Lesser occipital nerve

The lesser occipital nerve is derived mainly from the second cervical nerve (although fibres from the third cervical nerve may sometimes contribute). It passes first anterior to the plane of the spinal accessory nerve before winding around it and becoming anterior to it. It next ascends along the posterior margin of sternocleidomastoid. Near the cranium it perforates the deep fascia and passes up onto the scalp behind the auricle to supply the skin and connect with the great auricular and greater occipital nerves and the auricular branch of the facial nerve. Its auricular branch supplies the skin on the upper third of the medial aspect of the auricle and connects with the posterior branch of the great auricular nerve. The auricular branch is occasionally derived from the greater occipital nerve. It has been suggested that compression or stretching of the lesser occipital nerve contributes to cervicogenic headache.

Great auricular nerve

The great auricular nerve is the largest ascending branch of the cervical plexus. It arises from the second and third cervical rami, encircles the posterior border of sternocleidomastoid, perforates the deep fascia and ascends on the muscle beneath platysma with the external jugular vein. On reaching the parotid gland, it divides into anterior and posterior branches. The anterior branch is distributed to the facial skin over the parotid gland and connects in the gland with the facial nerve. This cross innervation between somatic sensory supply (great auricular) and parasympathetic secretomotor fibres to the parotid is considered to be part of the anatomical basis for the phenomenon of gustatory sweating (Frey’s syndrome) seen after parotid surgery, when the nerve is at risk of injury. The posterior branch supplies the skin over the mastoid process and on the back of the auricle (except its upper part); a filament pierces the auricle to reach the lateral surface where it is distributed to the lobule and concha. The posterior branch communicates with the lesser occipital nerve, the auricular branch of the vagus and the posterior auricular branch of the facial nerve.

Transverse cervical cutaneous nerve

The transverse cervical cutaneous nerve arises from the second and third cervical rami. It curves round the posterior border of sternocleidomastoid near its midpoint and runs obliquely forwards, deep to the external jugular vein, to the anterior border of the muscle. It perforates the deep cervical fascia, and divides under platysma into ascending and descending branches that are distributed to the anterolateral areas of the neck. The ascending branches ascend to the submandibular region, forming a plexus with the cervical branch of the facial nerve beneath platysma. Some branches pierce platysma and are distributed to the skin of the upper anterior areas of the neck. The descending branches pierce platysma and are distributed anterolaterally to the skin of the neck, as low as the sternum.

Supraclavicular nerves

The supraclavicular nerves arise from a common trunk formed from rami from the third and fourth cervical nerves and emerge at the posterior border of sternocleidomastoid. Descending under platysma and the deep cervical fascia, the trunk divides into medial, intermediate and lateral (posterior) branches, which diverge to pierce the deep fascia a little above the clavicle. The medial supraclavicular nerves run inferomedially across the external jugular vein and the clavicular and sternal heads of sternocleidomastoid to supply the skin as far as the midline and as low as the second rib. They also supply the sternoclavicular joint. The intermediate supraclavicular nerves cross the clavicle to supply the skin over pectoralis major and deltoid down to the level of the second rib, next to the area of supply of the second thoracic nerve. Overlap between these nerves is minimal. The lateral supraclavicular nerves descend superficially across trapezius and the acromion, supplying the skin of the upper and posterior parts of the shoulder.

Platysma

Platysma is a broad sheet of muscle of varying prominence which arises from the fascia covering the upper parts of pectoralis major and deltoid. Its fibres cross the clavicle and ascend medially in the side of the neck. Anterior fibres interlace across the midline with the fibres of the contralateral muscle, below and behind the symphysis menti. Other fibres attach to the lower border of the mandible or to the lower lip or cross the mandible to attach to skin and subcutaneous tissue of the lower face. Careful elevation of a myocutaneous flap in the subplatysmal plane as part of a neck dissection will include this muscle and its associated blood supply, thereby minimizing the risk of skin necrosis and wound breakdown.

Sternocleidomastoid

Sternocleidomastoid (Fig. 28.5) descends obliquely across the side of the neck and forms a prominent surface landmark, especially when contracted. It is thick and narrow centrally, and broader and thinner at each end. The muscle is attached inferiorly by two heads. The medial or sternal head is rounded and tendinous, arises from the upper part of the anterior surface of the manubrium and sterni and ascends posterolaterally. The lateral or clavicular head, which is variable in width and contains muscular and fibrous elements, ascends almost vertically from the superior surface of the medial third of the clavicle. The two heads are separated near their attachments by a triangular interval which corresponds to a surface depression, the lesser supraclavicular fossa. As they ascend, the clavicular head spirals behind the sternal head and blends with its deep surface below the middle of the neck, forming a thick, rounded belly. Sternocleidomastoid inserts superiorly by a strong tendon into the lateral surface of the mastoid process from its apex to its superior border, and by a thin aponeurosis into the lateral half of the superior nuchal line. The clavicular fibres are directed mainly to the mastoid process; the sternal fibres are more oblique and superficial, and extend to the occiput. The direction of pull of the two heads is therefore different, and the muscle may be classed as ‘cruciate’ and slightly ‘spiralized’.

