Observation and measurements of long thoracic nerve: a cadaver study and clinical consideration

Long thoracic nerve (LTN) is an important nerve originating from cervical nerve roots. It varies a lot in origins and branches, which lead to several clinical problems, such as diagnosis, prophylaxis and treatment of LTN injury. LTN was dissected in 38 cadavers in the present study. Origin, level of union, branches, sites where nerve entered the muscle, length of nerve trunk and branches as well as transverse diameter were documented. Different derivations of LTN were observed, and C4-7, C5-7, C5 and C7, C5-7, C5-8, C6 and C7, and branch from C6 was the most important components of LTN. After evolution, LTN trunk was composed by superior and inferior trunks at scalenus muscle or the three superior slips level. Branches of LTN traveled on the surface of the six superior slips of anterior serratus muscle and then penetrated through the inferior slips without correlation between different branches. Mean length of trunk of LTN is 111.73 (30.08) mm, axis of cross section was 2.27 × 0.96 mm at the union level and 1.91 × 0.68 mm at the end branch. Each slip was innervated by 1–4 branches of LTN. The observation and measurement data described in our study presented some variations and could provide clinicians with important information on diagnosis, prophylaxis and treatment of LTN injury and pursuing more suitable muscle flaps for reconstruction operation.     

Absence of the musculocutaneous nerve with innervation of coracobrachialis, biceps brachii, brachialis and the lateral border of the forearm by branches from the lateral cord of the brachial plexus

Anomalies of the brachial plexus and its terminal branches are not uncommon. Variations in the course and branches of the musculocutaneous nerve have been noted (Clemente, 1985; Bergman et al. 1988) and its absence was reported by Le Minor (1990). Several anomalies were present in the left plexus of a 59-y-old Japanese man (Fig.). There were no anterior and posterior divisions of the middle trunk, although there were communications between the posterior, medial and lateral cords. The musculocutaneous nerve was absent (Le Minor, 1990) and the medial and lateral roots of the median nerve did not unite in the axillary fossa but in the upper arm about 5 cm distal to the lower border of latissimus dorsi (Adachi, 1928; Buch-Hansen, 1955). The hitherto unreported findings were branches arising directly from the lateral cord to supply coracobrachialis, both heads of biceps brachii and brachialis. The lateral cutaneous nerve of the forearm was derived from the lateral cord with a small contribution from the medial root of the median nerve. Since there were communications between the posterior cord (a continuation of the middle trunk) and the medial and lateral cords, it is theoretically possibly, but not proven, that the root values of branches innervating the flexor muscles of the arm and forearm and the skin of lateral border of the forearm were normal.     

Spatial relationships between the morphologies and innervations of the scalene and anterior vertebral muscles

The prevertebral muscles are innervated by the cervical ventral rami. However, little information is available on the spatial relationships between the muscles and the supplying branches. This gross anatomical study investigated the prevertebral muscles and the nerves in 26 cadavers to elucidate their spatial interrelationships and the nerve pathways to each muscle. These muscles were characterized by the variations in the vertebral attachments. The scalenus medius was divisible into the dorsal and ventral parts. The scaleni anterior and medius attached to both the anterior and posterior tubercles of the cervical transverse processes. The oblique fibers arising from the transverse processes joined the vertical part of the longus colli. The rectus capitis anterior, the longus capitis and the scalene anterior and minimus were innervated by the ventromedial branches of the cervical ventral rami, and the branches passed between the origins of the proximal muscles to supply the longus colli. The rectus capitis lateralis and the scalenus medius were innervated by their dorsolateral branches, and the branches pierced the medius to the scalenus posterior. The roots of the brachial plexus passed between the scalenus anterior and the ventral part of the medius. The penetrations by the upper roots and the interconnecting fibers passing between the roots were found in the muscle bundles arising from the fourth or fifth cervical vertebrae. Their anomalies are the possible causes of the cervical-brachial disorders, and the knowledge of the innervation and the variations in this study seems to be useful for surgical and non-surgical treatments.     

