Anatomical entrapment of the dorsal scapular and long thoracic nerves, secondary to brachial plexus piercing variation

Circumscapular pain is a frequent complaint in clinical practice. The dorsal scapular and long thoracic nerves course through the neck, where they may become entrapped between or within adjacent scalene muscles. Additionally, a high frequency of brachial plexus "piercing" variants have recently been documented, and it is unclear how they influence branching patterns distally along the brachial plexus. In the project reported here we strived to identify and quantify variations in dorsal scapular nerve and long thoracic nerve secondary to brachial plexus piercing variation. Ninety brachial plexuses from human cadavers (45 female/45 male) were evaluated to identify nerve branching patterns, specifically piercing versus non-piercing variants in the brachial plexus roots and nerves. Anatomical entrapment of the dorsal scapular nerve and long thoracic nerve was found in high frequencies (60.8% and 44.6%, respectively). Anomalous brachial plexus piercing variants were associated with higher frequencies of distal nerve branches also coursing through the scalene musculature, and there was a statistically significant correlation between brachial plexus and long thoracic nerve piercings (p = 0.027). Anatomical entrapment of nerves within scalene musculature is common and may be causative factors for idiopathic circumscapular pain, dorsalgia, and dysfunction of scapulohumeral rhythm. This study revealed a link between anatomical arrangement of the brachial plexus and occurrence of long thoracic nerve entrapment, which may lead to a series of cascading neurologic effects in which affected individuals may suffer from increased incidence of thoracic outlet syndrome and long thoracic nerve entrapment resulting in additional symptoms of interscapular pain and compromised shoulder mobility.

Anatomical Variations of the Pectoralis Major Muscle: Notes on Their Impact on Pectoral Nerve Innervation Patterns and Discussion on Their Clinical Relevance

BACKGROUND

The presented study attempts to classify individual anatomical variants of the pectoralis major muscle (PM), including rare and unusual findings. Rare cases of muscular anomalies involving the PM or its tendon have been presented. An attempt has also been made to determine whether anatomical variations of the PM may affect the innervation pattern of the lateral and medial pectoral nerves.

MATERIAL AND METHODS

The research was carried out on 40 cadavers of both sexes (22 males, 18 females), owing to which 80 PM specimens were examined.

RESULTS

Typical PM structure was observed in 63.75% of specimens. The most frequently observed variation was a separate clavicular portion of the PM. In one female cadaver (2.5% of specimens) the hypotrophy of the clavicular portion of the PM was noticed. In two male cadavers (5% of specimens) the fusion between the clavicular portion of the PM and the deltoid muscle was observed. In one of those cadavers, small sub-branches of the lateral pectoral nerve bilaterally joined the clavicular portion of the deltoid muscle. The detailed intramuscular distribution of certain nerve sub-branches was visualized by Sihler's stain. PM is mainly innervated by the lateral pectoral nerve. In all specimens stained by Sihler's technique, the contribution of the intercostal nerves in PM innervation was confirmed.

CONCLUSIONS

Surgeons should be aware of anatomic variations of the PM both in planning and in conducting surgeries of the pectoral region.

[Transverse abdominal plane - anatomical and clinical aspects]

In medicine spectacular progress can be observed at many stages, which sometimes requires the redefinition of already known anatomical structures. One of them is the transverse abdominal plane, which was the focus of anaesthetists. It was observed that anaesthetics introduced locally into this plane have similar power to a traditional epidural procedure or spinal anaesthesia. The concept of the trans- verse abdominal plane is a relatively new anatomical term which was introduced into clinical medicine by anaesthetists. Because of the potential performance of anaesthetic pro- cedures through access to the transverse abdominal plane, there has been a growing interest not only expressed by anaesthetists, but also anatomists who wish to explore new anatomical aspects of this plane. It is generally believed that anatomical studies will provide more information on this plane, which can contribute to a wider spread of this pro- cedure among anaesthetists.

Restoration of winged scapula in upper arm type brachial plexus injury: anatomic feasibility

BACKGROUND

The patients who have C5-C6 root avulsion in brachial plexus injury, suffered from loss of elbow flexion, shoulder abduction and winged scapula. The purpose of study is to provide anatomic feasibility of thoracodorsal nerve (medial and lateral branches) and long thoracic nerve for restoration of the shoulder function caused by winged scapula.

MATERIAL AND METHOD

To study the length of thoracodorsal nerve and long thoracic nerve from the apex of the posterior axillary line to the insertion of the latissimus dorsi muscle and the serratus anterior muscle respectively, 10 fresh cadavers were dissected. The distance between the thoracodorsal nerve and long thoracic nerve, and the numbers of fascicles and axon were measured by histomorphometry. We transferred the lateral branch of the thoracodorsal nerve to the long thoracic nerve in order to restore the serratus anterior muscle function.

RESULTS

The mean length of the thoracodorsal nerve from apex of posterior axillary line to bifurcation before separation to medial and lateral branches was 31.5 mm. The average length of the thoracodorsal nerve and long thoracic nerve from bifurcation to the insertion of the latissimus dorsi muscle and the serratus anterior muscle were 10.3, 82.2, and 99.5 mm, respectively. The distance between the lateral branch of the thoracodorsal nerve and long thoracic nerve was 33.4 mm. The mean number of myelinated nerve fiber of the thoracodorsal nerve medial and lateral branches and long thoracic nerve were 973.8, 1843.3 and 1135.3 axons, respectively.

CONCLUSION

The anatomic study of the thoracodorsal nerve and long thoracic nerve showed that the lateral branch of the thoracodorsal nerve is proper in the length and numbers of axon to transfer to the long thoracic nerve for restoration of shoulder function caused by the winged scapula.

Angina pectoris symptoms caused by thoracic spine disorders. Neuro-anatomical considerations

The pain conducting systems in the thorax will be described. The diagnosis angina pectoris is a symptom diagnosis. The common medical assumption is that these symptoms are caused by decreased circulation in the coronary vessels. The truth is that exactly the same symptoms can be the results of pathological changes in for example the oesophagus, the mediastinum and the thoracic spine. Our knowledge of referred pain and the pathways for pain conduction permits us nowadays to understand how pain symptoms can have different origins and still be experienced as identical.

The sternalis muscle in cadavers: anatomical facts and clinical significance

The sternalis is an anomalous muscle located in the anterior wall of thorax and several past reports have described its presence with clinical implications. The sternalis muscle may be incidentally detected during routine cadaveric dissections and autopsies. We observed the presence of anomalous sternalis muscle on both sides of the anterior chest wall in 25 cadavers (n = 50), over a span of three years. Out of a 50 cases, we observed a single case of sternalis on the right side of the 55-year-old male cadaver (2%). The sternalis was found to be absent in the rest 49 cases (98%). The sternalis muscle displayed an oblique course in the anterior wall of the thorax. The muscle originated near the seventh costal cartilage extending obliquely upwards to insert into the second costal cartilage close to the sternum. The originating portion of the muscle was located at a distance of 3.5 cm lateral to the mid-sternal plane. The vertical length and the maximum width of the anomalous sternalis muscle measured 9 cm and 1.9 cm, respectively. The fibers of the muscle vertically ascended upwards. No other associated anomalies were observed in the same cadaver. The presence of sternalis muscle is considered to be a rare variation with no earlier studies being performed in the Malaysian population. The anomalous sternalis muscle may be important for reconstructive surgeons performing mastectomy and radiologists interpreting mammograms. Thus, the sternalis muscle may be academically, anthropologically and surgically important.

