A case of an accessory brachialis muscle

Functionally, the brachialis muscle serves a critical role as the primary flexor of the arm at the elbow. However, few reports exist in the literature, which describe variations of this muscle. We present a case of an accessory brachialis muscle (AcBr), found during routine dissection at Harvard Medical School during 2003. The AcBr originated medially from the mid-shaft of the humerus and the medial intermuscular septum. During its course medially, toward the elbow, the AcBr crossed both the brachial artery and the median nerve. The distal tendon split to surround the median nerve before inserting into the common tendon of the antebrachial flexor compartment muscles. Embryological origins and clinical considerations including median nerve entrapment are considered.     

Motor nerve lengths of twenty-seven muscles in upper extremity

The purpose of this study is to determine the lengths of motor nerves in the upper extremity. Motor nerves of 27 muscles in 10 cadavers (16 extremities) were dissected from their roots at the level of intervertebral foramen to the entry point of the nerves to the corresponding muscles. Distance between acromion and the lateral epicondyle of the humerus was also measured in all cadavers. Nerve length of the coracobrachialis muscle was the shortest (18.26 ± 1.64 cm), while the longest was the nerve of the extensor indicis (59.51 ± 4.80 cm). The biceps brachii, the extensor digitorum communis, and the brachialis muscles showed highest coefficient of variation that makes these nerve lengths of muscles inconsistent about their lengths. This study also offers quotients using division of the lengths of each nerve to acromion-the lateral epicondyle distance. Knowledge of the nerve lengths in the upper extremity may provide a better understanding the reinnervation sequence and the recovery time in the multilevel injuries such as brachial plexus lesions. Quotients may be used to estimate average lengths of nerves of upper extremity in infants and children. Moreover, reliability of the biceps brachii as a determinant factor for surgery in obstetrical brachial plexus lesions should be reconsidered due to its highest variation coefficient.     

Variant of the coracobrachialis muscle with a tunnel for the median nerve and brachial artery

This case report documents a variation in the insertion of the coracobrachialis muscle of the right arm of an adult male cadaver of unknown age. In addition to the normal insertion of the coracobrachialis muscle into the middle of the medial border of the humerus, an additional slender tendon passed inferiorly, crossing anterior to the median nerve and brachial artery before attaching to the medial epicondyle of the humerus. Most of the proximal part of the tendon gave rise to an aponeurotic expansion that inserted into the distal medial border of the humerus. The tendinous insertion and aponeurotic expansion may represent a variant of the coracobrachialis longus (Wood's) muscle and the internal brachial ligament, respectively. The median nerve and brachial artery traversed a tunnel bounded by the additional tendon and aponeurotic expansion as well as the usual humeral insertion of the coracobrachialis muscle. The clinical implication of this variation is that it may be a cause of median nerve entrapment and brachial artery compression.     

臂前群肌神经入肌点的定位

目的:借骨性标志确定肌皮神经肌支神经入肌点(N点)的位置。方法:成年尸体上肢,肩峰至颈静脉切迹连线为喙肱肌支N点的横向参考线(H_1),肱骨外上髁至内上髁连线为肱二头肌和肱肌支N点的横向参考线(H_2);肩峰至肱骨外上髁连线为纵向参考线(L)。解剖暴露N点,涂抹硫酸钡,CT扫描。N点在臂前体表上的投影点为P,P点通过N点后投射至臂后体表上的点为P′。经P的垂线与H线、水平线与L线的交点分别记为P_H和P_L。Syngo系统下确定P_H和P_L在H和L线上的位置及N点的深度。结果:喙肱肌支、肱二头肌短头、肱二头肌长头及肱肌支的P_H分别位于H_1的18.38%、H_2的56.85%、52.81%和57.52%处;P_L位于L的24.86%、50.20%、55.91%和64.31%处;经过P点的N点深度分别位于PP′线的23.16%、24.68%、26.32%和38.19%处。结论:这些神经入肌点的定位可提高臂前群肌痉挛神经溶解术的疗效和效率。     

High origin of the radial artery accompanied by muscular and neural anomalies

A high origin of the radial artery accompanied by muscular and neural abnormalities (three-headed biceps brachii, absence of the palmaris longus muscle, and communication between median and musculocutaneous nerves) were encountered during the dissection of a 25-year-old male cadaver. Co-existence of these variations has not, to our knowledge, been reported in the available literature.     

