Ultrasound-Guided Greater and Lesser Occipital Nerve Block

CLINICAL PERSPECTIVES

Ultrasound-guided blockade of the greater and lesser occipital nerves is useful in the diagnosis and treatment of occipital neuralgia and other pain syndromes subserved by the greater and lesser occipital nerves. This technique is also useful in providing surgical anesthesia of the tissues innervated by the greater and lesser occipital nerve for lesion removal and laceration repair and as an adjunct to general anesthesia for surgeries in the occipital region including craniotomies.

CLINICALLY RELEVANT ANATOMY

The greater occipital nerve is composed of fibers of the dorsal primary ramus of the second cervical nerve and to a lesser extent from fibers of the third cervical nerve, which is composed of fibers from the medial branch of the posterior division of the third cervical spinal nerve (Fig. 4.1). As the greater occipital nerve passes in a cephalad direction, it passes between the obliquus capitis inferior and the semispinalis capitis muscles (Fig. 4.2). Along with the occipital artery, the greater occipital nerve ultimately pierces the fascia just below the superior nuchal ridge (Fig. 4.3). The greater occipital nerve provides sensory innervation to the medial portion of the posterior scalp as far anterior as the vertex (Fig. 4.4).

The lesser occipital nerve is composed of fibers from the ventral primary rami of the second and third cervical nerves. The lesser occipital nerve passes superiorly along the posterior border of the sternocleidomastoid muscle perforating the deep fascia (see Fig. 4.3). The nerve then divides into several cutaneous branches that provide sensory innervation to the lateral portion of the posterior scalp and the cranial surface of the pinna of the ear (see Fig. 4.4). Communicating branches from the lesser occipital nerve to the greater occipital nerve, the greater auricular nerve, and the posterior auricular branch of the facial nerve are common.

ULTRASOUND-GUIDED TECHNIQUE

Ultrasound-guided occipital nerve block can be carried out using two different techniques. The first technique targets the nerve at the classic block site of the superior nuchal ridge. The second technique targets the nerve as it passes between the obliquus capitis inferior and semispinalis capitis muscles. To perform both techniques, the patient is placed in a sitting position with the cervical spine flexed and the forehead on a padded bedside table (Fig. 4.5). A total of 8 mL of local anesthetic is drawn up in a 12-mL sterile syringe. When treating occipital neuralgia or other painful conditions involving the greater and lesser occipital nerves, a total of 80 mg of depot steroid is added to the local anesthetic with the first block, and 40 mg of depot steroid is added with subsequent blocks.

Classic Technique

The occipital artery is palpated at the level of the superior nuchal ridge. After preparation of the skin with antiseptic solution, a linear high-frequency ultrasound transducer is placed in the transverse position across the superior nuchal ridge at the point where the pulsation of the occipital artery was identified (Fig. 4.6). Color Doppler can be utilized to help identify the occipital artery if palpation of the pulse is difficult (Fig. 4.7). The greater occipital nerve should be in close proximity to the occipital artery and should appear as a round or ovoid hypoechoic vascular structure that is noncompressible with the ultrasound transducer (Fig. 4.8). When the nerve is identified, a 3½-inch needle is inserted utilizing an in-plane approach and is advanced perpendicularly until the needle approaches the periosteum of the underlying occipital bone. A paresthesia may be elicited, and the patient should be warned of such. After gentle aspiration, 4 mL of local anesthetic and/or steroid is injected in a fan-like distribution with care being taken to avoid the foramen magnum, which is located medially. The needle is removed, and pressure is placed on the injection site to avoid hematoma formation.

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