Lecture 5 and (6?): Posterior Triangle of the Neck Flashcards
Describe the fascia of the neck (cervical fascial)
1) Superficial Fascia
- Contains fatty tissue together with the platysma muscle
- The platysma is a thin sheet of skeletal muscle that originates from superficial fascia of thorax and runs upward to attach to the mandible and blend with lower facial muscles.
- Inervation of the platysma muscle is the facial (VII) nerve.
- (lower part of the mandible to the upper part of the clavical)
2) Deep fascia
- Deep fascia contains investing fascia, pretracheal fascia, carotid sheath and prevetebral fascia.
- 1) Investing layer surrounds/invests all structures in neck and encloses peripheral muscles around neck (e.g. trapezius, sternocleidomastoid, infrahyoid muscles (strap muscles)).
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2) Pretracheal layer encloses the viscera of the neck; thyroid, larynx/trachea and pharynx/esophagus.
- The posterior border of this fascia is buccopharyngeal (operate a lot in this area).
- 3) Prevertebral layer is described as encompassing vertebral column and paravertebral muscles.
- 4) Carotid sheath (not a seperate entity- forms from the contribution from the other 3 fascia layers) surrounds _internal carotid artery, i_nternal jugular vein and vagus (X) nerve. It is connected to and reinforced by adjacent layers of fascia at different levels (e.g. investing fascia, pretracheal fascia, prevertebral fascia).
- Note that when you go above bifurcation of common carotid artery, only the internal carotid artery lies within carotid sheath.
*
- Note that when you go above bifurcation of common carotid artery, only the internal carotid artery lies within carotid sheath.
Describe the layers of the deep fascia in the cervical fascia
1) Investing layer surrounds/invests all structures in neck and encloses peripheral muscles around neck (e.g. trapezius, sternocleidomastoid, infrahyoid muscles (strap muscles)).
2) Pretracheal layer encloses the viscera of the neck; thyroid, larynx/trachea and pharynx/esophagus.
* The posterior border of this fascia is buccopharyngeal (operate a lot in this area for cancers).
3) Prevertebral layer is described as encompassing vertebral column and paravertebral muscles.
4) Carotid sheath (not a seperate entity- forms from the contribution from the other 3 fascia layers) surrounds internal carotid artery, internal jugular vein and vagus (X) nerve. It is connected to and reinforced by adjacent layers of fascia at different levels (e.g. investing fascia, pretracheal fascia, prevertebral fascia).
Note that when you go above bifurcation of common carotid artery, only the internal carotid artery lies within carotid sheath.
Describe the Cervical Spaces
There are potential (rather than actual) spaces (between the fascia) within the neck where disease may locally spread from the neck to the mediastinum.
- Pretracheal space is described as the region between investing layer and pretracheal layer. It extends inferiorly from the pharynx/larynx down to the anterior part of the superior mediastinum.
- Retropharyngeal space is situated between buccopharangeal fascia (posterior aspect of pharynx/esophagus) and prevertebral layer. It extends inferiorly from the base of the skull to the upper part of the posterior mediastinum.
- Prevertebral space is described as a potential space within prevertebral layer between vertebral bodies posteriorly and _prevertebral fascia anteriorly, l_imited laterally by transverse processes and extending from base of the skull to diaphragm. (We don’t know much about this space.)
An accurate understanding of the cervical fascia and its associated spaces is essential for differential diagnosis, predicting the spread of disease and surgical management. As surgical technology advances (e.g. endoscopic and robotic surgery), a precise understanding of the facial arrangement becomes crucial
Describe the neck regions (Lympathic drainage)
The lymphatic drainage of the neck can be divided into the following levels:
- Level I is from midline of submental triangle up to submandibular gland.
- Level II is from skull base to hyoid bone, anteriorly from posterior border of sternocleidomastoid m.
- Level III is from inferior aspect of hyoid bone to bottom cricoid arch, anteriorly to the posterior border of sternocleidomastoid m. up to midline.
