Three-headed biceps brachii muscle associated with duplicated musculocutaneous nerve

A unilateral three-headed biceps brachii muscle coinciding with an unusual variant of the musculocutaneous nerve was found during routine dissection of a 79-year-old male cadaver. The supernumerary bicipital head originated from the antero-medial surface of the humerus just beyond the insertion of the coracobrachialis, and inserted into the conjoined tendon of biceps brachii. Associated with this muscular variant was a duplicated musculocutaneous nerve. The proximal musculocutaneous nerve conformed to the normal pattern only in its proximal part, and terminated after innervating the coracobrachialis and biceps brachii muscles. The distal musculocutaneous nerve arose from the median nerve in the lower arm, then passed laterally between the supernumerary bicipital head and the brachialis muscles, supplying both and terminating as the lateral cutaneous nerve of the forearm. The supernumerary bicipital head and the accompanying anomaly of the musculocutaneous nerve seem to be unique in literature.     

A variation of the brachial plexus characterized by the absence of the musculocutaneous nerve a case report

A variation of the brachial plexus characterized by the absence of the musculocutaneous nerve on both sides was observed during the dissection of a 72 year-old female cadaver. The long thoracic nerve included only the fibers from C5 and C6 on the left side. The musculocutaneous nerve was absent and two branches from the lateral cord innervated the coracobrachialis muscle. The median nerve innervated the biceps brachii and brachialis muscles in the arm and also gave off the lateral antebrachial cutaneous nerve. Additionally, a communicating branch was found from the median nerve to the ulnar nerve in the forearm. The knowledge of the anatomical variations of the peripheral nerve system can help give explanation when encountering an incomprehensible clinical sign.     

Destination of the C4 component of the prefixed brachial plexus

This study was carried out to elucidate the destination of the C4 ventral ramus that forms the prefixed brachial plexus. A total of 43 sides of Korean adults (male, 22; female, 18; unknown: 3 and right, 23; left, 20) were investigated. The various C4 destinations and their frequencies were as follows: suprascapular nerve, 97.7% (42/43); musculocutaneous nerve, 79.1% (34/43); the axillary nerve, 48.8% (21/43); and the nerve to subclavius, 16.2% (7/43). The mean quantity of nerve fibers destined to the suprascapular, musculocutaneous, and axillary nerves and the nerve to subclavius was 441.8 ± 316.5 (Mean ± S.D.), 298.2 ± 209.8, 245.8 ± 239.0, and 66.4 ± 17.2, respectively. The mean nerve fibers number of C4 contributing to the brachial plexus was 983.6 ± 618.0 (range: 100-1729). The main component that contributes to the terminal nerves (suprascapular, musculocutaneous, axillary nerves, and nerve to subclavius) is C5. These results may be useful to surgeons and clinicians dealing with terminal nerves of the brachial plexus, especially the suprascapular, musculocutaneous, and axillary nerves.     

An abnormal muscle in the superficial region of the popliteal fossa

An abnormal muscle was observed in the superficial region of the popliteal fossa during a dissection procedure conducted for medical students. This abnormal muscle originated from the biceps femoris tendon and inserted into the medial head of the gastrocnemius muscle. The innervating nerve branched from the lateral sural cutaneous nerve. The distributing artery arose from a branch of the sural artery. This abnormal muscle mostly comprised one sheet of muscle mass (not tendon type) and ran transversely.     

肩胛上神经及其冈上肌干支入肌点的应用解剖

目的探讨肩胛上神经的行程和冈上肌干支入肌点,为肩部疾病的诊治提供解剖形态学基础。方法对15具(30侧)成人上肢标本,观察肩胛上神经及其分支冈上肌支的走行、分段、体表定位和冈上肌支入肌点进行研究。结果肩胛上横韧带前段的肩胛上神经主干长4.03～5.23(4.36±0.60)cm,外径2.21～4.45(4.22±0.63)mm;骨纤维管内肩胛上神经外径与入管前一样;出管后肩胛上神经的分支冈上肌干支长1.24～0.90(3.78±0.23)cm,外径为0.54～2.01(1.82±0.20)mm。冈上肌干支入肌点距孔后为1.15～2.01(8.22±5.20)mm。结论①肩胛上神经行程较长,穿越骨纤维管位置恒定,易发生卡压,其体表定位位于距离肩峰最外端约6 cm处。②冈上肌干支伴血管行走,距孔后约1 cm入肌体,位置相对恒定,其体表定位相当于锁骨锥状结节的后方约3 cm处,入肌内分有前、中、后三支。     

