← All decks
General Surgery
Neck General
Built from Skandalakis' Surgical Anatomy: The Embryologic and Anatomic Basis of Modern Surgery
What’s inside
15 sections · 197 slides
Overview
- Neck is a corridor: pharyngeal derivatives, great vessels, airway and gut all pass through it. Covered here: embryogenesis, surface anatomy, triangles, fasciae and spaces. Then vessels, lymphatics, neck masses and the nerves crossing the region. Organ-specific detail (thyroid, parathyroid, salivary glands) sits in its own chapters. Emphasis throughout is the plane the surgeon actually cuts through.
Embryogenesis of the Neck
- The adult neck does not exist as a region in the embryo. Its embryogenesis is that of the organs it contains: pharynx and derivatives, thyroid, parathyroid, thymus. Thymus is also counted as part of the superior mediastinum. Vessels running head to thorax are elongated and modified during development. Pharynx elongates at 5 weeks; the oesophagus elongates later. After the diaphragm descends, these structures separate head from the relatively large heart.
- By 7 weeks a neck is visible externally. Fifth week: prominent branchial arches mark the future site of the neck. Seventh week: arches are reduced and a constriction appears between head and thorax. Twelfth week onward: the true neck is present. Further differentiation and migration is described with each specific organ.
- Development of the neck at five, seven and twelve weeks
- Embryonic pharynx = a lateral branchial apparatus on each side plus an unpaired ventral floor. Each lateral apparatus: endodermal pouches, ectodermal clefts, mesodermal arches, branchial membranes. Branchial membranes (closing plates) are the bridges between arches, formed by ectoderm and endoderm. Four arches begin forming in the fourth and fifth weeks. Externally each side is marked by four ectodermal branchial (pharyngeal) clefts. Pouches develop internally at the same time and characteristically do not communicate with the clefts.
- Tissue components of the lateral branchial apparatus
- Human branchial apparatus in dorsal, lateral, facial and sectional views
- Branchial grooves, arches, pouches and closing plates
- Fistulas, external and internal sinuses and cysts follow failed obliteration of clefts and pouches. Thymic and parathyroid deficiency, e.g. DiGeorge syndrome, follows partial or total agenesis of both glands. Neck hygromas are congenital malformations of the cervical lymphatic system. Gidvani and Bhowmick: cystic hygromas are common congenital neck masses appearing early in life. They tend to develop in the left posterior triangle. The same authors reported a posterior cervical midline cystic hygroma.
Historical Landmarks
- The chapter tabulates the anatomic and surgical history of the neck and its organs. It spans the neck, thyroid, parathyroids, trachea and salivary glands. Entries run from ancient Egypt, India and China to twentieth century neck dissection. Use it to place eponyms you already meet daily: Kocher, Crile, Halsted, Frey, Delphian. The table follows on the next slides in full.
- Anatomic and Surgical History of the Neck, Thyroid, Parathyroids, Trachea, and Salivary Glands
- Anatomic and Surgical History of the Neck, Thyroid, Parathyroids, Trachea, and Salivary Glands (continued)
- Anatomic and Surgical History of the Neck, Thyroid, Parathyroids, Trachea, and Salivary Glands (continued)
- Anatomic and Surgical History of the Neck, Thyroid, Parathyroids, Trachea, and Salivary Glands (continued)
- Anatomic and Surgical History of the Neck, Thyroid, Parathyroids, Trachea, and Salivary Glands (continued)
- Anatomic and Surgical History of the Neck, Thyroid, Parathyroids, Trachea, and Salivary Glands (continued)
- Anatomic and Surgical History of the Neck, Thyroid, Parathyroids, Trachea, and Salivary Glands (continued)
- Anatomic and Surgical History of the Neck, Thyroid, Parathyroids, Trachea, and Salivary Glands (continued)
- Anatomic and Surgical History of the Neck, Thyroid, Parathyroids, Trachea, and Salivary Glands (continued)
- Anatomic and Surgical History of the Neck, Thyroid, Parathyroids, Trachea, and Salivary Glands (continued)
- Anatomic and Surgical History of the Neck, Thyroid, Parathyroids, Trachea, and Salivary Glands (continued)
- Anatomic and Surgical History of the Neck, Thyroid, Parathyroids, Trachea, and Salivary Glands (continued)
- Anatomic and Surgical History of the Neck, Thyroid, Parathyroids, Trachea, and Salivary Glands (continued)
- Anatomic and Surgical History of the Neck, Thyroid, Parathyroids, Trachea, and Salivary Glands (continued)
- Anatomic and Surgical History of the Neck, Thyroid, Parathyroids, Trachea, and Salivary Glands (continued)
- Anatomic and Surgical History of the Neck, Thyroid, Parathyroids, Trachea, and Salivary Glands (continued)
Surface Anatomy and Incisions
- Third cervical vertebra lies at the level of the hyoid bone. Fourth and fifth cervical vertebrae lie at the level of the thyroid cartilage. The common carotid bifurcates at C4, at the upper level of the thyroid cartilage. The sixth cervical vertebra is the level of the middle cervical sympathetic ganglion and cricoid cartilage. The thoracic duct crosses behind the great vessels at the level of C7.
- Vertebral levels of the hyoid bone and thyroid cartilage
- Sixth cervical vertebra
- Seventh cervical vertebra
- The surgeon chooses incision and placement in relation to the underlying pathology. Dermal connective tissue orientation creates skin tension lines: the lines of Langer. Langer's lines correspond to the skin creases of the body. Transverse incisions are generally cosmetically superior to vertical ones. Crossing normal skin lines produces a more prominent scar. Vertical incisions give excellent exposure for arterial surgery.
