Ultrasound-guided blockade of the cervical medial branch is useful in the diagnosis and treatment of cervicogenic headache, cervicalgia, arthritis of the cervical facet joints, and other pain syndromes subserved by the cervical medial branches. These disease processes present clinically as neck pain, suboccipital headache, and occasionally shoulder and supraclavicular pain. This technique is also useful as a prognostic indicator of the potential efficacy of destruction of the cervical medial branch with neurolytic agents such as phenol or with radiofrequency lesioning.

Except for the atlanto-occipital and atlantoaxial joints, the cervical facet joints (which are also known as the zygapophyseal joints) are formed by the articulations of the superior and inferior articular facets of adjacent vertebrae (Fig. 27.1). The cervical facet joints are true joints, which are lined with synovium, contain cartilage, menisci, and are enclosed in a true joint capsule. This joint capsule is richly innervated and supports the notion of the facet joint as a pain generator. The cervical facet joint is susceptible to arthritic changes and trauma caused by acceleration-deceleration injuries. Such damage to the joint results in pain secondary to synovial joint inflammation and adhesions.

Each facet joint receives innervation from two spinal levels, receiving fibers from the dorsal ramus at the same level as the vertebra as well as fibers from the dorsal ramus of the vertebra above (Fig. 27.2). This fact is important clinically for two reasons: (1) it provides an explanation for the ill-defined nature of facet-mediated pain and (2) it also explains why the medial branch from the vertebra above the painful joint as well as the medial branch at the level of the painful joint must both be blocked to provide complete pain relief. At each level, the dorsal ramus provides a medial branch that wraps around the convexity of the articular pillar of its respective vertebra (Fig. 27.3). This location is constant for the C3-C4 through the C8-T1 facet joints nerves and allows a simplified approach to ultrasound-guided medial branch block. The atlanto-occipital and atlantoaxial joints are not innervated by medial branches but by branches of the respective C1 and C2 ventral rami (see Chapters 1 and 2). The C2-C3 facet joint is innervated primarily by the third occipital nerve, which arises from medial branch fibers of the posterior division of the third cervical nerve (see Chapter 26).

Ultrasound-guided cervical medial branch block can be carried out by placing the patient in the lateral position. A total of 1 mL of local anesthetic is drawn up in a 10-mL sterile syringe for each medial branch to be blocked. If the painful condition being treated is thought to have an inflammatory component, 40 to 80 mg of depot steroid is added to the local anesthetic.

The mastoid process on the side to be blocked is then identified by palpation (Fig. 27.4). After preparation of the skin with antiseptic solution, a linear high-frequency ultrasound transducer is placed in a longitudinal plane with the cephalad end of the transducer resting at the base of the mastoid process, and the inferior border of the mastoid process is identified on ultrasound (Figs. 27.5 and 27.6). The transducer is then slowly moved in a posterior direction ˜¾ inch until the arch of C1 (atlas) and the articular pillar of C2 (axis) can be identified (Figs. 27.7 and 27.8). The transducer is then slowly moved in a caudad direction until the C2-C3 facet joints are visualized (Fig. 27.9). Counting from the C2-C3 facet joints, this process is repeated by slowly moving the ultrasound transducer in a caudad direction while counting the “hills,” which represent the articulations of each joint until the specific facet joint to be blocked is identified (Fig. 27.10A and B).