Atypical branching of the musculocutaneous and median nerves with associated unusual innervation of muscles in the anterior compartment of the arm: case report and plea for extension of the current classification system.

PURPOSE: Variations of the peripheral nervous system in the upper limb, especially of the musculocutaneous and median nerves, are common, but closer attention to the knowledge of the variant anatomy should be paid to avoid iatrogenic injury or to understand the unusual clinical signs. METHODS: During a routine dissection course, bilateral variations were observed in a Central European male cadaver. RESULTS: Variable branching of the musculocutaneous and median nerves associated with atypical innervation of the muscles in the anterior compartment of the arm and other concomitant variations were found bilaterally. In both cases, the musculocutaneous nerve innervated only the coracobrachialis muscle and terminated inside the muscle belly. Branches to the biceps brachii and brachialis muscles arose either directly from the median nerve or its branches. On the right side, two communicating branches between the roots of the median nerve were noted, and a common medial cutaneous trunk originated from the lateral cord. On the left side, a communicating branch extended from the lateral cord to the medial root of the median nerve and a tributary to the axillary vein passed through a window formed by the roots of the median nerve and the communicating branch. CONCLUSION: There exist only few cases in the literature describing similar variations, but the present arrangement has not yet been reported to the best of our knowledge. With the proposed extension to the existing classification system, we aim to provide clearer orientation in the variability of the musculocutaneous and median nerves.

The superficial anatomical landmarks are not reliable for predicting the recurrent branch of the median nerve.

PURPOSE: The variability of the recurrent branch (RB) of the median nerve lends itself to an increased risk of injury when performing the minimally invasive approach for carpal tunnel release without its direct visualization. This risk is less so when it is released via the more invasive open approach as the RB can be easily identified, but the drawback is that of longer postoperative patient recovery time. Therefore, performing these releases via the less invasive approach should be more favorable for patients providing it could be done safely. Hence with there being a positive link between the hypertrophy of the thenar musculature and the course of RB according to previous studies. METHODS: We dissected 28 hands of 14 donated bodies fixed using Thiel's method to try to demonstrate these findings of the associations among the RB, palmar creases and other superficial anatomical landmarks. Fisher's exact test was conducted to verify the relationship between those structures statistically. RESULTS: Statistically significant links were found between the type of the RB and the type of the palmar creases (p value = 0.0094) and between the RB type and the palmaris longus muscle presence (p value = 0.028). CONCLUSION: It was inferred that palmar creases and other superficial anatomical landmarks listed in the text could not be used to predict the variability of the RB and the choice of mini-invasive approach should not be based on their course.

Electrophysiological Findings in Common Median-Ulnar Nerve Interconnections and Their Clinical Implications.

Median and ulnar nerve interconnections commonly occur in the brachial plexus, forearm, and hand. Each is classified based on location, fiber type (sensory fibers, motor fibers, or both), and directionality (ie, carrying fibers from median to ulnar or vice versa). There are 4 main interconnections found in the forearm and hand: Martin-Gruber and Marinacci anastomoses in the forearm and Riche-Cannieu and Berrettini anastomoses in the hand. The presence of an interconnection may skew electrodiagnostic findings, possibly resulting in misdiagnosis and iatrogenic injury. Clinicians should perform nerve studies of both nerves at proximal and distal stimulation sites to rule out interconnections and guide treatment. This review details anatomy, electrodiagnostic findings, and clinical approach.

Hypoplastic superficial brachioradial artery coexisting with atypical formation of the median and musculocutaneous nerves: a rare combination of unusual topographical relationships.

The use of the term "brachioradial artery" was introduced for the high origin of the radial artery. Although the prevalence of the brachioradial artery reported by different authors varies from 4.67 to 15.6%, the presence of the hypoplastic brachial segment of the brachioradial artery is rare with an occurrence rate of 0.83%. Moreover, in just 0.6% of cases the loop of the median nerve may be placed near half of the length of the brachial artery, as in the case described in our report. A comprehensive understanding of anatomical variations of neurovascular structures in the upper limb is of great clinical significance. The presented case report illustrates a rare manifestation of persistent primitive developmental relationships in the arterial pattern of the upper limb (persistent, hypoplastic brachial segment of the superficial brachioradial artery), coexisting with atypical formation of the median and musculocutaneous nerves. Anatomical variations of vessels and nerves may coexist which should be taken into account when performing vascular, reconstructive or orthopedic surgery.