- Level IV is from inferior aspect of cricoid to top of manubrium of sternum, anteriorly to the posterior border of sternocleidomastoid m.
- Level V (posterior triangle) is posterior to sternocleidomastoid m. and anterior to trapezius m. above clavicle.
- Level VI is below hyoid bone and above jugular (sternal) notch in the midline.
- Level VII is below the level of jugular (sternal) notch.
What are the borders of the Posterior Triangle
Boundaries
- Anterior boundary is posterior border of sternocleidomastoid muscle (sternocleidomastoid itself is NOT part of posterior triangle)
- Posterior boundary is anterior border of trapezius muscle.
- Base of the triangle is middle third of the superior border of clavicle.
- Apex of the triangle is at _back of the skull o_n superior nuchal line.
Roof
- Roof is formed by i_nvesting layer of deep fascia._
- It may also include anything superficial to investing layer, including skin, s_uperficial fascia,_ sometimes posterior part of platysma muscle, superficial veins such as external jugular veins (post. external jugular veins run within superficial fascia).
Floor
- Floor is formed by prevertebral fascia, covering semispinalis capitis (most superior), s_plenius capitis,_ levator scapulae, s_calenus posterior,_ medius, anterior (most inferior).
Is the sternocleidomastoidpart of the posterior triangle?
NO
sternocleidomastoid itself is NOT part of posterior triangle
Anterior boundary formed from the posterior border of the sternocleidomastoid muscle
On this cross section, where are the boarders of the posterior triangle?
Anterior boundary is posterior border of sternocleidomastoid muscle (sternocleidomastoid itself is NOT part of posterior triangle)
Posterior boundary is anterior border of trapezius muscle.
Describe the Contents of the Posterior Triangle
Apex Content
At the apex, o_ccipital artery_ and greater occipital nerve emerge and runs upward on to the scalp. Numerous lymph nodes are found within the posterior triangle including occipital nodes at the apex.
Muscular Content
The omohyoid muscle passes across inferior part of posterior triangle before disappearing under the sternocleidomastoid muscle and emerging in the anterior triangle.
- The superior belly is in anterior triangle.
- The inferior belly crosses low in the medial part of posterior triangle.
Nervous Content
- A variety of nerves pass through or are within posterior triangle.
- These include C_ccessory nerve (XI),_ branches of cervical plexus (lesser occipital C2, great auricular nerve C2,3, transverse cervical C2,3, supraclavicular C3,4), components forming brachial plexus, and branches of brachial plexus.
- After you separate the fatty tissue, the first nerve you hit is the Great auricular nerve. Most of the time the accessory nerve runs 1-2cm above and deeper to the Great auricular nerve
Venous Content
- The external jugular vein is one of the major veins of the neck region. Formed by the retromandibular and _posterior auricular vein_s, it lies superficially, entering the posterior triangle after crossing the sternocleidomastoid muscle. Within the posterior triangle, the external jugular vein pierces the investing layer of fascia and empties into the subclavian vein.
- The subclavian vein is often used as a point of access to the venous system, via a central catheter
- The t_ransverse cervical_ and _suprascapula_r veins also lie in the posterior triangle
Arterial content
- The subclavian, transverse cervical and suprascapular veins are accompanied by their respective arteries in the posterior triangle.
The distal part of the subclavian artery can be located as it emerges between the anterior and middle scalene muscles. As it crosses the first rib, it becomes the axillary artery, which goes onto supply the upper limb.
Describe the Anatomy of Ophthalmic veins
Superior ophthalmic vein
Inferior ophthamic vein
They converge and pass through the superior or inferior orbital fissure (variability)
They communicate with teh cavernouse sinus
Describe the Concept of the Dangerous Triangle
Area from corners of mouth to bridge of nose
This is the area of communication between outside to inside the cranial cavity
This ‘triangle’ fascilitates spread of disease towards cavernous sinus.