- Use a superiorly based apron flap for neck dissection. Close the edges of the divided platysma carefully. Reapproximate the skin margins meticulously. Tension on skin is what produces the unsightly scar. Combinations of vertical and transverse incisions may be used when exposure demands it.
- Placement of neck incisions along the normal skin creases
- Incisions used for classic radical neck dissection
Penetrating Neck Injury
- Roon and Christensen's classification is still used, now expressed as zones. Zone I is the area they called low; zone II middle; zone III high. The zone I / II junction is described at the cricoid cartilage or at the top of the clavicles. Zone I injury carries the greater potential for intrathoracic great vessel injury. Zone III injuries reach towards the skull base.
- Zones of the neck
- Roon and Christensen noted that either high or low injuries can involve vessels where control is difficult. They advised immediate exploration. Biffl et al.: selective management of penetrating neck injury is safe. Selective management does not require routine diagnostic testing for asymptomatic zone II and III injuries. Demetriades et al.: physical examination and colour-flow Doppler are the diagnostic tools of choice.
- Bumpous et al.: zone II of the anterior neck was the most commonly injured area. Most commonly injured structures: trachea 69%, oesophagus 38%, larynx 31%. 31% underwent angiography but only 13% showed vascular injury. 81% had injury to more than one major structure of the neck. Neck exploration in 81%, tracheostomy in 75%. Long-term sequelae include dysphagia, hoarseness and prolonged tracheostomy.
- Algorithm for evaluation of penetrating neck injuries
- Penetrating neck injury management guideline
The Anterior Cervical Triangle
- The topography of the neck is described as a series of natural triangles. First division: anterior and posterior cervical triangles. Each is then divided into smaller triangular regions. The anterior triangle subdivides into submandibular, carotid, muscular and submental triangles. The dividing muscles are the digastric and the omohyoid.
- Subdivisions of the anterior triangle of the neck
- Demarcated by the inferior border of the mandible above. Bounded below by the anterior and posterior bellies of the digastric muscle. Largest structure and usual object of surgery: the submandibular salivary gland. The gland develops from oral ectoderm near the end of the sixth week, slightly later than the parotid. It forms as a solid primordium and canalises later. Severe gland inflammation can destroy all traces of normal anatomy.
- Anomalous digastric muscle with accessory bellies
- The four surgical planes of the submandibular triangle
- Composed of skin and superficial fascia enclosing the platysma and fat. Beneath lies the mandibular and cervical branches of the facial nerve (VII). Both arise from the cervicofacial division of the facial nerve. The cervicofacial division passes lateral to the retromandibular vein within the parotid in over 90%. In the remainder it passes medial to the vein. Landmark line: intertragic notch to the midpoint between mandibular angle and lowest part of the ear.
- First surgical plane of the submandibular triangle
- Nomenclature and topography of facial nerve branches are confusing and variable. The mandibular (marginal mandibular) nerve is usually the first branch of the cervicofacial division. In all individuals it crosses superficial to the facial vein within 2 cm below the angular notch. The facial vessels can be palpated at that point. It then ascends towards the angle of the lips. Anterior to the facial artery it crosses the lower border of the mandible.
- The curved course of these nerves gives the term neural hammocks. The mandibular nerve forms the first hammock of the triangle. Skandalakis et al. saw a hammock hanging so low that a high transverse incision would have severed it. The mandibular branch always passes posterior to the angle of the mandible. It lies between platysma and the deep cervical fascia and supplies quadratus labii inferioris. The cervical branch divides into descending and anterior branches.
- The descending branch innervates platysma. It communicates with the transverse cervical (C2, C3) and great auricular (C2, C3) cutaneous nerves. The anterior branch is the ramus coli mandibularis. It crosses the mandible superficial to the facial artery and vein. It joins the mandibular branch to help innervate the muscles of the lower lip. This anterior branch forms the second neural hammock and is frequently confused with the first.
- Neural hammocks of the mandibular and cervical branches of the facial nerve
- Injury to the mandibular branch gives very slight drooping of the corner of the mouth. Drooping is not noticeable at rest, only on movement such as smiling. It may be neuropraxia or permanent depending on the nature of the injury. Orbicularis oris and buccal-innervated muscles actually raise the commissure on the affected side. Injury to the anterior cervical branch produces minimal drooling. That drooling disappears in 4 to 6 months.
- Skandalakis et al. measured the two hammocks in 40 cadavers (80 cervicofacial dissections). In 50% of specimens the mandibular branch lay above the mandibular border, outside the triangle. Dingman and Grabb found the branch above the border in 81% of specimens. In Chinese adults the marginal mandibular branch ran above the lower border in 67%. This suggests ethnic variation in the topography of the branches. An incision at least 4 cm below the mandibular border spares even an exceptionally low branch.
- From superficial to deep: facial (anterior facial) vein, then retromandibular (posterior facial) vein. Then part of the facial (external maxillary) artery and its submental branch. Then the superficial layer of submaxillary (deep cervical) fascia. Then the lymph nodes, then the deep layer of submaxillary fascia. Deepest in this plane: the hypoglossal nerve (XII).
- Second surgical plane of the submandibular triangle
- The retromandibular vein is formed by union of the superficial temporal and maxillary veins. It divides near the angle of the mandible into anterior and posterior divisions. Posterior division joins the posterior auricular vein to form the external jugular vein. Anterior division joins the facial vein to form the common facial vein. The common facial vein empties into the internal jugular near the greater cornu of the hyoid. Identify, isolate, clamp and ligate both the facial vein and the anterior retromandibular division.
