Indications

Contraindications

Clinical anatomy

The cervical plexus is formed from the ventral rami of the upper four cervical nerves. The dorsal and ventral roots combine to form spinal nerves as they exit through the intervertebral foramina. The cervical nerves exit from the cervical spine through gutters in the transverse processes that run in an anterolateral direction, immediately posterior to the vertebral artery. The cervical plexus lies behind the sternocleidomastoid muscle, giving off both superficial (superficial cervical plexus) and deep (deep cervical plexus) branches.

The branches of the superficial cervical plexus supply the skin and superficial structures of the head, neck, and shoulder. There are four cutaneous branches, which become subcutaneous at the posterior border of the sternocleidomastoid muscle (Fig. 11.1). The lesser occipital and great auricular are derived from the C2 and C3 roots and run in a cephalad direction. The lesser occipital nerve supplies sensation to the upper side of the neck, the upper part of the auricle, and the adjoining skin of the scalp. The great auricular nerve is the largest cutaneous branch and divides into an anterior and a posterior branch. The posterior branch supplies the skin lying behind the ear and the medial and lateral surfaces of the lower part of the auricle. The anterior branch supplies the skin in the lower posterior part of the face and the concave surface of the auricle. The transverse cervical nerve, also from C2 and C3 roots, runs horizontally across the neck and provides sensory innervation to the anterolateral aspect of the neck from the mandible to the sternum. The supraclavicular branch, from the C3 and C4 roots, runs caudally over the clavicle and divides into three branches: medial, intermediate, and lateral. It provides sensory innervation to the lower aspect of the neck, acromial region of the neck, and as far as the second intercostal space on the chest.

Figure 11.1 Cadaver structures illustrating branches of the superficial cervical plexus. 1: sternocleidomastoid muscle; 2: clavicle; 3: transverse cervical nerve; 4: lesser occipital nerve; 5: great auricular nerve (anterior and posterior branches); 6: supraclavicular branches (medial, intermediate, and lateral branches).

The deep branches of the cervical plexus innervate the deeper structures of the neck, including the muscles of the anterior neck and the diaphragm (phrenic nerve).

Surface anatomy

The main landmarks for the superficial cervical plexus block (Fig. 11.2) include the mastoid process, suprasternal notch, and posterior border of the sternocleidomastoid muscle at the level of the cricoid cartilage. The sternocleidomastoid muscle and its posterior border can be accentuated by asking the patient to perform a head lift. The external jugular vein crosses the posterior border of the sternocleidomastoid muscle close to the injection site. It can be accentuated by asking the patient to perform a Valsalva maneuver. The carotid artery can be palpated medial to the sternocleidomastoid muscle and indicates the vascular nature of the territory.

Figure 11.2 Landmarks for the superficial cervical plexus block. The mastoid and suprasternal notch are marked with a pen and the posterior border of the sternocleidomastoid is outlined. The needle insertion point is at the midpoint of this line, which corresponds to the level of the cricoid cartilage.

The main landmarks for the deep cervical plexus block (Fig. 11.3) include the mastoid process; the posterior border of the sternocleidomastoid muscle at the level of the cricoid cartilage; C6 transverse process (the most prominent cervical transverse process); and the thyroid cartilage.

Figure 11.3 Landmarks for the deep cervical plexus block. The mastoid process, suprasternal notch, and transverse process of C6 are identified and marked. A line is drawn along the posterior border of the sternocleidomastoid muscle. A second line is drawn 1 cm posterior to the first line. The C4 transverse process is identified in relation to the transverse process of C6 or at the level of the superior aspect of the thyroid cartilage. Transverse processes of C3 and C2 are located 1.5 and 3 cm proximal from C4.

