An unusual innervation of pectoralis minor and major muscles from a branch of the intercostobrachial nerve

An uncommon, unilateral motor variation of the intercostobrachial nerve

The intercostobrachial nerve (ICBN) is commonly defined as a purely sensory nerve supplying the skin of the lateral chest wall, axilla, and medial arm. However, numerous branching patterns and distributions, including motor, have been reported. This report describes an uncommon variant of the right ICBN observed in both an 86-year-old white female cadaver and a 77-year-old white male cadaver. In both cases the ICBN presented with an additional muscular branch, termed the "medial pectoral branch", piercing and therefore innervating the pectoralis major and minor muscles. Clinically, the ICBN is relevant during surgical access to the axilla and can result in sensory deficits (persistent pain/loss of sensory function) to this region following injury. However, damage to the variation observed in these cadavers may result in additional partial motor loss to pectoralis major and minor.

The nerve supply to the pectoralis major: An anatomical study and clinical application of the denervation in subpectoral breast implant surgery

BACKGROUND

Using the subpectoral approach, animation deformity or breast distortion due to pectoralis muscle contraction is common. Although the anatomy of the pectoral nerves has been extensively studied, only few studies have related the location of these nerves to bony landmarks.

OBJECTIVE

Our aim is to clarify the anatomy and possible variations of the innervation of the pectoralis major in relation to bony landmarks useful for surgery and to identify the preferred level for (selective) denervation by 1) transecting the nerves and 2) splitting the muscle in subpectoral breast implant surgery in cadavers.

METHODS

Fourteen pectoral regions (both left and right side) were dissected on 7 formaldehyde-fixed cadavers. The origin, locations, and course were mapped and (distances to) landmarks were reported.

RESULTS

The lateral pectoral nerve, medial pectoral nerve, and ansa pectoralis were identified in all cadavers. Nerve branches pierce the pectoralis minor or run along its upper or lower border. The piercing nerves vary from one to three branches and were consistently located lateral to the midclavicular line. The horizontal and vertical distances to bony landmarks varied greatly and depended on the size and location of the pectoralis minor, except for the nerve running along the upper border of the PMin, which was located consistently around 30% of the clavicular line from the acromioclavicular joint to the sternoclavicular joint.

CONCLUSION

We were unable to define a fixed landmark to mark pre- or peroperatively. However, we could define guidelines that help to identify and excise or preserve nerves of interest.

An unusual finding of the pectoralis major muscle: decussation of sternal fibers across the midline

Variations of the pectoralis major muscle are commonly seen. However, during the routine dissection of an adult male cadaver, an apparently uncommon muscular variant was identified. In this cadaver, the sternal heads of the left and right pectoralis muscles crossed the midline and interdigitated with one another. In addition, the clavicular heads of both pectoralis major muscles were separated from the remaining parts of the muscles. Such anatomical variants such be kept in mind by clinicians and surgeons during patient evaluation and treatment.

Modified radical mastectomy for anterior thoracic nerve and intercostobrachial nerve protection (case report)

Modified breast cancer radical mastectomy is a more common operating method in breast surgery. Traditional modified radical mastectomy focuses on protecting the long thoracic nerve and thoracodorsal nerve while ignoring the protection of the anterior thoracic nerve and intercostobrachial nerve protection, which leads often to patients with upper medial arm numbness, acid swelling, pain, chest atrophy, and other problems. In the modified radical mastectomy of breast cancer, in this case, the author used an elaborative operation to protect the anterior thoracic nerve and intercostobrachial nerve and thoroughly dissected the third-level lymph nodes through the axillary approach.

Peripheral communications of intercostobrachial nerve Peripheral communications of the intercostobrachial nerve in relation to the alar thoracic artery

The intercostobrachial nerve (ICBN) is often encountered during axillary dissection for axillary lymph node dissection (ALND) for diagnostic and therapeutic surgery for mastectomy. The present report is a case observed in the Department of Anatomy at Vardhman Mahavir Medical College, Delhi during routine dissection of the upper extremity of a male cadaver for first year undergraduate medical students. On the right side, the medial cord of brachial plexus gave two medial cutaneous nerves of arm. Both the nerves were seen communicating with the branches of the ICBN. The ICBN and one of its branches were surrounding the termination of an alar thoracic artery. These peripheral neural connections of the ICBN with the branches of the medial cord can be a cause of sensory impairment during axillary procedures done for mastectomy or exploration of long thoracic nerves. The alar thoracic artery found in relation to the ICBN could further be a cause of vascular complications during such procedures.

An anatomic study of structure and innervation of the serratus anterior muscle

BACKGROUND

The structure and function of the serratus anterior muscle are partitioned into three parts. If the morphological characteristics in each part can be demonstrated in more detail, the cause of dysfunction will probably be identifiable more accurately. The purpose of this study was to demonstrate the details of the structure and innervation in each part of the serratus anterior muscle.

MATERIALS AND METHODS

This macroscopic anatomic study was conducted using ten sides from five cadavers. The structure and innervation in each part of this muscle were examined.

RESULTS

In the superior part, the independent branch was divided from a branch innervating the levator scapulae muscle. In the middle part, the long thoracic nerve descended on one-third of the anterior region between the origin and insertion. In the inferior part, the long thoracic nerve which ramified into many branches and branches from the intercostal nerves were distributed on all sides.

CONCLUSION

This study demonstrated that the innervation of the serratus anterior muscle was different in each part. The difference indicates that the superior part has an intimate relation with the levator scapulae muscle while the middle and inferior parts could be the actual serratus anterior muscle. Moreover, the distribution of branches from the intercostal nerves shows that the inferior part has a connection with some trunk elements. Understanding these characteristics of innervation is useful to identify the cause of dysfunction. In addition, we assert that the constant distribution of branches from the intercostal nerves is significant for the morphology.

T2 Contributions to the Brachial Plexus

Objective:

Recent advancements in neurotization and nerve grafting procedures have led to an increasing need for knowledge of the detailed anatomy of communicating branches between peripheral nerves. Although the surgical anatomy of the axilla has been well described, little is known regarding the degree or frequency of potential contributions to or communications with the brachial plexus. The aim of our study, therefore, was to explore extrathoracic, as well as potential intrathoracic, contributions to the brachial plexus from T2.

Methods:

The anatomy of the ventral primary ramus of T2 and the second intercostal nerve, including its lateral cutaneous contribution as the intercostobrachial nerve, was examined in 75 adult human cadavers (150 axillae), with particular emphasis on the communications with the brachial plexus.

Results:

Extrathoracically, communications were observed to occur in 86% of specimens. These contributions arose variably from either the intercostobrachial nerve or one of its branches and communicated with the medial cord (35.6%), medial ante-brachial cutaneous nerve (25.5%), or posterior antebrachial cutaneous nerve (24%). Whereas the majority of specimens (68.2%) were observed to have only one extratho-racic communication, 31.7% of specimens exhibited two. Intrathoracically, communications were observed to occur in 17.3% of specimens. These communications always arose from the ventral primary ramus of T2. When combining and comparing data within individual specimens, it was observed that those axillae without an extratho-racic contribution from the intercostobrachial nerve always contained an intrathoracic communication.

Conclusion:

Based on our findings, we conclude that 100% of specimens contained a communication branch between T2 and the brachial plexus. Considering the possible implications of this data, with regards to sensory innervation of the arm and axilla, further studies in this area of research could prove extremely beneficial.