Our Surgical Experience: Open Versus Endoscopic Carpal Tunnel Surgery.

Carpal tunnel release is one of the most common hand operations in the United States and every year approximately 500,000 patients undergo surgical release. In this article, we examine the argument for endoscopic carpal tunnel release versus open carpal tunnel release, as well as some of the literature on anatomical variants in the median nerve at the wrist. We further describe the experience of several surgeons in a large academic practice. The goals of this article are to describe key anatomic findings and to present several cases that have persuaded us to favor offering patients open carpal tunnel release.

Anatomic Variation of the Median Nerve Associated with an Anomalous Muscle of the Forearm.

Documented anatomical variations are important not only for the study of the subject of anatomy, but also in clinical situation. This knowledge would aid surgeons in planning a preoperative strategy for surgical procedures and reconstructive surgery. The right forearm of a 35-year-old embalmed male cadaver present a splitting of the median nerve in the proximal 1/3 of the forearm to form medial and lateral divisions that accommodate an anomalous muscle. The split median nerve reunites at the distal 1/3 and continues as a single nerve. The anomalous muscle arises by muscle fibers from flexor digitorum superficialis and inserted by tendon into flexor digitorum profundus. There was no such variation in the left forearm. The knowledge of such anatomical variations is important to clinicians and surgeons in interpreting atypical clinical presentations and avoiding unusual injury during surgery.

Median and ulnar nerve anastomoses in the upper limb: A meta-analysis.

INTRODUCTION: The most frequently described anomalous neural connections between the median and ulnar nerves in the upper limb are: Martin-Gruber anastomosis (MGA), Marinacci anastomosis (MA), Riche-Cannieu anastomosis (RCA), and Berrettini anastomosis (BA). The reported prevalence rates and characteristics of these anastomoses vary significantly between studies. METHODS: A search of electronic databases was performed to identify all eligible articles. Anatomical data regarding the anastomoses were pooled into a meta-analysis using MetaXL 2.0. RESULTS: A total of 58 (n = 10,562 upper limbs) articles were included in the meta-analysis. The pooled prevalences were: MGA, 19.5% (95% confidence interval [CI], 16.2%-23.1%); MA, 0.7% (95% CI, 0.1%-1.7%); RCA, 55.5% (95% CI, 30.6%-79.1%); and BA, 60.9% (95% CI, 36.9%-82.6%). The results also showed that MGA was more commonly found unilaterally (66.8%), on the right side (15.7%), following an oblique course (84.8%), and originating from the anterior interosseous nerve with a prevalence of 57.6%. CONCLUSIONS: As anastomoses between the median and ulnar nerves occur commonly, detailed anatomical knowledge is essential for accurate interpretation of electrophysiological findings and reducing the risk of iatrogenic injuries during surgical procedures. Muscle Nerve 54: 36-47, 2016.

Incidence of an Anomalous Course of the Palmar Cutaneous Branch of the Median Nerve During Volar Plate Fixation of Distal Radius Fractures.

PURPOSE: Volar plating of distal radius fractures using an approach through the flexor carpi radialis (FCR) sheath is commonplace. The palmar cutaneous branch of the median nerve (PCB) is considered to run in a position adjacent to, but outside, the ulnar FCR sheath. Anatomic studies have not identified anatomic abnormalities relevant to volar plating. The purpose of this study was to determine the frequency of anomalous PCB branches entering the FCR sheath during volar plating. METHODS: This observational study involved 10 attending hand surgeons during a 7-month period (July 2015-January 2016). Surgeons assessed, documented, and reported any PCB anomalies that were encountered during volar plating through a trans-FCR approach. RESULTS: There were 182 volar plates applied that made up the study group. There were 10 cases (5.5%) of anomalous PCBs entering the FCR sheath. In 4 cases, the PCB pierced the radial FCR sheath proximally, crossed beneath the tendon, and traveled distally on the ulnar side. In 4 other cases, the PCB entered the FCR sheath proximally on the ulnar or central aspect of the sheath and remained within the sheath, staying along the ulnar or dorsal side of the tendon. In 1 case, the PCB pierced the ulnar distal aspect of the sheath and split into 2 branches. In 1 case, the PCB ran within the sheath along the radial aspect of the FCR. CONCLUSIONS: Anomalies in the course of the PCB are more common than often considered. These variants are at risk during volar surgical approaches to the wrist that proceed through the FCR sheath. CLINICAL RELEVANCE: Although dissecting along the radial side of the FCR sheath may protect the PCB in most cases, care must be taken to identify anomalous branches (if present) and protect them during surgery.