A rare case of a four-headed biceps brachii muscle with a double piercing by the musculocutaneous nerve

A rare case of a four-headed biceps brachii muscle associated with a double piercing of one of the supernumerary heads by the musculocutaneous nerve was observed in the right arm of an 87-year-old female cadaver. One of the supernumerary heads of the biceps brachii originated from the humerus, in the area between the lesser tubercle and the coracobrachialis and brachialis muscles and joined the long head at the level where the latter joined the short head. The second supernumerary head originated from the humerus at the point where the coracobrachialis muscle inserted and joined the biceps brachii tendon and its bicipital aponeurosis at the inferior third of the arm. The musculocutaneous nerve originated from the lateral cord of the brachial plexus and, after piercing the coracobrachialis muscle, coursed along one of the supernumerary heads of the biceps brachii muscle before piercing it from deep to superficial and then again from superficial to deep. It then adopted its normal position between the biceps brachii and brachialis muscles before exiting in the lateral aspect of the arm and continuing as the lateral cutaneous nerve of the forearm.

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Un cas rare de muscle biceps brachial à 4 chefs accompagné d'une double perforation par le nerf musculo-cutané

Résumé Un cas rare associant un muscle biceps brachial à 4 chefs à une double perforation de l'un des chefs surnuméraires par le nerf musculo-cutané a été observé sur le bras droit du cadavre d'une femme de 87 ans. Un des chefs surnuméraires du muscle biceps brachial naissait de l'humérus, d'une zone située entre le tubercule mineur et les muscles coraco-brachial et brachial et rejoignait le chef long au niveau où celui-ci rejoignait le chef court. Le second chef surnuméraire naissait de l'humérus à l'endroit où le muscle coraco-brachial s'insèrait et il rejoignait le muscle biceps brachial et l'aponévrose bicipitale au tiers inférieur du bras. Le nerf musculo-cutané naissait du faisceau latéral du plexus brachial et, après avoir percé le muscle coraco-brachial, cheminait le long d'un des chefs surnuméraires du muscle biceps brachial avant de le traverser, de la profondeur à la surface, puis à nouveau de la surface à la profondeur. Il adoptait alors un trajet normal, entre les muscles biceps brachial et brachial, avant de sortir dans le sillon bicipital latéral, se poursuivant sous forme du nerf cutané latéral de l'avant-bras.

     

Radial artery running beneath the biceps tendon and its interrelation between the radial recurrent arteries

A radial artery running beneath the biceps tendon was found in the cadaver of a Japanese woman during a student dissection course at Kumamoto University School of Medicine in 2006. The brachial artery bifurcated into the radial artery and the ulnar artery in the cubital fossa, and the radial artery twisted laterally running beneath the biceps tendon, and when it was situated laterally to the tendon, twisted distally at the level of the radial tuberosity, and then twisted medially again. After the radial artery passed over the biceps tendon, it turned distally and continued as a normal radial artery. The superficial brachial artery, which coexisted with the brachial artery, was given off from the axillary artery and it continued to the final twist of the radial artery. The course of this radial artery is similar to the arterial rings surrounding the biceps tendon, found during the same dissection course. The arterial rings were formed between the brachial artery and the radial artery, and their proximal origins ran beneath the biceps tendon, while the distal origins were superficial. The present arterial variation is thought to have occurred when the normal part of the radial artery in the cubital fossa was substituted by the arterial ring, coexisting with the superficial brachial artery, which usually disappears during normal development. Furthermore, it is suggested that a part of the arterial ring always remains as a radial recurrent artery.     

