The anatomy of the extrathoracic intercostobrachial nerve

Anatomical variants of the intercostobrachial nerve and its preservation during surgery, a systematic review and meta-analysis

BACKGROUND

The anatomic variants of the intercostobrachial nerve (ICBN) represent a potential risk of injuries during surgical procedure such as axillary lymph node dissection and sentinel lymph node biopsy in breast cancer and melanoma patients. The aim of this systematic review and meta-analysis was to investigate the different origins and branching patterns of the intercostobrachial nerve also providing an analysis of the prevalence, through the analysis of the literature available up to September 2023.

MATERIALS AND METHODS

The protocol for this study was registered on PROSPERO (ID: CRD42023447932), an international prospective database for reviews. The PRISMA guideline was respected throughout the meta-analysis. A systematic literature search was performed using PubMed, Scopus and Web of Science. A search was performed in grey literature through google.

RESULTS

We included a total of 23 articles (1,883 patients). The prevalence of the ICBN in the axillae was 98.94%. No significant differences in prevalence were observed during the analysis of geographic subgroups or by study type (cadaveric dissections and in intraoperative dissections). Only five studies of the 23 studies reported prevalence of less than 100%. Overall, the PPE was 99.2% with 95% Cis of 98.5% and 99.7%. As expected from the near constant variance estimates, the heterogeneity was low, I2 = 44.3% (95% CI 8.9%-65.9%), Q = 39.48, p = .012. When disaggregated by evaluation type, the difference in PPEs between evaluation types was negligible. For cadaveric dissection, the PPE was 99.7% (95% CI 99.1%-100.0%) compared to 99.0% (95% CI 98.1%-99.7%).

CONCLUSIONS

The prevalence of ICBN variants was very high. The dissection of the ICBN during axillary lymph-node harvesting, increases the risk of sensory disturbance. The preservation of the ICBN does not modify the oncological radicality in axillary dissection for patients with cutaneous metastatic melanoma or breast cancer. Therefore, we recommend to operate on these patients in high volume center to reduce post-procedural pain and paresthesia associated with a lack of ICBN variants recognition.

Research Progress on Serratus Anterior Plane Block in Breast Surgery: A Narrative Review

Breast surgery, especially radical mastectomy, is often accompanied by moderate to severe acute pain, which significantly reduces postoperative quality of life. Effective pain management can accelerate patient recovery. Serratus anterior plane block (SAPB) is a new type of fascial plane block technique, which can better target the nerve network innervating the chest wall and breast and provide good analgesia in the anterolateral chest wall. Current clinical research evidence indicates that SAPB has significant benefits in breast surgery. Further research avenues for this technology include optimal local anesthetic dosing strategy, the type of SAPB which is more suitable for breast surgery, comparison of SAPB and pectoral nerve block II (PECS II) in breast surgery, and high-quality randomized controlled study with outcomes of chronic pain or cancer prognosis.

Anatomical basis of fascial plane blocks

Fascial plane blocks (FPBs) are regional anesthesia techniques in which the space ("plane") between two discrete fascial layers is the target of needle insertion and injection. Analgesia is primarily achieved by local anesthetic spread to nerves traveling within this plane and adjacent tissues. This narrative review discusses key fundamental anatomical concepts relevant to FPBs, with a focus on blocks of the torso. Fascia, in this context, refers to any sheet of connective tissue that encloses or separates muscles and internal organs. The basic composition of fascia is a latticework of collagen fibers filled with a hydrated glycosaminoglycan matrix and infiltrated by adipocytes and fibroblasts; fluid can cross this by diffusion but not bulk flow. The plane between fascial layers is filled with a similar fat-glycosaminoglycan matric and provides gliding and cushioning between structures, as well as a pathway for nerves and vessels. The planes between the various muscle layers of the thorax, abdomen, and paraspinal area close to the thoracic paravertebral space and vertebral canal, are popular targets for ultrasound-guided local anesthetic injection. The pertinent musculofascial anatomy of these regions, together with the nerves involved in somatic and visceral innervation, are summarized. This knowledge will aid not only sonographic identification of landmarks and block performance, but also understanding of the potential pathways and barriers for spread of local anesthetic. It is also critical as the basis for further exploration and refinement of FPBs, with an emphasis on improving their clinical utility, efficacy, and safety.

