Anatomic variation of the spinal origins of lateral and medial pectoral nerves

Lateral and medial pectoral nerves are distributed to the pectoralis major and minor muscles. The purpose of this study was to identify the spinal origins of lateral and medial pectoral nerves and to evaluate the participating amounts of each spinal nerve composing both pectoral nerves. Two types of spinal origins appeared in lateral pectoral nerves. The first type was composed of nerve fibers from C5, C6, and C7 with a frequency of 50.0% and the second type was composed of nerve fibers from C6 and C7 at a frequency of 50.0%. Regarding the average participating diameter to the lateral pectoral nerve, C7 was the thickest with a value of 1.60 +/- 0.35 mm (mean +/- SD), next was C6 at 0.83 +/- 0.18 mm, and C5 was the third at 0.42 +/- 0.24 mm. Three types of spinal origin appeared in the medial pectoral nerve. The first type was comprised of nerve fibers from C8 and T1 in 73.3% of cases. The second type was comprised of C8 only in 23.4% of cases, and the third type was comprised of T1 only in 3.3% of cases. The average participating diameter was 0.71 +/- 0.22 mm from C8 and 0.52 +/- 0.17 mm from T1. These results show that the spinal origins of the both pectoral nerves were various. Participating amounts of the lateral pectoral nerve appeared sequentially in the order of C7, C6, and C5. In the medial pectoral nerve, C8 participated more amounts than T1.     

Microanatomical study on the functional origin and direction of the thoracodorsal nerve from the trunks of brachial plexus

Ipsilateral C7 nerve root transfer or neurotization has been used for the repair of brachial plexus avulsions. In this procedure, the ipsilateral C7 nerve root is used as a donor nerve and is implanted into the damaged nerve of the brachial plexus in order to reinnervate distal muscles. However, this procedure may result in unintended injury to the thoracodorsal nerve, which receives motor fascicles form the cervical nerves of C6, C7, and C8, but mainly from C7. Damage to the thoracodorsal nerve ultimately results in weakness or paralysis of the latissimus dorsi muscle, which it innervates. In the present study, 20 adult cadaveric brachial plexus specimens and 3 fresh specimens were dissected using microscopy. The origin and direction of motor fascicles from the three trunks of the brachial plexus to the thoracodorsal nerve were investigated. Motor fiber counts of C7 and the thoracodorsal nerve were also performed. Several observations can be made: (1) The origin of the thoracodorsal nerve can be divided into three types: Type A, the thoracodorsal nerve originated from the superior and middle trunks; Type B, the thoracodorsal nerve originated from the inferior and middle trunks; and Type C, the thoracodorsal nerve originated from all three trunks. (2) More than 52% of the motor fibers in the thoracodorsal nerve originated in the C7 nerve root. (3) Motor fascicles from C7 to the thoracodorsal nerve were mostly localized in the posterior-internal part of C7 at the trunk-division boundary. In conclusion, we suggest that: (1) Because of variation in the origin of the thoracodorsal nerve, electromyography should be routinely performed intraoperatively during C7 nerve root transfer to determine the origin type and avoid thoracodorsal fascicle injury. (2) Preservation of the posterior-internal part of C7 (selective C7 transfer) can protect thoracodorsal nerve fascicles from damage and prevent postoperative dysfunction of the latissimus dorsi muscle.     

The spinal root origins and clinical implications of the lower subscapular nerve

The purpose of this study was to define the spinal root origins of the lower subscapular nerve and the amounts of participating nerve fibers from each spinal root and to discuss the clinical implications. Using a method of separating the nerve fascicles that traces the particular nerve fibers at the intrafascicular level, the spinal root origins of the lower subscapular nerve appeared as two types. The first type comprised 76.9% and was composed of the C5, C6, and C7 roots; the second type comprised 23.1% and was composed of the C6 and C7 roots. The number of nerve fibers was 357.2 +/- 139.7 (mean +/- SD) derived from C5, 1070.4 +/- 390.6 from C6, and 500.0 +/- 285.4 from C7. The nerve fascicles comprising the lower subscapular nerve traveled within the partially common fascicles composed of the axillary nerve. Therefore, injury of the lower subscapular nerve may be accompanied by a lesion of the axillary nerve, which generally consists of C5 and C6 roots composing the posterior cord of the brachial plexus.     

