The Potential Roles of Cervical Plexus Abnormalities in Occipital Neuralgia: An Anatomic Variant Explored

Abstract

Occipital neuralgia (ON) is a condition defined as a headache characterized by paroxysmal burning and stabbing pain located in the distribution of the greater occipital nerve (GON), lesser occipital nerve (LON), or third occipital nerves (TON). This condition can be severely impairing in symptomatic patients and is known to have numerous etiologies deriving from various origins such as trauma, anatomical abnormalities, tumors, infections, and degenerative changes. This study reports four cases of a previously undescribed anatomical variant in which the (spinal) accessory nerve (SAN) fuses with the LON before piercing the sternocleidomastoid (SCM). The fusion of these two nerves and their route through the SCM points to a potential location for nerve compression within the SCM and, in turn, another potential source of ON. This anatomical presentation has clinical significance as it provides clinicians with another possible cause of ON to consider when diagnosing patients who present with complaints of a headache. Additionally, this study explores the prevalence of piercing anatomy of the LON and GAN and discusses their clinical implications.

Keywords: accessory nerve; accessory nerve impingement; headache disorder; lesser occipital nerve; occipital neuralgia.

Figure 1

Dissection photo showing the spinal accessory nerve (SAN) as it pierces the sternocleidomastoid (SCM) and then wraps back superiorly towards the base of the scalp. A separation of the SCM was performed to allow for tracking and visualization of the course of the SAN as it traveled through the muscle.

Figure 2

Cadaveric photo of connection between spinal accessory nerve (SAN) and lesser occipital nerve (LON), both of which pierce through the sternocleidomastoid. In this individual, the GAN also pierces the SCM, but does so separately from the SAN. Abbreviations: GAN = greater auricular nerve; LON = lesser occipital nerve; SAN = spinal accessory nerve; SCM = sternocleidomastoid.

Figure 3

Cadaveric photo of left cervical and auricular regions showing variant with spinal accessory nerve (SAN) sending a small branch to join the lesser occipital nerve (LON): Superficial view (a) and deep view (b). Abbreviations: GAN = great auricular nerve; LON = lesser occipital nerve; SAN = spinal accessory nerve (CN XI); SCM = sternocleidomastoid.