Sonoanatomy

The cervical plexus is found at the level of the first four cervical vertebrae deep to the sternocleidomastoid, in the layer superficial to the scalenus medius and levator scapulae. The cervical plexus can be further divided into a superficial and deep portion. The superficial branches perforate the cervical fascia to supply skin and other integumental structures whilst the deep branches predominantly supply muscle. The patient is positioned supine with the head slightly turned to the opposite side. Perform a systematic survey from superficial to deep, medial to lateral and cranially. A high frequency ultrasound transducer is placed in a coronal plane anterolateral to the neck to identify the respective vertebral level The transverse process of C7 usually does not have an anterior tubercle, but only one prominent posterior tubercle (Fig 11.4). Additionally, the C6 transverse process is sonographically verified by tracing the course of the vertebral artery, which usually enters the foramen at that vertebra. After achieving a coronal echoplane with the depiction of the transverse processes of C6 and C7, the transducer is shifted cranially and the fourth cervical vertebra (C4) is identified by counting the respective vertebral levels upwards. Parts of the superficial plexus can be identified in the double fascial layer in all patients at the level of C4. This double fascial layer is formed by the fascia of the sternocleidomastoid muscle and the deep cervical fascia (Fig. 11.5). Here the C4 nerve root can also be seen arising between the anterior and posterior tubercles of the fourth transverse process (Fig. 11.5). This level correlates with the carotid bifurcation in most patients (Fig. 11.5).

Figure 11.4 The transverse process of C7 usually does not have an anterior tubercle, but only one prominent posterior tubercle (PT). R = nerve root.

Figure 11.5 The cervical plexus is seen as hypoechoic structures (arrows) in a double fascial layer between the sternocleidomastoid and deep cervical fascia using a high frequency transducer. SCM: sternocleidomastoid muscle; DCF: deep cervical fascia; LCM: longus coli muscle; ICA: internal carotid artery; ECA: external carotid artery.

Technique

Landmark based approach

Superficial cervical plexus

As for all regional anesthetic procedures, after checking that emergency equipment is complete and in working order, intravenous access, ECG, pulse oximetry, and blood pressure monitoring are established. Asepsis is observed.

The patient is placed in the supine position, with the head facing away from the side to be blocked. The mastoid process and suprasternal notch are identified and marked. The next step is to identify the posterior border of the sternocleidomastoid muscle between these two landmarks. The needle insertion site is marked at the midpoint of the posterior border of the sternocleidomastoid adjacent to the cricoid cartilage (Fig. 11.2).

The needle insertion site is infiltrated with local anesthetic using a 25-G needle. A 23-G needle is then inserted in a perpendicular fashion just behind the posterior border of the sternocleidomastoid muscle (Fig. 11.6). A ‘pop’ is often felt as the cervical fascia is penetrated. Incremental injection of local anesthetic (5 mL) is made with repeated aspiration. This is the preferred block site due to the tight arrangement of the plexus here. Local anesthetic injection should form a contour corresponding to the sternocleidomastoid muscle. The needle is then redirected both superiorly and inferiorly along the posterior border of the sternocleidomastoid while making subcutaneous injections (5-mL injections are made in each direction).

Figure 11.6 Superficial cervical plexus block technique. The needle is first inserted in a perpendicular plane to the skin and behind the posterior border of the sternocleidomastoid muscle. A loss of resistance is felt as the fascia surrounding the sternocleidomastoid is penetrated. Also, subcutaneous injections are made superiorly and inferiorly along the border of the sternocleidomastoid from this point.

Deep cervical plexus

The mastoid process and transverse process of C6 are identified and marked with a pen (Fig. 11.3). A line is drawn connecting these two points. A second line is drawn parallel and 1 cm posterior to the first line (Fig. 11.3). The transverse process of the fourth cervical vertebrae can be located, having previously located the transverse process of the sixth cervical vertebrae in relation to the cricoid cartilage. The transverse process of the fourth cervical vertebrae can also be located by drawing a horizontal line from the superior aspect of the thyroid cartilage. Although a single-injection technique at C4 can be used, block at C3 is also possible. C3 can be located 1.5 cm cephalad from C4.

Needle (23-G) orientation is perpendicular to the skin and slightly caudad (Fig. 11.7) until bony contact at 1–2 cm from the skin. A paresthesia in the distribution of the cervical plexus may be found. At this point the needle is gently withdrawn 1 mm and incremental injections of local anesthetic (3–5 mL) are made with repeated aspiration. The fingers of the palpating hand should be used to fix the skin at the transverse process of the level to be blocked. This decreases the depth of the needle insertion and makes the block both easier and safer to perform.