臀下神经转位阴部神经的应用解剖

目的：为重建单纯脊髓圆锥或阴部神经损伤后的会阴部功能提供解剖学基础。方法：对成人尸体的臀下神经和阴部神经进行了观测。结果：臀下神经以1支(45．00％)或2支(46．67％)从盆腔穿出为多，其中85．00％穿梨状肌下孔；其穿出点的位置主要在髂后上棘与坐骨结节连线的中1／3(50．00％)或上、中1／3交界处(48．33％)。神经干的长大于3cm，与阴部神经穿出处相距仅约2cm。阴部神经出盆处主要在髂后上棘与坐骨结节连线中1／3(46．67％)或中、下1／3交界(50．00％)。结论：两神经出盆处位置接近，臀下神经的长度足以直接与阴部神经缝接，用脊髓起源节段高的臀下神经转位脊髓起源节段低的阴部神经，切实易行。     

Spinal origins of the nerve branches innervating the coracobrachialis muscle: clinical implications

The coracobrachialis muscle (Cb M) receives nerve branches from the musculocutaneous nerve (Mc N). Many textbooks describe that the Cb M is innervated by the C5, C6, and C7 spinal nerves. The present study was performed to identify the spinal nerve composition of the nerve branches innervating the Cb M and to evaluate the number of myelinated axons of the nerve branches. Two types of spinal nerve compositions were observed: type I, composed of both C6 and C7 nerves, comprised 88.9% (40/45) of the sides; and type II, composed of only C7 nerves, comprised 11.1% (5/45) of the sides. Of the type I branches, 245.4 ± 26.3 (mean ± SD, range 201–267) of the myelinated nerve fibers were derived from C6 and 520.0 ± 41.8 (range 469–567) of the fibers were derived from C7. Of the type II branches, 836.4 ± 125.5 (range 709–991) of the nerve fibers were derived from C7. Imbroglio Modometer version 2.0 was used to count the number of fibers innervating the Cb M. The main component of these nerve branches was the C7 spinal nerve. The C5 spinal nerve, did not contribute to innervating the Cb M in the present study. The number of branches varied from one to four, with C7 being concentrated in the first and second branches. Therefore, these two branches may be suitable for the neurotization procedure as a donor nerve at the upper trunk (C5 and C6) lesion of the brachial plexus.     

Anatomical study of the pudendal nerve adjacent to the sacrospinous ligament

The pudendal nerve (S3-S5) is a major branch of the sacral plexus. After branching from the sacral plexus, the pudendal nerve travels through three main regions: the gluteal region, the pudendal canal, and the perineum. In the gluteal region, the pudendal nerve lies posterior to the sacrospinous ligament. The relationship of the pudendal nerve to the sacrospinous ligament has important clinical ramifications, but there is a lack of literature examining the variations in pudendal nerve anatomy in the gluteal region. This study investigates the pudendal nerve trunking in relation to the sacrospinous ligament in 37 cadavers (73 sides of pelves) of 21 males and 16 females, ranging from 18-83 years of age. Pudendal nerve trunking could be grouped into five types: Type I is defined as one-trunked (41/73; 56.2%), Type II is two-trunked (8/73; 11%), Type III is two-trunked with one trunk as an inferior rectal nerve piercing through the sacrospinous ligament (8/73; 11%), Type IV is two-trunked with one as an inferior rectal nerve not piercing through the sacrospinous ligament (7/73; 9.5%), and Type V is three-trunked (9/73; 12.3%). In summary, 56.2% of pudendal nerves adjacent to the sacrospinous ligament were one-trunked, 31.5% were two-trunked and 12.3% were three-trunked. Fifteen inferior rectal nerves originated independently from the S4 root and never joined the main pudendal nerve. Eight of fifteen inferior rectal nerves pierced through the sacrospinous ligament, perhaps making it prone for entrapment. We measured the average diameter of the main trunk of the pudendal nerve to be 4.67 +/- 1.17 mm. We also measured the average length of the pudendal nerve trunks before terminal branching to be 25.14 +/- 10.29 mm. There was no significant statistical difference in the average length, average diameter, number of trunks, and pudendal nerve variations between male and female or right or left sides of the pelves. A detailed study of pudendal nerve trunking in relationship to the sacrospinous ligament would be useful for instruction in basic anatomy courses and in relevant clinical settings as well.     