The surgical anatomy of the ansa pectoralis

Detailed anatomical knowledge of the pectoral nerves is of clinical importance in surgeries as diverse as limb neurotization, mastectomy, orthopedic procedures and operations related to trauma. The brachial plexus of 200 cadavers were examined in an attempt to clarify the normal origins, courses and variations of the nerves with special emphasis on the ansa pectoralis (AP). In 75% the MPN arose from the anterior division of the inferior trunk of the brachial plexus and in 25% it arose from the medial cord. In 40% of specimens, the LPN arose from a single contributing nerve (anterior division of the superior trunk, 11%; anterior division of the middle trunk 18%; lateral cord, 11%). In the remaining 60% of specimens, the LPN arose from the fusion of two rootlets derived variably from the anterior divisions of the superior and middle trunks and the lateral cord. A single AP was found to be present bilaterally in 200 (100%) of the specimens. Classification of the AP was based upon its origin from the upper or lower rootlet of the LPN, the LPN itself, or from the deep branch of the LPN. AP-1 (42%) arose from the deep branch of the LPN; AP-2 (28%) arose directly from the LPN; AP-3 (25%), arose from the lower rootlets of the LPN and rarely, the AP arose from the upper rootlet of the LPN and crossed posterior to the lower rootlet to communicate with the MPN (AP-4, 5%). Irrespective of the aforementioned types, the AP was found to be present, crossing the second segment of the axillary artery in 90% of the specimens. These results could prove useful during the preoperative planning of neurotization and other surgical procedures involving the axilla.

Medial and lateral pectoral nerves: Course and branches

During modified radical mastectomy or cosmetic surgery, denervation of the lower part of the pectoralis major frequently occurs and may reduce muscle spasm, with consequent better reconstruction of the breast. The aim of this study was to determine the relationship between the pectoral nerves and the pectoral muscles. Eight unembalmed female cadavers were dissected and vascular and radiologic studies performed. The lateral pectoral nerves showed a constant course, parallel to the thoraco-acromial vessels. They coursed for 55 +/- 7 mm inferomedially on the deep surface of pectoralis major, under its fascia. The medial pectoral nerves showed two main patterns of branching, which correlated with the extent of the costal attachments of the pectoralis minor muscles. In pattern A (56%), associated with costal attachments narrower than 6.0 cm, the nerve pierced the deep aspect of the pectoralis minor as a single trunk, ramified in the muscle, and gave some branches that appeared on the superficial aspect to enter the pectoralis major. In pattern B (44%), associated with costal attachments wider than 6.6 cm, the nerve divided before entering pectoralis minor and its branches passed through the muscle or round its lower border to reach pectoralis major. The most medial branch of the medial pectoral nerve directed to the pectoralis major muscle emerged from pectoralis minor at the third intercostal space in the midclavicular line, a mean of 10.3 cm lateral to the margin of the sternum. Knowledge of the relationship between the extent of the costal attachment of pectoralis minor and the two patterns of branching of the medial pectoral nerve may be useful when performing elective denervation of the major pectoralis muscle.

The gross anatomy of the extrathoracic course of the intercostobrachial nerve

Recent reports emphasize the importance of preserving the intercostobrachial nerve (ICBN) during surgical procedures (i.e., mastectomy, axillary clearance). However, a limited number of scientific reports explore the surgical anatomy of this nerve. We dissected 100 adult human formalin-fixed cadavers (200 axillae). In all the cadavers the ICBN was present with variant contributions from intercostal nerves T1, T2, T3, and T4. The arrangements of the ICBN were typed as I through VIII. The components of Type I (45% or 90 of our specimens) included a branch to the posterior antebrachial cutaneous nerve, a branch to the anterior and lateral parts of the axilla, a branch to the medial side of the arm, and a branch to the medial antebrachial cutaneous nerve. Type II (25%) describes the ICBN arising from T2 and giving off a branch to the brachial plexus. In Type III (10%), lateral cutaneous branches of T2 and T3 fuse as a common trunk and then split immediately after exiting the intercostal space to form an ICBN. In type IV (5%), T2 and T3 join distally to form an ICBN that ends as its terminal branches. Type V (5%): T3 joins T2 from the same intercostal space proximally, with Type VI (3%) showing a very proximal branching of the sensory terminal nerves. Type VII (5%) displayed a contribution from T3 and a branch to the brachial plexus with multiple terminating branches. A contribution from T3 and T4 and a branch to the brachial plexus with multiple branches of termination comprised Type VIII (2%).

Long thoracic nerve: anatomy and functional assessment

BACKGROUND

The anatomy and function of the long thoracic nerve are not fully understood. The purposes of this study were to clarify the anatomy of the long thoracic nerve and to propose a clinical test to assess the function of the upper division of the long thoracic nerve.

METHODS

The long thoracic nerve and the serratus anterior muscle were studied in fifteen fresh cadavera. Six patients had an operation to treat a brachial plexus injury, and the long thoracic nerve was electrically stimulated. The resulting shoulder motion was then observed.

RESULTS

The long thoracic nerve was formed by branches arising from the C5, C6, and C7 nerve roots. The C5 and C6 branches joined beneath the scalenus medius muscle to form the upper division of the long thoracic nerve, which was located 1 cm posteriorly and superiorly to the upper trunk origin. The union of the upper division with the branch from C7 occurred caudally, in the axillary region. Two branches from the upper division of the long thoracic nerve to the upper portion of the serratus anterior muscle were consistently identified. After electrical stimulation of the upper division branches, shoulder protraction was observed.

CONCLUSIONS AND CLINICAL RELEVANCE

In the supraclavicular region, the long thoracic nerve has a trajectory parallel to the brachial plexus, which is contrary to the schematic representation in most textbooks. The upper division of the long thoracic nerve can be assessed by the shoulder protraction test.

Anatomical variations of the second thoracic ganglion

In recent years the second thoracic ganglion has gained anatomical significance as an important conduit for sympathetic innervation of the upper extremity. Thoracoscopic excision of the second thoracic ganglion is now widely recognized as affording the most effective treatment option for palmar hyperhidrosis. This study recorded the incidence, location and associated additional neural connections of the second thoracic ganglion. Bilateral dissection of 20 adult cadavers was undertaken, and all neural connections of the second thoracic ganglion were recorded. Nineteen cadavers (95%) demonstrated additional neural connections between the first thoracic ventral ramus and second intercostal nerve. These were classified as either type A (47.5%) or type B (45%) using the intrathoracic ramus (nerve of Kuntz) between the second intercostal nerve and the ventral ramus of the first thoracic nerve as a basis on both right and left sides. The second thoracic ganglion was commonly located (92.5%) in the second intercostal space at the level of the intervertebral disc between the second and third thoracic vertebrae. Fused ganglia between the second thoracic and first thoracic (5%) and stellate (5%) ganglia were noted. These findings should assist the operating surgeon with a clear knowledge of the anatomy of the second thoracic ganglion during thoracoscopic sympathectomy with a view to improving the success rate for upper limb sympathectomy.