- The facial artery pierces the stylomandibular ligament. The ligament runs from the styloid process to the angle of the mandible. It may extend to the stylohyoid muscle and the posterior belly of the digastric. It is a thickened part of the deep layer of the parotid fascial capsule and separates parotid from submandibular gland. Ligate the artery before cutting it, to prevent bleeding after retraction. The facial artery enters the triangle deep to the posterior belly of digastric and stylohyoid.
- Submandibular lymph nodes lie within the envelope of the submandibular fascia. They lie in close relationship with the gland itself. Nodes also occur along the facial vessels. This is important in treating metastatic skin cancers. Differentiation between gland tissue and lymph nodes may be difficult. The facial artery crosses the gland posteriorly, passes over the mandible and always lies under platysma.
- From superficial to deep: mylohyoid muscle with its nerve. Then the hyoglossus muscle. Then the middle constrictor covering the lower part of the superior constrictor. Then part of the styloglossus muscle. These four muscles form the muscular floor of the triangle.
- Third surgical plane of the submandibular triangle
- DuPlessis: the mylohyoid muscles form a true diaphragm for the floor of the mouth. Above it lie the geniohyoid and the muscles of the tongue. Below it lie the anterior bellies of digastric and much of the submandibular gland. It arises from the mylohyoid line on the inner surface of the mandible. Posterior fibres insert on the body of the hyoid; anterior fibres into the midline raphe. Its superior surface relates to the lingual and hypoglossal nerves.
- Sehirli and Cavdar reported an accessory mylohyoid between the anterior digastric and normal mylohyoid. The hyoglossus is thin and quadrilateral, arising from the greater horn and body of the hyoid. It ascends into the side of the tongue between styloglossus laterally and inferior longitudinal muscle. The hypoglossal nerve and its venae comitantes enter over the posterior edge of mylohyoid, lateral to hyoglossus. The lingual artery passes deep to hyoglossus. It enters the floor of the mouth between hyoglossus laterally and genioglossus medially.
- The nerve to mylohyoid also supplies the anterior belly of digastric. It arises from the inferior alveolar branch of the mandibular division of the trigeminal nerve. It lies on the inferior surface of mylohyoid, between it and the digastric. Middle constrictor arises between the lesser and greater horns of the hyoid and from the stylohyoid ligament. It inserts into the median raphe, its highest fibres overlapping the superior constrictor. Styloglossus arises from the styloid process and stylomandibular ligament, inserting into the side of the tongue.
- Sublingual and submaxillary spaces lie above and below mylohyoid and are continuous at its posterior border. Both are involved in the diffuse cellulitis of Ludwig's angina. It commonly follows infection of the lower molar teeth. Streptococcus hemolyticus is the most common organism. The space is bounded tightly by fascia attached to mandible, hyoid, floor of mouth mucosa and digastric. Oedema and the swollen, displaced tongue can cause asphyxiation.
- Spread of submandibular space infection
- Contains the deep portion of the submandibular gland. Also the submandibular (Wharton's) duct and the lingual nerve. Also the sublingual vein, the sublingual gland and the hypoglossal nerve (XII). And the submandibular ganglion. The uncinate part of the gland rounds the posterior border of mylohyoid. The duct arises there and ends at the sublingual caruncle beside the frenulum.
- The submandibular duct lies below the lingual nerve, except where the nerve passes under it. It lies above the hypoglossal nerve. The lingual nerve therefore crosses the duct. The duct passes through the floor of the mouth to the sublingual caruncle. Order at this depth from above down: lingual nerve, duct, hypoglossal nerve.
- Fourth surgical plane of the submandibular triangle
- Submandibular nodes receive afferents from submental nodes, oral cavity and anterior face. Efferents drain mainly to jugulodigastric, jugulocarotid and juguloomohyoid nodes. These belong to the deep cervical chain along the internal jugular vein. A few channels pass via subparotid nodes to the spinal accessory chain. In radical neck dissection the triangle is cleared by removing the gland with its envelope and nodes. The capsule and all surrounding tissue are taken as well.
- The submental triangle contains lymph nodes. Its contents should be sacrificed in radical neck dissection. Its nodes receive lymph from the skin of the chin and the lower lip. Also from the floor of the mouth and the tip of the tongue. They send lymph to the submandibular and jugular chains of nodes.
- Protection of nerves and vessels and removal of lymphatic tissue is essential in this triangle. The posterior belly of digastric lies between the submandibular and carotid triangles. It is a reliable landmark in a dangerous area. Named structures lie deep to the posterior belly. Lymph is received by jugulodigastric, jugulocarotid and juguloomohyoid nodes. It also arrives from submandibular, submental, deep parotid and posterior deep cervical nodes.
- Contains the thyroid and parathyroid glands, trachea, oesophagus and sympathetic nerve trunk. Beahrs considered this triangle the least important. Strap muscles may occasionally be cut to facilitate thyroid surgery. Cut them across the upper third of their length. This avoids sacrificing their nerve supply. Lymphatic drainage of this triangle is described with the thyroid gland.
The Posterior Cervical Triangle
- Sometimes considered as two triangles, occipital and subclavian. They are divided by the posterior (inferior) belly of the omohyoid muscle. The chapter treats the posterior triangle as one entity. Between investing and prevertebral fascia lie the accessory nerve (XI) and part of the external jugular vein. Variably deeper: subclavian artery and vein, cervical nerves, brachial plexus. Also phrenic nerve, accessory phrenic nerve, spinal accessory nerve and lymph nodes.
- The posterior triangle of the neck
- Floor of the posterior triangle
- Superficial occipital nodes receive lymph from the occipital scalp and the back of the neck. Efferents pass to a deep occipital node, occasionally to more than one. That node drains into deep cervical nodes along the spinal accessory nerve. The chapter lists separate surgical points for the upper (occipital) part. And separate points for the lower (subclavian) part. The two parts differ in the structures at risk.