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.

Ultrasound-guided fascial plane blocks of the chest wall: a state-of-the-art review

Ultrasound-guided fascial plane blocks of the chest wall are increasingly popular alternatives to established techniques such as thoracic epidural or paravertebral blockade, as they are simple to perform and have an appealing safety profile. Many different techniques have been described, which can be broadly categorised into anteromedial, anterolateral and posterior chest wall blocks. Understanding the relevant clinical anatomy is critical not only for block performance, but also to match block techniques appropriately with surgical procedures. The sensory innervation of tissues deep to the skin (e.g. muscles, ligaments and bone) can be overlooked, but is often a significant source of pain. The primary mechanism of action for these blocks is a conduction blockade of sensory afferents travelling in the targeted fascial planes, as well as of peripheral nociceptors in the surrounding tissues. A systemic action of absorbed local anaesthetic is plausible but unlikely to be a major contributor. The current evidence for their clinical applications indicates that certain chest wall techniques provide significant benefit in breast and thoracic surgery, similar to that provided by thoracic paravertebral blockade. Their role in trauma and cardiac surgery is evolving and holds great potential. Further avenues of research into these versatile techniques include: optimal local anaesthetic dosing strategies; high-quality randomised controlled trials focusing on patient-centred outcomes beyond acute pain; and comparative studies to determine which of the myriad blocks currently on offer should be core competencies in anaesthetic practice.

Surgical anesthesia for proximal arm surgery in the awake patient

This education article discusses a combination of brachial plexus and peripheral nerve blocks aimed at providing complete surgical anesthesia to the proximal arm, while consistently avoiding diaphragmatic paresis. This type of approach may be warranted in patients with respiratory compromise of any etiology. In these settings awake surgery is recommended to preserve respiratory function and at the same time minimize the risk of infection of the healthcare team by avoiding the aerosol-generating medical procedures associated with general anesthesia.

Cadaveric study identifying clinical sonoanatomy for proximal and distal approaches of ultrasound-guided intercostobrachial nerve block

Background and objectives

The intercostobrachial nerve (ICBN) has significant anatomical variation. Localization of the ICBN requires an operator’s skill. This cadaveric study aims to describe two simple ultrasound-guided plane blocks of the ICBN when it emerges at the chest wall (proximal approach) and passes through the axillary fossa (distal approach).

Methods

The anatomical relation of the ICBN and adjacent structures was investigated in six fresh cadavers. Thereafter, we described two potential techniques of the ICBN block. The proximal approach was an injection medial to the medial border of the serratus anterior muscle at the inferior border of the second rib. The distal approach was an injection on the surface of the latissimus dorsi muscle at 3–4 cm caudal to the axillary artery. The ultrasound-guided proximal and distal ICBN blocks were performed in seven hemithoraxes and axillary fossae. We recorded dye staining on the ICBN, its branches and clinically correlated structures.

Results

All ICBNs originated from the second intercostal nerve and 34.6% received a contribution from the first or third intercostal nerve. All ICBNs gave off axillary branches in the axillary fossa and ran towards the posteromedial aspect of the arm. Following the proximal ICBN block, dye stained on 90% of all ICBN’s origins. After the distal ICBN block, all terminal branches and 43% of the axillary branches of the ICBN were stained.

Conclusions

The proximal and distal ICBN blocks, using easily recognized sonoanatomical landmarks, provided consistent dye spread to the ICBN. We encourage further validation of these two techniques in clinical studies.