Relationships of the musculocutaneous nerve and the coracobrachialis during coracoid abutment procedure (Latarjet procedure)

Purpose  The aim of this study was first to define first the anatomical relationships between the musculocutaneous nerve and the coracobrachialis, and then the induced modifications of these relationships by a preglenoid transposition of the vertical part of the coracoid process. Materials and methods  Twenty-one embalmed adult trunks and upper limb were dissected. First the coracobrachialis and the musculocutaneous nerve were identified through a deltopectoral approach. We measured the distances between the lateral cord of the brachial plexus and the entry point of the nerve, between the inferior tip of the tip of the coracoid process and the penetration of the nerve or its twigs, and finally the angle between the general axis of the coracobrachialis and the axis of the musculocutaneous nerve. The same measures were performed after the coracoid bone block abutment. Results  Proximal motor branches destined to the coracobrachialis varied from 0 to 3. Mean distance between the lateral cord of the brachial plexus and entry point of the nerve into the muscle was 47.2 mm before and 48.43 mm after the coracoid transfer. Mean angulations between the nerve and the muscle was 121° before and 136° after the transfer of the coracoid process. Mean distance between the inferior tip of the coracoid process and entry point of the nerve into the muscle was 55.7 mm, reduced to 48.6 mm after the coracoid transposition. Finally, the distance between the tip of the coracoid and the first motor twig entering the coracobrachialis was less than 50 mm in 75% of the cases with a mean value of 40.6 mm. Conclusions  Lesion of the musculocutaneous nerve is a known complication of the coracoid bone block abutment procedure (Latarjet–Bristow). From this study we know that they are due to lengthening of the nerve and modification of the penetration angle of the nerve into the coracobrachialis. We also infer that some motor nerve destined to the coracobrachialis might be damaged during the proximal medial release of the muscle after the detachment of the pectoralis minor muscle.     

Anatomy and surgical landmarks for the ansa pectoralis: application to pectoralis major nerve selective neurotomy

Background

Ansa pectoralis neurotomy is a surgical approach in the treatment of the pectoralis major muscle spasticity causing an attitude in adduction and internal rotation of the shoulder.

Objective

To establish the anatomical landmarks allowing an easier localisation of the ansa pectoralis during neurotomy.

Material and methods

Fifteen adult human cadavers (10 embalmed and 5 fresh) were dissected in order to determine anatomical landmarks allowing an easier localization of the ansa pectoralis during neurotomy.

Results

In all the cadavers, the lateral pectoral nerve arose from the lateral cord of the brachial plexus, 0.2 cm above to 1.5 cm below the inferior border of the clavicle with a mean distance of 0.76 cm for left and right side, whereas the medial pectoral nerve arose from the medial cord of the brachial plexus, 0.7–2.3 cm below the inferior border of the clavicle with a mean distance of 0.61 cm for the left side and 0.68 cm for the right side. We systematically found both the origin of pectoral nerves and the ansa pectoralis at the level of the middle third of the distance between the sternoclavicular and the acromioclavicular joints. Moreover, ansa pectoralis was constantly localized lateral to the thoracoacromial artery. In four cases, the division of the lateral pectoral nerve was not found. In one case, medial pectoral nerve did not exist.

Conclusion

Ansa pectoralis can be found by a curved incision made at the mid-third of the distance between the sternoclavicular and the acromioclavicular joints, the medial point being located just below the lower edge of the clavicle and the lateral point 2 cm below the inferior edge of the clavicle.     

Posterior approach technique for accessory-suprascapular nerve transfer: a cadaveric study of the anatomical landmarks and number of myelinated axons

Accessory-suprascapular nerve transfer by the anterior supraclavicular approach technique was suggested to ensure transferrance of the spinal accessory nerve to healthy recipients. However, a double crush lesion of the suprascapular nerve might not be sufficiently demonstrated. In that case, accessory-suprascapular nerve transfer by the posterior approach would probably solve the problem. The aim of this study was to evaluate the anatomical landmarks and histomorphometry of the spinal accessory and suprascapular nerve in the posterior approach. Dissection of fresh cadaveric shoulder in a prone position identified the spinal accessory and suprascapular nerve by the trapezius muscle splitting technique. After that, nerves were taken for histomorphometric evaluation. The spinal accessory nerve was located approximately halfway between the spinous process and conoid tubercle. The average distance from the conoid tubercle to the suprascapular nerve (medial edge of the suprascapular notch) is 3.3 cm. The mean number of myelinated axons of the spinal accessory and suprascapular nerve was 1,603 and 6,004 axons, respectively. The results of this study supported the brachial plexus reconstructive surgeons, who carry out accessory-suprascapular nerve transfer by using the posterior approach technique. This technique is an alternative for patients who have severe crushed injury of the shoulder or suspected double crush lesion of the suprascapular nerve.     