Describe the study looking at valves in Ophthamic veins
It was once believed that there wasn’t.
- It was once believed that opthamic veins did not have valves, and that the spread of disease from dangerous triangle to cavernous sinus was attributed to absence of valves.
- No valves were identified in the IOVs
- Valves identified in 75% SOV specimens.
- The valve orientation was towards the cavernous sinus in each specimen (direction of blood flow was towards the cavernous sinus)
- Majority of valves were bicuspid, but two in the tributaries of one SOV were tricuspid
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Conclusion:
- __It is not the absence of valves, but the communication between these veins and the cavernous sinus that facilitates spread of infection.
- This communication can be via the angular and SOV, or via the deep facial vein, pteygoid plexus and then the IOV or emissay veins int he foramen ovale.
What is the name of the most important nerve that runs in the posterior triangle?
Where is it found?
Accessory Nerve
(NO SURFACE MARKING)
After you separate the fatty tissue, the first nerve you hit is the Great auricular nerve. Most of the time the accessory nerve runs 1-2cm above and deeper to the Great auricular nerve
Describe the Accessory Nerve
A_ccessory (XI) nerve_ (very variable) is embedded in investing fascia, which forms roof of the triangle.
- It is j_ust under the skin (_prone to injury); and comes under sternocleidomastoid, between two heads of the muscle.
- It i_nnervates sternocleidomastoid_ and trapezius muscle, which is for shoulder shrugging (fully abduct arm).
“Surface Anatomy”
- After you separate the fatty tissue, the first nerve you hit is the Great auricular nerve. Most of the time the accessory nerve runs 1-2cm above and deeper to the Great auricular nerve
Describe the Arterial Content of the Posterior Triangle
Several arteries are found within the boundaries of the posterior triangle of the neck.
- The largest is third part of subclavian artery as it emerges from between anterior and middle scalene muscles to cross the base of the posterior triangle (with the trunks of the brachial plexus) lying under prevertebral fascia.
- Two other small arteries also cross the base of posterior triangle. These are transverse cervical and suprascapular arteries. They are both branches of thyrocervical trunk, which arises from first part of subclavian artery.
- Subclavian Artery And Its Branches
The first part of subclavian artery ascends to medial border of anterior scalene from either brachiocephalic trunk on right side or directly from arch of the aorta on left side.
The second part of subclavian artery passes behind anterior scalene. One branch (costocervical trunk) may arise from second part.
The third part of the subclavian artery extends from lateral border of anterior scalene muscle to lateral border of rib I where it becomes the axillary artery. A single branch (dorsal scapular artery) may arise from third part.
- Transverse Cervical And Suprascapular Arteries
Transverse cervical artery passes laterally and slightly posteriorly across base of the posterior triangle anterior to anterior scalene muscle and brachial plexus. Reaching deep surface of trapezius muscle, it divides into superficial and deep branches.
Suprascapular artery passes laterally, in a slightly downward direction across the lowest part of posterior triangle, and ends up posterior to the clavicle.
Label
- Splenius capitis muscle
- Levator scapulae muscle
- Posterior scalene muscle
- Trapezius muscle
- Acromion of scapula
- Inferior belly of omohyoid muscle
- Clavicle
- Middle scalene muscle
- Anterior scalene muscle
- Stenocleidomastoid muscle
Label
- Lesser occipital nerve
- Great auricular nerve
- Accessory nerve (XI)
- Supraclavicular nerves
- Transverse cervical nerve
Describe the lymph nodes of the head and neck
Components of lymphatic system of head and neck include:
- Superficial nodes around the head/skull;
- Superficial cervical nodes (easily palatable) along external jugular vein (content of roof of posterior triangle);
- Deep cervical nodes forming a chain along internal jugular vein.
Superficial Lymph Nodes (Head)
Drainage from the _occipital and mastoi_d nodes passes to the superficial cervical nodes along the external jugular vein.
Drainage from the pre-auricular and parotid nodes, the submandibular nodes, and the submental nodes passes to the deep cervical nodes.
