embryological perspective of a rare accessory brachial muscle with possible musculocutaneous nerve compression.

Both brachialis and biceps brachii are primary flexors of the arm and elbow from the biomechanical perspective. Numerous reports exist in anatomical literature regarding accessory heads of biceps brachii, although such accessory bellies in relation to brachialis muscle are less frequently elucidated. We report a unilateral case of a rare accessory muscle interposed between the biceps brachii and brachialis, having the musculocutaneous nerve (MCN) entrapped between the two. Furthermore, the muscle divided into two slips, upper slip was attached to biceps brachii and the other gained insertion to the brachial fascia. Innervation to this accessory muscle was derived from MCN. The embryological basis for such supernumerary muscle is discussed. Additionally, the case is considered under surgical and clinical perspective, highlighting the importance of familiarity with such variations. Anatomical variations of the brachial musculature may cause diagnostic perplexities while interpreting MRI or CT scans.

Effects of acetylo-L-carnitine in end-to-side neurorrhaphy: a pilot study.

PURPOSE: End-to-side (ETS) nerve repair allows for target-muscle reinnervation, with simultaneous preservation of donor-nerve function. Acetyl-L-carnitine (ALCAR) was shown to enhance axonal sprouting in early regeneration following transection and repair of the sciatic nerve in rodents. The purpose of this article was to determine the ability of ALCAR to enhance axonal regeneration in an ETS rodent model. METHOD: The right musculocutaneous nerve in 16 adult male Sprague-Dawley rats was transected to induce biceps muscle paralysis. The distal stump was then coapted by ETS neurorrhaphy through a perineurial window to the ipsilateral median nerve. Experimental groups received ALCAR for 1, 2, 3, and 4 weeks whereas controls received placebo. RESULTS: Weekly postoperative behavioral evaluations revealed increased functional return over control but the difference was not significant. Potentials from biceps were recorded from the third postoperative week in the experimental group and from the fourth week in the control group. Histomorphometric evaluations revealed higher musculocutaneous nerve axon counts, higher myelin thickness in the fourth postoperative week, and differences in the appearance and the number of motor-end-plates in the biceps in experimental versus control group. CONCLUSION: Intraperitoneal administration of ALCAR can expedite biceps muscle recovery in an ETS model by increasing the rate of axonal regeneration. Despite the morphological changes, no behavioral changes were noted and further studies are needed to confirm clinical efficacy of ALCAR for potential use in the development of therapeutic protocols.

Accidental intraneural injection into the musculocutaneous nerve visualized with ultrasound.

Ultrasound has become a widely used tool within the practice of regional anesthesia, offering real-time visualization of the nerves, needle, and local anesthetic during performance of a block. A successful ultrasound-guided axillary block was performed on a healthy adult male undergoing wrist surgery. Postoperative review of the ultrasound video recording of the block suggested that an intraneural injection had occurred during the procedure. The patient had an effective block and suffered no adverse neurological effects. Recording and reviewing ultrasound images of a regional block can be important for documentation and educational purposes.

Bilateral variant contributions in the formation of median nerve.

Bilateral variations in the formation of median nerve (Mn) and the recurrent course of its communications with musculocutaneous nerve (MCn) are very rare. These bilateral anomalies were observed during a routine dissection of the upper limbs of an adult male cadaver in the Department of Anatomy, PGIMER, Chandigarh. On both the sides, Mn was formed by the union of three roots. There was an additional lateral root on both sides. On the right side it was a contribution from the lateral cord and on the left it arose from the anterior division of the middle trunk. On the left side the lateral cord was formed distal than usual in relation to the second part of the axillary artery. On the right side a communicating branch arising from the additional lateral root followed a recurrent course and divided into two to unite separately with medial root of median, while on the left side a single communicating branch from an additional lateral root united with the medial root of median. Recurrent course of the communicating branch between lateral root of median and medial root of median has not been reported earlier. On the right side the MCn after piercing the coracobrachialis gave another communicating branch, which joined the Mn at the level of insertion of deltoid.

Confocal reflectance imaging of head and neck surgical specimens. A comparison with histologic analysis.

BACKGROUND: Confocal reflectance microscopy (CRM) is an optical method of imaging tissue noninvasively without the need for fixation, sectioning, and staining as in standard histopathologic analysis. Image contrast is determined by natural differences in refractive indices of organelles and other subcellular structures within the tissues. Gray-scale images are displayed in real time on a video monitor and represent horizontal (en face) optical sections through the tissue. We hypothesized that CRM is capable of discerning histologic characteristics of different tissues in the head and neck. OBJECTIVES: To examine the microscopic anatomy of freshly excised head and neck surgical specimens en bloc using CRM and to compare the findings with those generated by conventional histologic analysis. DESIGN: This was a pilot observational cohort study. Bone, muscle, nerve, thyroid, parotid, and ethmoid mucosa from human surgical specimens were imaged immediately after excision. Confocal images were compared with corresponding routine paraffin-embedded, hematoxylin-eosin-stained sections obtained from the same tissue. RESULTS: Characteristic histologic features of various tissues and cell types were readily discernible by CRM and correlated well with permanent sections. However, in all tissues examined, there was less microscopic detail visible in the CRM images than was appreciated in paraffin-embedded histologic sections. CONCLUSIONS: The CRM images revealed cytologic features without the artifacts of histologic processing and thus may have the potential for use as an adjunct to frozen-section analysis in intraoperative consultation.

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.

A variation of the musculocutaneous nerve absent.

A variation of the brachial plexus, characterized by the absence of the musculocutaneous nerve on the left arm, was found during the dissection of a 28-year old male cadaver. The whole lateral cord was joined to the median nerve, which it met in two points. One was a typical junction of both roots of the median nerve at the level of the coracoid process. The other was a junction of the remaining lateral cord and the median nerve, which was 92 mm away from the typical junction. This case provided some evidence about the absence of the musculocutaneous nerve, rather than a complete fusion of the median and musculocutaneous nerves. As the nerves are named due to their course or innervation, and not from their origin, it is reasonable to assume that the combined nerve was actually the median nerve, and that the musculocutaneous nerve did not exist.