An unusual origin for the accessory head of biceps brachii muscle

During the superficial dissection of the pectoral region and the arm, an abnormal biceps brachii muscle was observed unilaterally. This muscle had three heads. Whereas the short and long heads had their normal origin, the accessory head originated from the anterior surface of the distal part of the pectoralis major muscle, which formed the anterior axillary fold. To our knowledge, this variation has not been previously described. Innervation and vascular supply of this accessory head was from the musculocutaneous nerve and the brachial artery, respectively. © 1996 Wiley-Liss, Inc.     

Accessory muscles in the lower part of the anterior compartment of the arm that may entrap neurovascular elements

The aim of this study was to evaluate the incidence of abnormal muscular bands of the anterior compartment of the arm that may compress the median, the ulnar, and the medial antebrachial cutaneous nerve as well as the brachial artery and vein, thus causing entrapment at and above the elbow. A total of 56 adult cadavers were studied during routine dissections that occurred in our laboratory. In the 112 upper limbs studied, we found three variant muscles of the flexor compartment of the arm (2.68%) entrapping nerves and vessels. The first muscle was emerging from the tendon of long head of biceps brachii and coracobrachialis muscle insertion. The second muscle inserted partially into the belly of biceps brachii and should be considered as a supernumenary head of biceps brachii. The third muscle, in fact, represents an accessory fascicle of the brachialis muscle that is an embryonic remnant of that muscle. A number of structures cross anterior to the median, ulnar, and medial antebrachial cutaneous nerve as well as the brachial artery and vein. Compression of nerves and vessels may be caused by additional muscular bundles that pass anterior to these structures. These additional muscular bundles arise either from the brachialis, coracobrachialis, or biceps brachii muscle. Such variations have clinical implications and should be considered in patients, with a high median or ulnar or medial antebrachial cutaneous nerve paralysis with symptoms of lower brachial artery or brachial vein compression.     

锁骨下肌的临床解剖学观测

目的:为临床治疗锁骨下肌因素引起臂丛神经血管受压征提供解剖学资料。方法:26具常规防腐保存的尸体,重点观察锁骨下肌的形态、神经支配。结果:锁骨下肌缺如7.7％(4/52侧),肌性部长9.3±0.8cm,宽1.1±0.2cm,厚1.0±0.3cm,锁骨下肌的神经成分来源于颈5、6神经根,偶有发自膈神经或颈丛(4％),多见在于水平发出(32.5％)。发出平面为锁骨上2.3±1.0cm,外径约0.9cm。结论:锁骨下肌异常可影响到臂丛神经血管。行锁骨下神经切断术时,应在臂丛上干与肌的内1/3之间区域内寻找,防止损伤内侧的膈神经。     

Vascular anatomical basis of clavicular non-union

The middle third of the clavicle is commonly involved in any injury and account for 5–10% of all fractures in adults. Although non-unions are rare, their treatment has not been well defined yet. This report describes the arterial supply of the clavicle to clarify the pathological mechanism and the surgical procedure of non-unions. This study was based on delineation of the thoraco-acromial and suprascapular arteries with colored latex on 17 specimens (ten cadavers). Observations were made after macroscopic dissection and maceration. The main blood supply to the middle third of the clavicle was the periosteal. This supply came from the two branches of the thoraco-acromial trunk that penetrated the pectoralis major muscle and the deltoid muscle. In 13 cases, these two periosteal branches were anastomosed between these two muscle attachments. Periosteal vascularization was always seen on the superior surface and the anterior border of the bone, but never on the inferior surface or the posterior border. The suprascapular artery contributed to supply the middle third of the clavicle by several periosteal branches and also by an independent branch. This branch was born proximally near the internal, middle thirds union and passed along the posterior face of the subclavius muscle and pierced the bone through the nutria foramina located near the external, middle thirds union. Nevertheless, intraosseous arteries were noted only in four cases. In these cases, they were never more than 2cm long. Our results showed that the periosteal blood supply located between the muscles insertions and the arterial supply from the suprascapular artery could be twice compromised in case of important displacement or severe fracture. If treatments of clavicular fractures or non-unions cannot preserve the periosteal blood supply, bone grafting should be indicated.     

