Rare variations in the formation of median nerve--embryological basis and clinical significance.

During routine dissection in the Department of Anatomy, CMS, Nepal, anomalous median nerves with regard to their formation were found in three different adult male cadavers. In one cadaver, there was variation in the formation of the median nerve and its relation with the axillary artery. Another cadaver revealed the formation of the median nerve by three roots, while in the third one, the median nerve was found to be formed by four roots. However, in each of the three cadavers the distribution of the anomalous median nerve was normal in arm, forearm and palm. The arterial pattern in the arm (axillary and brachial arteries) was also found to be normal. In each case the opposite upper limb was also meticulously dissected to exclude bilateral abnormality. However, in each case the anomaly was unilateral. Photographs of the abnormalities were taken for proper documentation. The variations related to the formation of median nerve by more than two roots are relatively uncommon as compared to the other types of varations of median nerve. Some embryological explanations are available to explain these variations. Finally, knowledge of these variations is important particularly to the surgeons for carrying out surgical procedures in axilla and arm.