Cervical plexus

The cervical plexus (plexus cervicalis) is formed by the ventral branches (rr. ventrales nervorum spinalium) of the first four cervical nerves C1–C4 and their connections. This plexus is located on the scalenus medius muscle and on the levator scapulae muscle under the sternocleidomastoid muscle. It is covered by deep cervical fascia (lamina praevertebralis). The plexus gives rise to sensitive and motor nerves for the muscles and skin of the neck and for the diaphragm.

Sensitive nerves
They come to the surface in the middle of the back edge of the sternocleidomastoid muscle in a place called the punctum nervosum. They come to the surface very close to each other. From there, the sensitive nerves diverge to the respective innervation areas.

N. Minor occipital nerve (C2, C3)
Course: rises along the posterior edge of the sternocleidomastoid muscle to the lateral part of the occipital region.

Innervation: skin of the lateral part of the occipital region

N. N. Auricularis magnus (C2, C3)
Course: runs along the surface of thesternocleidomastoid muscle up under the bolt, giving off two branches:


 * r. anterior – often has a connection with n. facialis
 * r. posterior

Innervation:


 * r. anterior – a skin of the front side of the auricle (except for areas innervated by the IX. and X. cranial nerves), skin of the regio parotideomasseterica
 * r. posterior – a skin of the back of the auricle, skin of the mastoid region

N. transversus colli (C3)
Course: it goes forward medially through the sternocleidomastoid muscle under the skin of the neck muscle (platysma), it is divided into two branches:


 * r. superior – has a connection with r. colli nervi facialis – the so-called ansa colli superficialis
 * r. inferior

Innervation:


 * r. superior – skin in the suprahyoid region
 * r. inferior – skin in the infrahyoid region

Nn. supraclaviculares
They are made up of a variable number of thin sensitive nerves, which, after exiting the punctum nervosum descend in a fan-like fashion over the clavicle.

It creates 3 groups:


 * nn. supraclaviculares mediales – go caudally and medially, innervate the skin in the fossa jugularis and above the manubrium sterni
 * nn. supraclaviculares intermedii – descend caudally and innervate the skin in the lower part of the neck and in the clavicular and infraclavicular region (in the range of the pectoralis major muscle)
 * nn. supraclaviculares laterales –descend caudally and backwards, innervating the skin of the acromial region

Motor nerves
Short nerves: rr. musculares

Long nerve: n. phrenicus

Rr. musculares
They resign from all yrs. ''rr. ventrales'' cervical plexus.

Innervation:


 * C1 – m. rectus capitis lateralis
 * C1, C2 – m. rectus capitis anterior
 * C2, C3 – m. longus capitis
 * C2–C4 – m. longus colli

N. phrenicus (C4, secondary fibers from C3 and C5)
N. phrenicus is a relatively strong, mixed nerve with a predominance of motor fibers.

Course: it emerges from the cervical plexus at the lateral edge of the scalenus anterior muscle, and converges on its front surface through the apertura thoracis superior (placed in front of the n. vagus) caudally into the mediastina.


 * N. phrenicus dexter: descends further between a. et v. subclavia, along the right edge of v. brachiocephalica dextra and v. cava superior.
 * N. phrenicus sinister: descends between a. et v. subclavia, attaches to the left side of the arcus aortae (in the front of n. vagus sinister)

Both nerves then run caudally along the sides of the pericardium between the pericardium and the mediastinal pleura ventral to the pulmonary hilae. Part of the fibers passes to the right through the foramen venae cavae and part to the left through the hiatus oesophageusto the abdominal surface of the diaphragm.

Innervation:

Motor fibers:


 * rr. phrenici – innervate the diaphragm

Sensitive fibers:


 * rr. pericardia – fibers for the pericardium, mediastinal and diaphragmatic pleura
 * rr. phrenicoabdominales – innervates the peritoneum below the diaphragm up to the level of the gallbladder and pancreas

N. phrenicus accessorius – accessory fibers usually from C5 conducted as a separate branch from the brachial plexus

Clinical notes:

n. Phrenicus damage dx. or son causes paralysis of the corresponding part of the diaphragm. Irritation of the nerve causes twitching of the diaphragm, which may be a sign of inflammation of the peritoneum or brain damage. In the common case, it is a hiccup (singultus).