Applied anatomy for upper limb nerve blocks

The brachial plexus derives from C5, C6, C7, C8 and T1 nerves. It is made up of five roots, between the scalene muscles, three trunks (upper, middle and lower) lying in the posterior triangle, each of which divide into anterior and posterior divisions behind the clavicle to form lateral, medial and posterior cords in the upper axilla. The plexus gives rise to the definitive motor and cutaneous nerve supply to the upper limb. The plexus can be blocked by local anaesthetic infiltration at its root/trunk level in the fascial sheath compartment between the scalenes, or as it crosses the first rib. Block can also be performed around the axillary artery. Peripherally, the nerves may be blocked at the elbow, wrist or finger level.     

Ultrasonographic findings of the axillary part of the brachial plexus

In this prospective study we sought to determine anatomic variations of the main brachial plexus nerves in the axilla and upper arm via high-resolution ultrasonography (US) examination. Positions of nerves were studied via US in three sectional levels of the upper arm in 69 healthy volunteers (31 men and 38 women, median age 28 yr). Analysis was done by subdividing the US picture into eight pie-chart sectors and matching sectors for the position of the ulnar, radial, and median nerves. Shortly after the nerves pass the pectoralis minor muscle, they begin to diverge. At the middle level 9%-13%, and at the distal level, 30%-81% of the nerves are not seen together with the artery in the US picture. At the usual level of axillary block approach, we found the ulnar nerve in the posterior medial position in 59% of the volunteers. The other two nerves had two peaks in distribution: the radial nerve in posterior lateral (38%) and anterior lateral (20%) position, and the median nerve in anterior medial (30%) and posterior medial (26%) position. Applying light pressure distally can displace nerves to the side, especially when they are positioned anterior to the axillary artery. We conclude that an axillary block should be attempted as proximal as possible to the axilla. IMPLICATIONS: This prospective ultrasonography study demonstrates significant anatomic variations of the main brachial plexus nerves in the axilla and upper arm, which may increase the difficulty in identifying neural structures. Applying light pressure on the plexus can move nerves to the side, especially when they are positioned anterior to the axillary artery.     

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.     

AUTONOMIC NERVES CROSS THE POSTERIOR PLANE OF RECTAL DISSECTION

This investigation was an anatomical study to determine whether branches of the pre-sacral autonomic plexus cross the posterior plane of surgical dissection to supply the rectum. Initially four cadaver hemi-pelves were dissected. Twelve patients undergoing full rectal mobilization were then studied at operation. In all subjects the pre-sacral nerves were arranged as a plexus below the sacral promontory, rather than as individual left and right nerve trunks. Structures thought to be nerves were identified crossing the plane of posterior mobilization of the rectum. They were traced towards their origin and destination, photographed and representative fibres biopsied. A total of 42 such structures were biopsied (16 in cadavers, 26 in operative cases) and 40 were confirmed to be nerves. These nerves connect the pre-sacral autonomic plexus with the posterior aspect of the rectum and were found at all sacral levels. In the operative cases the level of the positive biopsies were S1-six, S2-six, S3-five. S4-four. S5-three. The posterior plane of rectal dissection is therefore crossed by autonomic nerves that innervate the rectum. The pre-sacral nerves have been found to form a plexus in all subjects.     

Anatomy of the spinal nerves and dermatomes

There are 31 pairs of spinal nerves: eight cervical, 12 thoracic, five lumbar, five sacral and one coccygeal. They form by fusion of a posterior sensory spinal root (bearing its posterior root ganglion) with an anterior motor root. These join at each intervertebral foramen. Typically, the nerve then divides into a posterior and an anterior primary ramus. The former supplies the vertebral muscles and dorsal skin. The anterior primary ramus in the thoracic region bears a white ramus communicans to the sympathetic ganglion. Each spinal nerve receives a grey ramus from the sympathetic chain. The nerves T2–T12 supply the skin and muscles of the trunk sequentially. The other nerves are arranged into the cervical, brachial, lumbar and sacral plexuses. The cervical plexus supplies the skin and anterior muscles of the neck and forms the phrenic nerve (C3–C5), while the brachial plexus supplies the skin and muscles of the upper limb, and the lumbar and sacral plexuses supply the skin of the lower limb and perineum and the muscles of the posterior abdominal wall, pelvis, perineum and lower limb. The segmental nerves are arranged to supply the skin (dermatomes), while the segmental supply to the limb muscles, the myotomes, is more complex.     