Surgical Applications of the Triangles
- The carotid sinus acts as a baroreceptor. It responds reflexively to changes in arterial pressure. Elevation of pressure or compression of the sinus can slow the heart rate. It can cause a sudden fall in arterial pressure. This may produce cerebral ischaemia. The result is ipsilateral and secondary syncope.
- A tiny bilateral lobular structure, 2 to 7 mm in size. Located at the carotid bifurcation or on the posteromedial side of the common carotid artery. May be partially embedded in the carotid adventitia, from which it developed embryologically. Composed of a fibrous capsule with septae dividing it into lobules. Lobules contain epithelioid glomus cells, supporting cells and sinusoids. Tumours of the carotid body present serious surgical problems, particularly haemorrhage.
- It is a chemoreceptor sensitive to low oxygen levels. Also to high carbon dioxide levels and to hydrogen ion concentration. It responds by reflexively increasing respiratory ventilation. It acts via its connections with the brainstem. Nerve supply is derived principally from the glossopharyngeal nerve. It also seems to receive fibres from the vagus.
- Carotid sinus, carotid body and their innervation
- The accessory nerve may lie medial or lateral to the internal jugular vein. Which one depends on how far cranially in the neck it is identified. Crossing occurs dorsally in 44% and ventrally in 56% of cases. Within sternocleidomastoid the nerve takes an S-shaped three-dimensional course, not a straight one. Following it blindly through the muscle would cut its communicating branches with the cervical plexus. Cervical plexus branches to trapezius are always subfascial.
- The accessory nerve is easily confused with the minor occipital nerve. The minor occipital nerve sometimes turns upward just medial to the anterior border of trapezius. The supposed accessory nerve must be followed to the anterior border of trapezius to confirm it. It must keep its craniocaudal direction. Most reliable measurement: at the posterior border of sternocleidomastoid, measured from the clavicle. Great auricular nerve and sternocleidomastoid itself show much more variability as landmarks.
- Supraclavicular, infraclavicular and jugular fossae
- Kline et al.: the surgeon palpates the rounded anterior border of scalenus anticus through fat and lymphoid tissue. This is an important clue; the novice tends to operate too far laterally and superiorly. Operating too far laterally misses the brachial plexus altogether. The surgeon can clear down to the anterior border of scalenus anticus with dispatch. The phrenic nerve is deep to the prevertebral fascia at this point. Divide scalenus anticus only after the phrenic is dissected free and the subclavian artery is seen to be free behind it.
- The phrenic nerve enters the thoracic cavity anterior to the internal thoracic artery. It passes anterior to the pulmonary hilum. It runs between the mediastinal pleura and the pericardium. The pericardiophrenic vessels are fellow travellers of the phrenic nerve. In the neck it lies on the anterior scalene, deep to the prevertebral fascia.
- Harry et al.: the plexus lay between anterior and middle scalene in only 60% of cases. The commonly described relationship is therefore not the rule in four cases out of ten. The subclavian artery may pierce the belly of the anterior scalene. The C5 and C6 roots may pierce the anterior scalene belly. Such variation alters the anatomy on which scalenotomy and plexus blocks rely.
- Compression of the subclavian artery and brachial plexus
- Variations between the scalene muscles and the brachial plexus
- Thoracic outlet syndrome actually refers to compression at the upper opening, the inlet or superior aperture. The word outlet is arguably incorrect, since the lower thoracic opening is the true outlet. Boundaries of the thoracic inlet: posterior, first thoracic vertebral body. Anterior, superior border of the manubrium of the sternum. Lateral, the first rib. Obuchowski and Ortiz: the inlet is best regarded as a zone, subdivided on MRI into visceral, neurovascular, pulmonary and spinal.
- The subclavian vein crosses the first rib ventral to the anterior scalene. There it is closely associated with, and often compressed by, the subclavius muscle. This can produce spontaneous or effort-related axillary and subclavian venous thrombosis. That is Paget-von Schroetter syndrome, unrelated to intercurrent illness or iatrogenic manipulation. Treatment: thrombolysis with anticoagulation, resection of the first rib and balloon angioplasty. Post-stenotic dilatation of the subclavian artery can harbour thrombi.
- Thrombi discharged distally from a post-stenotic subclavian dilatation produce confusing symptoms. Those symptoms can mimic carpal tunnel entrapment of the median nerve. Sanders and Pearce: 86% of thoracic outlet syndrome patients had a history of cervical trauma. Whiplash injury was the notable mechanism. In such individuals scalenectomy is preferable to resection of the first rib.
- Accessory scalene muscles, fascial bands or an atypical 7th cervical rib can compress artery, nerves or both. This produces scalenus anticus syndrome with pain, paraesthesia or weakened pulses. The 7th cervical rib forms in development then normally regresses to its transverse process. Makhoul and Machleder: in 390 transaxillary first rib resections, 66% of 175 patients had developmental variations. 86 scalene and 39 subclavius muscles were atypical; 20 scalene muscles were supernumerary; 17 ribs abnormal. A cervical rib is found in about 1% of cases and about 67% are bilateral.
- A cervical rib often indicates a variation in the scalene muscles or in the brachial plexus. In such cases the first thoracic nerve had little input, replaced by a major contribution from C4. When the C7 rib was incomplete, the regressed part was often replaced by a fibrous band. Machleder et al.: anterior scalene fibres show morphologic transformation in thoracic outlet syndrome. Fibres change from fast-twitch type 2 to hypertrophied slow-twitch type 1. These changes occur predominantly in young individuals in response to exercise.
