An Unusual Bilateral Neurovascular Variation in the Axillary Region

Amit Tirpude; A Anbarasan; Manisha Rajanand Gaikwad; Manwar Ali

doi:10.4103/NJCA.NJCA_39_20

CASE REPORT

Year : 2020 | Volume : 9 | Issue : 4 | Page : 173-175

An Unusual Bilateral Neurovascular Variation in the Axillary Region

Amit Tirpude¹, A Anbarasan², Manisha Rajanand Gaikwad³, Manwar Ali⁴
¹ Associate Professor, All India Institute of Medical Sciences, Bhubaneswar, Odisha, India
² Junior Resident, All India Institute of Medical Sciences, Bhubaneswar, Odisha, India
³ Additional Professor, Department of Anatomy, Associate Professor, All India Institute of Medical Sciences, Bhubaneswar, Odisha, India
⁴ Department of Surgery, All India Institute of Medical Sciences, Bhubaneswar, Odisha, India

Date of Submission	01-Jul-2020
Date of Decision	07-Aug-2020
Date of Acceptance	17-Sep-2020
Date of Web Publication	7-Dec-2020

Correspondence Address:
A Anbarasan
Department of Anatomy, All India Institute of Medical Sciences, Bhubaneswar - 751 019, Odisha
India

Source of Support: None, Conflict of Interest: None

DOI: 10.4103/NJCA.NJCA_39_20

Abstract

The neurovascular variations in the upper limb are not uncommon. About 16.9% of cases, the subscapular artery bilaterally arises from the second part of the axillary artery without any neuronal variations. However, in this study, we reported a rare case of bilateral subscapular artery variations along with an abnormal communication between the branches of brachial plexus. The knowledge about these bilateral unique neurovascular variations in the axillary region becomes essential, and it is of immense significance in various clinical procedures performed by the plastic surgeon, anesthetist, neurovascular surgeons, radiologists, clinical anatomists and also for interventional cardiologists.

Keywords: Axillary artery, intercostobrachial nerves, median nerve, neurovascular surgeons, subscapular artery

How to cite this article:
Tirpude A, Anbarasan A, Gaikwad MR, Ali M. An Unusual Bilateral Neurovascular Variation in the Axillary Region. Natl J Clin Anat 2020;9:173-5

How to cite this URL:
Tirpude A, Anbarasan A, Gaikwad MR, Ali M. An Unusual Bilateral Neurovascular Variation in the Axillary Region. Natl J Clin Anat [serial online] 2020 [cited 2021 Jan 16];9:173-5. Available from: http://www.njca.info/text.asp?2020/9/4/173/302566

Introduction

The axillary region comprises the most crucial neurovascular bundle, which connects the neck and thorax with the upper limb. The neurovascular variations in the axillary region of superior extremities are not uncommon. Several studies have reported a wide range of variation (16.9%–28%) in the branching pattern of the axillary artery with or without the association of neuronal variations.^[1],[2] The knowledge about the neurovascular variation is essential for anatomists, surgeons, and anesthetists during the axillary node dissection, sentinel lymph node biopsy, and regional anesthesia.^[3] Here, we are reporting a rare case of bilateral subscapular artery variations along with abnormal communication between the cords of the brachial plexus in the axillary region.

Case Report

During the routine dissection, we observed the bilateral neurovascular variation in the axillary region in a 70-year-old male cadaver. In the right axilla, the subscapular artery was arising from the second part of the axillary artery, which ran downward and further gave four branches, namely lateral thoracic artery, two unnamed branches, and circumflex scapular artery and then it continued as a thoracodorsal artery. On the same side, there were two intercommunicating branches noted between the intercostobrachial nerve and the medial cutaneous nerves of the arm. The median nerve was medial to the brachial artery instead of the usual lateral side [Figure 1].

Figure 1: Right axillary region; subscapular artery emerges from the II part of the axillary artery, and the medial cutaneous nerves of the arm had 2 intercommunicating branches with intercostobrachial nerve. CSA: Circumflex scapular artery, TDA: Thoraco-dorsal artery, STA: Superior thoracic artery, LTA: Lateral thoracic artery, ACH: Anterior circumflex humeral artery, PCH: Posterior circumflex humeral artery, MB: Muscular branch, AV: Axillary vein, MN: Median nerve, MAN: Medial cutaneous nerve of arm, IBN: Intercostobrachial nerve, *: Communicating branches, PM: Pectoralis minor

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The variant emergence of the subscapular artery in the left axillary region was the same as the vascular variation in the right axilla. Nevertheless, on the left side, there is an atypical pattern of the median nerve noted. Apart from the two usual roots of the median nerve, it was also receiving a communicating branch from the musculocutaneous nerve, which joined the median nerve 8cm away from its formation. Here, two intercostobrachial nerves emerged from the first and third intercostal spaces. The remaining branches of Axillary artery and brachial plexus of both sides followed the standard anatomical structure [Figure 2].

