Neuroanatomy of the brachial plexus: the missing link in the continuity between the central and peripheral nervous systems

The brachial plexus is a complex network of nerves which extends from the neck to the axilla and which supplies motor, sensory, and sympathetic fibers to the upper extremity. Generally it is formed by the union of the ventral primary rami of the spinal nerves, C5-C8 and T1, the so-called "roots" of the brachial plexus. The goal here is to examine the neural architecture of the brachial plexus. The most constant arrangement of nerve fibers will be delineated, and then the predominant variations in neural architecture will be defined, particularly the prefixed and postfixed plexus, as well as the microanatomy and anatomy of the major terminal branches of the plexus. Multiple tracts connect many parts of the nervous system, and multiple ascending and descending tracts connect the peripheral nervous system (PNS) and lower spinal centers with the brain. This reflects that the nervous system is able to extract different pieces of sensory information from its surroundings and encode them separately, and that it is able to control specific aspects of motor behavior using different sets of neurons. Examination of the major sensory or motor pathways reveals a highly and tightly organized nervous system. In particular, at each of many levels, we see fairly exact maps of the world within the brain. In an effort to understand the functional neuroanatomy of the brachial plexus, this paper will focus briefly on the nervous connections of the nerves of the upper extremity with the brain. The goal here is to better understand "what the brain sees" after nerve injury and repair.     

Surface mapping of peripheral nerves in children with a nerve stimulator

Defining anatomical landmarks may be difficult in the growing child. With the aid of a peripheral nerve stimulator, the path of many superficial peripheral nerves can be 'mapped' prior to skin penetration by stimulating the motor component of the peripheral nerve percutaneously with a 2-3.5 mA output. The required current will vary and is dependent upon the depth of the nerve and the moistness of the overlying skin. This 'nerve mapping technique' has proved particularly useful for brachial plexus, axillary, ulna and median nerve blocks in the upper limb and femoral and popliteal nerve blocks in the lower limb. It is a useful teaching tool and improves the success rate of peripheral nerve blocks in children of all ages.     

Iatrogenic upper limb nerve injuries: a systematic review

Purpose: Peripheral nerve injuries are among the most frequent iatrogenic complications and are responsible for considerable morbidity and litigation. Most occur within surgical settings and upper limb nerves are most frequently involved. Methods: A systematic review of major iatrogenic upper limb nerve injuries was undertaken to evaluate the contemporary spectrum of such injuries. The electronic databases MEDLINE, PubMed, Cochrane Library and Google Scholar were searched for relevant articles listed between January 2000 and May 2010. Iatrogenic injuries to the brachial plexus, radial, axillary, ulnar, median, musculocutaneous and major cutaneous nerves were analysed, focusing on context, mechanisms of injury and incidence. Results: Iatrogenic upper limb nerve injuries are relatively common and can affect patients in any surgical specialty. Even patients undergoing diagnostic procedures under general anaesthesia are at risk. Orthopaedic surgery and plastic and reconstructive surgery figure prominently in these complications. The spectrum of iatrogenic peripheral nerve injuries has changed in parallel with technological advances in surgery, anaesthesia and medicine. Conclusions: Some iatrogenic upper limb peripheral nerve injuries may be unavoidable, but most cases are probably preventable by an adequate knowledge of surgical anatomy and an awareness of the types of procedures in which peripheral nerves are particularly vulnerable.     

Axillary plexus block using a peripheral nerve stimulator: single or multiple injections

This prospective, randomized, double-blind study was undertaken to evaluate the success rates of axillary brachial plexus block performed with the help of a peripheral nerve stimulator when either one, two or four of the major nerves of the brachial plexus were located. Seventy-five patients undergoing upper limb surgery were randomly allocated to one of the following five groups according to the nerve and number of nerves to be located; G-1: musculo-cutaneous, radial, median and ulnar nerves; G-2: musculo-cutaneous plus one of the other three nerves; G-3: radial nerve; G-4: median nerve; G-5: ulnar nerve. The sensory block was evaluated before surgery and cutaneous anaesthesia was considered to be present when the needles of a Wartenberg Pinwheel were no longer felt in all the dermatomes of the nerves implicated in the surgical site. Otherwise, the block was considered to need completion before surgery. Only one out of the 15 patients in G-1 and G-2 needed completion of their block before surgery whereas seven out of 15 for G-3 and eight out of 15 for G-4 and G-5 needed completion of their block (P less than 0.01). We conclude that when performing an axillary block with the help of a peripheral nerve stimulator, stimulation of the musculo-cutaneous nerve and one other nerve or stimulation of all four major nerves of the brachial plexus gives a higher success rate than stimulation of only one nerve, whether the stimulated nerve is the median, radial or ulnar.     

