Neck Nerves
Cervical Plexus Block
used to provide regional anesthesia, usually for surgery in the neck region - such as carotid endarterectomy, thyroidectomy & cervical lymph node excision. The anesthetist inserts the needle containing the local anesthetic, midway up the posterior border of the sternocleidomastoid (the nerve point of the neck). They proceed to inject 3 times in a fan like fashion, with the needle pointing cranially, caudally & then anteriorly
Ansa Cervicalis
(goose's neck) is a loop of nerves, formed by nerve roots C1-C3. It gives off 4 muscular branches: 1.Superior belly of the omohyoid muscle 2.Inferior belly of omohyoid muscle 3.Sternohyoid 4.Sternothyroid These muscles (the infrahyoids) act to depress the hyoid bone; an important function for swallowing & speech.
Sensory Functions of phrenic nerve
Sensory fibers from the phrenic nerve supply the central part of diaphragm, including the surrounding pleura & peritoneum. The nerve also supplies sensation to the mediastinal pleura & pericardium.
Lesser Occipital nerve
derived solely from the C2 root. Supplies cutaneous sensation to posterosuperior scalp, & commonly communicates with the posterior branch of the greater auricular nerve. After its formation, the nerve curves around the accessory nerve, & passes superiorly, close to the posterior border of the sternocleidomastoid.
Greater Auricular Nerve
formed by fibers from C2 & C3 roots. Provides sensation to the external ear & skin over the parotid gland. It is the largest ascending branch of the plexus. nerve also communicates w/ auricular branch of vagus nerve & the posterior auricular branch of the facial nerve (which nn some small muscles around the ear)
Transverse Cervical Nerve
formed by fibers from C2 & C3. It curves around the posterior aspect of the sternocleidomastoid, & supplies sensation to the anterior neck. The nerve then pierces the deep cervical fascia & then gives branches that pass superiorly & inferiorly to supply the anterolateral skin of the neck & upper sternum.
Phrenic nerve motor functions
innervates the diaphragm
Phrenic nerve
is a bilateral, mixed nerve that originates in the neck & descends through the thorax to reach the diaphragm. As the only source of motor nn to the diaphragm, this nerve has an important role in breathing.
Phrenic Nerve Roots
Anterior rami of C3, C4 and C5
Left Phrenic Nerve
-Passes anteriorly to 1st part of the subclavian artery, & posteriorly to the subclavain vein. -Enters the thorax via the superior thoracic aperture. -Crosses the aortic arch & vagus nerve, & descends anteriorly to left lung root, down the left side of the pericardium. -Reaches the diaphragm a& pieces the muscle to supply the underlying surface
Right Phrenic Nerve
-Passes anteriorly to 2nd part of subclavian artery, & posteriorly to the subclavian vein. -Enters the thorax via the superior thoracic aperture. -Descends anteriorly to right lung root, down the right side of the pericardium. -Reaches the diaphragm & pieces the muscle to supply the underlying surface.
Nerves to geniohyoid & thyrohyoid
C1 spinal nerve gives rise to nerves to the geniohyoid (moves the hyoid bone anteriorly & upwards, expanding the airway) & thyrohyoid (depresses the hyoid bone & elevates the larynx). These nerves travel with the hypoglossal nerve to reach their respective muscles
Other Muscular Branches
C1-C2: Rectus capatis anterior & lateralis C1-C3: Longus capatis C2-C3: Prevertebral muscles & sternocleidomastoid C3-C4: Levator scapulae, trapezius & scalenus medius The middle & anterior scalenus muscles also receive nn directly from the cervical plexus.