Successive motor nerve blocks to identify the muscles causing a spasticity pattern: example of the arm flexion pattern

Botulinum Toxin A has been the main treatment for spasticity since the beginning of the 1990s. Surprisingly, there is still no consensus regarding injection parameters or, importantly, how to determine which muscles to target to improve specific functions. The aim of this study was to develop a systematic approach to determine this, using the example of the arm flexion pattern. We first determined anatomical landmarks for selective motor block of the brachialis nerve, using 20 forearms from 10 fresh cadavers in Ecole Européenne de Chirurgie and a university‐based dissection centre, Paris, France. We then carried out selective blocks of the motor nerves to the brachialis, brachioradialis and biceps brachii in patients with stroke with an arm flexion pattern, in a University Rehabilitation Hospital, Garches, France. We measured: the resting angle of the elbow angle in standing (manual goniometer), active and passive range of extension, and spasticity using the Held and Tardieu and the Modified Ashworth scales. Range of passive elbow extension was also measured with the shoulder in 90° of flexion. The resting angle of the elbow in standing decreased by 35.0° (from 87.6 ± 23.7 to 52.6 ± 24.2°) with inhibition of brachialis, by a further 3.9° (from 52.6 ± 24.2 to 48.7 ± 23.7°) with inhibition of brachioradialis and a further 14.5° (from 48.7 ± 23.7to 34.2 ± 20.7°) with inhibition of biceps brachii. These results were consistent with the clinical evaluation of passive elbow range of motion with the shoulder at 90°. Sequential blocking of the nerves to the three main elbow flexors revealed that the muscle that limited elbow extension the most, was brachialis. This muscle should be the main target to improve the arm flexion pattern. These results show that it is important not simply to inject the most superficial or powerful muscles to treat a spastic deformity. A comprehensive assessment is required. The strategy proposed in this paper should increase the effectiveness of botulinum toxin injections by ensuring that the relevant muscles are targeted.     

尺神经中第七颈神经成份的行径及临床意义

用神经束追踪分离法解剖观察100侧成人第七颈神经分布至尺神经内的纤维行径。结合临床观察认为,尺神经内部有来自颈七的纤维,主要经4个交通部位加入到尺神经分布区内。证明脊神经相应节段与骨骼肌或肌群的支配关系是恒定的,只是由于在胚胎发生上臂丛组合的不同,使脊神经的分支到所支配的骨骼肌间的行径出现差异。上述研究结果,对臂丛中、下干损伤准确定位诊断有重要意义。     

Anatomical considerations of subcoracoid neurovascular structures in anterior shoulder reconstruction

Anterior shoulder surgery, using open or arthroscopic technique, places subcoracoid neurovasculature at risk. This study examines the relationships of the brachial plexus and axillary artery to four bony landmarks and provides clinical correlations for anterior shoulder surgery. The musculocutaneous nerve (MN), posterior cord (PC), lateral cord (LC), and axillary artery (AA) were identified in 27 shoulders. Minimum distances (mm) were measured between neurovasculature and the coracoid tip, anterior midglenoid, inferior surface of the midclavicle, and anteromedial aspect of the acromioclavicular joint. Average distances from the coracoid to the MN, PC, LC, and AA were 69.7 ± 31.6, 50.5 ± 9.2, 41.8 ± 9.4, and 60.0 ± 8.0 mm, respectively; from the glenoid equator to the MN, PC, LC, and AA were 61.5 ± 38.5, 37.0 ± 6.1, 35.2 ± 8.7, and 45.2 ± 7.1 mm, respectively; from the midclavicle to the MN, PC, LC, and AA were 114.1 ± 33.9, 62.0 ± 13.6, 56.0 ± 19.7, and 69.9 ± 7.8 mm, respectively; and from the AC joint to the MN, PC, LC, and AA were 112.7 ± 36.5, 87.9 ± 10.6, 84.0 ± 12.0, and 100.9 ± 1.0 mm, respectively. The lateral cord was the closest structure to each bony landmark. The musculocutaneous nerve was the furthest structure from each bony landmark. Open procedures using a deltopectoral approach with the shoulder in the anatomical position, such as the Neer capsular shift and Warner capsular reconstruction, can use these results to prevent direct or retraction injuries. Results indicate a potential safe zone of 30 mm in diameter around the anteromedial coracoid tip for anteroinferior portal placement. Clin. Anat. 23:815–820, 2010. © 2010 Wiley‐Liss, Inc.     

