Exam III: Neck II Flashcards
Neck: Nerves
- Cervical
Cervical plexus: anterior rami of C1 – C4
Posterior rami: C2 – C5; innervate deep muscles of neck and back along with the skin that covers them - Cranial nerves
CN V – Trigeminal innervates anterior belly of digastric and mylohyoid muscles
CN VII – Facial innervates facial muscles, platysma, stylohyoid, posterior digastric muscles
CN IX – Glossopharyngeal innervates carotid body and sinus
CN X – Vagus
CN XII - Hypoglossal - Sympathetic chain
Spinal Nerve Cuts
- If you cut anterior roots, you won’t get motor function for skeletal muscles and length of muscle spindles; complain of weakness; carry GSE and GVE
- If you cut posterior roots, you lose sensory function from the skin/dermatome/numbness; posterior carry GSA and GVA
Posterior Ramus: muscles are paralyzed/weakness along with skin on top of it/in that dermatome
Anterior Ramus: sensory and motor; numbness, loss of sensation; anterior rami all carry GSE/innervate muscle
Rami have GVE, GVA, GSA, and GSE (mixed)
Cervical Plexus
Loops: interconnections between C1 and C2, C2 and C3, etc.; have axons from C1 come down and mix with C2 aka many nerves at various spinal cord levels
Sensory Nerves: innervate skin; 4 cutaneous nerves, proprioception, the subtrapezial plexus joins the CN XI to go down to trapezius
Motor nerves: innervate skeletal muscle; most are derived from ansa cervicalis (loops that connect C1 to C3/thyrohyoid); innervate strap muscles; phrenic nerve (closest to anterior scalene muscle)
Hitchhiking: CN XII comes down and the cervicalis joins and travel together as one nerve and then split off again later
Gray rami: unmyelinated on all 31 levels; postganglionic sympathetic leave the sympathetic chain and go to the spinal nerve
Nerve Point
All of the cutaneous nerves (C1 – C4 anterior rami) that come from cervical plexus come from nerve point:
Greater auricular
Transverse Cervical
Lesser occipital: goes through the platysma and innervates the skin over top of it
Supraclavicular: skin over trapezius and clavicle
Nerve Point: located on the posterior border of the SCM; at this point where all cutaneous nerves emerge and then distribute; goes through the platysma
Ansa Cervicalis, Superior Root, Hypoglossal Nerve Functions
Ansa Cervicalis; if cut, it will no longer innervate the strap muscles within the anterior triangle (digastric muscles, stylohyoid, thyrohyoid, sternohyoid, omohyoid, sternothyroid, mylohyoid, and geniohyoid)
Cutting the superior root: no motor to innervated infrahyoid muscles; instability in swallowing and weakness in infrahyoid muscles
CN XII/Hypoglossal: if cut, it will no longer innervate the posterior belly of the digastric muscle, stylohyoid, hyoglossus, mylohyoid, and tongue; trouble moving the tongue, and difficulty swallowing; also realize there are hitchhiking with other nerves so can affect those as well
Scalene Triangle and Brachial Plexus
Runs underneath the clavicle: suprascapular
Transverse cervical artery runs front to back; nerve is back to front
Accessory phrenic nerve
Between anterior and middle scalene: brachial plexus and subclavian artery goes through the triangle
Innervation of Trapezius and SCM
Cut accessory nerve (CN XI) before SCM: SCM and trapezius affected causing weakness when shrugging shoulder, abduction above 90 degrees of humerus, and hard to turn head to opposite side
Cut accessory nerve after SCM: trapezius only because innervated by accessory nerve XI
Vagus Nerve: CN X
Skeletal muscle is inside viscera
GVE – glands, parasympathetic fibers that control the secretions
SVA – taste (special visceral afferent)
GVA – damage to vagus nerve
Off the vagus nerve above digastric muscles there is a superior laryngeal nerve, which divides into an external branch and internal branch (one goes outside and on goes inside the larynx)
CN X, the pre ganglionic in brain stem and post is in the wall of the organ in this case larynx; very short post ganglionic for parasympathetic
Vagus nerve innervates 2/3 of the organs within the body; vagus means wonderer because it goes around the body within the carotid sheath (when in the neck)
Distribution of CN X in the Neck
Pharyngeal branches
Superior laryngeal nerve: internal laryngeal and external laryngeal nerves
Recurrent/Inferior laryngeal nerve
External laryngeal nerve innervates only 1 muscle
Recurrent nerve on the right goes underneath subclavian; on the left goes underneath the aorta
Goes under subclavian and go back up towards the larynx
Neurovascular Pairs Involving the Larynx
- Internal laryngeal nerve runs w/ superior laryngeal artery
- External laryngeal nerve runs w/ superior thyroid artery
- Recurrent laryngeal nerve runs w/ inferior thyroid artery
Need to ligate these vessels during a thyroidectomy causing injury and damage
Lesions of Vagus Nerve: Etiologies
Vagus nerve damaged due to:
- Carotid Surgery
- Thyroid Surgery
- Aortic Aneurysm
- Bronchial Carcinoma
Cervical Sympathetic Chain
The cervical sympathetic ganglia are fused: Superior Cervical (C1 - 4) Middle Cervical (C5 - 6) Vertebral Inferior Cervical (C7 - 8)
Inferior cervical (C7-8) and T1 fuse= form stellate ganglion Information in the whole chain ganglion originate from T1 T4 The C number reference= spinal NERVE levels (not spinal cord levels)
Branches from the Cervical Sympathetic Chain
- Gray rami: are how we distribute from the sympathetic chain back into spinal nerves
- Sympathetic cardiac: develops in the neck and carried down
- Internal and external carotid nerves associated with the internal and external carotid arteries
- Cervical sympathetic cardiac: remnant of development from when your heart moved from in front of your head to your chest
- Laryngopharyngeal Branches:
Cervicothoracic Ganglion Block & Lesion of the Cervical Sympathetic Trunk
Sympathetic chain affects upper extremities
Raynaud’s: lack of blood supply due to vasospasm of sympathetic in fingers
If you have a tumor and invades the sympathetic chain, what happens? Skin can’t sweat so becomes dry, sebaceous glands aren’t working, vasodilation and loss of vasculature tone so face and neck become flushed, lesions of the sympathetic chain give rise to Horner’s syndrome
Axon Types in Lesser Occipital and Ansa Cervicalis
What axon types are present in the:
1. Lesser Occipital Nerve: innervate skin (GSA), GVE, GSE, and GVA; cell bodies are dorsal root ganglia for GSA; GVE pre is in IML and post is in sympathetic chain
2. Ansa cervicalis GSE – cell body in anterior horn GSA – posterior root ganglion GVE – T1-T4 of IML and cell bodies in sympathetic chain GVA - posterior root ganglion T1-T4
Every nerve will have autonomics