Usefulness of high-resolution ultrasound for small nerve blocks: visualization of intercostobrachial and medial brachial cutaneous nerves in the axillary area

INTRODUCTION

High-resolution ultrasound (HRU) allows one to identify small nerves, but in the clinical setting, intercostobrachial nerve (ICBN) and medial brachial cutaneous nerve (MBCN) are not identified with conventional portable ultrasound (CPU) devices. The aim of this study is to identify both nerves and describe their relation with specific anatomical structures which could be easily identified with the ultrasound devices available in the clinical setting.

METHODS

21 healthy patients were scanned using HRU bilaterally in the axillary area located over the conjoint tendon to find the ICBN and MBCN and describe their anatomic relations. 5 fresh cadavers were used to validate the previous anatomical findings. ICBN and MBCN ultrasound-guided block was performed with 5 mL of methylene blue and iodine contrast, and the distribution was assessed by both CT scan and dissection.

RESULTS

ICBN and MBCN were identified in all cases. The average distance of the ICBN branches to the artery was 35±6 mm in men and 27±5 mm in women. Constant identification of the muscle-tendon junction of the latissimus dorsi muscle with respect to the location of the branches of the ICBN nerve was observed. Dissection and CT scan confirmed these findings.

CONCLUSION

HRU is a useful tool to identify ICBN and MBCN nerves, and to describe structures which can be easily identified with CPU use in the clinical setting.

Adding a PECS II block for proximal arm arteriovenous access - a randomised study

BACKGROUND

Brachial plexus block is often utilised for proximal arm arteriovenous access creation. However, the medial upper arm and axilla are often inadequately anaesthetised, requiring repeated, intraoperative local anaesthetic supplementation, or conversion into general anaesthesia. We hypothesised that the addition of a PECS II block would improve anaesthesia and analgesia for proximal arm arteriovenous access surgery.

METHODS

In this prospective, double-blinded, randomised proof-of-concept study, 36 consenting adults with end-stage renal disease aged between 21 and 90 years received either a combined supraclavicular and PECS II block (Group PECS, n = 18), or combined supraclavicular and sham block (Group SCB, n = 18) for proximal arm arteriovenous access surgery. Primary outcome was whether patients required intraoperative local anaesthetic supplementation by the surgeon.

RESULTS

In Group PECS, 33.3% (6/18) needed local anaesthetic supplementation vs. 100% (18/18) in Group SCB. Group SCB had three times (RR 3.0, 95% CI 1.6-5.8; P < 0.001) the risk of requiring intraoperative local anaesthetic supplementation. Group PECS required lower volume of supplemental local anaesthetic compared to Group SCB (0.0 ml, IQR 0.0-6.3 ml vs. 15.0 ml, IQR 7.4-17.8 ml; P < 0.001). Group SCB had twice [RR 2.2, 95% CI 1.1-4.4; (P = 0.019)] the risk of needing additional sedation or analgesia. There were no significant differences between the groups with respect to postoperative visual analogue scale pain scores, time to first rescue analgesia or patient satisfaction.

CONCLUSION

The results suggest that adding a PECS II block to a supraclavicular block improves regional anaesthesia for patients with end-stage renal disease undergoing proximal arm arteriovenous access surgery.

The intercostobrachial nerve as a sensory donor for hand reinnervation in brachial plexus reconstruction is a feasible technique and may be useful for restoring sensation

ABSTRACT Objective Few donors are available for restoration of sensibility in patients with complete brachial plexus injuries. The objective of our study was to evaluate the anatomical feasibility of using the intercostobrachial nerve (ICBN) as an axon donor to the lateral cord contribution to the median nerve (LCMN). Methods Thirty cadavers were dissected. Data of the ICBN and the LCMN were collected, including diameters, branches and distances. Results The diameters of the ICBN and the LCMN at their point of coaptation were 2.7mm and 3.7mm, respectively. The ICBN originated as a single trunk in 93.3% of the specimens and bifurcated in 73.3%. The distance between the ICBN origin and its point of coaptation to the LCMN was 54mm. All ICBNs had enough extension to reach the LCMN. Conclusion Transfer of the ICBN to the LCMN is anatomically feasible and may be useful for restoring sensation in patients with complete brachial plexus injuries.

