Overview
The
cervical plexus is a collection of nerves arising from the anterior, posterior
and lateral roots of C1 – C5, lying deep to the prevertebral fascia.
Collectively they provide motor supply to muscles of the neck and cutaneous
supply to antero-lateral neck, posterior scalp and lateral face.
Gross Anatomy
Anterior root
· C1 runs in close proximity to the Hypoglossal
nerve (CN XII). It provides motor fibres to geniohyoid & thyrohyoid, as
well as supplying the superior root of the Ansa Cervicalis. The word ansa
cervicalis originates from the Latin for ‘handle of the neck’
· The inferior root of the Ansa
Cervicalis arises from C2 and C3 fibres. Once the two roots merge, they provide
motor supply to omohyoid, sternohyoid and sternothyroid
· C2 is the sole contributor to the
lesser occipital nerve, which pierces prevertebral fascia near the apex of the
posterior triangle of the neck and moves superficially to supply sensory fibres
to the lateral scalp, posterior to the ear
· C2 and C3 unite to form the great
auricular nerve and transverse cervical nerve, deep to sternocleidomastoid.
Both nerves exit the posterior triangle, looping around the posterior border of
SCM. The great auricular nerve contains sensory fibres to the skin over the
angle of the mandible, parotid gland and lower part of the auricle. The
transverse cervical supplies the skin over the anterior neck
· Fibres from C3 and C4 form the
supraclavicular nerve, which emerges posterior to sternocleidomastoid with the greater
auricular and transverse cervical nerves. It soon divides to provide sensory
supply to the skin over the lower neck, upper chest and postero-superior aspect
of shoulder
· C4 fibres, along with contributions
from C3 and C5 descend to become the phrenic nerve
Posterior root
· C1 dorsal root fibres run in close
proximity to the vertebral artery as the suboccipital nerve to supply muscles
of the suboccipital triangle (obliquus capitis superior and inferior, and
rectus capitis posterior major)
· C2, with some minor contribution
from C3, forms the greater occipital nerve. This exits through the prevertebral
fascia at the apex of the posterior triangle and supplies sensory fibres to the
skin over the posterior occiput
Lateral root
· Fibres from C1 – C5 ascend as the
spinal accessory nerve within the subarachnoid space lateral to the cord,
passing through the foramen magnum posterior to the vertebral artery to join
the cranial root
Clinical Anatomy
·
Although uncommon, insult to the spinal
accessory nerve, either traumatic or iatrogenic, results in weakness in turning
the head to the opposite side against resistance, and drooping of the shoulder
·
Infiltration of local anaesthetic along
the posterior border of sternocleidomastoid produces a cervical plexus block,
useful in neck surgery. Caution must be taken however, as the block will also
affect the phrenic nerve and thus paralysis the ipsilateral hemidiaphragm
Quick Anatomy
Key Facts
Aide-Memoire
Summary
The cervical plexus provides sensory fibres to the majority
of the neck and posterior head/scalp and motor supply to deep muscles of the
neck. It is relatively well protected at its origin, and using the landmark of the
posterior border of the sternocleidomastoid, can be blocked to provide regional
anaesthesia.