Digastric

Digastric has two bellies and lies below the mandible, extending from the mastoid process to the chin (Fig. 28.5). The posterior belly, which is longer than the anterior, is attached in the mastoid notch of the temporal bone, and passes downwards and forwards. The anterior belly is attached to the digastric fossa on the base of the mandible near the midline, and slopes downwards and backwards. The two bellies meet in an intermediate tendon which perforates stylohyoid and runs in a fibrous sling attached to the body and greater cornu of the hyoid bone and is sometimes lined by a synovial sheath. The two bellies of digastric mark out the borders of the submandibular triangle.

Stylohyoid

Stylohyoid arises by a small tendon from the posterior surface of the styloid process, near its base. Passing downwards and forwards, it inserts into the body of the hyoid bone at its junction with the greater cornu (and just above the attachment of the superior belly of omohyoid). It is perforated near its insertion by the intermediate tendon of digastric (Fig. 28.5). The muscle may be absent or double. It may lie medial to the external carotid artery and may end in the suprahyoid or infrahyoid muscles.

Stylohyoid ligament

The stylohyoid ligament is a fibrous cord extending from the tip of the styloid process to the lesser cornu of the hyoid bone. It gives attachment to the highest fibres of the middle pharyngeal constrictor and is intimately related to the lateral wall of the oropharynx. Below, it is overlapped by hyoglossus. The ligament is derived from the cartilage of the second branchial arch, and may be partially calcified.

Sternohyoid

Sternohyoid is a thin, narrow strap muscle that arises from the posterior surface of the medial end of the clavicle, the posterior sternoclavicular ligament and the upper posterior aspect of the manubrium (Fig. 28.5). It ascends medially and is attached to the inferior border of the body of the hyoid bone. Inferiorly, there is a considerable gap between the muscle and its contralateral fellow, but the two usually come together in the middle of their course, and are contiguous above this. Sternohyoid may be absent or double, augmented by a clavicular slip (cleidohyoid), or interrupted by a tendinous intersection.

Omohyoid

Omohyoid consists of two bellies united at an angle by an intermediate tendon (Fig. 28.5). The inferior belly is a flat, narrow band, which inclines forwards and slightly upwards across the lower part of the neck. It arises from the upper border of the scapula, near the scapular notch, and occasionally from the superior transverse scapular ligament. It then passes behind sternocleidomastoid and ends there in the intermediate tendon. The superior belly begins at the intermediate tendon, passes almost vertically upwards near the lateral border of sternohyoid and is attached to the lower border of the body of the hyoid bone lateral to the insertion of sternohyoid. The length and form of the intermediate tendon varies, although it usually lies adjacent to the internal jugular vein at the level of the arch of the cricoid cartilage. The angulated course of the muscle is maintained by a band of deep cervical fascia, attached below to the clavicle and the first rib, which ensheathes the tendon. A variable amount of skeletal muscle may be present in the fascial band; either belly may be absent or double; the inferior belly may be attached directly to the clavicle and the superior is sometimes fused with sternohyoid.

Sternothyroid

Sternothyroid is shorter and wider than sternohyoid, and lies deep and partly medial to it (Fig. 28.5). It arises from the posterior surface of the manubrium sterni inferior to the origin of sternohyoid and from the posterior edge of the cartilage of the first rib. It is attached above to the oblique line on the lamina of the thyroid cartilage, where it delineates the upward extent of the thyroid gland. In the lower part of the neck the muscle is in contact with its contralateral fellow, but the two diverge as they ascend.

Thyrohyoid

Thyrohyoid is a small, quadrilateral muscle that may be regarded as an upward continuation of sternothyroid (Fig. 28.5). It arises from the oblique line on the lamina of the thyroid cartilage, and passes upwards to attach to the lower border of the greater cornu and adjacent part of the body of the hyoid bone.

Rectus capitis anterior

Rectus capitis anterior is a short, flat muscle situated behind the upper part of longus capitis. It arises from the anterior surface of the lateral mass of the atlas and the root of its transverse process, and ascends almost vertically to the inferior surface of the basilar part of the occipital bone immediately anterior to the occipital condyle.