Anatomical variations of rami communicantes in the upper thoracic sympathetic trunk☆

OBJECTIVE

The aim of this study was to clearly delineate the anatomical variations of the communicating rami in the upper thoracic sympathetic nervous system and to help develop better surgical method for essential palmar hyperhidrosis.

METHODS

Anatomical dissections of the upper thoracic sympathetic chains with sympathetic ganglia and communicating rami have been carried out in 42 adult Korean cadavers (male 26, female 16). The rami communicantes were classified into three types (Normal: transverse or oblique rami connected to the intercostal nerve of the same level; AR: ascending rami connected to the higher level; DR: descending rami to the lower level) based on the anatomical relationship of the thoracic sympathetic ganglia to the intercostal nerves. Both sides of the upper thoracic sympathetic nervous system were compared in the same individual. The number of the communicating rami was recorded in 32 cadavers (64 sides). The distance from the rami communicantes to the sympathetic trunk was measured in 26 cadavers (52 sides).

RESULTS

The incidence of AR (ascending rami) and DR (descending rami) arising from the second sympathetic ganglion was 53.6% (45/84), 46.4% (39/84). From the third thoracic sympathetic ganglion, the incidence of AR was 5.9% (5/84) and that of DR was 26.2% (22/84). And in the fourth thoracic sympathetic ganglion, the incidence of AR was 4.8% (4/84) and DR was 8.3% (7/84), respectively. When we compared anatomical structures of both sides among the 42 cadavers dissected, only 14.3% (6/42) had similar anatomy of the rami communicantes bilaterally. Among 32 cadavers (64 sides), the mean number of rami communicantes at the second thoracic sympathetic ganglion was 2.1/2.5 in the left and the right side. At the third and the fourth thoracic sympathetic ganglion, the mean number was 1.9/1.6 and 1.7/1.7 in each side. The mean distance from the thoracic sympathetic chain to the most distal communicating rami of the left and right side at the second intercostal nerve was 7.81/9.40 mm among 26 cadavers. The mean distance of each side was 6.81/7.94 mm at the level of the third intercostal nerve. And at the level of the fourth intercostal nerve, the mean distance was 7.48/10.92 mm, respectively.

CONCLUSION

On the basis of this study, the anatomical variations of communicating rami could explain some surgical failures and recurrences. Moreover, in addition to the conventional surgical methods (sympathectomy, sympathicotomy, clipping of sympathetic chain and ramicotomy), dividing the inconstant sympathetic pathways (nerve of Kuntz, ascending or descending rami communicantes) on the second, the third and the fourth ribs will help to get better surgical effect.

Distal variations of the neurovascular pedicle of the serratus anterior muscle as a flap

The serratus anterior muscle has recently been suggested as a versatile and reliable flap for reconstruction of complex craniofacial and neck lesions, extremity and sacroiliac region injuries, as well as intrathoracic and extrathoracic reconstruction procedures. The muscle has been used as a microvascular flap or a pedicled transfer and has been transferred in combination with other muscles, bones, and skin. We performed 15 dissections of adult axilla regions that were examined under x3.5 loupe magnification to collect anatomic data regarding the neurovascular pedicle of the serratus anterior muscle. The serratus muscle and fascia were found to have a dual blood supply, with the upper part supplied by the lateral thoracic artery and the lower part by terminal branches of the thoracodorsal artery. The lateral thoracic artery was noted to supply the upper four slips but it extended into the lower serratus anterior muscle in two cases. Seven branching patterns were found in the lower serratus anterior muscle. In type I, the only branch of serrati proceeded over the long thoracic nerve. Type II had the only branch of serrati proceeding under the long thoracic nerve. In type III, double branches of serrati proceeded over the long thoracic nerve; while in type IV branches of serrati ran with a double branch under the long thoracic nerve. In type V, three serrati branches proceeded over the long thoracic nerve. Type VI serrati branches were branches of thoracodorsalis, which was hypoplastic, and the supply was maintained from the lateral thoracic artery. In type VII, one serrati branch ran over the long thoracic nerve. There was no connection between the branches of serrati and the branches of the lateral thoracic artery. The length of the long thoracic nerve, the number of motor axons and the vascular network in anatomic proximity to this nerve make it an expendable but powerful source of reconstructions of head, neck, chest wall and extremity defects. Results of this study provide an anatomic framework to improve current reconstructive or aesthetic procedures on the serratus anterior neurovascular structures.

In situ images of the thoracic paravertebral space

BACKGROUND AND OBJECTIVES

In situ knowledge about the anatomic structures and the path of a needle percutaneously placed into the paravertebral space is an area that continues to be investigated. We describe an endoscopic technique that permits imaging of the contents and boundaries of the thoracic paravertebral space in cadavers.

TECHNIQUE

A 43-year-old, 157-cm, 45-kg unembalmed female cadaver was placed in the prone position. Using a 2.3-mm diameter, 0 degree optical angle, fiberoptic ankle arthroscopy scope, trocar, introducer, and light source, thoracic paravertebral blocks were performed. To produce quality images, the trocar was advanced the length of the shaft, approximately 8 cm. The arthroscopy scope was then exchanged with the introducer. The trocar and arthroscopy scope were then gradually withdrawn posterior.

RESULTS

Representative images that show the anatomic pathway of a needle as it would be directed into the paravertebral space as well as the boundaries of the thoracic paravertebral space were obtained. These included the costotransverse ligament, the spinal nerve, and the parietal and visceral pleura.

CONCLUSIONS

The images help show the relationship of structures that are encountered during a paravertebral block. This new technique may be helpful in examining the spread of local anesthetic using dye or imaging the location of continuous catheters without having to dissect the insertion area.

Anatomical basis for a successful upper limb sympathectomy in the thoracoscopic era

In this clinico-anatomical study, factors potentially responsible for unsuccessful upper limb sympathectomy (ULS) by the thoracoscopic route were evaluated. This study comprised two subsets: 1) in the clinical subset, 25 patients (n = 50 sides) underwent bilateral second thoracic ganglionectomy for palmar hyperhidrosis, and factors predisposing to unsuccessful ULS were identified; and 2) in the anatomical subset, the neural connections of the first and second intercostal spaces were bilaterally dissected in 22 adult cadavers (22 right, 21 left; n = 43 sides). Alternate neural pathways (ANP) were noted in 9 of 50 sides in the 25 clinical cases (18%). In three asthenic patients (5 sides), fascia overlying the longus colli muscle mimicked the sympathetic chain. The right superior intercostal vein (SIV) was located anterior to the second thoracic ganglion in 6 of 50 sides (12%) and predisposed to troublesome bleeding in 2 of 50 cases; the SIV was posterior to the ganglion in 19 of 50 sides (38%), posing no technical problem. On the left, the SIV was noted outside the field of dissection in all but one case. A successful outcome to sympathectomy was noted in all 25 patients. A spectrum of sympathetic contributions to the first thoracic ventral ramus for the first intercostal space was noted in 37 of 43 anatomical cases (86%). These were categorized according to the arrangements of the intrathoracic ramus between the second intercostal nerve and the first thoracic ventral ramus. The cervicothoracic ganglion (37/43 cases; 86%) and an independent inferior cervical ganglion (6/43 cases; 14%) were always located above the second rib. The second thoracic ganglion was consistently located in the second intercostal space. This study demonstrates that ANPs have little clinical significance when a second thoracic ganglionectomy is undertaken. Technical failures may be avoided if the surgeon is mindful of anatomical variations at surgery.