The nerve branches to the external anal sphincter: the macroscopic supply and microscopic structure

The study was performed using 45 pelvic half section specimens (41 fetal ones and four adults). The macroscopic dissection followed the nerve branches from their spinal roots up to the external anal sphincter. Three nerve branches were found: the anterior ramus arising from the external perineal nerve, the inferior rectal nerve and an independent posterior branch. The anterior and the inferior rectal nerve branches always emerged from the pudendal plexus. The posterior branch arising either from S4 or from the inferior rectal nerve was only found in (31%) of our cases. Five anatomical distributions are described, percentages of every type notified. The fibre content of these nerve bundle branches was evaluated through histological sections using Heidenhain's azan stain and Luxol fast blue. The branches consisted of 2,896 to 2,137 fibres, 20% of them being unmyelinated and 80% containing various myelinated fibres. The nomenclature of these nerve branches has to be debated. The terms of anterior, middle and posterior anal nerves seem more suitable.     

Absence of musculocutaneous nerve with variations in course and distribution of the median nerve

Variations in the brachial plexus and its terminal branches are not uncommon. A communicating branch arising from the musculocutaneous nerve to the median nerve is a frequent variation, but complete merging of musculocutaneous nerve into the median nerve is very rare. Here, we observed variations in the origin, course and distribution of the median nerve in the left upper limb. The musculocutaneous nerve was absent. The median nerve was formed in the upper part of the arm, in front of the brachial artery. The median nerve supplied the biceps, coracobrachialis and brachialis muscles and gave the lateral cutaneous nerve of the forearm. The present report provides evidence of variation in important nerves of the anterior compartment of the arm.     

前、中斜角肌与颈3、4神经根卡压关系的解剖学研究

目的:研究颈３、４神经根与前、中斜角肌起点之间的解剖学关系。方法:在２５具(４７侧)成人尸体标本上,解剖观察颈３、４神经根与其周围组织特别是和前、中斜角肌起点的关系。结果:颈椎横突前后结节均有前、中斜角肌的起点,颈３、４神经根被前、中斜角肌起点处的交叉纤维组织包裹。结论:前、中斜角肌起始部交叉纤维是卡压颈３、４神经根的主要原因,解除前、中斜角肌及其起始部交叉纤维对颈３、４神经根卡压,是治疗颈３、４神经根严重卡压的主要方法。     

Two rare anomalies of the brachial plexus

Morphological variations of the brachial plexus and variants in the distribution of the anterior division of the middle trunk are relatively frequent. Two of the rarest anomalies occurred in the left brachial plexus of a 62-y-old Japanese male, 1 of 104 plexuses dissected between 1996 and 1997 at Kanazawa University Faculty of Medicine. The superior trunk of the brachial plexus was formed by the anterior primary division of C5 and C6 and a thin branch (0.5 mm in diameter) from C4, the middle trunk by the C7, and the inferior trunk by C8 and T1 (Fig.). We could not determine whether there was a branch derived from T2 to T1, since the subject had died of lung carcinoma. The entire anterior division of the middle trunk crossed the axillary artery and joined the medial root of the median nerve which was the continuation of the medial cord after the cord branched off the ulnar nerve. The lateral cord pierced coracobrachialis and divided into the musculocutaneous nerve and the lateral root of the median nerve just after emerging from the muscle, finally joining the medial root of the median nerve superficial to the brachial artery ∼115 mm distal to the lower border of latissimus dorsi to form the median nerve. The musculocutaneous nerve gave rise to the nerves to biceps brachii, brachialis, and the long head of biceps brachii and finally continued as the lateral cutaneous nerve of the forearm. The branch to coracobrachialis had already been cut and its course could not be traced.     

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.     