- Frequently associated with thrombosis of the axillary-subclavian vein from exertion. Hence the phrase effort vein thrombosis. It develops as an abrupt swelling of the upper extremity. Makhoul and Machleder: 55% had hypertrophy of the subclavius tendon. The same patients had enlargement of the insertion tubercle. Flye: even with early medical treatment, complete resolution occurs in only 15% to 30% of patients.
Fasciae and Spaces of the Neck
- Lies beneath the skin. Composed of loose connective tissue, fat and the platysma muscle. Also contains cutaneous branches of the cervical plexus and the cervicofacial division of VII. And small cutaneous blood vessels. Cutaneous nerves and the anterior and external jugular veins lie between platysma and deep cervical fascia. For practical purposes there is no space between this layer and the deep fascia.
- Superficial fascia and its contents
- Attaches above to the occipital and temporal bones and the mandible. Attaches posteriorly to the cervical spines and supraspinous ligaments. Attaches below to the clavicle, scapula and manubrium of the sternum. Envelops two muscles: trapezius and sternocleidomastoid. Envelops two glands: parotid and submandibular. Forms two spaces, supraclavicular and suprasternal, and roofs both cervical triangles.
- Described either as investing the strap muscles anteriorly, merging with the investing layer. Or as a lamina passing deep to the strap muscles and uniting with the investing layer lateral to them. A posterior layer envelops the thyroid gland, forming the false capsule. This layer is fixed to the thyroid and cricoid cartilages above. Anteriorly it attaches above to the hyoid and below to the fibrous pericardium. Laterally it contributes to the carotid sheath.
- Posteriorly the middle cervical fascia becomes ill-defined. This permits an enlarging thyroid gland to extend posteriorly. This posterior portion is the visceral part of the layer. It is continuous with the buccopharyngeal and oesophageal fasciae (Grodinsky and Holyoke). Because of that continuity, some prefer the name visceral layer to pretracheal layer. It terminates inferiorly near the tracheal bifurcation, blending with the alar prevertebral fascia.
- Layers of the deep cervical fascia below the hyoid bone
- Ligament of Berry, the anchor of the thyroid gland
- Lies in front of the prevertebral muscles. Originates from the spinous processes and ligamentum nuchae posteriorly. Covers the cervical spine muscles including the scalenes, and the vertebral column anteriorly. At its attachment to the cervical transverse processes it divides. This creates a space in front of the vertebral bodies. The anterior leaf is the alar fascia; the posterior leaf keeps the name prevertebral fascia.
- Fascial layers and spaces above the hyoid bone
- Fascial layers of the neck in cross section
- Chief fascial layers below the hyoid bone in longitudinal section
- Formed by three fasciae: investing, pretracheal and prevertebral. Together these form a fascial tube beneath sternocleidomastoid. Contents: common carotid artery, internal jugular vein, vagus nerve and deep cervical lymph nodes. In the upper neck the sheath blends with the fascia of stylohyoid and posterior belly of digastric. Higher still it becomes adherent to the adventitia of the vessels. Inferiorly it is adherent to the sternum and clavicle and fused posteriorly with the first rib and Sibson's fascia.
- Behind the sheath the prevertebral fascia covers the scalene muscles and the phrenic nerve. The prevertebral fascia provides origin for the axillary sheath. In the root of the neck the visceral fascia passes on to the alar fascia of the carotid sheath. It continues into the thorax to the fibrous pericardium of the heart and great vessels. As the sheath enters the thorax its connective tissue separately encloses each structure as they diverge. This continuity is a direct route from neck to mediastinum.
- The potential danger space of Grodinsky and Holyoke lies between the alar and deep muscular prevertebral fascia. It provides a plane for the spread of fluids or pathologic processes. That plane runs from the base of the skull to the thoracic diaphragm. It is continuous, without interruption, above and below the hyoid bone. Under normal circumstances it is a potential rather than an actual space. It is the reason a neck abscess can become a posterior mediastinal one.
- Continuous below with the visceral fascial covering of the oesophagus. Superiorly it covers the posterior and lateral surfaces of the pharynx. It continues forward over the external surface of the buccinator muscle. It is joined loosely by delicate areolar tissue to the alar layer of prevertebral fascia. The interval between them is the retropharyngeal space, from skull base to the upper thorax. It can be infected by descending infection, oesophageal perforation, or infected deep cervical nodes.
- Relations of the superficial fascia to the parotid gland
- Contents: larynx, trachea, thyroid, parathyroid glands and part of the oesophagus. The lower part is subdivided into anterior pretracheal and posterior retrovisceral spaces. The two are separated by lateral attachments of the oesophagus to the prevertebral fascia. The spaces are confluent above. These spaces, with the carotid sheath, are the chief pathways of infection. Pearse: mediastinal spread was retrovisceral in 71%, carotid sheath 21%, pretracheal 8%.
- Two views of the visceral compartment of the neck
- Chronic and acute retropharyngeal abscess
- Formed by a splitting of the superficial investing layer of the deep cervical fascia. The anterior lamina attaches to the anterior surface of the sternum. The posterior lamina attaches to the posterior aspect of the manubrium. Within it lie the lower ends of the anterior jugular veins. Also an interconnecting venous arch between them. Some lymphatic and fatty tissue is often present as well.
Vascular Supply of the Neck
- The neck is supplied by the common carotid arteries. The right common carotid arises from the bifurcation of the brachiocephalic trunk. The left common carotid arises directly from the aortic arch. The artery is divided arbitrarily into inferior, middle and superior parts. The inferior part is behind the sternoclavicular joint on the right, and intrathoracic on the left. The superior part bifurcates into internal and external carotid arteries.