Electrophysiological studies of muscles in the human upper limb: The biceps brachii

The biceps brachii (BB) belongs to elbow flexors. However, because the BB acts not only as the flexor, but also as a forearm supinator in humans, its activities are much different from those of the other flexors (the brachialis and brachioradialis: BR and BRR, respectively). The present paper describes unique characteristics of the BB that emerged from recent studies using electrophysiological techniques (i.e. electromyography (EMG), electrical neuromuscular stimulation (ENS), Hoffmann (H)-reflex and post-stimulus time-histogram (PSTH)) in normal human subjects. The EMG studies have shown reciprocal contractions between the BB and the other flexors during forearm pronation/supination movements. Comparisons of EMG activities of the flexors between the pronated and supinated positions of the forearm have indicated clear differences of contraction properties between the BB and the other flexors. The ENS studies have shown that reciprocal activation between the BB and BRR following stimulation can produce a motion of supination with maintenance of flexion. This finding supports the theory that the reciprocal contractions should occur to keep constant force in flexion for supporting weight below the elbow. Studies using H-reflex and PSTH techniques have shown neural connections, which are spinal reflex arcs modulating motoneuron excitabilities with excitatory and inhibitory inputs from low-threshold muscle afferent fibers, among muscles in the human upper limb. These studies have demonstrated inhibitory neural connections between the BB and BRR. Moreover it has been shown that the connections concerning the BB differ from those concerning the BRR. Several reports have shown differences in connections between humans and animals. Therefore, the BB in humans has been compared with that in animals.     

Patterns of connections between the musculocutaneous and median nerves in the axilla and arm

Variations in connections between the musculocutaneous and median nerves in the arm are not as uncommon as was once thought. This opinion led us to perform a study in 138 cadavers (66 male, 72 female). These variations were seen in 64 cadavers (46.4%), 9 bilaterally and 55 unilaterally (26 right and 29 left); in total, therefore, variations were observed in 73 out of 276 arms (26.4%), 42 male and 31 female. No statistically significant differences by gender and side were observed. We classify the variations in three main patterns: Pattern 1, fusion of both nerves (14 arms, 19.2%); Pattern 2, presence of one supplementary branch between both nerves (53 arms, 72.6%); and Pattern 3, two branches (5 arms, 6.8%). Pattern 2 was further subdivided into a sub-group 2a when a single root from the musculocutaneous nerve contributed to the connection (51 arms, 69.9%), and 2b when there were two roots from the musculocutaneous nerve (2 arms, 2.7%). A combination of Patterns 1 and 2a was observed in one case (1.4%). Further variations are described, published classification systems are reviewed and a meta-analysis of previous results is presented. An overall incidence of 33% of variant arms was observed. Of these variant arms, Pattern 1 represented 13.1%, Pattern 2 represented 75.4%, and Pattern 3, 8.5%, similar to our figures.     