三角肌神经入肌点定位及肌内神经分布的研究

目的　揭示三角肌神经入肌点和肌内神经分支分布 ,为其临床应用提供较为详尽的形态学资料。方法　①用经甲醛固定 2年以上的成人尸体 (2 0～ 5 0岁 ) 12具 (男 9,女 3)共 2 4侧。以肩峰后角为骨性标志 ,测量三角肌各亚部神经支入肌点的位置。②用经甲醛固定 1年以内的童尸 3具 (3～ 10岁 )及成人尸体 2具 (2 0、4 0岁 )完整取下三角肌 ,采用Sihler′s肌内神经染色法观察肌内神经分支分布。结果　①三角肌各亚部神经入肌点的体表投影 :三角肌前亚部、中亚部、后亚部的神经入肌点分别在距肩峰后角下方 (5 7± 0 7)cm、(5 9± 0 8)cm、(4 8± 0 5 )cm处的水平线上 ,距三角肌前缘外后方 (3 6± 0 4 )cm处及距三角肌后缘外前方 (3 5± 0 6 )cm、(2 3± 0 3)cm处 ,上述三点均在肌的中 1/3部。②肌内神经分布 :三角肌前、后亚部的肌内神经支在肌内为直接横过肌纤维中部 ,沿途再发出分支与肌纤维并行走行 ;而中亚部肌内神经支在各个羽内 ,与肌纤维相交 ,行向短肌纤维的起止端。结论　①三角肌的神经入肌部位及入肌形式与该肌的形态和功能有关联 ;②三角肌的肌内神经分支分布可能与该肌的肌纤维长度及肌纤维型有关 ;③三角肌中亚部的肌内神经吻合网较宽而致密 ,推测有着更精细的神经调节。     

Bilateral multiple complex variations in the formation and branching pattern of brachial plexus

Bilateral variations in the formation and branching of brachial plexus are extremely rare. Multiple bilateral variations in brachial plexus right from divisions to branching pattern were observed during the dissection in an adult male cadaver. Lateral and medial cord formation showed deviation from the usual pattern. Anterior division of upper trunk continued as lateral cord. Medial cord was formed by the union of anterior division of lower trunk and anterior division of middle trunk, thus receiving fibers from both the trunks. Anterior division of middle trunk bifurcated into upper and lower branches. We encountered two lateral roots bilaterally and two medial roots of median nerve on the left side with anomalous origin. There were three upper subscapular nerves on the left and two on the right side with variations in their origin. Anomalous origin of many other branches on both sides was encountered. It is extremely uncommon to find so many variations in one body and bilateral variations are still too rare. Understanding of such variations is clinically important for diagnosing unexplained clinical signs and symptoms as well as during nerve blocks and certain surgical procedures around the neck and proximal arm.     

Marked lateral deviation of the phrenic nerve due to variant origin and course of the thyrocervical trunk: a cadaveric study

Phrenic nerve impairment can often lead to serious respiratory disorders under various pathological conditions. During routine dissection of an 88-year-old Japanese male cadaver, a victim of heart failure, we recognized an extremely rare variation of the right thyrocervical trunk arising from the subclavian artery laterally to the anterior scalene muscle. In addition to that, the ipsilateral phrenic nerve was drawn and displaced remarkably laterad by this vessel. We examined all of the branches arising from subclavian arteries, phrenic nerves and diaphragm muscles. The embryological background of this arterial variation is considered. The marked displacement with prolonged strain had a potential to cause phrenic nerve impairment with an atrophic change of the diaphragm muscle. Recently many image diagnostic technologies have been developed and are often used. However, it is still possible that rare variations like this case may be overlooked and can only be recognized by intimate regional examination while keeping these rare variations in mind.     

Palmaris profundus: One name,several subtypes,and a shared potential for nerve compression

The palmaris profundus is a rare, but known anatomic variation which may lead to compression of the median nerve and/or its branches. Two patients with carpal tunnel syndrome are presented in whom a palmaris profundus was discovered at operation. In these cases, median nerve compression at the wrist was attributed to the course of the extra tendon and its local mass effect on the nerve (i.e., the palmaris profundus and median nerve shared a common sheath); more commonly, the resultant decreased available space for the median nerve within the carpal tunnel due to the presence of an accessory (10th) flexor tendon is thought to be responsible. Postoperative 3 Tesla magnetic resonance imaging (MRI) was performed to demonstrate the full course of the variant muscle; despite variations in the size and longitudinal extent of the accessory musculotendinous unit, an important similarity was noted: the intimate relationship of the median nerve and the palmaris profundus. These two cases and our review of the literature highlight the fact that one name (i.e. palmaris profundus) reflects several anatomic subtypes. However, the close relationship of the palmaris profundus with the median nerve in the forearm and the palm is a common theme which emphasizes the potential pathoanatomic consequences of this relationship: nerve compression. Clin. Anat. 22:643–648, 2009. © 2009 Wiley‐Liss, Inc.     