Rectus capitis lateralis

Rectus capitis lateralis is a short, flat muscle that arises from the upper surface of the transverse process of the atlas and inserts into the inferior surface of the jugular process of the occipital bone. In view of its attachments and its relation to the ventral ramus of the first spinal nerve, rectus capitis lateralis is regarded as homologous with the posterior intertransverse muscles.

Longus capitis

Longus capitis (Fig. 28.6) has a narrow origin from tendinous slips from the anterior tubercles of the transverse processes of the third, fourth, fifth and sixth cervical vertebrae and becomes broad and thick above, where it is inserted into the inferior surface of the basilar part of the occipital bone.

Longus colli

Longus colli (Fig. 28.6) is applied to the anterior surface of the vertebral column, between the atlas and the third thoracic vertebra. It can be divided into three parts which all arise by tendinous slips. The inferior oblique part is the smallest, running upwards and laterally from the fronts of the bodies of the first two or three thoracic vertebrae to the anterior tubercles of the transverse processes of the fifth and sixth cervical vertebrae. The superior oblique part passes upwards and medially from the anterior tubercles of the transverse processes of the third, fourth and fifth cervical vertebrae to be attached by a narrow tendon to the anterolateral surface of the tubercle on the anterior arch of the atlas. The vertical intermediate part ascends from the fronts of the bodies of the upper three thoracic and lower three cervical vertebrae to the fronts of the bodies of the second, third and fourth cervical vertebrae.

Scalenus anterior

Scalenus anterior lies at the side of the neck deep (posteromedial) to sternocleidomastoid (Fig. 28.5; see also Fig. 28.18). Above, it is attached by musculotendinous fascicles to the anterior tubercles of the transverse processes of the third, fourth, fifth and sixth cervical vertebrae. These converge, blend and descend almost vertically, to be attached by a narrow, flat tendon to the scalene tubercle on the inner border of the first rib, and to a ridge on the upper surface of the rib anterior to the groove for the subclavian artery.

Fig. 28.18 The root of the neck. Note the sympathetic chain, the middle and inferior cervical sympathetic ganglia, the trunks of the brachial plexus, the phrenic nerve and the vertebral artery.

(From Sobotta 2006.)

Scalenus medius

Scalenus medius, the largest and longest of the scaleni, is attached above to the transverse process of the axis and the front of the posterior tubercles of the transverse processes of the lower five cervical vertebrae (Fig. 28.6). It frequently extends upwards to the transverse process of the atlas. Below it is attached to the upper surface of the first rib between the tubercle of the rib and the groove for the subclavian artery.

Scalenus posterior

Scalenus posterior is the smallest and most deeply situated of the scalene muscles (Fig. 28.6). It passes from the posterior tubercles of the transverse processes of the fourth, fifth, and sixth cervical vertebrae to the outer surface of the second rib, behind the tubercle for serratus anterior, where it is attached by a thin tendon.

Scalenus posterior is occasionally blended with scalenus medius. The scalene muscles vary a little in the number of vertebrae to which they are attached, in their degree of separation, and their segmental innervation.

Superior thyroid artery

The superior thyroid artery is the first branch of the external carotid artery, and arises from the anterior surface of the external carotid just below the level of the greater cornu of the hyoid bone (Figs 28.7A, 28.8). It descends along the lateral border of thyrohyoid to reach the apex of the lobe of the thyroid gland. Lying medially are the inferior constrictor muscle and the external laryngeal nerve: the nerve is often posteromedial, and therefore at risk when the artery is being ligatured. Occasionally it may issue directly from the common carotid.

Ascending pharyngeal artery

The ascending pharyngeal artery is the smallest branch of the external carotid. It is a long, slender vessel which arises from the medial (deep) surface of the external carotid artery near the origin of that artery. It ascends between the internal carotid artery and the pharynx to the base of the cranium. The ascending pharyngeal artery is crossed by styloglossus and stylopharyngeus, and longus capitis lies posterior to it. It gives off numerous small branches to supply longus capitis and longus colli, the sympathetic trunk, the hypoglossal, glossopharyngeal and vagus nerves and some of the cervical lymph nodes. It anastomoses with the ascending palatine branch of the facial artery and the ascending cervical branch of the vertebral artery. Its named branches are the pharyngeal, inferior tympanic and meningeal arteries.

