Median Nerve

Published on 08/03/2015 by admin

Filed under Neurosurgery

Last modified 08/03/2015

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Chapter 11 Median Nerve



The skin incision in the arm is placed over the course of the nerve. The pulsating brachial artery is the guide.

The surgeon must distinguish the median, ulnar, radial, and cutaneous nerves in the proximal arm. The median nerve is lateral to and closely applied to the artery (Figures 11-5 and 11-6).

Pathology frequently results in close adhesion of the adjacent nerve and artery. In the majority of cases, the nerve can be carefully separated by sharp dissection (Figure 11-7).

If the surgeon encounters more than minimal adherence of the nerve to the artery, the artery must be dissected out both proximal and distal to the point of nerve injury. Tapes are loosely passed around the vessel at those points and serve as a guide to vascular occlusion, should this be required.

Vascular clamps must be part of the peripheral nerve instrumentation set and the operating room nurse must know where a full vascular set is available, should this be required.

In the event of hemorrhage, pressure is applied calmly and accurately, compressing the artery against the humerus. The assistant then applies the vascular clamps in an accurate and unhurried fashion, at the previously prepared sites proximal and distal to the arterial injury. Done in this manner, there is no further injury to the nerve or vessel; both, however, can easily occur if the surgeon has not prepared for brisk hemorrhage ahead of time.

It is difficult to gain extra length when operating on the median nerve in the arm, so grafts are frequently required.

The musculocutaneous nerve runs between the two heads of the coracobrachialis. A phylogenetically degenerate third head may persist and may compress the median nerve. A downward and medially pointing bone spur may be present on the anterior aspect of the distal humerus. This will be missed on a routine anteroposterior x-ray film but may be seen in profile on an oblique view. A ligament runs from this spur to the medial epicondyle (ligament of Struthers) and the ligament may compress the median nerve. (This situation is similar to a cervical rib, where the band from the tip of the rib is the culprit, rather than the rib itself.)

Only on rare occasions is there a median branch communicating with the ulnar nerve (an arm-level Martin-Gruber anastomosis) or a branch from the median nerve to an antebrachial cutaneous nerve.

This is in contrast to the frequent back-and-forth communications between the lateral and medial cords, and sometimes the posterior cord, as the median nerve is being formed proximally.

The Elbow and Proximal Forearm