Anatomical variations of the cords of brachial plexus and the median nerve

The variations in formation, location, and courses of the cords of brachial plexus and the median nerve were studied in both axillae of 172 cadavers. The total prevalence of variation was 12.8% (CI, 7.6-17.4) and it was found in 13.2% (CI, 7.5-18) of male and in 10.7% (CI, -0.6-19.6) of female cadavers. These variations were divided into three groups. The first group was abnormal location of the cords, which was either posterolateral or anteromedial in relation to the axillary artery in 2.3% (CI, 0.1-4.5) cadavers. The lateral cord and the medial root of the median nerve had received communicating branches from the posterior cord in most of the cases of this group. The second group was absence of the posterior cord in 3.5% (CI, 0.7-6.1) of cadavers. The lateral and medial cords of this group were connected with the communicating branches, which had a course in front of the axillary artery. The third group was abnormal formation and course of the median nerve in 7% (CI, 3.1-10.6) of cadavers. In all cases of this group the medial root received communicating branch/branches either from the lateral or posterior cord. In eight (4.7%) cadavers, both roots of the median nerve were joined on medial side of the axillary artery to form a median nerve, which traveled medial to the artery. In four (2.3%) cadavers the roots of the median nerve did not join and both traveled separately anteromedial to the axillary and brachial arteries. This study indicates that all three cords and median nerve vary considerably in levels of origin, location and course in relation to the axillary artery and these variable cases were joined with the communicating branch/branches. The observed variations are of anatomical and clinical interest. These kinds of variations are more prone to injury in radical neck dissection and in other surgical operation of the axilla.     

Anatomical study and clinical significance of the rami communicantes between cervicothoracic ganglion and brachial plexus

The aim of this study was to provide a detailed characterization of the rami communicantes between the stellate (or cervicothoraic) ganglion (CTG) and brachial plexus (BP). Rami communicantes of 33 fixed adult cadavers were macroscopically observed, and connection between CTG and spinal nerves and branching was investigated. In all cases, except one, the hibateral medial rami communicantes was found to be positioned symmetrically between the CTG and C7, C8 spinal nerves. Gray rami communicantes arising from the CTG joined C8, C7, C6 nerve roots on 66, 63, and 6 sides, respectively, and branched from the rami communicantes to C7, C6, C5 nerve roots lying on 51, 41, and 2 sides, respectively. Forty‐five sides of the branches from rami communicantes derived from CTG to C8 were observed to ascend through the transverse foramina of the C7 nerve. The branches from rami communicantes derived from CTG to C7 to the C6 nerve were observed ascending through the foramen transversarium of the six cervical vertebrae along with the vertebral artery and joining the C6 spinal nerve in 41 sides. Knowledge about the general distribution and individual variations of the rami communicantes between CTG and BP will be useful toward studies involving the inference of sympathetic nerve stimulation of the upper limbs and could be important for surgeons who perform surgical procedures in the cervical region or medical blockade of nerve fibers. Clin. Anat. 23:811–814, 2010. © 2010 Wiley‐Liss, Inc.     

Thoracic outlet: An anatomical redefinition that makes clinical sense

The diagnosis of thoracic outlet syndrome (TOS) is intrinsically difficult, and the literature about it is full of confusing terminology. Symptoms may arise due to compression of neural and/or vascular elements in one or more of three different locations. A number of tests were developed during the early part of this century, and a variety of syndromes have been described that relate to these tests, all of which are now considered to be subtypes of the thoracic outlet syndrome. Yet anatomists and clinicians fail to agree on even the definition of the thoracic outlet. It is proposed that anatomists not use the term thoracic inlet as a synonym for the superior thoracic aperture, nor thoracic outlet for the inferior thoracic aperture. What many clinicians call the thoracic outlet should be called the scalene triangle by both anatomists and clinicians, divisible into a lower portion to be called the thoracic outlet (for subclavian vessels and nerve roots C.8 and T.1) and an upper portion, the cervical outlet (for nerve roots C.5, C.6, and normally C.7). What is currently called thoracic outlet syndrome should be renamed the cervico-axillary syndrome (CAS), divisible into three subtypes: thoracic outlet, costoclavicular, and pectoralis minor syndromes. Compression of the upper roots of the brachial plexus between the anterior and middle scalene muscles should be recognized as cervical outlet syndrome, and all terms containing the word scalenus should be discarded. © 1996 Wiley-Liss, Inc.     