Isolated compression of the pectoral nerve resulting in atrophy of the major pectoral muscle

We report on two cases of isolated damage to a muscle branch of the lateral pectoral nerve. Diagnosis was established by the clinical presentation and electromyographic examination. In the few reported cases of such injuries, the cause was trauma to this region. However, in both of our patients, focal muscle atrophy gradually developed after initiation of training schedules to increase the cross-section of the major pectoral muscle; we therefore assume that compression injury to the nerve by repetitive muscle contractions may be of pathogenic relevance. Anatomical studies of this region showed that the nerve branches of the lateral pectoral nerve, having to pierce through a connective tissue septum that is thicker here by a few millimeters, may be subjected to additional risk of compression. Early recognition and treatment are vital to prevent associated morbidity of these rare but serious injuries.

Sonographic mapping of the normal brachial plexus

BACKGROUND AND PURPOSE

Mapping of the brachial plexus with MR imaging has been reported and may have potential clinical applications (eg, precise localization of traumatic or tumoral nerve lesions, selective anesthesia of the brachial plexus). We sought to demonstrate that mapping of the brachial plexus may be performed by means of sonography.

METHODS

Twelve healthy adult volunteers (seven women and five men; age range, 24-38 years; mean, 31 years) underwent bilateral sonographic examination for the assessment of the nerve structures of the brachial plexus from the extraforaminal part to the axillary part. Four formolated cadavers (two male and two female; age range, 66-84 years; mean, 77.5 years) were frozen and sawed into 3-mm-thick contiguous sections in the same plane as that used for the sonographic exploration.

RESULTS

A satisfactory sonographic examination was performed in 10 of 12 volunteers, leading to a good association with anatomic sections. Two volunteers were excluded from the study because a clear depiction of the brachial plexus was difficult owing to a short neck and low echogenicity at examination. The association between sonographic images and anatomic sections allowed us to map the brachial plexus. The subclavian and deep cervical arteries were useful landmarks for this mapping. The eighth cervical nerve root and the first thoracic nerve root were the most difficult part of the brachial plexus to depict because of their deep location.

CONCLUSION

The brachial plexus can be mapped with sonography. However, this technique requires a good grounding in anatomy and may be impossible in short-necked individuals.

Allatostatins of the tiger prawn, Penaeus monodon (Crustacea: Penaeidea)

More than 40 peptides belonging to the -Y/FXFGL-NH(2) allatostatin superfamily have been isolated and identified from the central nervous system (CNS) of the tiger prawn, Penaeus monodon (Crustacea: Penaeidea). The peptides can be arranged in seven sub-groups according to the variable post-tyrosyl residue represented by Ala, Gly, Ser, Thr, Asn, Asp, and Glu. Two of the residues (Thr and Glu) have not been observed in this position previously in either insects or crustaceans. Also reported for the first time for allatostatins, two of the peptides are N-terminally blocked by a pyroglutamic acid residue. The yields of certain peptides with similar amino acid sequences to each other were, in some instances, very different. As an example, the yield of ANQYTFGL-NH(2) was 2pmol, compared with ASQYTFGL-NH(2), with a yield of 156 pmol. There are several possibilities to account for this. If, as in all species so far investigated, there is a single allatostatin gene in P. monodon, then it would appear that different sub-populations have contributed mutant forms of particular peptides to the extract. Another, less likely possibility is that this species has more than one allatostatin gene, producing a variable array of peptides albeit in different molar ratios. Several peptides were present apparently as a result of the loss of one or more residues at the N-terminus of a larger form, either due to N-terminal degradation or specific post-translational processing. The number of peptides identified exceeds that for any other insect or crustacean species previously investigated. None is identical to any of the 60-70 insect allatostatins so far identified, and only three are common to other crustaceans. Immunohistochemical study of the CNS of P. monodon, with the same antisera as used to monitor the purification, confirms the widespread nature and complexity of allatostatinergic neural pathways in arthropods. Thus, all neuromeres of the brain, and all except one of the ventral cord ganglia, possess allatostatin neurons and extensive areas of allatostatin-innervated neuropile. In addition to the cytological evidence that the allatostatins act as neurotransmitters, associated with tissues as varied as eyes and legs, their presence in neurohemal areas such as the sinus gland and the perineural sheath of the thoracic ganglia suggests a neuroendocrine function. As well as posing a challenge to physiologists assigning specific functions to the allatostatins, their extensive intra-species multiplicity, linked to their inter-species variability, also presents a complex problem to geneticists and evolutionists.

Cutaneous nerve to the subacromial region originating from the lateral pectoral nerve

During dissection practice, a cutaneous branch to the deltoid region, which originated from the lateral pectoral nerve, was found bilaterally in one Japanese male (two of 125 sides, 1.6%). The branch originated from the superior surface of the lateral pectoral nerve, ran on the superior surfaces of the coracoid process and the coraco-acromial ligament, and pierced the deltoid muscle close to the tip of the acromion. The distribution area of this cutaneous branch was similar to the cutaneous branch of the suprascapular nerve. Although the branch from the suprascapular nerve has been reported in man and primates, a minute description of such a branch from the lateral pectoral nerve is not currently available in the literature. According to the detailed analyses of the roots of the lateral pectoral nerve and the suprascapular nerve, the roots of both nerves are close to each other in the upper part of the superior trunk of the brachial plexus. Therefore, these cutaneous branches have different courses, but are considered to be a single nerve to complement the supraclavicular nerves.

Thoracic origin of a sympathetic supply to the upper limb: the 'nerve of Kuntz' revisited

An understanding of the origin of the sympathetic innervation of the upper limb is important in surgical sympathectomy procedures. An inconstant intrathoracic ramus which joined the 2nd intercostal nerve to the ventral ramus of the 1st thoracic nerve, proximal to the point where the latter gave a large branch to the brachial plexus, has become known as the 'nerve of Kuntz' (Kuntz, 1927). Subsequently a variety of sympathetic interneuronal connections down to the 5th intercostal space were reported and also described as the nerve of Kuntz. The aim of this study was to determine: (1) the incidence, location and course of the nerve of Kuntz; (2) the relationship of the nerve of Kuntz to the 2nd thoracic ganglion; (3) the variations of the nerve of Kuntz in the absence of a stellate ganglion; (4) to compare the original intrathoracic ramus with sympathetic variations at other intercostal levels; and (5) to devise an appropriate anatomical classification of the nerves of Kuntz. Bilateral microdissection of the sympathetic chain and somatic nerves of the upper 5 intercostal spaces was undertaken in 32 fetuses (gestational age, 18 wk to full term) and 18 adult cadavers. The total sample size comprised 99 sides. Sympathetic contributions to the first thoracic nerve were found in 60 of 99 sides (left 32, right 28). Of these, 46 were confined to the 1st intercostal space only. The nerve of Kuntz (the original intrathoracic ramus) of the 1st intercostal space had a demonstrable sympathetic connection in 34 cases, and an absence of macroscopic sympathetic connections in 12. In the remaining intercostal spaces, intrathoracic rami uniting intercostal nerves were not observed. Additional sympathetic contributions (exclusive of rami communicantes) were noted between ganglia, interganglionic segments and intercostal nerves as additional rami communicantes. The eponym nerve of Kuntz should be restricted to descriptions of the intrathoracic ramus of the 1st intercostal space. Any of these variant sympathetic pathways may be responsible for the recurrence of symptoms after sympathectomy surgery.