An arterial island pattern of the axillary and brachial arteries: a case report with clinical implications.

The variability of axillary and brachial arteries is often associated with neural anomalies in arrangement of the brachial plexus. The current report is focused on the coexistence of two brachial arteries of axillary origin with an atypical median nerve formatted by three (two lateral and a medial) roots in the right arm of a 68-year-old male cadaver. Medially, the brachial artery located in front of the median nerve was named superficial brachial artery and anastomosed with the brachial artery situated posterolateral to the median nerve, hence it is referred as the main brachial artery or brachial artery. Subsequently, the two arteries were recombined and the created arterial complex, like an island pattern, ended dividing into radial and ulnar arteries, at the level of the radial neck. To our knowledge, the combination of the above-mentioned arterial pattern to an abnormally formatted median nerve has not yet been cited. The current neurovascular abnormalities followed by an embryological explanation may have clinical implications.

Five Roots Pattern of Median Nerve Formation.

An unusual combination of median nerve's variations has been encountered in a male cadaver during routine educational dissection. In particular, the median nerve was formed by five roots; three roots originated from the lateral cord of the brachial plexus joined individually the median nerve's medial root. The latter (fourth) root was united with the lateral (fifth) root of the median nerve forming the median nerve distally in the upper arm and not the axilla as usually. In addition, the median nerve was situated medial to the brachial artery. We review comprehensively the relevant variants, their embryologic development and their potential clinical applications.

Ulnar neuropathy with prominent proximal Martin-Gruber anastomosis.

Martin-Gruber anastomosis (MGA) is the most common nerve anastomosis in the upper extremities and it crosses from the median nerve to the ulnar nerve. Proximal MGA is an under recognized anastomosis between the ulnar and median nerves at or above the elbow and should not be missed during nerve conduction studies. We presented two patients with ulnar neuropathy mimicking findings including numbness and tingling of the 4th and 5th digits and mild weakness of intrinsic hand muscles. However, both cases had an apparently remarkable conduction block between the below- and above-elbow sites that was disproportionate to their clinical findings. To explain this discrepancy, a large MGA was detected with stimulation of the median nerve at the elbow. Thus, proximal MGA should be considered in ulnar neuropathy at the elbow when apparent conduction block or/and discrepancy between clinical and electrodiagnostic findings is found.

Sonographic diagnosis of anatomical variations associated with carpal tunnel syndrome.

Bifid median nerve is an anatomic variation that occurs in about 18% of patients with symptoms suggestive of carpal tunnel syndrome and in about 15% of symptom-free subjects. Reversed palmaris longus is a rare anatomic muscular variation. The simultaneous presence of a bifid median nerve and a reversed palmaris longus has been very rarely described, usually during surgical exploration or in cadavers. We present two cases where ultrasound showed the presence of both abnormalities, allowing a correct diagnosis and influencing the treatment plan.

Electrophysiological and ultrasonographic findings in ulnar neuropathy with Martin-Gruber anastomosis.

INTRODUCTION: It is important to understand the presence of Martin-Gruber anastomosis in patients with complete ulnar neuropathy at the elbow. CASE REPORT: We describe a patient with complete ulnar neuropathy at the elbow and Martin-Gruber anastomosis in the forearm, mimicking incomplete ulnar neuropathy with complete conduction block in the forearm segment. Ultrasonography of the ulnar nerve around the elbow demonstrated severe swelling of the ulnar nerve, which was compatible with severe ulnar neuropathy at the elbow. CONCLUSIONS: This case report demonstrates that combination of ultrasonography with electrophysiological studies can provide more detailed information about the changes of nerve structures and lesion sites.

