Description
The cervical sympathetic trunk lies deep in the neck, between the carotid sheath and prevertebral fascia. It consists of a superior and middle cervical ganglion, along with an inferior cervical ganglion that is usually fused with the first thoracic ganglion.
The preganglionic sympathetic neurons originate from the lateral gray horn of the thoracic spinal cord and enter the cervical ganglia via the white rami communicans. These preganglionic neurons ascend within the cervical sympathetic trunks to synapse with the neuronal cell bodies of the postganglionic sympathetic neurons in the superior, middle, and inferior cervical ganglia. The postganglionic neurons reach the cervical nerves via the gray rami communicantes and are subsequently distributed to the effector organs.
The superior cervical ganglion is the largest of the cervical ganglia and lies inferior to the occiput and anterior to the transverse processes of the second and third cervical vertebrae, in front of the longus capitis muscle (Civelek et al., 2008). It is related anteriorly to the internal carotid artery. Inferiorly, the ganglion connects with the middle cervical ganglion via an interganglionic branch. The superior cervical ganglion sends postganglionic sympathetic fibers to the heart, via the superior cervical cardiac nerve; the larynx and pharynx, via the pharyngeal plexus; to the head via the external and internal carotid plexuses.
The middle cervical ganglion is the smallest of the three cervical paravertebral ganglia. It is present in 48%-74% of the time and is situated somewhere between the transverse process of the fifth to seventh cervical vertebrae (Civelek et al., 2008). The middle cervical ganglion sends postganglionic sympathetic fibers to the heart, via the middle cervical cardiac nerve; to the neck and upper limb.
The inferior cervical ganglion may be fused with the first thoracic ganglion to form a cervicothoracic or stellate ganglion, which lies adjacent to the seventh cervical vertebra. The cervicothoracic ganglion sends postganglionic sympathetic fibers to the heart, via the inferior cervical cardiac nerve; and to the head, neck, and upper limb.
Additionally, neurons in the cervical paravertebral ganglia will innervate blood vessels, sweat glands, and arrector pili muscles at segmental locations roughly corresponding to the dermatome of the equivalent spinal nerve.
References
Civelek, E., Karasu, A., Cansever, T., Hepgul, K., Kiris, T., Sabanci, A. & Canbolat, A. (2008) Surgical anatomy of the cervical sympathetic trunk during anterolateral approach to cervical spine. European spine journal: official publication of the European Spine Society, the European Spinal Deformity Society, and the European Section of the Cervical Spine Research Society, 17(8), 991-995.