Nerves of the thorax: atlas of normal and pathologic findings

An anatomic and imaging atlas was created to provide detailed information about the six pairs of thoracic nerves (phrenic nerves, vagus nerves, recurrent laryngeal nerves, sympathetic trunks, costal nerves, long thoracic nerves). Serial axial computed tomographic (CT) scans of the normal thorax were obtained and included in the atlas, along with drawings showing the proper location of each nerve relative to adjacent anatomic structures. CT scans obtained in both symptomatic and asymptomatic patients with various thoracic diseases were paired with appropriate drawings and normal CT scans in the atlas. This format was designed to help determine the presence and severity of related disease, including injury from surgery, trauma, or penetrating injury, metastatic disease involvement, and, rarely, primary tumor. Although the nerves of the thorax are rarely identified at cross-sectional imaging, their location can be inferred by localizing easily identified anatomic landmarks. Familiarity with the functional anatomy and clinical significance of the nerves of the thorax is important for the correct interpretation of thoracic images.

Anatomical bases of the posterior approach to the brachial plexus for repairing avulsed spinal nerve roots

Avulsion of nerve roots from the cervical spinal cord has always been considered as an untreatable injury, even by surgeons with expertise in this area. However, numerous experimental studies in animals, as well as a human case report, showed that if continuity is restored between the spinal cord and nerve roots, axons from spinal motor neurons can regrow into the peripheral nerve graft with a subsequent recovery of motor function. The posterior subscapular approach, based on the evolution of the posterolateral approach for removal of the first rib, is the only way to expose the entire brachial plexus from C5 to T1 from the ventral and dorsal roots to the distal nerve trunks. The purpose of this study is to investigate the topographic anatomy of the brachial plexus, with particular emphasis on the relationships important to the posterior approach and reimplantation of the ventral rootlets within the cord, either directly or using peripheral nerve grafts. The major advantage of the procedure is the proximal exposure of the plexus, with evaluation of the lesions being excellent (intradural, foraminal and proximal trunks). Reimplantation of ventral roots into the cord is relatively easy from C5 to C7, more difficult for C8 and problematic for T1, whereas reimplantation of dorsal roots into the cord is easy from C5 to T1. The disadvantages of this approach for exposure of the plexus and nerve root avulsion repair are significant: the surgical technical steps are difficult mainly because of the cervical paraspinal muscle mass, which cannot be easily "elevated and retracted" despite previous descriptions; bleeding from the venous plexus can be excessive as suggested by dissection and our own experience; the stability of the cervical spine may be compromised following extensive laminectomy with total unilateral facetectomy; exposure of the plexus distal to the division of the trunks is difficult; there may be injury to the long thoracic nerve and subsequent winging of the scapula; and pneumothorax. This approach is therefore only applicable in highly selected cases involving multiple avulsed roots with proximal lesions extending as far as the division of the trunks.

Surgical relationship of the medial pectoral nerve to the musculocutaneous nerve: a cadaveric study

OBJECTIVE

For purposes of neurotization of the musculocutaneous nerve (MCN) with the medial pectoral nerve (MPN) after upper trunk brachial plexus injuries, the anatomic relationship between these two nerves was defined in a cadaveric model.

METHODS

Thirty-five brachial plexuses in 18 adult cadavers were dissected. The distance between the origin of the MPN from the medial cord to the origin of the MCN from the lateral cord was measured. The length, diameter, branching, and location of the MPN were recorded. The diameter of the proximal MCN was recorded.

RESULTS

Thirty-seven percent of the MPNs, when detached from the pectoralis muscles, were too short to reach the proximal MCN by a mean distance of 15 mm. The MPN pierced the pectoralis minor muscle in 80% of the dissections. The cross sectional area of the MCN was always larger than the cross sectional area of the MPN by an average factor of 2.5.

CONCLUSION

When planning to use the MPN for neurotization of the MCN, one should be prepared to harvest an interposition graft, because over one-third of MPNs may not have enough length to reach the MCN in a tension-free manner. Diameter mismatch occurs predictably between the distal MPN and the proximal MCN.

Anatomic study of the cervicothoracic spinal nerves and their relation to the pedicles

Twelve cadavers were dissected for the study of the cervicothoracic junction. The results showed that the mean heights and widths of the ganglia tend to decrease from the C-6 to T-4 nerve. The mean distances between the dura and the ganglion and the mean spinal nerve angles increased consistently from C-5 to T-4. The mean distances from the spinal nerves to the superior and inferior pedicles ranged 0.8-2.3 mm. It was noted that the mean value was significantly greater for the distance from the spinal nerve to the superior pedicle than that to the inferior pedicle for the spinal nerves C5-7 (P< or =.05). This information, in conjunction with imaging studies, may minimize spinal nerve injury during posterior pedicle screw fixation in the cervicothoracic spine.

The anatomy of the extrathoracic intercostobrachial nerve

BACKGROUND

In the past decade surgeons have become increasingly aware of the morbidity caused by the division of the intercostobrachial nerve (ICBN) during axillary dissection. To prevent this problem and also to explain its variable occurrence, a detailed knowledge of the anatomy of the nerve is required.

METHODS

Twenty-eight axillary dissections were performed demonstrating the anatomy of the ICBN.

RESULTS

In all dissections the nerve originated from the second intercostal space, with contributions from the first and third intercostal nerve each on one occasion. The posterior axillary branch was constant but may branch early, simulating a second nerve. The ICBN had a variable relationship to the lateral thoracic vein: anterior, posterior or wrapping around it. In 36% there was a connection to the medial cord of the brachial plexus in the axilla. In the upper arm the nerve lies in the subcutaneous fat; in the majority it supplied at least the proximal half of the arm, and in one-third it reached the level of the elbow joint. In 18% there was a connection to the medial cutaneous nerve of the arm.

CONCLUSION

The ICBN and its main branch (the posterior axillary nerve) were constant in all dissections. But its origin, size, connection to the brachial plexus and medial cutaneous nerve of the arm were variable, as was its ultimate destination in the arm.

Anatomic basis of vascularized nerve graft using the long thoracic nerve

Vascularized nerve transplants can lead to satisfactory functional reconstruction for nerve defects. These include defects following traumatic nerve severance, iatrogenic severance during tumour resection and extensive defects in poorly vascularized transplant sites. No previous description of the long thoracic nerve as a vascularized nerve graft is available. The aim of this study was to demonstrate the anatomic and initial clinical application of such a graft. The long thoracic nerve was dissected in 84 cases to examine its length, diameter, ramification and type of perfusion. On removal of the nerve, adequate perfusion through the thoracodorsal artery and a constant anatomic course with minimal loss of function were found. The long thoracic nerve is accessible anatomically, easily dissected and removed. This may be carried out together with the thoracodorsal vein and artery and even with a pedicled myocutaneous latissimus dorsi transplant, an osseo-myocutaneous scapulo-latissimus dorsi transplant or an osseous scapular transplant. The long thoracic nerve transplant can be employed for extensive facial defects together with simultaneous osseous and myocutaneous transplants of the shoulder region.