Coexistence of multiple anomalies in the carpal tunnel

We determined the frequency of anomalous structures within the carpal tunnels of 89 cadaveric forearm-hand specimens. We also examined these same specimens for variations in the branching pattern of the median nerve, and analyzed the range in length and width of the lumbricals. Many of the hands contained extra tendinous slips from the long flexors within the tunnel, subligamentous thenar branches of the median nerve, or lumbricals with bipennate origins. Only one hand had an anomalous muscle belly within the tunnel, two had persistent median arteries, two had high division of the median nerve in the distal forearm, and eight had lumbricals with lengths or widths that were greater or less than 2 standard deviations (SD) from the mean. Twenty-nine percent of all hands examined had two to five anomalies/variations per tunnel, whereas another 27% had one anomaly or variation per tunnel. More right hands (17%) than left (11%) contained two to five anomalous/variant structures per carpal tunnel. More right hands (19%) than left (8%) contained only one variant/anomalous structure per carpal tunnel. Anticipation of the frequency and multiplicity of anomalous structures and variations within this region is of importance to clinicians, particularly surgeons.     

面听神经血管压迫综合征患者小脑下前动脉血管袢与患者典型面听神经症状的MRI研究

目的 探讨小脑下前动脉前(AICA)血管袢的位置对面听神经血管压迫综合征患者典型面、听神经症状的影响。方法 回顾性研究。纳入兰州大学第二医院核磁共振科311例患者(622侧耳)内耳MR可变翻转角三维快速自旋回波(3D-SPACE)序列影像资料,其中男113例、女198例,年龄22~77(48±10.8)岁。统计AICA血管袢发生率及其Chavda分型占比。311例中,单侧面肌痉挛患者107例,比较其患侧(107侧)与健侧(107侧)AICA血管袢发生率、Chavda分型占比,以及AICA走行全程与神经有无接触。自血管袢阳性患者中选择90例(148侧)为血管袢组,比较不同Chavda分型AICA血管袢患者临床表现的差异;将ChavdaⅡ型及Ⅲ型的63侧耳纳入内耳道内血管袢组,将内耳道中的神经分布分为4个象限,观察AICA血管袢与面、听神经接触的位置象限不同的患者间典型面、听神经症状的差异。结果 本组311例622侧患者AICA血管袢的发生率为65.43%(407/622),其中双侧AICA血管袢形成144例、单侧119例,ChavdaⅠ型170侧(41.77%)、Ⅱ型189侧(46.44%)、Ⅲ型48侧(11.79%)。107例单侧面肌痉挛患者健侧AICA血管袢发生率为71.96%(77/107)、患侧70.09%(75/107),两侧比较差异无统计学意义(P＞0.05);健侧和患侧神经血管接触率分别为57.9%(62/107)、43.9%(47/107),差异有统计学意义(χ²=4.207, P＜0.05)。血管袢组90例(148侧)中,不同Chavda分型患者面肌痉挛、听力下降、耳鸣症状的发生率比较,差异均无统计学意义(P值均＞0.05);内耳道内血管袢组共63侧,内耳道内AICA血管袢所处象限不同患者的典型面、听神经症状比较,差异均无统计学意义(P值均＞0.05)。结论 内耳MR 3D-T₂-SPACE成像可清晰显示AICA血管袢及其与内耳道的位置关系,血管袢深度、位置对面听神经压迫综合征典型面、听神经症状无明显影响。     

臂内侧中下段皮肤穿支动脉的解剖学观察

目的观察臂内侧中下段皮肤动脉的解剖学特点,为制作吻合臂内侧穿支动脉的微型皮瓣提供解剖学基础。方法3侧经动脉灌注红色乳胶的成年上臂新鲜标本,以臂内侧中下段深筋膜为基点,观察臂内侧中下段皮肤的穿支血管数量及每一穿支的外径、供血范围及各穿支之间的位置关系。结果臂内侧中下段皮肤动脉通常出现3个较大的皮肤穿支,标本1的3支完全来自肱动脉直接穿支,标本2的3支完全来自尺侧下副动脉穿支,标本3的3支中来自肱动脉穿支1支与尺侧下副动脉皮支2支,其中肱动脉的直接穿支为主。结论臂内侧中下段皮肤穿支动脉变异较大,距肱骨内上髁约80 mm左、右、上、下10 mm可找到一根较粗皮肤穿支动脉。建议在切取吻合臂内侧穿支动脉的微型皮瓣时应注意须先在距肱骨内上髁约80 mm左右作一纵形切口,先切开一侧,找到其中一支较大皮肤穿支动脉,再以该穿支血管为中心设计皮瓣。     