- Both common carotid arteries seen from behind
- In most cases the common carotid has no branches in the neck. The superior thyroid artery is often seen arising from the superior part, just below the bifurcation. That is the most common location of the carotid body. At the sternoclavicular level the two arteries are 2.5 to 3.5 cm apart, separated by the trachea. From that point each has a length of 8 to 12 cm. They terminate at C4, at the superior level of the thyroid cartilage.
- The surface marking runs from the sternoclavicular joint to the neck of the mandible posteriorly. The larynx separates the two arteries by 5.5 to 6.5 cm. In the muscular triangle a hypertrophic thyroid gland covers the artery. The middle thyroid vein crosses anterior to the artery there. To expose it: incise platysma and investing fascia, retract sternocleidomastoid medially, incise the strap muscles and their fasciae. In the carotid triangle, above omohyoid, the superior thyroid artery and vein cross the carotid.
- At the right sternoclavicular joint the common carotid is medial to the internal jugular vein. The left carotid lies behind the internal jugular vein. The thoracic duct is dorsal to the artery on the left. The right recurrent laryngeal nerve crosses the dorsal side of the first part of the right common carotid. The artery has important anterior, posterior and medial relations in the carotid triangle. Variations of the great arteries of the carotid triangle were studied by Lucev et al.
- Common carotid artery with internal and external carotid arteries
- After ligation, collateral circulation is carried on chiefly by named channels described by Montgomery. There are communications between the two sides of the body. There are also longitudinal anastomoses along each side. These channels determine whether ligation is tolerated. The figure shows cross-communications on the right and longitudinal anastomoses on the left.
- Collateral channels after ligation of the common carotid artery
- Located within the carotid triangle. Lies under and deep to the stylohyoid muscle and the posterior belly of digastric. Gives no branches in the neck, as its supply is limited to intracranial structures. It is crossed laterally by the hypoglossal nerve. Cole and May reported an aberrant internal carotid artery as a middle ear abnormality; 45 cases collected. Papon et al. described anastomoses between internal carotid and vertebral arteries in the neck.
- Meder et al. reported six cases of segmental agenesis of the internal carotid artery. Carsten et al. recommended Doppler screening to detect asymptomatic carotid stenosis. Kuehne et al.: outcome after internal carotid injury is improved by a defined algorithm. That algorithm uses liberal angiography, a predefined surgical approach and selective observation. Those authors do not advocate ligation of the internal carotid artery. They were able to repair the majority of injuries using standard techniques.
- Begins at the bifurcation of the common carotid at C4. Ends posterior to the neck of the mandible, about 1.5 cm below the zygomatic arch. There it divides into the maxillary and superficial temporal arteries. Superior thyroid, lingual and facial arteries arise from its ventral aspect near the origin. Ascending pharyngeal, occipital and posterior auricular branches arise from its dorsal side. Eight variable branches in all, including the two terminal arteries.
- Internal and external carotid arteries
- The hypoglossal nerve passes lateral and anterior to the external carotid just above the hyoid. The external carotid is superficial, somewhat anterior and medial to the internal carotid. Several anatomic entities intervene between the internal and external carotid arteries. Anatomy of individual branches is described with the related organs. Marien and Thompson reported an occipital artery arising from the cervical internal carotid artery. Normally the occipital artery arises from the posterior wall of the external carotid.
- Embryology, anatomy, physiology and pathology of the carotid body
- Ligation guidelines
- Ballotta et al.: cranial and cervical nerve injury after carotid endarterectomy is a common complication. It may be major or minor. Guterman et al.: endarterectomy for revascularisation of the cervical bifurcation is a good alternative to open surgery. That applies to patients at risk of excessive morbidity and mortality. Kuehne's algorithm relies on liberal angiography and selective observation. Repair, not ligation, is advocated for the internal carotid artery.
Veins of the Neck
- The principal vein of the head and neck. It is the downward continuation of the sigmoid sinus. It exits the skull through the jugular foramen with cranial nerves IX, X and XI. Up to the superior border of the thyroid cartilage it lies lateral to the internal carotid artery. Below that it lies lateral to the common carotid within the carotid sheath. Close to its termination it lies anterior to the artery, under sternocleidomastoid.
- Internal jugular vein
- Passes obliquely and superficial to sternocleidomastoid, deep to platysma. Begins near the angle of the mandible. Formed by the junction of the posterior division of the retromandibular vein with the posterior auricular vein. Receives transverse cervical and suprascapular veins in the neck. Usually ends by piercing the investing layer of deep fascia to join the subclavian vein. It may instead terminate in the internal jugular vein.
- Erb's point is where the external jugular crosses the posterior border of sternocleidomastoid. Here the vein is closely related to several cervical cutaneous nerves. The great auricular and transverse cutaneous nerves are particularly important. They supply the lower ear and the lower face near the angle of the mandible. This is also the site of exit of cranial nerve XI. The external jugular may be ligated with impunity if the internal jugular vein is intact.
Lymphatic Structures of the Neck
- Bailey and Love: about 800 lymph nodes in the body, 300 of them in the neck. Gray's Anatomy: only 400 to 450 nodes in the adult body, with 60 to 70 in the head and neck. Carlson estimated the total could be approximately 150 to 300. Many first echelon nodes of the oral cavity and oropharynx are never surgically removed. Drinker and Yoffey: all lymphoid tissue is nearly 1% of total body weight. That is a mass about half the weight of the liver.