Relationship of the long thoracic nerve to the scapular tip: an aid to prevention of proximal nerve injury

OBJECTIVE

The objective was to determine the course of the long thoracic nerve relative to the scapula as an aid to the prevention of proximal long thoracic nerve injuries.

METHODS

Eighteen fresh cadavers (7 male, 11 female) were studied. Each was sequentially placed in the transaxillary and posterolateral thoracotomy positions, and the distance of the long thoracic nerve from the scapular tip and anterior scapular border was measured. The measurements were made bilaterally; the mean, standard deviation, and 99% confidence interval were calculated for each position by gender.

RESULTS

Distances from the scapular tip to the long thoracic nerve are listed as mean/outer range: transaxillary thoracotomy, male 4.9/7.0 cm left, 5.2/7.5 cm right; female 4.3/5.0 cm left, 4.7/6.0 cm right; posterolateral thoracotomy, male 3.1/6.0 cm left, 4.5/5.1 cm right; female 3.2/4.5 cm left, 3.8/5.5 cm right. In all instances, the long thoracic nerve was furthest from the scapula at its tip.

CONCLUSION

For patients positioned for a transaxillary thoracotomy, incision sites should be at least 7.5 and 6.0 cm anterior to the scapular tip for male and female patients, respectively. For patients in posterolateral thoracotomy positioning, incisions should be 6.0 and 5.5 cm anterior to the scapular tip for male and female patients, respectively. By using these anatomic guidelines, we believe that the incidence of iatrogenic proximal long thoracic nerve injury can be minimized.

Vulnerability of long thoracic nerve: an anatomic study

The anatomic course of 40 long thoracic nerves was studied in relation to anatomic landmarks and reference lines, that is, the axillary lines and first 2 ribs. After its supraclavicular course, the nerve passes beneath the clavicle within the axillary sheath and then emerges from the axillary sheath. As it passes inferiorly and posteriorly from the point of emergence to the posterior angle of the second rib (that is, the attachments of serratus anterior muscle), it makes a posterior angle of 30.7 degrees +/- 4.3 degrees on average, relative to the anterior axillary line. It then continues to descend inferiorly between the middle and posterior axillary lines. When the arm is raised, the axillary neurovascular bundle moves superiorly with the movements of the arm. The long thoracic nerve is angulated and stretched at the point it passes out of the axillary sheath.

A comparative study of structures comprising the thoracic outlet in 250 human cadavers and 72 surgical cases of thoracic outlet syndrome

OBJECTIVE

We have hypothesized that variations in fibrous, muscular and osseous structures with the potential to entrap the brachial plexus occur within the thoracic outlet of the normal population; and that these variations are different in pattern and frequency from those in patients presenting with thoracic outlet syndrome (TOS).

METHODS

Structural anomalies with potential for entrapping elements of the brachial plexus were examined following dissections of the posterior triangle of the neck in 250 human cadavers (N = 500 thoracic outlet dissections) and catalogued jointly by an anatomist and a thoracic surgeon. The pattern and frequency of anomalies in the 250 cadavers was compared to that encountered in 72 surgical cases of removal of the first rib for relief of symptomatic TOS (N = 72 procedures, 55 patients).

RESULTS

Relevant structural variations were encountered in 46% of cadavers, exhibiting no left right or gender preference overall. When compared with the surgical group in which 100% exhibited structurally relevant anomalies, significant differences in pattern of anomalous structures and gender distribution were revealed. Anomalies posterior to the brachial plexus, ranging from fibrous bands to cervical ribs in both groups, were prevalent in the surgical group. A 'scissors-like' pattern, with neural entrapment by anterior and posterior anomalies was frequently encountered in females.

CONCLUSIONS

Based on these data and embryological considerations, we propose a revised and simplified classification of impingement mechanisms within the anatomic thoracic outlet. Comparing these data to radiological imaging and observations at surgery, we offer a new perspective for the investigation and management of patients with TOS.

Anatomical variant of the lateral pectoral nerve innervating the anterior portion of the deltoid muscle: a case report

BACKGROUND

The deltoid muscle is innervated by the axillary nerve. There is no collateral nerve supply described for this muscle. Palsy of the axillary nerve is common in shoulder trauma due to its close relationship to the surgical neck of humerus.

METHODS

A dissection of the pectoral and axillary regions of two female cadavers was performed bilaterally for a detailed analysis of the innervation of the deltoid muscle.

RESULTS

A branch of the lateral pectoral nerve provided supplemental innervation to the anterior portion of the deltoid muscle bilaterally in both cadavers.

CONCLUSION

A branch of the lateral pectoral nerve could provide collateral nerve supply to the deltoid muscle. The frequency of this anatomical variation requires further exploration.

The brachial plexus in the chacma baboon (Papio ursinus)

The brachial plexus in each of ten embalmed, mature chacma baboons was dissected to document the structure and branching pattern of this nerve plexus in this increasingly used research animal. In general, the brachial plexus in the chacma baboon was similar to the plexuses in the vervet and other Old World monkeys. However, several aspects were comparable to those observed in domestic animals. Thus the bipedal and quadrupedal abilities of the chacma baboon were reflected in the structure of its brachial plexus.

The hypogastric and thirteenth thoracic ganglia of the rat: effects of age on the neurons and their extracellular environment

Morphometric analyses of the neurons and microvessels of perfusion-fixed hypogastric (HG) and 13th thoracic (T13) ganglia have been performed in male Wistar rats aged 4, 24 and 30 mo. Estimations of HG volume employing the Cavalieri principle have also been performed and showed that the size of the aged HG is increased by 42%. Routine histological staining of the ganglia with Masson's trichrome indicated that this may be due to the increased amount of interstitial connective tissue which was apparent in the aged animals. The number of neurons per unit area progressively decreased by 38% between ages 4 and 24 mo and by 16% between ages 24 and 30 mo in the HG and by 25% (4 and 24 mo) and 2% (24 and 30 mo) in the T13 ganglion. The total number of neurons in the HG however, estimated by a physical disector analysis, was constant with age. The number of microvessels per unit area, microvessel diameter, neuronal and nuclear areas did not differ significantly between the 3 age groups studied. This observed increase in ganglionic volume and decrease in neuronal packing density may be associated with changes in the extracellular matrix, in particular in glycosaminoglycans whose presence was indicated by metachromasia of the ganglia with toluidine blue. The extracellular matrix was therefore characterised using a panel of monoclonal antibodies against glycosaminoglycans and laminin. Chondroitin-6 sulphate and chondroitin-4 sulphate were present in the interstitial connective tissue, and there was an increase in the expression of both these epitopes at 24 mo, noteably surrounding neuron cell bodies. The expression of chondroitin-4 sulphate/dermatan sulphate was unchanged, thus implying a decreased expression of dermatan sulphate with age. Keratan sulphate and the native chondroitin sulphate epitopes were absent from the ganglia at both ages. Laminin expression was increased in the aged ganglia. It is therefore clear that the constituents of the extracellular matrix are not constant throughout the adult lifespan and that the extracellular matrix may influence neuronal survival in old age. This is the first report characterising age-related changes in the extracellular matrix of autonomic ganglia.