Superficial Cervical Lymph Nodes
Superficial cervical nodes are along external jugular vein on superficial surface of sternocleidomastoid muscle, they drain into deep cervical nodes.
Deep Cervical Lymph Nodes
All lymph nodes around the head and neck eventually get drained to the deep cervical lymph nodes. This includ_e jugulodigastric_ (upper) and juguloomohyoid (lower) node.
From deep cervical nodes, lymphatic vessels form the right and left jugular trunks, which empty into the right lymphatic duct on right side, or the _thoracic duct o_n left side.
Describe the 2 ways of doing the Central Vein Catherterization
Central venous catheters are used widely for central venous pressure monitoring, the administration of irritant or chemotherapeutic agents into the central circulation, and for recurrent long-term venous access.
Central venous catheters are inserted via _the internal jugular vein, subclavian vein or their junctio_n.
- Venous catheterisation is not without risk and relations with the nearby pleura and major arteries (4-9%) mean that complications due to a misplaced needle can be life threatening. These include pneumothorax and arterial puncture, leading to haemorrhage or haemothorax.
- As the subclavian vein passes inferiorly, posterior to the clavicle, it passes over the apex of the lung. Any misplacement of a needle into or through this structure may puncture the apical pleura, producing pneumothorax. Inadvertent arterial puncture and vein laceration may also produce a hemopneumothorax.
- A puncture of the internal jugular vein carries fewer risks, but local hematoma and damage to the carotid artery are again important complications.
- The risk of complications increases with the number of attempts at catheterisation, therefore it is important to increase the likelihood of successful catheterisation. Ultrasound guidance (with a sound anatomical understanding of the structures you would expect to see) is a useful adjunct, but it is not always available.
Regardless of this, knowledge of relevant surface anatomy is important in planning the approach.
- In the commonly used posterior approach, the patient is placed in the trendelenburg position with contralateral rotation of the head to dilate internal jugular vein (IJV).
- The point at which the vein crosses the posterior border of sternocleidomastoid is a key landmark in this approach.
Describe the study looking at better ways of undergoing Lymph node biopsy in the posterior triangle so we reduce the risk of Spinal Accessory Nerve Injury
Aim: using ultrasound to avoid SAD
Results:
- Accessory nerve passed deep to both sternocleidomastoid heads in 1/3 of the cases and passed deep to sternal head and superficial to the clavicular head in 2/3 of the cases.
- Straight in 56% of cases and Tortuous in 44% of cases
Discussion
- SAN consistently and reliably visualised using ultrasound
- SAN has extremely variable anatomy
- Surface landmarks are not reliable
- Limitations: only 1 sonographer and only used healthy subjects
An elderly man with cervical lymphadenopathy in the posterior triangle has had his lymph node removed.
What are the possible lymph node biopsy- related injuries? (lymph node was at middle of posterior triangle
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Accessory nerve (just under the skin)
- Ask patient to shrug shoulder to check/fully abduct the arm
- May damage superficial branch of transverse cervical artery
- Patient has an enlarged neck, needs drainage
- Cutaneous and great auricular nerve also at risk
Decribe the levels of lymph node levels
Superficial and deep nodes
- Level 1a: floor of mouth, anterior tongue, lower lip, anterior alveolar ridge of mandible
- Level 1b: oral cavity, nasal cavity, submandibular gland, soft tissue of midface
- Level 2a: oral cavity, nasal cavity, nasopharynx, oropharynx, hypopharynx, larynx and parotid
- Level 2b: as above but less likely from larynx and hypopharynx
- Level 3: oral cavity, nasopharynx, oropharynx, hypopharynx and larynx
- Level 4: hypopharynx, larynx, thyroid and cervical oesophagus
- Level 5: nasopharynx, oropharynx and skin
- Level 6: thyroid, pyriform sinus, subglottic larynx, cervical oesophagus and cervical trachea
What are the different types of neck incisions?