The venous drainage of nerves; anatomical study and clinical implications

The venous drainage of the peripheral nerves was studied in the upper and lower limbs of two human fresh cadaver subjects after total body perfusion with a radio-opaque lead oxide mixture. Four patterns of extraneural drainage were identified in which the venae nervosa drained: directly to the venae comitantes of the neurovascular bundle; indirectly via nearby veins, derived usually from muscles; to the periarterial venous plexus; or, in the case of the cutaneous nerves, to the perivenous plexus. The various patterns of the drainage along the length of the radial, median, ulnar, sciatic, anterior and posterior tibial nerves were identified. A rich longitudinal plexus of veins exists on and within the nerve which appears to be mainly free of valves. The large venae nervosa usually contained valves, whereas the tiny veins draining the nerves were valveless or exhibited a sentinel valve at their entry point into a larger venous channel. The clinical implications of these results are discussed in relation to the mobilisation of nerves, the use of island nerve flaps, possible donor sites for free arteriolised neurovenous flaps and the compressive nerve syndromes.     

A cadaveric study of the motor nerves to the levator scapulae muscle

Understanding the surgical anatomic relationships of the motor nerves to the levator scapulae muscle is imperative for reducing postoperative shoulder dysfunction in patients undergoing neck dissection. To elucidate this relevant anatomy, cervical (C3, C4) and brachial (C5 via dorsal scapular nerve) plexi contributions to the levator scapulae were assessed with respect to posterior triangle landmarks in 37 human cadaveric necks. An average of approximately 2 (actual 1.92) nerves from the cervical plexus (range 1 to 4 nerves) emerged from beneath the posterior border of the sternocleidomastoid muscle in a cephalad to caudad progression to enter the posterior triangle of the neck on their way to innervating the levator scapulae. These cervical plexus contributions exhibited a fairly regular relationship to the emergence of cranial nerve XI and the punctum nervosum along the posterior border of the sternocleidomastoid muscle. After emerging from the posterior border of the sternocleidomastoid to enter the posterior triangle of the neck, cervical plexus contributions to the levator scapulae traveled for a variable distance posteriorly and inferiorly, sometimes branching or coming together. Ultimately these nerves crossed the anterior border of the levator scapulae as 1 to 3 nerves (average 1.94) in a regular superior to inferior progression. The dorsal scapular nerve from the brachial plexus exhibited highly variable anatomic relations in the inferior aspect of the posterior triangle, and was found to penetrate or give branches to the levator scapulae in only 11 of 35 neck specimens. We have found that the levator scapulae receives predictable motor supply from the cervical plexus. Our data elucidate surgical anatomy useful to head and neck surgeons. (Otolaryngol Head and Neck Surg 1997;117:671-80.)     

腰神经后支应用解剖与射频热凝的实验研究

目的 探讨可阻断腰神经后支痛觉传导的射频热凝有效温度。方法 在１５具成人尸体上解剖腰神经后支;用射频热凝机分别为６０℃、７０℃、８０℃、９０℃热凝家兔坐骨神经后,在不同时间内观察神经纤维的超微结构、感觉神经传导速度（ＳＣＶ）及传导痛觉的无髓纤维波形（Ｃ波）的变化。结果 腰神经后支途径的“横突根部”与“横突点”可作为腰神经后支热凝的初步标志,方法刺激可使位确切化;动物实验热凝温度为８０℃时,痛觉传入     