- Surgically the nodes are divided into five groups or levels. There is no widespread agreement on nomenclature; the chapter prefers Healey's system. Level I: all nodes within the submental and submandibular triangles. That is between the anterior midline and the anterior border of the posterior belly of digastric. Level II: all deep jugular nodes in the upper third of the neck. Its lower limit follows the great auricular nerve crossing sternocleidomastoid; jugulodigastric node belongs here.
- Level III, midjugular chain: bounded below by the anterior belly of omohyoid. Bounded posteriorly by the middle third of the posterior border of sternocleidomastoid, and medially by the hyoid. Level IV, lower jugular chain: bounded by the lower third of sternocleidomastoid posteriorly. Bounded superiorly by omohyoid and inferiorly by the clavicle; contains juguloomohyoid and deep lower jugular nodes. Level V is the posterior triangle, including spinal accessory, inferior horizontal chain and scalene nodes. Kraus et al. reported a small incidence of supraspinal node metastasis in node-negative oral and oropharyngeal cancer.
- Cervical lymph node chains in Healey's classification
- Drainage into the intermediate vertical (jugular) chain
- The table lists each named node group with its location. It gives what each group receives lymph from, and where it sends lymph to. The groups are arranged as superior horizontal, vertical and inferior horizontal chains. Anterior visceral nodes are listed separately. Use it to work backwards from an enlarged node to a probable primary site.
- Lymph Nodes and the Lymphatic Drainage of the Head and Neck
- Lymph Nodes and the Lymphatic Drainage of the Head and Neck (continued)
- Lymph Nodes and the Lymphatic Drainage of the Head and Neck (continued)
- The opening between nasal and oral cavities and the pharynx is guarded by lymphoid structures. Collectively these are the ring of Waldeyer. Pharyngeal tonsil (adenoids) sits on the roof of the nasopharynx, at the superior aspect of the ring. Lingual tonsils lie at the inferior aspect, on the sides of the base of the tongue. Palatine tonsils laterally guard the entrance to the pharynx. A lateral band of superficial lymphoid nodules may lie between pharyngeal and palatine tonsils.
- Lymphoid structures of the tonsillar ring of Waldeyer
- Originates from the cisterna chyli and terminates in the left subclavian vein. It is 38 to 45 cm long. It arises at about the level of the 2nd lumbar vertebra. The cisterna is absent in about 50% of cases; the duct then arises from the lumbar and intestinal trunks. It ascends right of the midline, crossing between the 7th and 5th thoracic vertebrae to the left. It passes behind the great vessels at C7, ventral to the vertebral artery.
- It descends slightly as it passes behind the common carotid to enter the left subclavian vein. It enters at the junction with the left internal jugular vein. It may have multiple entrances; contributing trunks may enter the subclavian or jugular vein independently. It collects lymph from the whole body below the diaphragm and much of the left thorax. Injury in supraclavicular node dissection gives copious lymphorrhoea and loss of fluid, protein and electrolytes. It can be ligated with impunity; Wechselberger et al. used a sternocleidomastoid flap for chronic fistula.
- Thoracic duct and the main left lymphatic trunks
- A variable structure about 1 cm long. Formed by the right jugular, transverse cervical, internal mammary and mediastinal lymphatic trunks. If those trunks enter the veins separately there is no right lymphatic duct. When present it enters the superior surface of the right subclavian vein at the junction with the right IJV. It drains the right head, right upper limb, most of the right thorax and the lower two-thirds of the left lung. It is the remnant of the original bilaterally symmetric embryonic thoracic ducts.
- Formation of the right lymphatic duct
Masses in the Neck
- The neck is designed so that swelling of a normal structure or an abnormal one is readily apparent. Neoplasms and infections can affect any of the 60 to 70 nodes or the dozen-plus fascial spaces. Persistent embryonic structures may occupy spaces no longer available to them. Structures are packed so tightly that nearly every lesion expresses itself as a visible or palpable bulge. In most cases even a perfunctory physical examination will reveal the swelling.
- Skandalakis et al. examined 7,748 neck masses from 232,256 surgical admissions between 1954 and 1972. 3,625 were of thyroid origin, 46.8 percent. 4,123 were of nonthyroid origin, 53.2 percent. Rounding those figures produced two rules for diagnosing nonthyroid neck masses. The Rule of 80 is expressed as a series of 80 percent statements. The Rule of 7 gives a probable diagnosis from the average duration of the patient's symptoms.
- AIDS may have changed these numbers, as most such patients have several other node groups involved. Axillary and inguinal nodes are commonly involved as well. Both rules were based on hospitalised patients with cervical lymphadenopathy. Most such patients are now managed as outpatients, so the analysis could not be repeated today. The authors still consider both rules useful and worth remembering. Best diagnosis of primary or metastatic head and neck masses: complete clinical evaluation and biopsy.
- Lyles et al. and Feldman et al. found fine-needle aspiration reliable and safe in head and neck squamous carcinoma. Lee et al. studied metastatic squamous carcinoma of the neck with an occult primary. They advised thorough evaluation prior to surgery to locate the primary tumour. Surgery, irradiation or both can cure about 50% of patients with an unknown primary. Johns: low clonogenic efficiency below 0.005% was associated with good probability of survival. High cloning efficiency was associated with early recurrence or death from disease.
Nerves of the Neck
- Nerves travel a peculiar pathway from above downward, crossing the whole neck. Their anatomic destiny is to supply vessels of the head, intracranial area, neck and upper extremities. Five cranial nerves are involved: VII, IX, X, XI and XII. They are covered in detail with their related organs elsewhere in the book. Emphasis here is on the topography of the sympathetic ganglia and their branches. Sir William Turner: 'The sympathetic begins nowhere.'
