Superior cervical ganglion

Superior cervical ganglion is an elongated oval-shaped ganglion that marks the superior extent of the cervical sympathetic trunk. It is situated at the level of second and third cervical vertebrae (C2–C3). It is the largest of all cervical ganglia and provides sympathetic innervation to the head and neck region.

The superior cervical ganglion receives preganglionic sympathetic neurons from the lateral gray horns of the upper thoracic spinal segments. These pre-ganglionic neurons travel an extra-long distance by ascending in the sympathetic trunk to reach the superior cervical ganglion. Here they synapse with cell bodies of postganglionic sympathetic neurons, which in turn, get distributed to various regions of the head and neck and mediastinum via the following routes:

• Post-ganglionic neurons travel with the internal and external carotid arteries as the internal and external carotid nerves, respectively. These nerves form neuronal plexuses around internal carotid and external carotid arteries and follow the arterial branches to spread out to various parts of the brain and the head and neck regions,

• Post-ganglionic neurons reach out to the ventral rami of C1 to C4 cervical spinal nerves in the cervical plexus, through gray rami communicantes,

• Post-ganglionic neurons could join the pharyngeal plexus (along with vagus and glossopharyngeal nerves) to innervate the pharynx,

• Lastly, post-ganglionic neurons reach out to the cardiac plexus via superior cardiac nerves, to innervate the heart.

Inferiorly, the superior cervical ganglion is connected with the middle cervical ganglion via interganglionic branches, as part of the sympathetic trunk.

The superior cervical ganglion receives arterial blood supply from the ascending pharyngeal artery–a branch of external carotid artery–while the venous drainage is via the internal jugular vein.

Damage to superior cervical ganglion or upper sympathetic trunk–for instance, during anterior neck surgery or by tumor infiltration–could lead to Horner’s syndrome, manifesting as ptosis, miosis, anhidrosis and facial flushing.