Sensory functions of phrenic nerve
Innervates the central part of the diaphragm, the pericardium & the mediastinal part of the parietal pleura
Erb's point
Where sensory branches of the cervical plexus all enter the skin at the middle of the posterior border of sternocleidomastoid. Is utilized when performing a cervical plexus nerve block
Supraclavicular nerves
a group of nerves formed from the C3 & C4 roots. They arise from the behind the posterior border of sternocleidomastoid, & provide sensation to the skin overlying the suprascapular fossa & upper thoracic region & sternoclavicular joint
Cervical Plexus
a network of nerve fibers that supplies nn to some of the structures in the neck & trunk. Located in the posterior triangle of the neck, halfway up the sternocleidomastoid muscle, & within prevertebral layer of cervical fascia. The plexus is formed by the anterior rami (divisions) of cervical spinal nerves C1-C4
Muscular branches of cervical plexus
are located deep to the sensory branches. They supply some of the muscles of the neck, back & diaphragm. After arising from the cervical plexus, the muscular branches tend to travel initially in an anteromedial direction. This is in contrast to the cutaneous branches, which travel posteriorly -phrenic nerve, nerves to geniohyoid & thyrohyoid, Ansa cervicalis, other muscular branches
Phrenic Nerve
arises from the anterior rami of C3-C5. Provides motor nn to the diaphragm. After arising from the cervical plexus, the nerve travels down the surface of the anterior scalene muscle, & enters the thorax. In the thoracic cavity, the nerve descends anteriorly to the root of the lung to reach the diaphragm. A good memory aid for the roots of the phrenic nerve is C3,4,5 keeps the diaphragm alive
Branches of the cervical plexus
cervical plexus gives rise to numerous branches which supply structures in the head & neck. Can be divided into 2 groups - muscular branches & sensory branches
Sensory branches of cervical plexus
cutaneous branches of the cervical plexus supply skin of neck, upper thorax, scalp & ear. These nerves all enter the skin at the middle of the posterior border of the sternocleidomastoid. This area is known as the nerve point of the neck (Erb's point), & is utilized when performing a cervical plexus nerve block.
Phrenic Nerve Course
mainly originates from C4 spinal root, but also receives contributions from C3 & C5. Also receives some communicating fibers from the cervical plexus. Nerve begins at lateral border of the anterior scalene muscle. It then continues inferiorly over the anterior surface of anterior scalene, deep to the prevertebral layer of deep cervical fascia. From here, the course of the phrenic nerve differs between the left and right
Diaphragmatic Paralysis
phrenic nerve provides motor nn to the diaphragm. If the nerve becomes damaged, paralysis of the diaphragm will result. Numerous causes of phrenic nerve lesions: -Mechanical trauma: ligation or damage to the nerve during surgery. -Compression: due to a tumor within the chest cavity. -Myopathies: such as myasthenia gravis. -Neuropathies: such diabetic neuropathy. Paralysis of the diaphragm produces a paradoxical movement. The affected side of the diaphragm moves upwards during inspiration, & downwards during expiration. A unilateral diaphragmatic paralysis is usually asymptomatic, & is most often an incidental finding on x-ray. If both sides are paralyzed, pt may experience poor exercise tolerance, orthopnea (shortness of breath) & fatigue. Lung function tests will show a restrictive deficit. Management of diaphragmatic paralysis is two-fold. Firstly, the underlying cause must be identified & treated (if possible). The second part of treatment deals with symptomatic relief. This is usually via non-invasive ventilation, such as a CPAP (continuous positive airway pressure) machine.
Phrenic Nerve Motor Functions
provides motor nn to diaphragm; main muscle of respiration. As the phrenic nerve is a bilateral structure, each nerve supplies the ipsilateral side of the diaphragm (i.e. the hemi-diaphragm on the same side as itself).
Cervical plexus
spinal nerves C1 - C4 form the basis of the cervical plexus. At each vertebral level, paired spinal nerves leave the spinal cord via the intervertebal foramina of the vertebral column. Each nerve then divides into anterior & posterior nerve fibers. The cervical plexus begins as the anterior fibers of the spinal nerves C1, C2, C3 & C4. These fibers combine with each other to form the branches of the cervical plexus