A map of distal leg motor neurons in the thoracic ganglia of four decapod crustacean species

We describe the numbers, central positions, and axonal exit routes of the distal leg motor neurons of four decapod species: squat lobsters (Munida quadrispina), spiny sand crabs (Blepharipoda occidentalis), mole sand crabs (Emerita analoga), and signal crayfish (Pacifastacus leniusculus). As predicted by previous physiological and anatomical identification of axons at the periphery in crayfish and lobsters, cobalt backfills reveal about seventeen cell bodies, which are found in four areas in the ganglion. By comparing their positions and neurite morphologies with the previously identified neurons, functional identifications could be assigned to most of them. The common inhibitor and stretcher inhibitor are located posterior-medial. An anterior-lateral cluster of about twelve somata includes the opener identical to stretcher excitor, one of two bender excitors (bender excitor alpha), four flexor excitors, and two excitors each to the extensor, reductor, and closer muscles. Three cell bodies are posterior-lateral. Of these, the opener inhibitor and the second bender excitor (bender excitor beta) are on about the same dorsoventral plane. The third posterior-lateral cell, the accessory flexor excitor, is noticeably more dorsal than the other two posterior-lateral cell bodies. The reductor muscle is innervated by at least three neurons: the putative common inhibitor and fast and slow excitors. None of the leg motor neurons project into the contralateral hemiganglion. The most variable feature across species is the nerve through which motor axons exit the ganglion: axons leave the ganglia via different routes in each of the four species examined. These differences in the axons' pathway, however, are insufficient to explain the differences in motor output and behaviour of these four species.

[The courses and the segmental origins of the cutaneous branches of the thoracic dorsal rami]

It is described in many textbooks that the medial cutaneous branches (RCM) from the medial branches of the upper six thoracic dorsal rami supply the upper half of the back of the body, the lateral cutaneous branches (RCL) from the lateral branches of the lower six thoracic dorsal rami supply the lower half of it, and the area supplied by both branches is limited to a few segments. Unlike those descriptions, we had frequently observed RCL from the second or the third thoracic dorsal ramus penetrating the rhomboideus muscle during previous research concerning the double innervation of the superficial muscles of the back by both the ventral and the dorsal rami (Kumaki et al., 1984). To make clear the origin of the discrepancy between the description in the textbooks and our observations, we examined the segmental origins, the courses, and the distributions of both the medial and the lateral branches of the thoracic dorsal rami on 20 sides of 11 bodies dissected in the years 1986 and 1989. Consequently, RCL from the second thoracic dorsal ramus (Th 2) was observed in 25% of the cases and RCL from Th 3 and Th 4 were observed in 50% and in 70%, respectively. The highest segment of RCL was Th 2 in 25%, Th 3 in 25%, Th 4 in 35%, Th 6 in 10%, or Th 8 in 5%, and the mean was Th 3.65 +/- 1.53. On the other hand, the lowest segment of RCM was Th 6 (15%), Th 7 (35%), Th 8 (25%), Th 9 (15%), or Th 10 (10%), and the mean was Th 7.70 +/- 1.19. The mean number of the segments at which the dorsal ramus of the thoracic nerve sent both RCM and RCL was 4.55 +/- 1.50 (Max: 9 segments). Thus, we made clear that RCL from the upper thoracic nerves were commonly observed and that the number of segments sending both RCM and RCL was larger than hitherto described. The course of the upper RCL was bent at the points where the RCL penetrated the superficial muscles of the back forming a "Z"-shape, i.e., RCL changed its course from an infero-lateral to an infero-medial direction at the point of penetrating the rhomboid muscle and from an infero-medial to a lateral direction at the point of penetrating the trapezius muscle or the latissimus dorsi muscle. These directions might be associated with the development of the muscles. Sometimes RCL was sharply pulled in a medial direction by the trapezius muscle to penetrate the muscle near the median plane and appeared as RCM. Therefore, we supposed that the main reason why the upper RCL had been overlooked was because the complicated zigzag course of the RCL was damaged by the inadequate dissection or RCL was mistaken for the RCM. While the points where the cutaneous branches penetrated the superficial muscles were variable, the points where they penetrated the thoraco-lumbar fascia were relatively stable. This point of the RCM was generally near the tip of the spinal process of the same segmental number of the nerve, and the same point of RCL was generally at the gap between the longissimus and the iliocostal muscles in the intercostal space one segment lower than the segment of the RCL. The RCL from the last thoracic to the third lumbar dorsal rami communicated with one another to form a nerve plexus under the lumbo-dorsal aponeurosis, then penetrated that aponeurosis forming several nerve bundles, crossed over the iliac crest and supplied the hip skin as the superior cluneal nerves. Therefore, each bundle was not equivalent to each segment, but was composed of two or more segments.

Does the nerve supply to both the superficial and deep surfaces of pectoralis major imply two separate developmental origins?

The nature of the nerve supply to the "pocket' of pectoralis major was examined on 7 randomly selected sides of 5 embalmed cadavers. The pocket was a U-shaped muscular fold, opening cranially. The anterior limb and inner surface of the fold were supplied by nerve branches that originated from the middle segment of the pectoral nerve loop and penetrated pectoralis minor. The outer surface of the posterior limb was supplied by one or two branches that extended from the caudal segment of the pectoral nerve loop. If the muscular U-shaped fold is unfolded, it becomes obvious that the posterior wall of the pocket forms the most caudal part of pectoralis major and is supplied from both the superficial (anterior) and deep (posterior) surfaces. This dual surface supply does not suggest any aspect of the developmental origin of the pocket but may simply be due to the relative positions of the pectoralis major and its nerve.

The sensate deep inferior epigastric musculocutaneous flap and the twelfth thoracic nerve

A detailed anatomical study of the terminal branches of the twelfth thoracic nerve (subcostal nerve) based on observations made during dissections of 23 embalmed cadavers is presented. In all 23 cadavers, the twelfth thoracic nerve had an ascending branch which joined the deep inferior epigastric vascular pedicle about half way between the lower border of the umbilicus and the symphysis pubis. This observation, we believe, explains how it is possible to preserve sensation in the deep inferior epigastric musculocutaneous flap.

Dorsal scapular nerve compression. Atypical thoracic outlet syndrome

The dorsal scapular nerve and long thoracic nerve of 10 cadavers (20 sides) and 36 patients with dorsal scapular nerve compression were studied anatomically. The origin of the dorsal scapular nerve of a section frequently shared a common trunk with the long thoracic nerve, and went through the scalenus medius anterointernally and posterolaterally with the presence of some tendinous tissues. Leaving the long thoracic nerve, it might give branches to the shoulder and the subaxillary region and finally have the branches join the long thoracic nerve again. The compression of the section near the origin caused discomfort and sourness of the neck, shoulder and back region. Clinically, the severance of the scalenus anterior and medius ameliorated or relieved the compression of the dorsal scapular nerve. Complete decompression required cutting of the scalenus medius and its tendinous tissue superficial to the dorsal scapular nerve. Among 24 sides of 22 patients undergoing surgery, the symptoms of 20 sides of 19 patients were completely or partially relieved.

