Neuroanatomy, Superior Cervical Ganglion

Structure and Function

The superior cervical ganglia are made up of the paravertebral ganglia of cervical vertebral levels one through four (C1-C4).[3][4] The superior cervical ganglia are oval shaped, cylinder-like, and elongated. They contain neurons.[1][5][6] They receive presynaptic signals from the sympathetic trunk. Postsynaptic signals then convey information from the superior cervical ganglia to targets in the head and neck.[2]

Embryology

The superior cervical ganglia derive from neural crest cells. Neural crest cells come from the ectoderm in embryological development. Many structures of the head, neck, face, and cardiovascular system also originate from the neural crest cells.[5][7]

Blood Supply and Lymphatics

Branches from the ascending pharyngeal artery, coming off of the external carotid artery, provide blood supply to the superior cervical ganglia. Venous drainage is through the internal jugular vein through direct posterior branches. There is a noted deficiency in gross blood supply at the junction of the upper one third and lower two-thirds of the neck; this is important for surgical considerations mentioned in the later part of this activity.[8]

The superior cervical ganglia are anterior to the retropharyngeal lymph nodes.[1][2]

Nerves

As previously described, the superior cervical ganglia are made up of the paravertebral ganglia of cervical vertebral levels one through four (C1-C4).[3][4] The superior cervical ganglia themselves contain neurons that supply sympathetic innervation to the head and neck.[5][6] The superior cervical ganglia provide postsynaptic fibers via the deep petrosal nerve to provide vasoconstriction to the lacrimal gland.[9] The superior cervical ganglia also supply gray rami communicantes to the ventral rami in the cervical plexus.[10] The superior cervical ganglia connect to the next closest ganglia, the middle cervical ganglia, inferiorly via the sympathetic trunk.[4]

Muscles

The superior cervical ganglia provide sympathetic innervation.[10] Their location is lateral to the longus colli muscles.[1][2]

Physiologic Variants

The superior cervical ganglia are typically present at cervical vertebral levels one and two (C1 and C2). However, they have been found between the cervical vertebral levels one through five. (C1-C5).[1] The ranges of the length of the superior cervical ganglia are from 10 to 30mm. The width of the superior cervical ganglia ranges from 5 to 8mm.[1] See Figures. Cervical Portion of the Sympathetic System, Cervical Portion, Sympathetic System.

Branches coming off of the superior cervical ganglia include the:

• Pharyngeal branch
• The communicating branch of the cervical nerve
• The internal carotid branch
• The communicating branch of the pharyngeal mucosa
• The communicating branch of the vagus nerve
• The communicating branch of the superior laryngeal nerve
• The laryngeal branch
• The communicating branch of the internal jugular vein

There are reports of up to seven different types of branch combinations coming off of the superior cervical ganglia.[2]

It is crucial to recognize that these are common variants of branches coming off of the superior cervical ganglia as damaging these may lead to consequences such as the development of Horner syndrome as described later in this activity.[1]

Surgical Considerations

It is important to avoid this the superior cervical ganglia during open anterior neck surgeries. When the superior cervical ganglia are damaged, Horner syndrome can develop. Horner syndrome comes from tension on the sympathetic trunk during anterior neck surgeries such as anterior cervical disc fusions. The tension causes damage to the fibers along the sympathetic trunk. More about Horner syndrome is described later in this activity.[1][4][11] Knowing the anatomy and landmarks regarding the neck helps to avoid damaging important neurovasculature in the area.[1]

Anterior surgical procedures to the neck area such as anterior cervical discectomies can cause a disruption of the blood supply to the superior cervical ganglia, causing ischemic damage to the ganglia. This ischemic damage can also cause symptoms similar to Horner syndrome.[7]

To prevent damage to the sympathetic ganglia during an anterior approach to the cervical spine, it is always advisable to create longus colli gutter and then place the retractors within the same, thereby minimizing the risk of inadvertent injury to the ganglia that lie lateral to the muscle.

Clinical Significance

The superior cervical ganglia can be a site for locally injected anesthetics such as opioids, which is useful for neuropathic pain management of the face.[1][2] The superior cervical ganglia are the main source of sympathetic innervation to the head and face. Buprenorphine has been specifically utilized in these ganglionic local opioid analgesia injections to provide pain relief to patients suffering from neuropathic facial pain stemming from atypical facial pain, postherpetic neuralgia, and trigeminal neuralgia.[12] Understanding the anatomic positioning of the superior cervical ganglia allows this injection to be performed safely by avoiding important structures such as the internal carotid arteries which lie close to the superior cervical ganglia.[1][2][12]. Ultrasound guidance can be utilized to visualize the superior cervical ganglia during this procedure properly.[12]

Damage to the superior cervical ganglia can cause a postganglionic pattern of Horner syndrome. The symptoms of Horner syndrome include miosis, facial anhidrosis, and partial ptosis; this is due to the superior cervical ganglia's role in providing sympathetic innervation to these targets.[4][11] These symptoms arise from the disruption of the sympathetic nervous system, which includes superior cervical ganglia. Care is necessary during superior cervical ganglia blocks as well as head and neck procedures to prevent Horner syndrome from occurring.[11]

Other Issues

The superior cervical ganglion can appear as pathologic retropharyngeal lymph nodes on imaging. The superior cervical ganglia are anterior to the retropharyngeal lymph nodes.[1][2] The proximity of the superior cervical ganglia to the retropharyngeal lymph nodes can make the staging of neck neoplasms difficult. Nasopharyngeal cancer, thyroid cancer, as well as oropharyngeal cancer, typically metastasizes to the retropharyngeal lymph nodes, therefore delineating them from the superior cervical ganglia is very important.[1][2][3] Magnetic resonance imaging can be utilized to delineate the difference between pathologic retropharyngeal lymph nodes from the superior ganglia.[1][2]