Supernumerary head of biceps brachii and branching pattern of the musculocutaneus nerve in Japanese

Summary Out of 546 upper limbs (273 cadavers), supernumerary heads of the biceps brachii were found in 75 limbs (13.7%) of 58 cadavers (21.3%). The form, origin, and insertion of the supernumerary heads, and branching pattern of the musculocutaneus nerve were studied. In addition, the dimensions of the heads were measured. In many cases, the supernumerary head arose from the humerus, between the insertion of the coracobrachialis and the upper part of the origin of the brachialis, and/or from the medial intermuscular septum. In a few cases, a supernumerary head arose from the tendon of the pectoralis major or the deltoid, or from the articular capsule, or from the crest of the greater tubercle. The supernumerary heads typically joined the common belly, or the aponeurosis of the biceps brachii. Some heads joined the belly of the long head or that of the short head. In the examination of the branching pattern of the musculocutaneus nerve, communication between the musculocutaneus nerve and the median nerve was found in 43 out of the 75 limbs (57.3%). The communicating branch ran from the musculocutaneus nerve to the median nerve in 24, from the median nerve to the musculocutaneus nerve in 12, in both directions in 5, or in another type of pattern in 2 out of 43 limbs. Sometimes a branch of the musculocutaneus nerve ran around a supernumerary head and then fused with the present trunk. The presence of a supernumerary head seemed to affect the course and branching of the musculocutaneus nerve.

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Chef surnuméraire du biceps brachial et organisation du nerf musculo-cutané chez les japonais

Résumé A partir de l'étude de 546 membres supérieurs (273 cadavres) nous avons trouvé 75 cas (chez 58 cadavres) de chef surnuméraire de muscle biceps brachial (21.3%). Nous en avons étudié la forme, le trajet, la taille et les insertions ainsi que l'organisation des divisions du nerf musculo-cutané. Dans de nombreux cas le chef surnuméraire provient soit de l'humérus où il s'insère entre le m. coraco-brachial et la partie proximale du muscle brachial soit/et du septum intermusculaire médial. Dans quelques cas un chef surnuméraire a été observé à partir du tendon du m. grand pectoral ou du m. deltoïde ou encore de la capsule articulaire, voire du tubercule majeur. II rejoint habituellement le chef commun du m. biceps brachial ou son aponévrose. Parfois la jonction se fait sur l'un ou l'autre des deux corps musculaire. L'étude du n. musculo-cutané montre une anastomose avec le nerf médian dans 43 des 75 membres concernés (57.3%). Cette branche anastomotique va du n. musculo-cutané au nerf médian dans 24 cas et du n. médian au n. musculo-cutané dans 12 cas, elle va dans les deux directions dans 5 cas; dans les 2 cas restant le modèle d'anastomose est variable. Parfois une branche du n. musculo-cutané entoure le chef surnuméraire et fusionne ensuite avec le tronc du nerf. La présence d'un chef surnuméraire semble donc modifier le trajet et les connexions du nerf musculo-cutané.

     

Surgical anatomy of the platysma motor branch as a donor for transfer in brachial plexus repair

Object  Nerve transfers have become a major weapon in the battle against brachial plexus lesions. Recently, a case involving the successful use of the platysma motor branch to re-innervate the pectoralis major muscle was reported. The present anatomical study was conducted to clarify the surgical anatomy of the platysma motor nerve, in view of its potential use as a donor for transfer. Methods  Microsurgical dissections of the facial nerve and its terminal branches were performed bilaterally in five formaldehyde-fixed cadavers, thereby yielding ten samples for study. The relationships between the platysma motor branch and adjacent structures were studied and measurements performed. Specimens were removed and histologically studied. Results  The platysma branch of the facial nerve was found to arise from the cervicofacial trunk. In five instances, one main nerve innervated the platysma muscle, and there was a smaller accessory nerve; in four cases, there was just a single branch to the muscle; and in one case, there was a main branch and two accessory branches. The distance between the gonion and the platysma motor branch averaged 0.8 cm (range 0.4–1.1 cm). The platysma branch received thin anastomotic rami from the transverse superficial cervical plexus. The neural surface of the platysma motor branch, on average, was 76% the surface area of the medial pectoral nerve. Conclusion  The anatomy of the platysma motor branch is predictable. Contraction of the platysma muscle is under voluntary control, which is an important quality for a donor nerve selected for transfer. The clinical usefulness of platysma motor branch transfer still must be elucidated.     