The relative contributions of the medial sural and peroneal communicating nerves to the sural nerve

The medial sural cutaneous nerve (MSCN) and peroneal communicating nerve (PCN) conjoin in the calf area to form the sural nerve (SN). In previous anatomic studies, there was unresolved debate as to the main contributor to the sural nerve, and the relative contributions of MSCN and PCN had not been studied. The purpose of this study is to determine their relative neurophysiologic contributions to the SN by nerve conduction study (NCS). A total of 47 healthy subjects (25 males and 22 females, mean age 29.6 +/- 10.4 yrs, range 20-59 yrs) participated in the study. This study employed the orthodromic nerve conduction technique: stimulation at the ankle and recording at the mid calf (SN); specifically, we preformed stimulation at the mid calf (MSCN, PCN) and recording at 14 cm proximal to the middle of the popliteal fossa (MSCN) and fibular head (PCN). The onset and peak latencies (ms) were SN 2.3 +/- 0.2 and 3.0 +/- 0.2; MSCN 2.1 +/- 0.2 and 2.8 +/- 0.2; and PCN 2.1 +/- 0.2 and 2.8 +/- 0.2. The peak-to-peak amplitudes (microV) and areas (nVsec) of the SN, MSCN, and PCN were 9.7 +/- 3.9, 7.0 +/- 4.7, and 5.0 +/- 3.2; and 7.2 +/- 2.9, 5.7 +/- 3.4, and 4.0 +/- 2.4, respectively. The side-to-side difference was not statistically significant. The main contributor to the SN was found to be the MSCN. The relative contribution ratio of the MSCN to the PCN was 1.37:1 by amplitude and 1.42:1 by area. However, in 32.9% of the subjects, the contribution of the PCN was greater than that of the MSCN.     

颈椎脊神经沟内口和颈神经的观测

目的　探讨颈椎脊神经沟内口与颈神经受嵌压的关系。方法　取 2 0具成人尸体的颈椎标本 ,选用完整的成人颈椎 4 4套 ,测量颈椎脊神经沟内口的宽度和颈神经穿过脊神经沟内口时的横径 ,并统计两者之间的比值。结果　颈神经穿过脊神经沟内口处的横径为 :C3 为 2 .7± 0 .7mm ,C42 .7± 0 .7mm ,C5为 2 .8± 0 .8mm ,C64.8± 0 .9mm ,C75 .3± 1.1mm。脊神经沟内口的宽度分别为 :C3 为 5 .8± 1.0mm ,C45 .5± 0 .9mm ,C55 .6± 1.0mm ,C65 .5± 1.1mm ,C76 .2± 1.0mm ;颈神经穿过脊神经沟内口时的横径与脊神经沟内口宽度的比值 :C3 为 1∶2 .15 ,C41∶2 .0 5 ,C51∶1.98,C61∶1.14 ,C71∶1.18。结论　脊神经沟内口与穿过内口的颈神经受累关系密切 ,下颈段 (C6、C7)颈神经受累的机率大于上颈段 (C3 、C4)。     

The effects of delayed nerve repair on neuronal survival and axonal regeneration after seventh cervical spinal nerve axotomy in adult rats

It has been proposed clinically that delayed surgery after traumatic brachial plexus injury may adversely affect functional outcome. In the present experimental study the neuroprotective and growth-promoting effects of early and delayed nerve grafting following proximal seventh cervical spinal nerve (C7) axotomy were examined. The ventral branch of C7 spinal nerve was transected and axons projecting out of the proximal nerve stump were labelled with Fast Blue (FB). At the same time, the biceps brachii muscle was denervated by transecting the musculocutaneous nerve at its origin. Neuronal survival and muscle atrophy were then assessed at 1, 4, 8 and 16 weeks after permanent axotomy. In the experimental groups, a peripheral nerve graft was interposed between the transected C7 spinal nerve and the distal stump of the musculocutaneous nerve at 1 week [early nerve repair (ENR)] or 8 weeks [delayed nerve repair (DNR)] after axotomy. Sixteen weeks after nerve repair had been performed, a second tracer Fluoro-Ruby (FR) was applied distal to the graft to assess the efficacy of axonal regeneration. Counts of FB-labelled neurons revealed that axotomy did not induce any significant cell loss at 4 weeks, but 15% of motoneurons and 32% of sensory neurons died at 8 weeks after injury. At 16 weeks, the amount of cell loss in spinal cord and dorsal root ganglion (DRG) reached 29 and 50%, respectively. Both ENR and DNR prevented retrograde degeneration of spinal motoneurons and counteracted muscle atrophy, but failed to rescue sensory neurons. Due to substantial cell loss at 8 weeks, the number of FR-labelled neurons after DNR was significantly lower when compared to ENR. However, the proportion of regenerating neurons among surviving motoneurons and DRG neurons remained relatively constant indicating that neurons retained their regenerative capacity after prolonged axotomy. The results demonstrate that DNR could protect spinal motoneurons and reduce muscle atrophy, but had little effect on sensory DRG neurons. However, the efficacy of neuroprotection and axonal regeneration will be significantly affected by the amount of cell loss already presented at the time of nerve repair.     

