Introduction: Lumbar plexus is one of the main nervous pathways supplying the lower limb which is bound to show variations. Clinicians esp. surgeons should be aware of the potential variations to plan the surgical therapies to avoid possible injuries to the structure. Current research aimed to study the formation of the lumbar plexus, observe its branching pattern and its relation with psoas major muscle and to document any variations in the formation and branching pattern. Material and methods: It was an observational study involving 50 dissections from 25 embalmed cadavers were done in the Institute of Anatomy, Madurai Medical College, Madurai, India over a period of 2 years from June 2015-June 2017. Results: Many significant variations were found in the anatomy of the lumbar plexus' branches namely iliohypogastric, ilioinguinal, genitofemoral, lateral femoral cutaneous nerve and accessory obturator nerve. Conclusion: Knowledge of the variations in the branching pattern and formation of the lumbar plexus is essential to prevent nerve injury during routine surgical procedures like iliac bone graft, inguinal hernia surgery, low transverse incision of gynecological procedures, etc., The unusual pattern may create confusion in interpretation due to mismatch between symptoms of the patient and the findings in imaging modalities.

BACKGROUND Variations in the branching of the human aortic arch have clinical significance. An Aberrant Right Subclavian Artery (ARSA) arises as the last branch of the left-sided aortic arch distal to the normally-positioned left subclavian artery. ARSA usually remains asymptomatic and is revealed incidentally either radiologically or during anatomy dissection. It is associated with several congenital cardiovascular anomalies and some chromosomal syndromes. MATERIALS AND METHODS Fifty cadavers were dissected and observed for aortic arch branching pattern variations during routine undergraduate dissection over a period of two years in Institute of Anatomy, Madurai Medical College, Madurai, Tamilnadu. RESULTS One case of aberrant right subclavian artery was noted. The right subclavian artery arose from the right lateral surface of proximal part of descending aorta distal to ligamentum arteriosum. It was seen to course upwards, obliquely towards the right, passing posterior to trachea and oesophagus. The right recurrent laryngeal nerve on arising from the right vagus ran transversely towards inferior pole of the right lateral lobe of thyroid gland and entered the larynx behind the cricothyroid joint. The course of right laryngeal nerve was short and non-recurrent. CONCLUSION Awareness of this anatomical variation will provide useful knowledge to anatomists, radiologists, cardiologists, vascular and thoracic surgeons and thereby prevent injury to aberrant right subclavian artery and right recurrent laryngeal nerve during radiological and surgical interventions.