Figure 11.7 Deep cervical plexus block technique. The needle is oriented perpendicular to the skin and slightly caudad until bony contact at 1–2 cm. The needle is withdrawn 1–2 mm and 3–5 mL of local anesthetic is injected.

Ultrasound-guided approach

Intravenous access, electrocardiogram (ECG), pulse oximetry and blood pressure monitoring are established. Maximized comfort for the operator and patient is an important step in pre-procedure preparation. For the ultrasound-guided cervical plexus block, the patient is placed in the supine position, with the head turned slightly to the side opposite that to be blocked. The operator stands or sits adjacent to the side to be blocked. The ultrasound screen, transducer, needle, and plane of imaging should all be placed in one view for the operator. For the cervical plexus block, the ultrasound screen is placed above the shoulder on the side to be blocked (Fig 11.8). Room lights may be turned down to enhance image viewing. The operating lights can be used to maintain some working lighting in the background. The patient is asked to raise their head to identify the interscalene groove.

Figure 11.8 Global view of ultrasound-guided cervical plexus block.

The skin is disinfected with antiseptic solution and draped. A sterile sheath (CIVCO Medical Instruments, Kalona, IA, USA) is applied over the ultrasound transducer with sterile ultrasound gel (Aquasonic, Parker Laboratories, Fairfield, NJ, USA). Another layer of sterile gel is placed between the sterile sheath and the skin. The cervical plexus is scanned in transverse plane. The ultrasound screen should be made to look like the scanning field. That is, the right side of the screen represents the right side of the field. Adjustable ultrasound variables such as scanning mode, depth of field, and gain are optimized.

Developing and maintaining a predetermined basic scanning routine is of enormous help in improving operator confidence and success. A transverse image of the superficial cervical plexus is obtained (Fig. 11.5). The superficial cervical plexus is kept in the center of the field of view. The needle entry site is at the lateral-most end of the linear transducer. A free hand technique, rather than the use of a needle guide, is preferred. A 21-GA × 50-mm needle (B.Braun, Bethlehem PA) is inserted parallel to the axis of the beam of the ultrasound transducer with the bevel facing the transducer (Fig 11.9). The needle is attached to sterile extension tubing, which is connected to a 10-mL syringe and flushed with local anesthetic solution to remove all air from the system. It is then introduced at the lateral-most end of the transducer and visualized along its entire path to the superficial cervical plexus (Fig 11.10). It is important not to advance the needle without good visualization. This may require needle or ultrasound transducer adjustment.

Figure 11.9 Ultrasound transducer and needle positioning during ultrasound-guided cervical plexus block. Note the needle orientation in the same plane as the ultrasound beam.

Figure 11.10 Real time imaging of needle insertion for the cervical plexus block. Notice the needle shaft marked with arrows and the needle tip (N) in close proximity to the cervical plexus. N = needle tip; SCM = sternocleidomastoid muscle; DCF: deep cervical fascia; LCM: longus coli muscle; CB: cervical plexus; ICA: Internal carotid artery; ECA: external carotid artery.

Once the needle has approached the superficial cervical plexus, 1–2 mL of local anesthetic may be injected to confirm correct needle placement. Local anesthetic appears as a hypoechoic image. Correct needle placement is confirmed by observing solution surrounding the superficial cervical plexus (Fig 11.11). For a superficial cervical plexus block, local anesthetic should be injected between the double layer of the fascia rather than deep to it. Penetrating the fascia will lead to a deep cervical plexus block rather than a superficial cervical plexus block. Local anesthetic injected deep to the fascia does not consistently reach all relevant superficial parts of the cervical plexus. Following confirmation of correct needle placement, 10 mL of local anesthetic solution can be injected to achieve blockade.

Figure 11.11 Transverse ultrasound image of the cervical plexus showing local anesthetic spread using a a 8–14 MHz linear ultrasound transducer. LA: local anesthetic; N: needle tip; SCM: sternocleidomastoid muscle; SMM: scaleus medius muscle; CB: cervical plexus; ICA: Internal carotid artery; ECA: external carotid artery.

Adverse effects