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The superior cervical ganglion arises from the fusion of three or four upper cervical ganglia. It lies medial to the vagus trunk, in front of the longus capitis muscle and behind the internal carotid artery, and in the angle of the vertebrae and transverse processes of the second and third cervical vertebrae (Figs. 14.1 and 14.2). In the literature, its long, flat, or spindle-like extension is described as being 14–43 mm in length, 6–8 mm in breadth, and 3–5 mm in depth [1, 2] (Figs. 14.2 and 14.4). The superior cervical ganglion is thought to contain 760,000–1,000,000 nerve fibers in all, 5,000–12,000 of which are preganglionic. Some 5,000 of these fibers are myelinated [1, 2]. This underlines its importance as a switchpoint with numerous double or triple connections to neighboring ganglia, nerves, and vessels (Fig. 14.3). The superior cervical ganglion takes its preganglionic fibers mainly from the spinal nerves coursing thoracically, with only a few being drawn from the neighboring cervical nerve roots. An unknown number of these preganglionic fibers pass through the ganglion toward the higher carotid ganglia, without switching. Rami communicantes connect the superior cervical ganglion with numerous organs, vessels, muscles, bones, joints, the last four cranial nerves, the vertebral plexus, and also the phrenic nerve. It supplies the upper cervical spinal nerves with gray rami communicantes, and it sends off vascular fibers to the internal and external carotid arteries. Autonomic branches pass from the ganglion to the larynx, pharynx, heart, and—together with vascular plexuses—to the salivary and lacrimal glands, to the hypophysis, thyroid, and other glands. There are also contacts with the middle cervical ganglion and to the tympanic plexus. There are connections with the pterygopalatine ganglion via the nerve of the pterygoid canal, deep petrosal nerve, and greater superficial petrosal nerve. A variable number of fibers from the superior cervical ganglion pass to the inferior ganglion of the vagus nerve, to the hypoglossal nerve, and to the posterior root of the ansa cervicalis [1, 2]. The superior cervical cardiac nerve may be absent, more often on the right side. In these cases, it is replaced by a branch of the vagus nerve from the external branch of superior laryngeal nerve. |