Scalene muscles and the brachial plexus: Anatomical variations and their clinical significance

Anatomical variations may be clinically significant, but many are inadequately described or quantified. Variations in neck anatomy are important to surgeons performing surgical procedures in this region. Thirty-two female and 19 male adult cadavers were studied. The commonly described anatomical relationship of the brachial plexus (BP) lying between the anterior scalene (AS) and middle scalene (MS) muscles was found in only 60%; of instances. Scalenus minimus was present in 46%; of instances (bilateral in 14 cadavers). The most common variation was the penetration of the AS by the C5 and/or C6 ventral rami. The C5 and C6 roots may fuse before piercing AS (15%; cases, bilateral in 4 cadavers), or the C5 root alone pierce the belly of AS (13%; cases, bilateral in 3 cadavers). The roots also may pierce AS independently (6%; cases, bilateral in 1 cadaver). In 3%;, the C5 root was found to be completely anterior to AS. Clin. Anat. 10:250–252, 1997. © 1997 Wiley-Liss Inc.     

人颈7神经根干股束支运动纤维含量及其临床意义

目的：为临床选择性颈7神经根移位治疗臂丛损伤提供进一步依据。方法：选择6侧新鲜成人尸体臂丛标本，分离颈7神经根干、股及其发出到上肢各主要神经的主要纤维束，并分别进行胆碱酯酶染色。结果：人类颈7神经根含运动纤维约8893根，其中前股3010根，后股5883根；颈7前股中，加入肌皮神经的成分约589根(占肌皮神经总运动纤维约20％)，正中神经193l根(占其外侧头70％)；颈7后股中，加入腋神经成分6Il根(占其运动纤维的25％)，桡神经4036根(占58％)，胸背神经994根(占60％)．结论：颈7神经根前后股均有足够的运动纤维量；同侧颈7神经根移位时建议保留前股；采用颈7神经根移位，修复多条受损神经是可行的。     

The origin of the premotor potential recorded from the second lumbrical

PURPOSE: When recording with a palm electrode, a premotor potential (PMP) precedes the compound muscle action potential evoked from the second lumbrical muscle following median nerve stimulation. The origin of the premotor potential has remained uncertain. The aim of this study was to determine whether the PMP-2L is a SNAP derived from antidromically activated digital sensory branches of the median nerve. METHODS: We recorded three active electrodes were placed over the second lumbrical muscle, the third lumbrical muscle, the fourth lumbrical muscle by multi-channel recordings. RESULTS: PMPs are recorded only over the median digital sensory branches after stimulating the median nerve, while they are recorded only over the ulnar branch after stimulating the ulnar nerve. CONCLUSIONS: We conclude that the origin of the PMP is a SNAP arising from antidromically activated digital sensory branches.     

Surgical anatomy of the pudendal nerve and its clinical implications

A study of the surgical anatomy of the pudendal nerve (PN) was performed in 13 female and 7 male cadavers. The knowledge of the precise anatomy and anomalies of this important nerve would help in better localization of the nerve and its roots and branches for neurostimulation or for pudendal canal decompression in pudendal canal syndrome. Two routes were used in the dissection: gluteal and perineal. The PN was identified and its course was followed from its roots to its termination. The PN was composed of three roots derived from the 2nd, 3rd, and 4th anterior sacral rami (S 2,3,4). The roots received a contribution from S 1 in five cadavers and from S 5 in one. The three roots formed two cords. The first root continued as the upper cord while the second and third root fused together producing the lower cord. The PN was formed by union of the two cords a short distance proximal to the sacrospinous ligament, and then crossed the back of the ligament. In no specimen did the nerve cross the ischial spine. The inferior rectal nerve arose from the PN in the pudendal canal in 18 cadavers. In two cases it came out proximal to the canal; this would spare the two subjects the anorectal manifestations of the pudendal canal syndrome. As the PN crossed the back of the sacrospinous ligament, it gave origin to a branch that supplied the levator ani muscle. This branch was only found in male cadavers and we call it “accessory rectal nerve”; the levator ani muscle in such cadavers was doubly innervated on its perineal aspect. © 1995 WiIey-Liss, Inc.