Extra- and intramuscular nerve supply of the muscles of the anterior antebrachial compartment: applications for selective neurotomy and for botulinum toxin injection

Hypertonia of the upper limb due to spasticity causes pronation of the forearm and flexion of wrist and fingers. Nowadays this spasticity is often treated with injections of botulinum toxin and sometimes with selective fascicular neurotomy. To correctly perform this microsurgical technique, it is necessary to get precise knowledge of the extramuscular nerve branching in order to be better able to select the motor branches which supply the muscles involved in spasticity. The same knowledge is required for botulinum toxin injections which must be made as near as possible to the zones where intramuscular nerve endings are the densest, which is also where neuromuscular junctions are the most numerous. Thus, it is necessary to better know these zones, but their knowledge remains today imprecise. The muscles of the anterior compartment of 30 forearms were dissected, first macroscopically, then microscopically, to study the extra- and intramuscular nerve supply and the distribution of terminal nerve ramifications. The results were then linked to surface topographical landmarks to indicate the precise location of motor branches for each muscle with the aim of proposing appropriate surgical approaches for selective neurotomies. Then for each muscle, the zones with the highest density of nerve endings were divided into segments, thus determining the optimal zones for botulinim toxin injections.     

喉返神经在颈部的应用解剖研究

目的　为在甲状腺手术中避免误伤喉返神经提供解剖学基础。方法　对 5 0具 (男 3 0具 ,女 2 0具 )成人尸体解剖喉返神经和甲状腺下动脉之间的关系进行解剖观测。结果　喉返神经平均横径为 ( 1.93± 0 .3 5 )mm。喉返神经入喉支以 2～ 5干型为多见 ,占 70 .0 0 %。甲状腺下动脉的直径为 ( 2 .61± 0 .2 3 )mm。喉返神经和甲状腺下动脉之间的关系 ,左右均有明显差异。结论　喉返神经横径平均在 ( 1.93± 0 .3 5 )mm之间 ;喉返神经在甲状腺峡平面分支的最为常见 ;神经位于动脉主干之后的为多见 ,占 5 4.0 0 % ;神经位于动脉前及动脉分支之间的例数相近 ,左侧神经位于动脉之后的多见 ,而右侧神经位于动脉之前的多见 ,左右有明显差异 ,为临床颈部外科手术时参考。     

Bilateral subclavian arteries passing in front of the scalenus anterior muscles

Herein, we present a very rare case of bilateral subclavian arteries passing in front of the scalenus anterior muscles in a cadaver. This abnormality was observed in a 73-year-old Japanese male cadaver during a dissection session for students in 2004 at Osaka Dental University. The bilateral scalenus anterior muscle originated from the anterior tubercle of the transverse processes of the fifth and sixth cervical vertebrae and inserted into the scalene tubercle of the first ribs. The right scalenus minimus muscle was observed, but no left scalenus minimus muscle was observed. The aortic arch was a type A according to Adachi's classification. The origin of the internal thoracic artery was distal to that of the thyrocervical trunk. The bilateral brachial plexuses was formed by the union of the ventral rami from the fifth cervical to the first thoracic nerves and passed between the scalenus anterior and the scalenus medius muscles. To our knowledge, such a case has not been reported previously.     