Branching patterns of the facial nerve and its communication with the auriculotemporal nerve

This study examines the anatomic relationships and variability of the facial nerve trunk and its branches, with emphasis on the intraparotid connections between the divisions. Microdissections were performed on 30 Korean half-heads, and the facial nerve trunks and branches were exposed. The average depth of the stylomastoid foramen from the skin surface was 21.0±3.1 mm, and the distance between the stylomastoid foramen and the bifurcation of the temporofacial (upper) and cervicofacial (lower) divisions was 13.0±2.8 mm. In 26 of 30 dissections (86.7%), the facial nerve trunk bifurcated into two main divisions, and a trifurcation pattern was seen in the other four cases (13.3%). According to the origin of the buccal branches, we classified the branching patterns of the facial nerve into four categories. In type I (13.8% of cases), the buccal branches arose from the two main divisions of the trunk but not from other branches of the facial nerve. In type II (44.8% of cases), the buccal branches arising from the two main divisions were interconnected with the zygomatic branch. In type III (17.3% of cases), the marginal mandibular branch sent nerve twigs to the buccal branch, which originated from the upper and lower divisions. In type IV (17.3% of cases), the nerve twigs from the zygomatic and marginal mandibular branches merged to the buccal branch arising from the two main divisions. Communications between the facial and auriculotemporal nerve branches, which are known as communicating auriculotemporal nerves, were observed in 28 of the 30 cases (93.3%). Familiarity with these common variations in the facial anatomy provides useful information for the surgeon in careful dissection, preservation of the facial nerve, and complete removal of the tumors in parotidectomies.     

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.     

颈神经后支的解剖及其临床意义

目的为临床诊治椎孔外颈神经后支卡压提供解剖学基础。方法对20具(40侧)成人尸体的颈神经后支起源、走行、分支、分布及其与颈椎周围组织的解剖关系进行观测。结果C     

Morphologic study of the connections between the accessory nerve and the posterior root of the first cervical nerve

The purpose of this study was to evaluate the anastomotic relationships between the accessory nerve and the posterior root of the first cervical nerve and to determine the course of the posterior root nerve fibers after anastomosis. The relationships between these two nerves were studied in 100 sides of the spinal cord and then classified into four types. In the most common type of anastomosis (38% of cases), either a branch from the posterior C1 root was seen to course cranially and join the accessory nerve, or the posterior root and accessory nerve fused as they coursed orthogonal to one other. In the second most common type (36% of cases), the accessory nerve anastomosed with a posterior C1 root that had no direct connection with the spinal cord; the nerve fibers of the posterior root were observed in stained samples to course caudally along the accessory nerve and join the posterior C2 root. In the least common type (6% of cases), no connection was observed between the accessory nerve and the posterior C1 root. In the next least common type (20% of cases), the posterior C1 root was absent and a connecting branch was sometimes observed between the accessory nerve and the anterior C1 root.     

面神经颊支的应用解剖

目的：观测分析面神经颊支的分支类型及其与腮腺管之间的解剖关系，为腮腺区手术提供解剖学基础。方法：60例成人头部标本，观测面神经颊支的分支类型、行程、神经与腮腺管的位置关系。结果：面神经颊支以双干型多见(58．3％)，三干型次之(28．3％)。神经多行于腮腺管浅面(73．3％)。腮腺管走行在颊支之问的占61．7％，导管距上颊支垂直距离约4．86mm；腮腺管走行在神经下方者占11．7％，距下颊支的垂直距离约1．71mm；腮腺管走行在神经上方者占26．7％，距上颊支的垂直距离约2．56mm。结论：面神经颊支多行于腮腺管浅层，与腮腺管关系十分密切，腮腺区手术时循颊支向后追踪面神经是比较安全、有效的方法，容易掌握。     

An aberrant anatomic variation along the course of the ulnar nerve above the elbow with coexistent cubital tunnel syndrome

We report on a patient with an unusual anatomic variation along the course of ulnar nerve above the elbow who had cubital tunnel syndrome. The variation consisted of a cutaneous neural branch that was originating at a distance of approximately 40 mm proximal to the medial epicondyle, and from the radial aspect of the main trunk of ulnar nerve. The branch had a superficial course and it was passing distally, anterior to the medial epicondyle without penetrating the fascia of the flexor muscles origin. Anterior intramuscular transposition of the ulnar nerve was performed leaving the newly found branch over the fascia between the muscles and the adipose subcutaneous tissue.     