Review article: anatomical considerations for ultrasound guidance for regional anesthesia of the neck and upper limb

Purpose

The purpose of this narrative review is to describe an anatomical approach for residents-in-training and anesthesiologists who are learning techniques of ultrasound-guided regional anesthesia of the neck and upper limb

Sources

Relevant articles relating anatomy and anatomical variation to the emerging practice of ultrasound-guided regional anesthesia for the neck and upper limb were sourced via both Medline and PubMed databases. Also, our approach to teaching ultrasound technique has developed from using anatomical resources and cadaveric workshops. This approach emphasizes precise image acquisition, a detailed knowledge of anatomy and anatomical variations, and, importantly, visual interpretation of sonographic landmarks based on pattern recognition when interpreting sonograms.

Principal findings

Typical sonographic patterns orient the examiner to nerve position, which is necessary for executing successful regional anesthesia of the neck and upper limb. Only by understanding the typical anatomical arrangement can the examiner then visually interpret any individual anatomical variation that may occur.

Conclusion

Simple sonographic anatomical patterns can provide a strategy to correctly locate nerves when performing ultrasound-guided cervical and brachial plexus anesthesia.     

Brachial plexus avulsion injury repairs with nerve transfers and nerve grafts directly implanted into the spinal cord yield partial recovery of shoulder and elbow movements

OBJECTIVE: Complete avulsion of the brachial plexus is a devastating injury that primarily affects young adults. The current treatment is based on nerve transfers, which yield very limited recovery. In this study, brachial plexus injuries were repaired with nerve transfers and nerve grafts directly implanted into the spinal cord. METHODS: Eight patients with complete brachial plexus avulsion injuries were surgically treated. Roots or target nerves of the brachial plexus were repaired with peripheral nerve grafts directly implanted into the spinal cord and with extraplexal nerve transfers. RESULTS: Muscle reinnervation was observed for six patients who received spinal implants. Among those patients, one recovered M4 muscle power. Reinnervation was observed only in proximal upper limb muscles. CONCLUSION: Muscle reinnervation through nerve grafts directly implanted into the spinal cord was demonstrated. It seems that the combination of intra- and extradural neurotizations improves the proximal muscle function results. However, the extent of this improvement is limited and, in our opinion, does not justify the use of spinal implants.     

Transscalene brachial plexus block: a new posterolateral approach for brachial plexus block

Depending on the approach to the upper brachial plexus, severe complications have been reported. We describe a novel posterolateral approach for brachial plexus block which, from an anatomical and theoretical point of view, seems to offer advantages. Twenty-seven patients were scheduled to undergo elective major surgery of the upper arm or shoulder using this new transscalene brachial plexus block. The success rate was 85.2% for surgery. Two patients required additional analgesia with IV sufentanil. In two others, regional anesthesia was inadequate. The side effects of this technique included reversible recurrent laryngeal nerve blockade in two patients and a reversible Horner syndrome in one patient. Further studies are needed to compare the transscalene brachial plexus block with other approaches to the brachial plexus.     

经斜角肌臂丛神经阻滞：一种后侧入路臂丛神经阻滞的新方法

现有文献报道指出高位臂丛神经阻滞存在许多严重并发症。此文描述了一种从后侧方入路的臂丛神经阻滞新方法．该方法在解剖学上和理论上都有许多优点。27例拟行择期上臂或者肩部较大手术的患者接受了这种新的阻滞方法。成功率达到了85．2％。有两例患者加用静脉舒芬太尼镇痛，另有两例患者阻滞效果不佳。这种方法的副作用包括：两例患者出现了可逆的喉返神经阻滞，一例患者出现了可逆的Homer综合征。还需要进一步的研究将这种经斜角肌臂丛神经阻滞的方法与其他方法进行比较。     

Upper limb nerve blocks

Regional anaesthesia of the upper limb can be achieved by injecting local anaesthetic solutions into the brachial plexus according to many described techniques. The level at which injections are made into the neurovascular sheath will largely determine the block pattern. Terminal nerves of the brachial plexus can also be blocked further distal than the brachial plexus, either as a sole regional anaesthetic technique, or as a supplement to a brachial plexus block. The popular axillary approach has been the subject of a significant amount of research and it is now largely accepted that multiple-injection techniques provide more complete and reliable analgesia of the arm. A single injection into the plexus using median nerve stimulation often results in insufficient spread of the local anaesthetic to the retroarterial region. This could lead to incomplete anaesthesia because the radial nerve is not blocked. The musculocutaneous nerve also needs to be blocked separately. The advance of ultrasound-guided regional anaesthesia may improve the safety, success rate and ease of performance of some of the methods of brachial plexus block. It has helped the renewed interest in some of the less popular approaches to the brachial plexus, such as the infraclavicular block. However, further research is required to establish the definitive role of ultrasound in this area.     