Development of the spinal nerves in the mouse with special reference to innervation of the axial musculature

Development of the mouse spinal nerves was studied. On E11 (11th day of gestation), the primitive spinal nerve fascicle extended ventrally in the anterior half of the sclerotome. Spinal nerves in the forelimb region united with each other to form the primitive brachial plexus. Their terminal segment was covered by a peculiar cell mass. On E12, five primary branches developed along the primitive spinal nerve trunk. The ramus dorsalis was originally a cutaneous nerve, supplying two series of branches to the skin of the back. The medial series was derived from the dorsal ramus of C2-C8, and the lateral series from C8 and the more caudal dorsal rami. Nerves of the former series took the presegmental course through the intermyotomic space, while those of the latter the postsegmental course. The ramus cutaneous lateralis was a nerve that took the presegmental course to become cutaneous. The ramus intercostalis externus was a muscle branch whose distribution was restricted within the segment. The ramus anterior was a muscle branch from the end of the primitive spinal nerve trunk. The ramus visceralis connected a thoracic nerve with the para-aortic sympathetic cell cord. On E13-16 the ramus anterior secondarily gave off a cutaneous branch (ramus cutaneous anterior). The ramus intercostalis externus extended ventrally deep to the intercostalis externus muscle, crossing just caudal to the ramus cutaneous lateralis that secondarily gave off branches to the obliquus externus abdominis muscle.

Selective video-assisted thoracoscopic sympathectomy

Video-assisted and thermometrically controlled thoracoscopic sympathectomy demonstrates new ways in the treatment of upper-limb hyperhidrosis. An anatomical portrayal of the sympathetic chain is possible as a result of the improved visualization and magnification of the operative area provided by the video-optic technique. The difference in temperature, registered by means of a thermometric sensor in the palm of the hand, indicates that the sympathetic nerves responsible for the hyperhidrotic segments have been severed. The number of postoperative Horner's syndromes will be reduced significantly with this method. Until now, we have successfully treated six thermometrically controlled patients. No recurrences have arisen during an 18 months observation period. Neither intraoperative nor postoperative complications were recorded. One patient complained of increased compensatory sweating of the trunk. Thermometrically controlled thoracoscopic sympathectomy is expected to improve the various forms of treatment available for sympathetic reflex dystrophies in the future.

A technique for maximizing biceps recovery in brachial plexus reconstruction

In 21 cadaver dissections the intramuscular anatomy of the musculocutaneous nerve and the relative relationship of the motor and sensory components of this nerve were evaluated. Nearly one half of the fibers entering the musculocutaneous nerve terminate in cutaneous receptors. We report five cases in which biceps reinnervation was performed by a surgical technique that minimizes the period of denervation by using motor nerves (medial pectoral nerves) very close to the biceps muscle. This technique also redirects the cutaneous portion (lateral antebrachial cutaneous nerve) of the musculocutaneous nerve into the biceps muscle to ensure that the motor fibers are not directed toward cutaneous receptors.

[The human superior posterior serratus muscle supplied by both the intercostal and dorsal scapular nerves]

A case of the superior posterior serratus muscle on the left side supplied by both the intercostal and dorsal scapular nerves was observed in a 67-year-old Japanese male cadaver at Sapporo Medical College, 1991. The innervation and intramuscular nerve distribution of this case was investigated using a binocular microscope. The belly of this muscle consisted of three parts, which were inserted into the second, third and fourth ribs, respectively (Fig. 1). The second part inserted into the third rib consisted of two offshoots, namely a medial and a lateral offshoot. The latter almost totally covered the first part inserted into the second rib. This muscle was innervated by twigs from the dorsal scapular nerve (C5) and the superficial intercostal nerves (Th1 & Th2) of Kodama (Kodama, 1986). The superficial intercostal nerve of the first thoracic segment gave off two twigs to the muscle, the superior (medial) and inferior (lateral) (Fig. 1). The intramuscular nerve distribution of this case demonstrated that, except for the lateral offshoot, the innervation of the muscle belly showed roughly segmental tendency though all of the twigs communicated with each other (Fig. 2). The lateral offshoot was chiefly innervated by the twig from the dorsal scapular nerve. It is apparent that the muscle primordium with the twig from C5, which ordinarily is situated at the cranialmost portion of the belly, instead came to rest between the first part and the medial offshoot of the second part. As a result, this muscle belly was innervated partially in a non-segmental manner.(ABSTRACT TRUNCATED AT 250 WORDS)

Compartmentalization in the pig latissimus dorsi muscle

Portions of the latissimus dorsi (LD) muscle are frequently employed as free muscle or myocutaneous grafts. The functional consequences for both the graft and the remaining donor tissue must depend in part on the neural organization of the muscle. Previous anatomical and clinical reports have suggested that the LD is organized into independently innervated segments, but experimental documentation has been lacking. This study investigated the neural organization of the LD in pigs using (1) synchronous electromyography (EMG) of several sites within the LD and motion analysis of the shoulder and forelimb, and (2) dissection and stimulation of the primary branches of the thoracodorsal nerve, followed by histochemical analysis, to delineate the areas innervated by each. The findings indicated that while there is minor overlap between adjacent segments, the LD can be considered as consisting of three semi-independent compartments. Further, the teres major is linked to the LD functionally as well as anatomically, so that the two muscles can be considered as a four-part complex.

[A study on the communication between the pectoral nerve and the extramural nerve branches of the intercostal nerves]

Kumaki et al. (1979) defined the extramural nerve as the rudimentary sensory nerve which appeared on the upper thoracic wall; it branched off the root of the lateral cutaneous nerve of the second, third or fourth intercostal nerve, ran inferomedially adhering to the fascia of the intercostalis externus muscle and ended supplying the membrane covering the adjacent rib. They also stated that the extramural nerve (Rxm) occasionally became a cutaneous nerve which pierced the pectoralis muscles and supplied the skin covering the thoracic wall similar to the lateral cutaneous nerve (Rcl) or the anterior cutaneous nerve (Rca). Further, they proposed that the muscular nerves to the obliquus externus abdominis muscle which are usually situated below the fifth rib might be considered a part of this Rxm series. Although the definition of Rxm is still not widely accepted, Rxm is thought to be a key morphological factor influencing the variations of peripheral nerve arrangement on the thoracic wall. In the student course of gross anatomy dissection at Iwate Medical University School of Medicine during the years 1987-1991, three cases of Rxm communicating with the pectoral nerve and supplying the pectoralis major muscle were observed. Some cases have been reported in which Rcl innervates part of the pectoral muscles. However, the communication between the pectoral nerve and Rxm has not yet been discussed. Therefore, to clarify the morphological significance of the communication between Rxm and the pectoral nerve, the branching pattern and the distribution of the pectoral nerves were extensively investigated and the intramuscular nerve supply of some pectoral nerves, especially the pectoral nerves which communicated with Rxm, was examined in detail under a stereomicroscope. The results are summarized as follows: 1. In the first case, Rxm of the second intercostal nerve originated from Rcl, ran inferomedially adhering to the fascia of the intercostalis externus muscle and pierced the origin of the pectoralis minor muscle at the third intercostal space. Then Rxm turned superolaterally to communicate with a pectoral nerve which originated from the loop composed of the lateral and medial pectoral nerves and passed inferior to the pectoralis minor muscle. After communication, the pectoral nerve with Rxm supplied the caudalmost part of the sternocostal portion of the pectoralis major muscle. In the second case, a similar branch of Rxm of the second intercostal nerve passed inferior to the pectoralis minor muscle.(ABSTRACT TRUNCATED AT 400 WORDS)