The lesser occipital nerve (or small occipital nerve) is a cutaneous spinal nerve of the

cervical plexus The cervical plexus is a nerve plexus of the anterior rami of the first (i.e. upper-most) four cervical spinal nerves C1-C4. The cervical plexus provides motor innervation to some muscles of the neck, and the diaphragm; it provides sensory inne ...

. It arises from second cervical (spinal) nerve (C2) (along with the greater occipital nerve). It innervates the skin of the back of the upper neck and of the

scalp The scalp is the area of the head where head hair grows. It is made up of skin, layers of connective and fibrous tissues, and the membrane of the skull. Anatomically, the scalp is part of the epicranium, a collection of structures covering th ...

posterior to the

ear In vertebrates, an ear is the organ that enables hearing and (in mammals) body balance using the vestibular system. In humans, the ear is described as having three parts: the outer ear, the middle ear and the inner ear. The outer ear co ...

Structure

Origin

It arises from the (lateral branch of the

ventral ramus The ventral ramus (: rami) (Latin for 'branch') is the anterior division of a spinal nerve. The ventral rami supply the antero-lateral parts of the trunk and the limbs. They are mainly larger than the dorsal rami. Shortly after a spinal nerve e ...

) of cervical spinal nerve C2; it (sources differ) receives or may also receive fibres from cervical spinal nerve C3. It originates between the

atlas An atlas is a collection of maps; it is typically a bundle of world map, maps of Earth or of a continent or region of Earth. Advances in astronomy have also resulted in atlases of the celestial sphere or of other planets. Atlases have traditio ...

, and

axis An axis (: axes) may refer to: Mathematics *A specific line (often a directed line) that plays an important role in some contexts. In particular: ** Coordinate axis of a coordinate system *** ''x''-axis, ''y''-axis, ''z''-axis, common names ...

. The lesser occipital nerve is one of the four cutaneous branches of the

Course and relations

It curves around the accessory nerve (CN XI) to come to course anterior to it. It then curves around and ascends along the posterior border of the

sternocleidomastoid muscle The sternocleidomastoid muscle is one of the largest and most superficial cervical muscles. The primary actions of the muscle are rotation of the head to the opposite side and Anatomical terms of motion#Flexion and extension, flexion of the neck. ...

; rarely, it may pierce the muscle. Near the cranium, it perforates the

deep cervical fascia The deep cervical fascia (or fascia colli in older texts) lies under cover of the platysma, and invests the muscles of the neck; it also forms sheaths for the carotid vessels, and for the structures situated in front of the vertebral column. Its ...

. It is continued upwards along the scalp posterior to the auricle. It divides into medial and lateral segments between the inion, and intermastoid line.

Branches

It has an auricular, a mastoid, and an occipital branch. Its auricular branch supplies the skin of the upper and back part of the auricula, communicating with the mastoid branch of the

great auricular The great auricular nerve is a cutaneous (sensory) nerve of the head. It originates from the second and third cervical (spinal) nerves (C2-C3) of the cervical plexus. It provides sensory innervation to the skin over the parotid gland and the mas ...

. This branch is occasionally derived from the greater occipital nerve.

Distribution

The nerve provides sensory innervation to the upper part of the back of the neck and adjacent scalp posterior to the auricle; it may also contribute to the sensory innervation of the auricle itself.

Communications

It communicates with the greater occipital nerve,

great auricular nerve The great auricular nerve is a Cutaneous nerve, cutaneous (sensory) nerve of the head. It originates from the second and third spinal nerve, cervical (spinal) nerves (C2-C3) of the cervical plexus. It provides sensory innervation to the skin over ...

, and the auricular branch of the facial nerve.

Variation

Rarely, the lesser occipital nerve may be duplicated or triplicated.

Clinical significance

Problems with the lesser occipital nerve cause

occipital neuralgia Occipital neuralgia (ON) is a painful condition affecting the posterior head in the distributions of the greater occipital nerve (GON), lesser occipital nerve (LON), third occipital nerve (TON), or a combination of the three. It is paroxysmal, l ...

Nerve block Nerve block or regional nerve blockade is any deliberate interruption of signals traveling along a nerve, often for the purpose of pain relief. #Local anesthetic nerve block, Local anesthetic nerve block (sometimes referred to as simply "nerve b ...

is difficult due to variation in the course of the nerve.

Additional images

File:Gray784.png, Dermatome distribution of the trigeminal nerve

References

External links

* * http://www.dartmouth.edu/~humananatomy/figures/chapter_47/47-2.HTM * http://www.dartmouth.edu/~humananatomy/figures/chapter_47/47-6.HTM {{Authority control Optic nerve