The prevention of injuries of the brachial plexus secondary to malposition of the patient during surgery

Brachial plexus injuries that occur secondary to malposition of the patient during general anesthesia have been described in the medical literature for nearly a century. However, little can be found in the orthopedic literature. Of the peripheral nerve groups, the brachial plexus may be the most vulnerable to injury from malpositioning. This study presents three such cases of brachial plexus injury and reviews the literature concerning the subject. Pertinent anatomy, etiology, and pathogenesis of injury to the brachial plexus reveal that injury can occur from stretch or compression of nerves and is usually caused by a combination of the two. With awareness of risk factors and the positions which are likely to cause injury to the brachial plexus, careful positioning of the upper extremity can prevent injury and potential disability to the patient.     

Nerve repairs for traumatic brachial plexus palsy with root avulsion

Thirty-six patients with traumatic brachial plexus lesions and root avulsions were treated surgically between 1972 and 1986 and were followed for more than 24 months (average, 42.6 months). Neurotization of the musculocutaneous nerve with intercostal nerves or the spinal accessory nerve resulted in satisfactory elbow flexion in 21 of the 33 cases (64%). Combined nerve repairs (i.e., intercostal and spinal accessory neurotization of the terminal branch of the brachial plexus in combination with nerve grafts from the upper spinal nerves of the brachial plexus) created a useful function in at least one functional level of the upper limb for 11 of the 15 cases so treated. Nerve repairs resulted in stability of the shoulder and elbow function controllable with a sensible hand for patients with root avulsion injury of the brachial plexus.     

Functional contribution of T1 to the brachial plexus in infants

To determine the contribution of the T1 root to movements of the upper limb in infancy, 40 infants presenting with obstetrical brachial plexus palsy who underwent resection and reconstruction of all brachial plexus roots with the exception of the T1 root were assessed in the early postoperative period. The movements of the limb were recorded using the Hospital for Sick Children active movement scale and demonstrated considerable variability. All movements of the upper limb were observed in this group with the exception of external rotation of the shoulder and elbow flexion. Classical accounts of the function of T1 have limited its activity to the small muscles of the hand and were based on anatomical dissection, brachial plexus injuries and electrical stimulation. By contrast, this study isolated the physiological activity of T1 and analysed the functional contribution of this root to arm movement. We show a greater than generally recognized contribution of T1 to the function of the upper limb in infants.     

Brachial Plexopathy/Nerve Root Avulsion in a Football Player: The Role of Electrodiagnostics

Electromyography (EMG) studies are a useful tool in anatomical localization of peripheral nerve and brachial plexus injuries. They are especially helpful in distinguishing between brachial plexopathy and nerve root injuries where surgical intervention may be indicated. EMG can also assist in providing prognostic information after nerve injury as well as after nerve repair. In this case report, a football player presented with weakness in his right upper limb after a traction/traumatic injury to the right brachial plexus. EMG studies revealed evidence of both pre- and postganglionic injury to multiple cervical roots. The injury was substantial enough to cause nerve root avulsions involving the C6 and C7 levels. Surgical referral led to nerve grafts targeted at regaining function in shoulder abduction and elbow flexion. After surgery, the patient's progress was monitored utilizing EMG to assist in identifying true axonal regeneration.     

Continuous costoclavicular brachial plexus block in a pediatric patient for postfracture rehabilitation

The costoclavicular approach to the brachial plexus block has been recently described as a technique for anesthesia or postoperative analgesia of distal upper limb. In this article, we describe a case in which a continuous costoclavicular brachial plexus block was performed in a pediatric patient for conservative treatment of a traumatic radial fracture with severe elbow rigidity. Perineural catheter placement is a valuable option for pain control and functional prognosis during rehabilitation.     

The anatomy of the pectoral nerves and their significance in brachial plexus reconstruction