A new anatomical variation of the musculocutaneous and the median nerve anastomosis.

Variations of the brachial plexus and its terminal branches are not uncommon.Therein, the anatomical variations of the musculocutaneous and the median nerve are classified into 5 types, while the communicating branches between the musculocutaneous and the median nerve are classified into 3 types, depending on their position related to the coracobrachial muscle. The case reviewed in this paper presents a variation similar to that of the second variety, but is significantly different due to the appearance of the proximal musculocutaneous nerve and its communicating branching, the site rising from the communicating branch (through the coracobrachial), and important clinical implications of this new variation. Despite the communicating branch being located in the upper third of the upper arm, it should not be considered as being a double lateral root of the median nerve.

Median nerve (anatomical variations) and carpal tunel syndrome - revisited.

Carpal tunnel syndrome belongs to the most common causative factors of surgical interventions in the wrist region. Anatomy of carpal tunnel and median nerve is a subject of current revision. Authors paid attention to etiology of the syndrome based on review of literature and their own anatomical studies. They remind basic knowledge on the median nerve and indicate that only based on number of dissections a good orthopedic surgeon may acquire experience necessary to perform procedures in a most appropriate way.

Unusual formation of the median nerve associated with the third head of biceps brachii.

Unilateral variations in the formation of the median nerve, with the presence of the third head of the biceps brachii entrapping the nerve are very rare. These variations were observed on the right side, of a 30-year-old male cadaver during routine dissection at the Department of Human Anatomy, University of Nairobi. The median nerve was formed by the union of three contributions; two from the lateral cord and one from the medial cord. An additional head of the biceps brachii looped over the formed median nerve. On the left side, the median nerve was formed classically by single contributions from the medial and the lateral cords. These variations are clinically important because symptoms of high median nerve compression arising from similar formations are often confused with more common causes such as radiculopathy and carpal tunnel syndrome.

A coexisting anatomical variation of median and ulnar nerves in a cadaver palm.

During a routine dissection we observed an anatomical variation of the median nerve and an atypical anastomosis in the palm region of a male cadaver. There were four distinct recurrent motor branches of the left median nerve, and the palmar cutaneous branch of the ulnar nerve communicated directly with the third common palmar digital nerve. The presence of such an anatomical variant in the hand should keep surgeons alert in the management of hand pathology especially in carpal tunnel syndrome, which is a routine operation for many medical centres.

Variations in the formation of the median nerve and its clinical correlation.

Variations in the formation of the median nerve are of interest to anatomists, radiologists, and surgeons. These variations may be vulnerable to damage in surgical operations, but their knowledge also helps in the interpretation of a nervous compression having unexplained clinical symptoms. We studied the variation in the formation of the median nerve in 87 cadavers, i.e. 174 upper limbs of formalin preserved cadavers at the department of Anatomy, Subharti medical college. We observed an additional root taking part in the formation of the median nerve in 26.4% of upper limbs, unusual low formation of the median nerve in the arm in front of the brachial artery in 18.4% of upper limbs, and median nerve formation medial to the axillary artery in 10.3% of upper limbs. Knowledge of such anatomical variations is of interest to the anatomist and clinician alike. Surgeons who perform procedures involving neoplasm or trauma repair need to be aware of these variations.

Asymmetric bilateral variations in the musculocutaneous and median nerves with high branching of brachial artery.

Brachial Plexus is formed by the union of the anterior rami of cervical 5, 6, 7, 8 and thoracic 1 nerves. These nerves unite and divide to form the key nerves innervating the upper limb. Variations in the course of these nerves are clinically important to anesthetists, neurologists and orthopedicians. We report bilateral variations in the arterial and neural structures in the upper limb of a 65 year old cadaver. The muscles of the arm on one side were innervated by the median nerve with absence ofmusculocutaneous. While on the other side the musculocutaneous nerve contributed to the formation of the median nerve. There was a presence of high bifurcation of brachial artery on both sides. Knowledge of such variations in the innervations of muscles and the arterial supply of the limbs are important to remember before performing any reconstructive procedures or interventions on the limb.