Asymmetry of magnetic motor evoked potentials recorded in calf muscles of the dominant and non-dominant lower extremity

The aim of the study was to determine the applicability of magnetic stimulation and magnetic motor evoked potentials (MEPs) in motor asymmetry studies by obtaining quantitative and qualitative measures of efferent activity during low intensity magnetic stimulation of the dominant and non-dominant lower extremities. Magnetic stimulation of the tibial nerve in the popliteal fossa was performed in 10 healthy male right-handed and right-footed young adults. Responses were recorded from the lateral head of the gastrocnemius muscles of the right and left lower extremities. Response characteristics (duration, onset latency, amplitude) were analyzed in relation to the functional dominance of the limbs and in relation to the direction of the current in the magnetic coil by use of the Wilcoxon pair sequence test. The CCW direction of coil current was related to reduced amplitudes of recorded MEPs. Greater amplitudes of evoked potentials were recorded in the non-dominant extremity, both in the CW and CCW coil current directions, with the statistical significance of this effect (p = 0.005). No differences in duration of response were found in the CW current direction, while in CCW the time of the left-side response was prolonged (p = 0.01). In the non-dominant extremity longer onset latencies were recorded in both current directions, but only for the CW direction the side asymmetries showed a statistical significance of p = 0.005. In the dominant extremity the stimulation correlated with stronger paresthesias, especially using the CCW direction of coil current. The results indicate that low intensity magnetic stimulation may be useful in quantitative and qualitative research into the motor asymmetry.     

视交叉前间隙有关结构的解剖观察及其临床意义

目的为经额入路行蝶鞍区手术提供外科解剖学依据。方法对30个经福尔马林固定的成年人尸头标本的视交叉前间隙及有关结构在肉眼和SXQ鄄Ⅱ型手术显微镜下进行观察,对视交叉前间隙的面积进行测算。结果①视交叉前间隙之间的面积为(28.4±6.2)mm2。两侧视神经颅内段越长,夹角越小,视交叉前间隙越大;两侧视神经颅内段越短,夹角越大,视交叉前间隙越小。②视交叉前缘至鞍结节之间的距离为(4.1±0.8)mm,两侧视神经于视交叉前之间的夹角为63.2°±5.8°。③颈内动脉自前床突内侧向上穿过硬脑膜之后,先向前、内、上方行至视神经下面,再弯向后、外、上方行于视神经外侧。④分布于视交叉上后面的视交叉上动脉来源于两侧大脑前动脉水平部段和前交通动脉。分布于视交叉下前面的视交叉下动脉来源于两侧颈内动脉和后交通动脉。结论经额入路蝶鞍区手术主要是通过视交叉前间隙,在颈内动脉之间的间隙操作,手术中应注意保护好视神经和视交叉的营养动脉,以减少并发症的发生。     

Magnetic resonance imaging based classification of anatomic relationship between the cochleovestibular nerve and anterior inferior cerebellar artery in patients with non-specific neuro-otologic symptoms

In this study, we aimed to assess anatomical relationship between the anterior inferior cerebellar artery (AICA) and cochleovestibular nerve (CNV) in patients with non-specific cochleovestibular symptoms using magnetic resonance imaging (MRI). One-hundred and forty patients with non-specific neuro-otologic symptoms were assessed using cranial and temporal MRI. Classification was performed according to four different types of anatomical relationship observed between the AICA and CVN. In type 1 (point compression), the AICA compresses only a limited portion of the CVN. In type 2 (longitudinal compression), the AICA approaches the CVN as both traverse parallel to each other. In type 3 (loop compression), the vascular loop of the AICA encircles the CVN. In type 4 (indentation), the AICA compresses the CVN so as to make an indentation in the nerve. The anatomical relationship between the CVN and AICA was encountered in 19 out of 140 (13.6%) patients (20 ears). The VCC was unilateral in 18 patients (94.7%) and bilateral in one patient (5.3%). There was no other vascular structure causing VCC to the CVN except for vertebral artery that was seen in 2 out of 140 patients (1.4%). These were unilateral cases. There were tinnitus, vertigo or dizziness, hearing loss, and both hearing loss and vertigo in 5 (25%), 13 (65%), 1 (5%) and 1 (5%) ears of 20 patients, respectively. There was no relationship between the cochleovestibular symptoms and type of compression (p>0.05). Neurovascular relationship between the CVN and AICA can be imaged properly using MR and MR based classification may help reporting this relationship in a standard way. Although, MR images can show the anatomical relationship accurately, diagnosis of vascular conflict should not be based on imaging findings alone.