The occipital nerves are a pair of nerves located at the back of the head, playing a role in the sensations experienced in this region. These nerves originate from the upper spinal cord and extend upward, providing sensory innervation to various parts of the scalp and neck.
Understanding the Occipital Nerves
The occipital nerves consist of three main branches: the Greater Occipital Nerve, the Lesser Occipital Nerve, and the Third Occipital Nerve. These nerves arise from the upper cervical spinal nerves, primarily C2 and C3, and follow distinct pathways to innervate specific areas of the head and scalp.
The Greater Occipital Nerve (GON) is the largest of these nerves, originating from the medial division of the dorsal ramus of the C2 spinal nerve, sometimes with contributions from C3. It ascends between the first and second cervical vertebrae, traversing muscles like the inferior capitis oblique and semispinalis capitis. The GON then typically pierces the semispinalis capitis and trapezius muscles before becoming superficial, supplying sensation to the posterior scalp, extending up to the crown of the head, and sometimes around the ear and above the parotid gland.
The Lesser Occipital Nerve (LON) arises from the anterior rami of the C2 and C3 spinal nerves, branching from the cervical plexus. It ascends along the posterior border of the sternocleidomastoid muscle. Near the base of the skull, it pierces the deep cervical fascia and continues upwards, providing sensory supply to the skin on the side of the scalp, behind the ear, and the skin of the external ear.
The Third Occipital Nerve (TON) originates from the posterior ramus of the C3 spinal nerve. It follows a path medial to the Greater Occipital Nerve, piercing muscles like the semispinalis capitis, splenius capitis, and trapezius as it ascends. The TON primarily provides sensation to the skin of the lower occiput and upper neck region, and also supplies the C2/C3 zygapophyseal joint.
Functions of the Occipital Nerves
The primary function of the occipital nerves is sensory innervation, meaning they transmit sensations from specific areas of the head and neck to the brain. These nerves are responsible for conveying feelings such as touch, temperature, and pain.
The Greater Occipital Nerve provides sensation to the posterior scalp, extending forward to the vertex or crown of the head. It also contributes to sensation around the ear and the skin just above the parotid gland. The Lesser Occipital Nerve supplies sensory input to the lateral scalp and the skin around the external ear.
The Third Occipital Nerve provides sensory innervation to the lower occiput and upper neck region. While primarily sensory, the Third Occipital Nerve also contributes some motor fibers to the semispinalis capitis muscle. All three occipital nerves are interconnected through communicating branches, allowing for a comprehensive sensory network in the posterior head and neck.
Common Conditions Linked to Occipital Nerves
The anatomical pathways of the occipital nerves can make them susceptible to compression, inflammation, or irritation, leading to pain. A common condition is occipital neuralgia, a type of headache characterized by distinct pain patterns in the back of the head, neck, and scalp.
Occipital neuralgia often presents as sharp, shooting, or electric-shock-like pain that starts at the base of the skull and can radiate upwards to the scalp, behind the ears, or even behind the eye on the affected side. This pain can be intermittent, lasting seconds to minutes, and may be accompanied by a persistent aching, burning, or throbbing sensation between severe episodes. The scalp in the affected area might also be tender to the touch, and sensitivity to light can occur.
The anatomical course of these nerves, particularly where they pierce muscles or fascia, makes them vulnerable to entrapment or irritation. For instance, the Greater Occipital Nerve can be compressed as it passes through the semispinalis capitis or trapezius muscles. Causes of occipital neuralgia include head or neck trauma, tight neck muscles, inflammation, or nerve compression as it exits the spine, sometimes due to conditions like osteoarthritis. Certain movements, such as turning the head or brushing hair, can trigger or worsen the pain.