Brachial Plexus Surgery: Exposure

Exposure of the brachial plexus is a major task. Indications include trauma, tumors, and thoracic outlet syndrome. In this chapter, we describe the supraclavicular and infraclavicular approaches that expose the brachial plexus elements from the spinal nerve root level to the beginning of the major terminal branches. In a step-by-step fashion, the anatomy of the brachial plexus and the associated structures are described, aided by surgical photographs. The posterior subscapular approach is rarely required and is not discussed in this chapter. Common intraoperative complications and their avoidance are also addressed.

65.2 Patient Selection

Surgical pathology of the brachial is diverse and encompasses a wide variety of causes. These include the full spectrum of traumatic, neoplastic, vascular, and congenital causes. The natural history, diagnosis, nonsurgical treatment, and surgical goals are different for each cause and are outside the scope of this chapter, which focuses on exposure. Strategies for restoration of function are described in Chapter 66.

65.3 Preoperative Preparation

General anesthesia is the most common mode of anesthesia administered in brachial plexus cases. It is essential to avoid prolonged muscle relaxants to avoid interference with the intraoperative nerve stimulation. The patient is placed supine with the head rotated to the contralateral side at 45 to 90 degrees. A padded shoulder roll is placed under the ipsilateral scapula to bring the supraclavicular region toward the surgeon but to allow the shoulder joint to drop away from the surgeon. The ipsilateral arm is kept adducted to the patient’s trunk as the abducted arm changes the orientation of the plexus, particularly the infraclavicular components. The ipsilateral neck, shoulder, axilla, arm, and hand, as well the ipsilateral hemithorax, are all prepared and draped. Exposing the arm and the forearm intraoperatively allows harvesting medial brachial, antebrachial, and superficial sensory radial nerves as grafts, if needed, in severe cases. Both legs are prepared and draped as well for the possibility of bilateral sural nerve grafts. A urinary catheter insertion is necessary because such a procedure may take few hours. The drapes are sutured or stapled around the surgical field.

65.4 Operative Procedure and Potential Intraoperative Complications

65.4.1 Incision

The classic zigzag incision for the brachial plexus is excellent for exposure; however, it usually leaves an unpleasant and lengthy scar ( ▶ Fig. 65.1). It starts with the upper limb parallel to posterior border of the sternocleidomastoid (SCM), followed by the transverse limb 2-3 cm above and parallel to the clavicle extending to the anterior border of the trapezius and then vertically down and medial to the coracoid process all the way to the axilla.

Fig. 65.1 Postoperative photograph depicting the healed continuous classic zigzag incision for complete brachial plexus exploration, with the horizontal limb placed just above, at or as in this case just below the level of the clavicle.

A simple transverse incision 1 to 2 cm above and parallel to clavicle with generous subplatysma dissection is usually adequate for exposing the supraclavicular elements (see ▶ Fig. 65.2 b), and generally we use this in almost all cases. ¹ If deemed necessary, another separate incision for the infraclavicular plexus will evaluate the infraclavicular elements. Skin incisions may need to be tailored according to the state of the skin over the plexus, particularly if the patient has had prior surgery or penetrating injuries ( ▶ Fig. 65.2).

Fig. 65.2 The incision for brachial plexus exploration may be tailored to avoid dealing with scars or to interfere with skin healing. This is true in cases of gunshot wounds to the plexus as the entrance or rarely the exit of the bullet or shrapnel is at the area of the planned incision. Standard zigzag with the horizontal limb below the clavicle (a), simple transverse incision below the scar (b), supraclavicular incision above or below the bullet entrance (c), supraclavicular incision with the horizontal limb above the clavicle (d).

65.4.2 Supraclavicular Approach

After identification of the lateral border of the SCM muscle, there are usually two sensory nerves curving around the muscle and supplying the anterior skin of the neck and around the ear lobule; respectively, these are transverse cervical and great auricular nerves ( ▶ Fig. 65.3). The clavicular head of the SCM muscle is identified and separated from the underlying tissue with blunt finger dissection pushing the internal jugular vein away, before being incised (the muscle is later reapproximated at closure). This maneuver maximizes the exposure to the lower plexus elements. The external jugular vein is usually evident in the field and is a good marker for the sensory supraclavicular nerves, located on the vessel and beside it. These nerves are usually intact and need to be preserved as injury may cause an unpleasant paresthesia of the anterior chest well ( ▶ Fig. 65.4). The next step is to find the inferior belly of the omohyoid muscle, which is a key muscle with an oblique course in the inferior part of the field. It marks the course of the deeper suprascapular nerve and thereby the upper trunk ( ▶ Fig. 65.5). Once found, it is circumferentially dissected as far as the clavicle, and then it can either be retracted inferiorly or divided. A supraclavicular pad of fat is found next at the floor of the field, attached softly to the lateral border of the SCM anterior border of the trapezius and continuous with the infraclavicular fat. This fat is mobilized using a combination of sharp and blunt dissection in a medial-to-lateral direction. Small vessels and lymphatic channels are coagulated and incised within the fat pad. Within its deepest level or posterior to this fat pad, the transverse cervical and the suprascapular vessels can be found with variable caliber and branches. These vessels can be ligated and divided with impunity. This exposes the scalene anterior muscle, which is located posterior and slightly lateral to the SCM. The phrenic nerve is found lying on top of anterior scalene muscle with thin, transparent fascia bounding it to the muscle. Electric stimulation, with ipsilateral diaphragmatic contraction, confirms the phrenic nerve, and it is marked using vessel loop (avoid tension) or marked by blue ink surgical marker. Phrenic nerve release needs to done carefully but fully over a distance to avoid traction injury. Phrenic nerve detection is useful as tracing it superiorly will lead to C5 spinal nerve root, which is usually evident emerging lateral to the scalene anterior muscle. It is important to remember that the roots are more or less stacked on top of each other in a slightly oblique orientation ( ▶ Fig. 65.6). Bearing in mind the orientation of the plexus, the dissection is continued in a systematic fashion. C6 nerve root is seen just inferior to C5, and their union forms the upper trunk; occasionally resection of the lateral scalene anterior is required to visualize C6. The upper trunk is followed distally to identify its divisions, which are usually located above the clavicle from a rostral to caudal (and lateral to medial) direction, namely, the suprascapular nerve, posterior division, anterior division, and nerve to subclavius ( ▶ Fig. 65.7). The divisions are circumferentially dissected and encircled by Penrose drains or vessel loops. To explore C7 (and lower trunk), resection of anterior scalene is almost always required. This is safely done by keeping an eye on the phrenic nerve while using bipolar cautery to coagulate and divide the muscle. The resection of the muscle is not complete until one ensures that the posterior fascia of the muscle is completely divided as well. The posterior fascia tends to be thicker than the anterior thinner fascia.

Fig. 65.3 Intraoperative photograph depicting the transverse cervical nerve (lower vessel loop) and the greater auricular nerve (upper vessel loop). These are sensory nerves, derived from the cervical plexus, which are usually intact and care should be taken to preserve them to avoid postoperative numbness and scar/neuroma pain.

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