Lingual artery

The lingual artery provides the chief blood supply to the tongue and the floor of the mouth (Fig. 28.8; see Ch. 30). It arises anteromedially from the external carotid artery opposite the tip of the greater cornu of the hyoid bone, between the superior thyroid and facial arteries. It often arises with the facial or, less often, with the superior thyroid artery. It may be replaced by a ramus of the maxillary artery. Ascending medially at first, it loops down and forwards, passes medial to the posterior border of hyoglossus and then runs horizontally forwards deep to it. The lingual artery next ascends again almost vertically, and courses sinuously forwards on the inferior surface of the tongue as far as its tip. The further course of the lingual artery is described on page 505.

Suprahyoid artery

The suprahyoid artery is a small branch which runs along the upper border of the hyoid bone to anastomose with the contralateral artery. It supplies adjacent structures.

Dorsal lingual arteries

The dorsal lingual arteries are described on page 505.

Sublingual artery

The sublingual artery is described on page 505.

Facial artery

The facial artery (Figs 28.7, 28.8; see Figs 29.13, 29.18) arises anteriorly from the external carotid in the carotid triangle, above the lingual artery and immediately above the greater cornu of the hyoid bone. In the neck, at its origin, it is covered only by the skin, platysma, fasciae and often by the hypoglossal nerve. It runs up and forwards, deep to digastric and stylohyoid. At first on the middle pharyngeal constrictor, it may reach the lateral surface of styloglossus, separated there from the palatine tonsil only by this muscle and the lingual fibres of the superior constrictor. Medial to the mandibular ramus it arches upwards and grooves the posterior aspect of the submandibular gland. It then turns down and descends to the lower border of the mandible in a lateral groove on the submandibular gland, between the gland and medial pterygoid. Reaching the surface of the mandible, the facial artery curves round its inferior border, anterior to masseter, to enter the face: its further course is described on page 490. The artery is very sinuous throughout its extent. In the neck this may be so that the artery is able to adapt to the movements of the pharynx during deglutition, and similarly on the face, so that the artery can adapt to movements of the mandible, lips and cheeks. Facial artery pulsation is most palpable where the artery crosses the mandibular base, and again near the corner of the mouth. Its branches in the neck are the ascending palatine, tonsillar, submental and glandular arteries.

Occipital artery

The occipital artery arises posteriorly from the external carotid artery, approximately 2 cm from its origin (Figs 28.7A, 28.8). At its origin, the artery is crossed superficially by the hypoglossal nerve, which winds round it from behind. The artery next passes backwards, up and deep to the posterior belly of digastric, and crosses the internal carotid artery, internal jugular vein, hypoglossal, vagus and accessory nerves. Between the transverse process of the atlas and the mastoid process, the occipital artery reaches the lateral border of rectus capitis lateralis. It then runs in the occipital groove of the temporal bone, medial to the mastoid process and attachments of sternocleidomastoid, splenius capitis, longissimus capitis and digastric, and lies successively on rectus capitis lateralis, obliquus superior and semispinalis capitis. Finally, accompanied by the greater occipital nerve, it turns upwards to pierce the investing layer of the deep cervical fascia connecting the cranial attachments of trapezius and sternocleidomastoid, and ascends tortuously in the dense superficial fascia of the scalp where it divides into many branches.

The occipital artery has two main branches (upper and lower) to the upper part of sternocleidomastoid in the neck. The lower branch arises near the origin of the occipital artery, and may sometimes arise directly from the external carotid artery. It descends backwards over the hypoglossal nerve and internal jugular vein, enters sternocleidomastoid and anastomoses with the sternocleidomastoid branch of the superior thyroid artery. The upper branch arises as the occipital artery crosses the accessory nerve, and runs down and backwards superficial to the internal jugular vein. It enters the deep surface of sternocleidomastoid with the accessory nerve.

Posterior auricular artery

The posterior auricular artery is a small vessel which branches posteriorly from the external carotid just above digastric and stylohyoid. It ascends between the parotid gland and the styloid process to the groove between the auricular cartilage and mastoid process, and divides into auricular and occipital branches which are described with the face on page 491. In the neck, it provides branches to supply digastric, stylohyoid, sternocleidomastoid and the parotid gland. It also gives origin to the stylomastoid artery – described as an indirect branch of the posterior auricular artery in about a third of subjects – which enters the stylomastoid foramen to supply the facial nerve, tympanic cavity, mastoid antrum air cells and semicircular canals. In the young, its posterior tympanic ramus forms a circular anastomosis with the anterior tympanic branch of the maxillary artery.