Lumbar plexus and psoas major muscle: not always as expected

BACKGROUND AND OBJECTIVES: Conflicting definitions concerning the exact location of the lumbar plexus have been proposed. The present study was carried out to detect anatomical variants regarding the topographical relation between the lumbar plexus and the psoas major muscle as well as lumbar plexus anatomy at the L4-L5 level. METHODS: Sixty-three lumbar plexuses from 32 embalmed cadavers were dissected to determine the topographical relation between lumbar plexus and psoas major muscle. At the L4-L5 levels variability in the course of the femoral as well as obturator nerve were described. RESULTS: The lumbar plexus was situated within the psoas major muscle in 61 of 63 cases. In 2 of 63 cases the entire plexus was localized posterior to the psoas major muscle. In the 61 of 63 cases in which the lumbar plexus was situated within the psoas major muscle, emergence of the individual nerves most often occurred on the posterior or posterolateral surface. CONCLUSIONS: Our results synthesize contrasting assumptions in previous literature, by demonstrating that both locations of the lumbar plexus may be encountered in clinical practice: within and posterior to the psoas major muscle. However, the latter situation represents a minor variant. At the level of L4-L5 the femoral nerve, showing a remarkable degree of branching, as well as the obturator nerve, were found within the psoas major muscle in the vast majority of specimens.     

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.     

Vascularized ulnar nerve graft

The purpose of this article is to describe the indications, anatomy, and harvesting technique of vascularized ulnar nerve graft based on the superior ulnar collateral artery (SUCA) for reconstruction of upper extremity function. The ulnar nerve has an extrinsic blood supply consisting of multiple dominant systems: the SUCA, the inferior ulnar collateral artery, the posterior ulnar recurrent artery, and the ulnar artery. The entire length of the ulnar nerve can survive based on the SUCA and its venae comitantes. The vascularized ulnar nerve graft is used when there is a hopeless prognosis for ulnar nerve repair. This technique may be selected if there is a definite evidence of preganglionic injuries of the C8 and T1 roots in brachial plexus injuries. This technique can be recommended for reconstruction of a large defect of the median or radial nerves in selected cases, such as upper arm replantation.     

Brachial plexus anatomy

The brachial plexus may be visualized simply as beginning with five nerves and terminating in five nerves. It begins with the anterior rami of C5, C6, C7, C8, and the first thoracic nerve. It terminates with the formation of the musculocutaneous, median, ulnar, axillary, and radial nerves. The intermediate portions are displayed in sets of threes: three trunks are formed, followed by three divisions, then three cords. Each trunk gives rise to two divisions and each cord gives rise to two branches. The lateral cord divides into the musculocutaneous nerve and the lateral branch of the median nerve. The medial cord divides into the medial branch of the median nerve and the ulnar nerve. The posterior cord divides into the axillary and the radial nerves. The anatomy of the brachial plexus can be confusing, especially because of frequent variations in length and caliber of each of its components.     

从盆腔筋膜的外科解剖来理解直肠全系膜切除术的层次

目的探讨直肠系膜与盆腔筋膜和神经的关系，以明确直肠全系膜切除术合理的切除平面。方法对24具尸体的盆腔进行解剖。结果直肠周围的层次是连续的，可以分为2段3层，2段指耻骨联合至坐骨棘和坐骨棘至骶岬；3层分别为脏筋膜、膀胱腹下筋膜和壁筋膜。在膀胱腹下筋膜与脏筋膜之间存在盆丛及其膀胱、子宫神经分支，而在脏、壁筋膜之间存在腹下神经和盆内脏神经。结论直肠全系膜切除术的层次在直肠后方为脏、壁筋膜之间，而在直肠侧方实际上位于脏筋膜和膀胱腹下筋膜之间。侧后方的腹下神经、侧前方的盆丛及其分支是正确层次的标记。     

Neurotization via the spinal accessory nerve in complete paralysis due to multiple avulsion injuries of the brachial plexus