Twenty-nine brachial plexuses from 13 embalmed and 5 fresh cadavers were examined under x3.5 loupe magnification to collect systematic and topographic anatomical data regarding the lateral and medial pectoral nerves. Additionally, nerve biopsy specimens were harvested in 5 fresh cadavers to obtain histomorphometric data. In all dissections the pectoral nerves exited at the trunk level as 3 distinct nerves. The superior pectoral nerve (from the anterior division of the superior trunk) commences just distal to the suprascapular nerve and courses laterally to innervate the lateral clavicular portion of the pectoralis major muscle (PM) with 2 to 4 branches. The middle pectoral nerve (from the anterior division of the middle trunk) courses distally and enters the infraclavicular fossa with 2 constant branches. The superficial branch terminates in the medial clavicular and upper sternal parts of the PM. The deep branch always forms a plexus with the medial pectoral or inferior pectoral nerve (from the anterior division of the inferior trunk), which courses at a right angle around the the lateral thoracic artery. From this plexus several branches terminate in the Pm. The branch to the lower aspect of the PM pierces the pectoralis minor muscle in two thirds of cases, whereas it passes its inferior border to reach the lower aspects of the PM with an average length of 15 cm in one third of cases. Knowledge of the detailed anatomy of the pectoral nerves, as outlined in this study, clarifies the obscure anatomic relationship of the lateral and medial pectoral nerves and allows easy intraoperative location of the medial pectoral nerve at the exit of the lateral thoracic artery. The length of the inferior pectoral nerve, the number of motor axons, and the anatomical proximity of this nerve make it an expendable but powerful source of reinnervation to the musculocutaneous nerve in upper brachial plexus injuries.     

Contemporary treatment of peripheral nerve and brachial plexus lesions

Summary The paper outlines modern microsurgical techniques utilized in the repair of injured peripheral motor and sensory neurons. The diagnostic evaluation and its timing, which depend on the level and the extent of the lesion, are proposed. The author stresses the need during the operation for close monitoring, which is a prerequisite of proper coaptation of the severed nerve structures. A technically perfect microsurgical repair provides optimal conditions for regeneration of the divided peripheral nerves and/or brachial plexus. The repair of avulsion injuries of the brachial plexus still poses many technical problems; the author proposes the use of intercostal nerves as new sources for grafts. Pain, which is one of the major problems occurring with peripheral nerve injuries, especially with lesions to the brachial plexus, is not dealt with in detail. The author maintains that the contemporary treatment of peripheral nerve injuries as a rule yields good results, while this is not yet true of the management of brachial plexus lesions.     

Diagnosis of compressive neuropathies in patients with fibromyalgia

The hand surgeon relies on the Tinel sign in the physical examination of the patient suspected of having a peripheral nerve entrapment. Fibromyalgia is recognized by the American College of Rheumatology as a condition characterized by having tender points on physical examination. This article reviews the location of the 9 bilateral critical diagnostic fibromyalgia points as they relate to known sites of anatomic entrapment of peripheral nerves in the upper extremity. The interpretation of this article is that the Tinel sign may be used with validity to identify the site of a peripheral nerve compression in the upper extremity in the patient with fibromyalgia.     

Surgical treatment of a tomaculous neuropathy

Compressive neuropathy of the ulnar nerve at the elbow is the second most common nerve entrapment in the upper limb. Eight possible anatomical points of constriction have been identified. The most common constriction being the intermuscular septum proximally or between the two heads of the flexor carpi ulnaris in the cubital canal distally. Surgical release is successful in 80-90% of cases. Certain rare genetic conditions can predispose susceptible peripheral nerves to similar compressive neuropathies but there is no literature on surgical treatment of such patients. We present a case of hereditary neuropathy with liability to pressure palsy (HNPP) often known as 'tomaculous' neuropathy, in a patient with ulnar nerve symptoms who underwent a surgical release.     

Peripheral nerve compression secondary to adjacent lipomas

BACKGROUND: Nonneural sheath origin tumors include some rare benign and malignant lesions, and the compression of peripheral nerves by benign fatty tumors is infrequently reported in the medical literature. This study aims to review the authors' experience in treating patients with peripheral nerve compressions secondary to adjacent lipomas. METHODS: This study is a retrospective analysis of data about the patients who presented peripheral nerve compressive symptoms secondary to lipomas in the upper and lower limbs, treated during the period of 1999 to 2006. Included in the cases were those wherein the tumor was in contact with the nerve and the symptoms matched a respective nerve sensitive and/or motor innervation pattern. RESULTS: The upper extremity was the site of 5 (62.5%) of 8 lipomas, followed by the lower limb (2 lesions, 25%), and 1 tumor involved the brachial plexus (12.5%). In 5 cases, the clinical picture was similar to some entrapment neuropathy. Ultrasound imaging was useful to define the mass as a nonneural sheath origin tumor; MRI allowed a better analysis of the relationship of the tumor with other vascular, bony, or ligamentous structures. The lesions were ressected in all the patients, and there was good outcome in 7 cases (87.5%). Otherwise, we could identify signs of external compression on the direct inspection of the involved nerves in only 2 cases. CONCLUSIONS: The surgical treatment offers good outcomes in pain relief and neurological recovery, but one should not expect a real compression effect of the lipoma on the nerve during surgery.