The abducens nerve is characterized by a long intracranial course and complex topographical relationships. Anatomical knowledge may help to understand both the etiology and clinical symptoms of abducens nerve palsy. Typically, the single trunk of the abducens nerve travels on both sides. However, occasionally different variants of unilateral or bilateral duplications of the abducens nerve may be observed. Th e presented paper is a detailed anatomical description of bilateral duplication of the abducens nerve, with atypical appearance of the nerve in the cavernous sinus and normal distribution within the lateral rectus muscle on both sides of one cadaver. On the right side both trunks of the abducens nerve fused within the subarachnoid space and pierced the dura mater together. On the left side both trunks of the duplicated abducens nerve pierced the dura mater separately, entered the petrous apex separately and fused just below the petrosphenoidal ligament. Within the cavernous sinus the nerve divided once again into two filaments, which reunited into one trunk aft er crossing the horizontal segment of the intracavernous part of internal carotid artery. Th e orbital segments of the abducens nerve showed a typical course on both sides. Duplication of the abducens nerve is anatomical variation which should be taken into account during diagnostic and surgical procedures performed within the petroclival region and cavernous sinus.

The musculocutaneous nerve (C5–C7) is a terminal branch of the lateral cord of the brachial plexus and provides motor innervation to the anterior compartment of arm muscles. Both the musculocutaneous and median nerve may show numerous anatomical variations. Keeping in mind possible aberrations in the course of the upper limb nerves may increase the safety and success rate of surgical procedures. The presented report is a detailed anatomical study of the fusion between the median and musculocutaneous nerve, supplemented by intraneural fascicular dissection. In the presented case, the musculocutaneous nerve was not found in its typical location in the axillary cavity and upper arm during the preliminary assessment. However, a careful intraneural fascicular dissection revealed that musculocutaneous nerve was fused with the median nerve and with its lateral root; Those nerves were surrounded by a common epineurium, however they were separable. The muscular branch to the biceps brachii muscle arose from the trunk ( fascicular bundle) dissected out from the median nerve and corresponding to the musculocutaneous nerve. Such variation may be of utmost clinical importance, especially during reconstructions of the brachial plexus or its branches.