Figure 2: Left axillary region. Subscapular artery emerging from the II part of the axillary artery and fusion of the lateral and medial root of the median nerve forming median nerve then receiving communicating branch from the musculocutaneous nerve. CSA: Circumflex scapular artery, TDA: Thoraco dorsal artery, STA: Superior thoracic artery, LTA: Lateral thoracic artery, ACF: Anterior circumflex humeral artery, PCF: Posterior circumflex humeral artery, MB: Muscular branch, AV: Axillary vein, MN: Median nerve, IBN: Intercostobrachial nerve, **: Communicating branches, PM: Pectoralis minor

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Discussion

The subscapular artery arises from the third part of the axillary artery along with the anterior circumflex humeral and posterior circumflex humeral arteries. Usually, the thoracoacromial artery and lateral thoracic artery are the branches arising from the second part of the axillary artery, which is posterior to the pectoralis minor muscle. The subscapular artery is one of the biggest branches of the axillary artery, which courses along the lower margin of the subscapularis muscle to the inferior angle of the scapula. It gives rise to two terminal branches around 4 cm below its origin. The circumflex scapular artery is the first and most extensive branch of the subscapular artery, which winds around the lateral border of scapula; then, it enters into the infraspinous fossa. After giving the circumflex scapular artery, it continues as the thoracodorsal artery, which runs along with the thoracodorsal nerve, related to the lateral border of the scapula.^[4],[5]

Previous studies reported the similar origin of the subscapular artery from the second part of the axillary artery in 52.8% of cases.^[1] However, in addition to that, we observed the lateral thoracic artery and thoracodorsal arteries were arising from the variant subscapular artery. Such origin of the lateral thoracic artery from the subscapular artery was observed in 5.4% of cases.^[6] Further, in the third part of the axillary artery, we observed one muscular branch, anterior circumflex humeral, and posterior circumflex humeral arteries. A previous study classified the subscapular artery based on its branching pattern from eighty specimens, but our findings were not fitting under their classification.^[7] Another study reported that nine out of forty cadavers (22.5%) showed the lateral thoracic artery emerging from subscapular artery, in which thoracoacromial trunk was absent.^[8] In our case, the unique features were that the lateral thoracic artery emerged from the subscapular artery, which is from the second part of the axillary artery with an intact thoracoacromial trunk [Figure 1] and [Figure 2]. Anatomical variations of these vessels are helpful to the recipient regions for autologous microsurgical restoration with free flaps.^[7] The thoracodorsal pedicle is meticulously preserved in all mastectomies done for malignancies or benign conditions, hence knowledge about these variation is of paramount importance to a breast surgeon. Careful dissection and expecting a variation can prevent inadvertent injuries during surgery.

During the development of the superior extremities, the arterial system is involved in five stages. The axial system of vessels like the axillary artery is developed in stages 1 and 2. This axis artery is derived from the seventh intersegmental artery under the influences of vascular endothelial growth factors, and these signaling factors help to navigate channels, collateral formations, and disintegrations. The adult pattern is formed from the regression and anastomosis of the existing arteries.^[9] During angiogenesis, if there is the defective formation of vascular plexus occurs in stage 1 leads to arterial variations in this study.

A Previous study of Hayashi et al. classified the connections between the median nerve and musculocutaneous nerve into five types in relation to the muscular branches to brachial flexors (coracobrachialis, biceps brachii, and brachialis) and the lateral root.^[10] Type 0 is a fusion of median nerve and musculocutaneous nerve; Type 1 is communication between the lateral root and the branch to coracobrachialis; Type 2 is a communication between the branch to coracobrachialis and the branch to biceps brachi, Type 3 is a communication between the branch to biceps brachi and the branch to brachialis, and Type 4 is a branch arising distal to brachialis branch.^[10] The median nerve was observed to have abnormal origin and course in 28%.^[2] In the present case, we noticed the Type 2 variety of communication, which is observed in 3.1% of the cases of the previous literature.^[10] In Le Minor’s classification, our study falls under Type 2, which is a connection between the musculocutaneous and the median nerve. During the regional anesthesia to block the brachial plexus for surgery or pain management, these variation should be kept in mind by anesthetists.^[11]

Communication between the first intercostobrachial nerve and medial cutaneous nerve of the arm was reported in 36.4% of the cases. Furthermore, 73.3% of cases shown the other intercostobrachial nerve that passes through axilla and supplies the arm.^[12] A meta-analytical study reported 41.3% of cases showing communicating branches between intercostobrachial nerve and brachial plexus.^[13] We noticed that on the right side, there is a network connection of two nerve fibers among the intercostobrachial nerve and the medial cutaneous nerve of the arm. On the left side, we observed the first and second intercostobrachial nerve, which was arising from first and third intercostal branches. These nerves have to be preserved to prevent postmastectomy sensation loss if possible, as many times during axillary lymph node clearance, they are inevitably sacrificed.

Conclusion

The knowledge about these bilateral rare neurovascular variations in the axillary region becomes essential and of immense significance in various clinical procedures performed by the plastic surgeon, anesthetist, neurovascular surgeons, radiologists, clinical anatomists, and also for an interventional cardiologist.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

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