- Indications: carotid endarterectomy, superficial neck surgery
- Landmarks: mastoid process, sternocleidomastoid muscle, C6 transverse process
- Equipment, superficial: 1½-in, 25-gauge needle
- Equipment, deep: 2-in, 22-gauge, short bevel needle connected to a syringe via a flexible tubing
- Local anesthetic: 15–20 mL
Needle insertion for superficial cervical plexus block. The needle is inserted behind the posterior border of the sternocleidomastoid muscle.
Cervical plexus block can be performed using two different methods. One is a deep cervical plexus block, which is essentially a paravertebral block of the C2-4 spinal nerves (roots) as they emerge from the foramina of their respective vertebrae. The other method is a superficial cervical plexus block, which is a subcutaneous blockade of the distinct nerves of the anterolateral neck. The most common clinical uses for this block are carotid endarterectomy and excision of cervical lymph nodes. The cervical plexus is anesthetized also when a large volume of local anesthetic is used for an interscalene brachial plexus block. This is because local anesthetic invariably escapes the interscalane groove and layers out underneath the deep cervical fascia where the branches of the cervical plexus are located.
The sensory distribution for the deep and superficial blocks is similar for neck surgery, so there is a trend toward favoring the superficial approach. This is because of the potentially greater risk for complications associated with the deep block, such as vertebral artery puncture, systemic toxicity, nerve root injury, and neuraxial spread of local anesthetic.
The cervical plexus is formed by the anterior rami of the four upper cervical nerves. The plexus lies just lateral to the tips of the transverse processes in the plane just behind the sternocleidomastoid muscle, giving off both cutaneous and muscular branches. There are four cutaneous branches, all of which are innervated by roots C2-4. These emerge from the posterior border of the sternocleidomastoid muscle at approximately its midpoint, and they supply the skin of the anterolateral neck (Figures 11-2 and 11-3). The second, third, and fourth cervical nerves typically send a branch each to the spinal accessory nerve or directly into the deep surface of the trapezius to supply sensory fibers to this muscle. In addition, the fourth cervical nerve may send a branch downward to join the fifth cervical nerve and participates in formation of the brachial plexus. The motor component of the cervical plexus consists of the looped ansa cervicalis (C1-C3), from which the nerves to the anterior neck muscles originate, and various branches from individual roots to posterolateral neck musculature (Figure 11-4). The C1 spinal nerve (the suboccipital nerve) is strictly a motor nerve, and is not blocked with either technique. One other significant muscle innervated by roots of the cervical plexus includes the diaphragm (phrenic nerve, C3,4,5) (Table 11-1).