The authors report their experience with 21 cases of neurotization via the spinal accessory nerve for multiple nerve root avulsion injuries of the brachial plexus associated with total paralysis of the upper limb. They performed microneuroanastomoses with interposed cable nerve grafts between the spinal accessory nerve taken in the supraclavicular fossa and the musculocutaneous nerve at its entrance into the biceps muscle. Surgical indications depend on the accurate diagnosis of spinal nerve root avulsion, especially C5. The anatomicosurgical basis of this technique is as precise as are the indications. As many as two-thirds of the patients with a neurotized musculocutaneous nerve can be expected to achieve strength of at least Grade 3 on late muscle testing. Nevertheless, these results are always inferior to those obtainable when grafting is performed with carefully selected unavulsed C5 or C6 spinal nerve root fibers in the intervertebral foramina. Therefore, neurotization via donor nerves extrinsic to the plexus should only be considered as a second-choice intervention.     

Anatomy of the lumbar and sacral plexuses and lower limb peripheral neuropathies

The lumbosacral plexus originates from the anterior rami of the lumbar and sacral nerve roots forming a network of nerves which supply the lower half of the body. The lumbar plexus (L1–L4) is situated within the upper two-thirds of psoas major and gives rise to the iliohypogastric nerve, ilioinguinal nerve, genitofemoral nerve, lateral femoral cutaneous nerve, femoral nerve and obturator nerve. The sacral plexus (L4–S4) is located within the pelvis and gives rise to the superior gluteal nerve, inferior gluteal nerve, sciatic nerve, posterior cutaneous nerve, perforating cutaneous nerve and the pudendal nerve. Peripheral neuropathy of these nerves may occur from an autoimmune, inflammatory, endocrine, infective, congenital, traumatic, neoplastic, vascular, degenerative or metabolic cause. This article will give an overview of the relevant anatomy of the lumbosacral plexus and neuropathies which affect the peripheral nerves of the lower limb.     

Combined nerve transfers for repair of the upper brachial plexus injuries through a posterior approach

The upper brachial plexus injury leads to paralysis of muscles innervated by C5 and C6 nerve roots. In this report, we present our experience on the use of the combined nerve transfers for reconstruction of the upper brachial plexus injury. Nine male patients with the upper brachial plexus injury were treated with combined nerve transfers. The time interval between injury and surgery ranged from 3 to 11 months (average, 7 months). The combined nerve transfers include fascicles of the ulnar nerve and/or the median nerve transfer to the biceps and/or the brachialis motor branch, and the spinal accessory nerve (SAN) to the suprascapular nerve (SSN) and triceps branches to the axillary nerve through a posterior approach. At an average of 33 months of follow-up, all patients recovered the full range of the elbow flexion. Six out of nine patients were able to perform the normal range of shoulder abduction with the strength degraded to M3 or M4. These results showed that the technique of the combined nerve transfers, specifically the SAN to the SSN and triceps branches to the axillary nerve through a posterior approach, may be a valuable alternative in the repair of the upper brachial plexus injury. Further evaluations of this technique are necessary.     

Block of the brachial plexus branches by the humeral route. A prospective study in 503 ambulatory patients. Proposal of a nerve-blocking sequence

BACKGROUND: Brachial plexus is usually approached by the supraclavicular or axillary route. A technique for selective blockade of the branches of the plexus at the humeral canal using electrolocation has recently been proposed. The aim of the present study was to assess the feasibility of this technique in the ambulatory patient and to determine the optimal sequence of nerve-blocking. METHODS: The nerves originating from the brachial plexus were located in the humeral canal, at the junction of the proximal and the middle third of the arm, with a stimulator and blocked using either lidocaine or a mixture of lidocaine and bupivacaine, depending on the anticipated duration of surgery. The minimal stimulating intensity eliciting an adequate response, type of local anaesthetic and injected volume, and time of onset of surgical anaesthesia were collected. RESULTS: The study included 503 consecutive ambulatory patients due to undergo surgery of the elbow, wrist or hand in one year. Suitable anaesthesia was obtained with the humeral blockade in 82.1% of cases. In the remaining 17.9%, an additional block at the elbow was required, mainly for ulnar and median nerves. The onset times of sensory blocks were the longest for the median nerve, similar for the radial and ulnar nerves, shorter for the musculocutaneous nerve and the shortest for the medial brachial and antebrachial cutaneous nerves. The difference was more significant with the lidocaine-bupivacaine mixture, than with lidocaine alone (P<0.001 vs P<0.05, respectively). The onset times of motor blocks were the longest for the median nerve (P<0.05) and the shortest for the musculocutaneous nerve (P<0.001). Neither nervous nor vascular complications occurred. CONCLUSION: This study shows that the nerve block at the humeral canal is an efficient and safe technique. Considering the onset times of nerve blocks, the following sequence for blockade can be recommended: median, ulnar, radial, musculocutaneous, medial (brachial and antebrachial) cutaneous nerves. The selective blockade of the main nerves of the upper limb at the humeral canal can be recommended for surgery of the forearm and the hand in the ambulatory patient.     