Musculocutaneous and median nerve branching: anatomical variations. Case Series from UR clinical anatomy and literature review

IntroductionThe brachial plexus is highly variable, which is a well-known anatomical fact. Repeated observations on anatomical variations, however, constitute current trends in anatomical research.Case seriesIn an anatomical dissection course, three uncommon variations in the brachial plexus were identified in three young adults'' cadavers. In one case, the musculocutaneous nerve gave a branch to the median nerve, while the median nerve gave or received musculocutaneous branches in the two remaining corpses.ConclusionAnatomical variations of the brachial plexus do occur in our setting. The cases we presented are about anatomical variations of branching patterns of the median and musculocutaneous nerves. Knowledge of those variations is essential for surgery and regional anesthesia of the upper limbs.     

Survival and regeneration of cutaneous and muscular afferent neurons after peripheral nerve injury in adult rats

Peripheral nerve injury induces the retrograde degeneration of dorsal root ganglion (DRG) cells, which affects predominantly the small-diameter cutaneous afferent neurons. This study compares the time-course of retrograde cell death in cutaneous and muscular DRG cells after peripheral nerve transection as well as neuronal survival and axonal regeneration after primary repair or nerve grafting. For comparison, spinal motoneurons were also included in the study. Sural and medial gastrocnemius DRG neurons were retrogradely labeled with the fluorescent tracers Fast Blue (FB) or Fluoro-Gold (FG) from the homonymous transected nerves. Survival of labeled sural and gastrocnemius DRG cells was assessed at 3 days and 1–24 weeks after axotomy. To evaluate axonal regeneration, the sciatic nerve was transected proximally at 1 week after FB-labeling of the sural and medial gastrocnemius nerves and immediately reconstructed using primary repair or autologous nerve grafting. Twelve weeks later, the fluorescent tracer Fluoro-Ruby (FR) was applied 10 mm distal to the sciatic lesion in order to double-label sural and gastrocnemius neurons that had regenerated across the repair site. Counts of labeled gastrocnemius DRG neurons did not reveal any significant retrograde cell death after nerve transection. In contrast, sural axotomy induced a delayed loss of sural DRG cells, which amounted to 22% at 4 weeks and 43–48% at 8–24 weeks postoperatively. Proximal transection of the sciatic nerve at 1 week after injury to the sural or gastrocnemius nerves neither further increased retrograde DRG degeneration, nor did it affect survival of sural or gastrocnemius motoneurons. Primary repair or peripheral nerve grafting supported regeneration of 53–60% of the spinal motoneurons and 47–49% of the muscular DRG neurons at 13 weeks postoperatively. In the cutaneous DRG neurons, primary repair or peripheral nerve grafting increased survival by 19–30% and promoted regeneration of 46–66% of the cells. The present results suggest that cutaneous DRG neurons are more sensitive to peripheral nerve injury than muscular DRG cells, but that their regenerative capacity does not differ from that of the latter cells. However, the retrograde loss of cutaneous DRG cells taking place despite immediate nerve repair would still limit the recovery of cutaneous sensory functions.     

An anomalous muscle in the superficial region of the popliteal fossa, with special reference to its innervation and derivation

An anomalous muscle was found in the superficial region of the right popliteal fossa in a 90-year-old Japanese female cadaver during dissection practice for medical students. The muscle ran transversely between the medial head of the gastrocnemius muscle and the tendon of the biceps femoris muscle, covering the nerves, vessels and muscle in the popliteal fossa. The muscle received its nerve supply from the common peroneal nerve. Based on the result of nerve fiber analysis, we speculated that the anomalous muscle might be close to the short head of the biceps femoris muscle in its derivation.