Morphological study of the ansa cervicalis and the phrenic nerve

Morphological features of ansa cervicalis and phrenic nerve were studied in 106 cadavers. Ansa cervicalis was located medial to the internal jugular vein in 63% (medial type) and lateral to the vein in 33.7% (lateral type). Ansa cervicalis was derived from a combination of C1-C4 spinal segments, with C1-C3 being the most frequent pattern (87.5%). In >60% the ansa was bilaterally symmetrical. The distribution of medial and lateral types was equal on left and right sides of the body. The segmental composition of the inferior root was higher in the medial type and also on the left side of the body. In the lateral type the branches that formed the inferior root frequently (75%) formed a common trunk before joining the superior root, but in 74.8% of the medial type they joined the superior root independently. The phrenic nerve was derived from C4 and C5 in 52%. The C4 segment was present in the phrenic nerve in all cases except one. Additional phrenic components that pass anterior to the subclavian vein were defined as accessory phrenic nerves and found in 28.7%, while those passing posterior to the same vein were defined as secondary phrenic nerves (19.8%). Most of the accessory phrenic nerves contained a C5 segment and the nerve to subclavius was the commonest source. Various relationships between the ansa cervicalis and the phrenic nerve are investigated and, based on these findings, two separate classifications for the two nerves are suggested.     

颈椎脊神经沟及其沟内段脊神经形态学观察

目的　探讨脊神经沟与沟内段脊神经受嵌压的关系。方法　取 6 0具成尸 (男 2 8,女 32 ) 12 0侧颈椎 ,对脊神经沟外口宽度、深度及其沟内段脊神经前支横径进行观察 ,并统计脊神经前支横径与脊神经沟外口宽度之比。结果　①脊神经沟外口宽度、深度自颈 3至颈 6均逐渐增大 ,其平均值分别为 4 5± 1 2mm和4 3± 1 2mm ;② 3到 7颈神经前支横径逐渐增大 ,平均值为 2 9± 1 0mm ;③颈神经前支横径与脊神经沟外口宽度之比 ,颈 5最小 (1∶1 5 4 ) ,颈 4次之 (1∶1 6 7) ,颈 3最大 (1∶1 75 )。结论　脊神经沟与沟内段脊神经受累关系密切 ,下颈段 (5、6 )颈神经受累机率可能大于上颈段 (3、4 )。     

Semiquantifying of fascicles of the C7 spinal nerve in the upper and lower subscapular nerves innervating the subscapularis and its clinical inference in Erb's palsy

To elucidate anatomic basis of susceptibility for contracture of the subscapularis muscle in Erb's palsy of the brachial plexus, we semiquantitatively studied the spinal nerve origins of the subscapular nerves innervating the subscapularis, with special reference to the contribution of C7 innervation to the subscapularis. Thirty‐three sides of formalin‐fixed upper extremities were dissected to obtain the intact brachial plexus. After immersed in 10% acetic acid for 2 weeks, the upper and lower subscapular nerves innervating the whole subscapularis, were dissected retrogradely to verify their spinal nerve origins. The cross‐sectional area by C7 innervation and that by the upper trunk innervation was calculated respectively to obtain the constituent percentage of different components in the upper and lower subscapular nerves. In the upper subscapular nerve, fascicles of C7 accounted for 0% (interquartile range, 0–1.1%) of cross‐sectional area and those of the upper trunk, 100% (98.9–100%). In the lower subscapular nerve, fascicles of C7 accounted for 40.5% (23.5–47.5%) and those of the upper trunk, 59.5% (52.5–76.5%). In total, 18.6% (13.3–27.3%) of fascicles in the subscapular nerves innervating the subscapularis originated from C7, while 81.4% (72.7–86.7%) of those came from the upper trunk. It is confirmed that innervation of the subscapularis originates from more spinal cord segments than that of infraspinatus and teres minor, and this may be the main reason for which in Erb's palsy, functional recovery of the subscapularis is often faster than that of lateral rotators of the shoulder, resulting in medial rotation contracture of the shoulder. Clin. Anat., 2013. © 2012 Wiley Periodicals, Inc.