- Lies in the prevertebral fascia. Sits between the carotid sheath in front and the longus colli and longus capitis muscles behind. Extends above into the skull as a plexus surrounding the internal carotid artery. Continues downward with the sympathetic trunk of the thorax. Formed by three ganglia: superior, middle and inferior. Each gives grey rami communicantes to cervical nerves, a cardiac nerve, and a plexus to an artery.
- The uppermost and largest of the three ganglia. A reddish, flat, ellipsoidal structure. Located just behind the sheath of the internal carotid artery. Rests on the prevertebral fascia at the level of the transverse processes of C2 and C3. Gives grey rami to cervical nerves 1 to 4, forms a plexus round the external carotid, gives a branch to the pharyngeal plexus. Gives origin to the superior cardiac nerve and the carotid nerve.
- The smallest of the three, about 3 mm in diameter. Located at the level of the 6th cervical vertebra and the cricoid cartilage. The inferior thyroid artery is an excellent landmark for its topography. The ganglion lies anterior or posterior to that artery. McGregor and DuPlessis considered it always present, and the chapter agrees. Gives grey rami to C5 and C6, a plexus round the inferior thyroid artery, and the middle cardiac nerve.
- Situated behind the vertebral artery. Lies between the transverse process of C7 and the neck of the 1st rib. Lies medial to the descending branch of the costocervical branch of the subclavian artery. Larger than the middle ganglion but smaller than the superior cervical ganglion. Gives grey rami to C7 and C8, a plexus round the subclavian artery, and the inferior cardiac nerve. The 1st thoracic and inferior cervical ganglia are often united as the stellate ganglion.
- The cervical sympathetic trunk
- Kline et al.: ansae or small rootlets enter and leave T1. These can lead the surgeon to the stellate ganglion and then to the caudal thoracic sympathetic chain. Another landmark is the vertebral artery. It is found originating from the proximal subclavian, running upward and medially toward the C6 transverse process. By elevating the proximal vertebral artery the stellate ganglion is usually found posterior to it. The rest of the chain lies inferior to it, beneath the subclavian vessels and in the upper mediastinum.
- Formed by the anterior divisions of spinal nerves C1 to C4. Located between the middle scalene muscle and the levator scapulae. It is covered by the sternocleidomastoid muscle. Its branches form two groups, superficial and deep. The superficial group is sensory, from C2, C3 and C4. The deep group is motor, from C1 to C4.
- Superficial and deep cervical plexuses
- Formed by the anterior primary divisions of C2, C3 and C4. Its physiologic destiny is sensory. All its nerves are seen near the middle of the posterior border of sternocleidomastoid. That point is where the superficial plexus exits. The great auricular and transverse cutaneous nerves supply the lower ear and lower face. The great auricular and transverse cervical nerves are both C2, C3.
- Superficial group of the cervical plexus
- The deep group is motor. It innervates the strap muscles of the neck. It also supplies the skin and the diaphragm. Its branches are formed by the anterior divisions of C1 to C4. It lies deep to sternocleidomastoid, on the muscular floor of the posterior triangle. The phrenic nerve is its most important branch surgically.
- Deep group of the cervical plexus
- Formed by the anterior divisions of the four lower cervical nerves, C5 to C8, with T1. Communications from C4 and T2 may also be present. Formed successively of roots, trunks, divisions, cords and terminal branches. It emerges between the anterior and middle scalene muscles and rests on the middle scalene. Roots and trunks lie in the neck, related to the subclavian artery. It lies in the posterior triangle, adjacent to clavicle, sternocleidomastoid and anterior scalene.
- As the nerves emerge they are ensheathed with the prevertebral fascia covering the scalene muscles. That connective tissue investment becomes the axillary sheath. The sheath can be injected with anaesthetic for procedures on the upper limb. The lowest trunk lies on the first rib and marks it. It is sandwiched between the subclavian artery in front and the middle scalene behind. If the upper trunk at Erb's point is stretched or torn at birth, Erb's palsy of the upper arm may result.
- Schema of the brachial plexus
- Formation of the brachial plexus and its branches in the neck
- Erb's point is where C5 and C6 meet to form the upper trunk. The anterior and posterior divisions of the upper trunk arise there. The suprascapular nerve arises at this point. So does the nerve to subclavius. Stretch or tear of the upper trunk at birth may produce Erb's palsy of the upper arm. The same eponym is also used for the point where the external jugular crosses sternocleidomastoid.
- Erb's point in the brachial plexus
Summary and Sources
- Neck is layered: skin, superficial fascia with platysma, then investing, pretracheal and prevertebral fasciae. Cutaneous nerves and jugular veins lie between platysma and deep fascia; ligate before dividing. The danger space runs from the skull base to the diaphragm and has no floor in the neck. Retrovisceral route accounts for 71% of mediastinal spread, carotid sheath 21%, pretracheal 8%. Ludwig's angina kills by airway obstruction, not by sepsis. Submandibular triangle is approached as four numbered surgical planes.
- Incise at least 4 cm below the mandibular border to spare the marginal mandibular nerve. Posterior belly of digastric is the landmark: everything dangerous lies deep to it. Accessory nerve is superficial in the posterior triangle and is at risk in node biopsy. Sympathetic chain lies behind the carotid sheath, not within it; the vagus is inside. Thoracic duct is dorsal to the left common carotid at the root of the neck; ligate a leak. Divide strap muscles across their upper third to preserve their nerve supply.
- Sources cited in the text
- Sources cited in the text (continued)
- Sources cited in the text (continued)
- Sources cited in the text (continued)
- Sources cited in the text (continued)
- Sources cited in the text (continued)
- Skandalakis' Surgical Anatomy: The Embryologic and Anatomic Basis of Modern Surgery
- Join our WhatsApp groups