Origin, Branching, and Communications of the Intercostobrachial Nerve: a Meta-Analysis with Implications for Mastectomy and Axillary Lymph Node Dissection in Breast Cancer

The intercostobrachial nerve (ICBN), which usually originates from the lateral cutaneous branch of the second intercostal nerve, innervates areas of the axilla, lateral chest, and medial arm. It is at risk for injury during operative procedures that are often used in the management of breast cancer and such injury has been associated with postoperative sensory loss and neuropathic pain, decreasing the quality of life. PubMed, Excerpta Medica Database (EMBASE), ScienceDirect, Google Scholar, China National Knowledge Infrastructure (CNKI), Scientific Electronic Library Online (SciELO), Biosciences Information Service (BIOSIS), and Web of Science were searched comprehensively. Data concerning the prevalence, branching, origin and communications of the ICBN were extracted and pooled into a meta-analysis. A total of 16 studies (1,567 axillas) reported data indicating that the ICBN was present in 98.4% of person. It most often (90.6%) originated from fibers at the T2 spinal level and commonly coursed in two branching patterns: as a single trunk in 47.0% of cases and as a bifurcating pattern in 42.2%. In the latter cases, the bifurcation was usually unequal (63.4%). Additionally, the ICBN presented with anastomosing communication to the brachial plexus in 41.3% of cases. The ICBN is a prevalent and variable structure at significant risk for injury during operative procedures of the axilla. In view of the postoperative pain and paresthesia experienced by patients following injury, surgeons need to exercise caution and aim to preserve the ICBN when possible. Ultimately, careful dissection and knowledge of ICBN anatomy could allow postoperative complications to be reduced and patient's quality of life increased.

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.

Medial pectoral pedicle is a reliable landmark for axillary lymph node dissection

BACKGROUND

The anatomical orientation of structures in the axilla has not been well studied, although it is essential for a neat and safe dissection. The objective of this study was to determine the relations between neurovascular structures in the axilla as they were encountered during axillary lymph node dissection (ALND) for breast cancer.

METHODS

This was a prospective study of 29 consecutive ALNDs accompanying either mastectomy or wide local excision. The dissections were conducted in a stepwise manner and the orientation of the structures was determined as the dissections advanced from superficial to deeper planes.

RESULTS

The medial pectoral pedicle was the most superficial neurovascular structure encountered during the dissections and was curled around the lateral border of the pectoralis minor muscle in most cases. The intercostobrachial nerve lay 1-2 cm behind and below, and the axillary vein was located 2-3 cm behind and above the pedicle. The long thoracic nerve was constantly found 2-3 cm behind the intercostobrachial nerve. The thoracodorsal nerve was always accompanied by a posterior tributary of the axillary vein.

CONCLUSION

Relations between neurovascular structures in the axilla are predictable. The medial pectoral pedicle, which is consistently found and superficially located, could be used as a landmark for ALND.

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.

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%).

Complications of surgery for thoracic outlet syndrome

Having read through the previous litany of potential disasters and complications, one could ask the obvious question, "Why would anyone want to do this kind of surgery?" The answer is that most people elect not to! Nevertheless, for those who decide to venture into this field, there is the tremendous reward of being able to help patients who would otherwise continue to live with extremely disabling and disheartening symptoms. A sound knowledge of the regional anatomy and tutelage by those knowledgeable in particular areas of surgery that may not have been a part of the individual surgeon's prior training is essential. The author was fortunate to have the help of a very accomplished and generous vascular surgeon, Dr. William Abbott of the Massachusetts General Hospital for many months when I began on what I have considered a fascinating and intellectually rewarding odyssey.