经椎体前路移位健侧颈7神经根修复臂丛上中干根性撕脱伤

目的探讨健侧颈7神经根经椎体前路移位，修复臂丛上、中干根性撕脱伤的最短通路及其安全性，并分析其应用指征和临床疗效。方法将颈部双侧前斜角肌切断，经椎体前、食管后间隙构制健侧颈，神经根移位通路，将颈7神经根自锁骨后股束交界处切断，近端游离至椎间孔，通过皮神经桥接或直接缝合修复患侧颈5、6神经根或上干前后股。2005年12月-2007年5月，对8例臂丛上、中干根性撕脱伤伴下干部分损伤，或合并副、膈神经损伤的患者进行修复。结果术后1周内，8例患者在咳嗽、进食时健侧手指有轻度麻木感，2～3周后症状逐步消失；体感诱发电位（豁口）在术后3个月时均能引出，7个月时能引出支配肌复合肌肉动作电位（CMAP）；术后12个月肩、肘功能部分恢复。结论切断双侧前斜角肌不仅可以缩短移植神经的长度，且健侧颈7神经根翻转通路更通畅、安全。直接修复或短段皮神经移植极大地缩短了神经再生的距离，利于患肢肩、肘功能的恢复。术后早期禁食可以减轻食道的组织创伤反应，利于颈7神经根缝合口的愈合。     

颈胸交感神经的解剖及临床意义

目的 通过对颈、胸交感神经的大体和显微解剖,观察交感神经的位置与毗邻关系,为临床治疗提供依据.方法 对30具60侧成人尸体标本作解剖学研究,观察其与周围相邻组织结构的关系和位置,以及交感神经节之间的联系.结果 颈交感干与椎动脉、臂丛神经存在广泛交通支;上胸段交感神经多位于相应的肋间,随着节段下移,出现在下位肋骨上缘或者表面的几率逐渐增高.颈胸交感神经节之间还存在额外的交通支.结论 切除交感神经可治疗由交感神经过度兴奋引起的多种病症,但切除的范围难以确定.颈胸交感神经节之间可能存在相互代偿作用,相互影响.     

Extent of blockade with various approaches to the lumbar plexus

The extent of blockade when four different techniques were used for blocking the lumbar plexus was prospectively evaluated in 80 adult patients. The extent of blockade was measured by testing motor function of all nerves except the lateral and posterior femoral cutaneous nerves, which were evaluated by pinprick response. The posterior approaches of Dekrey at L3 (n = 20) and Chayen at L4-5 (n = 20) proved similarly effective in producing blockade of the femoral, obturator, and lateral femoral cutaneous nerves, as well as the nerves to the psoas muscle. The anterior approach of Winnie (femoral sheath or 3-in-1 block) using paresthesia (n = 20) or peripheral nerve stimulation (n = 20) proved effective in producing blockade of the femoral and lateral femoral cutaneous nerves, but ineffective for obturator nerve blockade. None of the four techniques produced blockade of the sacral plexus. Perhaps our means of assessing blockade (motor) is what produced the difference between our findings and those of others.