Carotid sinus and carotid body

The common carotid artery shows two specialized organs near its bifurcation, the carotid sinus and the carotid body. They relay information concerning the pressure and chemical composition of the arterial blood respectively, and are innervated principally by carotid branch(es) of the glossopharyngeal nerve, with small contributions from the cervical sympathetic trunk and the vagus nerve.

The carotid sinus usually appears as a dilation of the lower end of the internal carotid, and functions as a baroreceptor.

The carotid body is a reddish-brown, oval structure, 5–7 mm in height and 2.5–4 mm in width. It lies either posterior to the carotid bifurcation or between its branches, and is attached to, or sometimes partly embedded in, their adventitia. Occasionally it takes the form of a group of separate nodules. Aberrant miniature carotid bodies, microstructurally similar but with diameters of 600 μm or less, may appear in the adventitia and adipose tissue near the carotid sinus.

The carotid body is surrounded by a fibrous capsule from which septa divide the enclosed tissue into lobules. Each lobule contains glomus (type I) cells which are separated from an extensive network of fenestrated sinusoids by sustentacular (type II) cells (Fig. 28.9). Glomus cells store a number of peptides, particularly enkephalins, bombesin and neurotensin, and amines including dopamine, serotonin, adrenaline (epinephrine) and noradrenaline (norepinephrine), and are therefore regarded as paraneurones. Unmyelinated axons lie in a collagenous matrix between the sustentacular cells and the sinusoidal endothelium, and many synapse on the glomus cells. They are visceral afferents which travel in the carotid sinus nerve to join the glossopharyngeal nerve. Preganglionic sympathetic axons and fibres from the carotid sinus synapse on parasympathetic and sympathetic ganglion cells, which lie either in isolation or in small groups near the surface of each carotid body. Postganglionic axons travel to local blood vessels: the parasympathetic efferent fibres are probably vasodilatory and the sympathetic ones are vasoconstrictor.

Fig. 28.9 The cellular, neural and vascular architecture of the carotid body: functional pathways are indicated.

The carotid body receives a rich blood supply from branches of the adjacent external carotid artery, which is consistent with its role as an arterial chemoreceptor. When stimulated by hypoxia, hypercapnia or increased hydrogen ion concentration (low pH) in the blood flowing through it, it elicits reflex increases in the rate and volume of ventilation via connections with brain stem respiratory centres. The bodies are most prominent in children and normally involute in older age, when they are infiltrated by lymphocytes and fibrous tissue. Individuals with chronic hypoxia, or who live at high altitude or suffer from lung disease, may have enlarged carotid bodies as a result of hyperplasia.

Other small bodies, resembling carotid bodies, and also considered to be chemoreceptors, occur near the arteries of the fourth and sixth pharyngeal arches and hence are found near the aortic arch, ligamentum arteriosum and right subclavian artery, and are supplied by the vagus nerve.

Parts of the subclavian arteries

Vertebral artery

The vertebral artery arises from the superoposterior aspect of the first part of the subclavian artery. It passes through the foramina in the transverse processes of all of the cervical vertebrae except the seventh, curves medially behind the lateral mass of the atlas and enters the cranium via the foramen magnum (Fig. 28.11). At the lower pontine border it joins its fellow to form the basilar artery. Occasionally it may enter the cervical vertebral column via the fourth, fifth or seventh cervical vertebra (Fig. 28.10).

Fig. 28.11 A dissection of the brain stem and the upper part of the spinal cord after removal of large portions of the occipital and parietal bones, the cerebellum and the roof of the fourth ventricle. On the left side, the foramina transversaria of the atlas and the third, fourth and fifth cervical vertebrae have been opened to expose the vertebral artery. On the right side the posterior arch of the atlas and the laminae of the succeeding cervical vertebrae have been divided and have been removed together with the vertebral spines and the contralateral laminae. The tentorium cerebelli and the transverse sinuses have been divided and their posterior portions removed.

Fig. 28.10 The level of entry of the vertebral artery into the foramina transversaria of the cervical vertebrae. Note that 90% enter at the level of the sixth cervical vertebra.

(Redrawn with permission from Sobotta 2006.)

Internal thoracic artery

The internal thoracic artery arises inferiorly from the first part of the subclavian artery, 2 cm above the sternal end of the clavicle, opposite the root of the thyrocervical trunk.

Thyrocervical trunk

The thyrocervical trunk is a short wide artery which arises from the front of the first part of the subclavian artery near the medial border of scalenus anterior, and divides almost at once into the inferior thyroid, suprascapular and superficial cervical arteries.

Inferior thyroid artery

The inferior thyroid artery loops upwards anterior to the medial border of the scalenus anterior, turns medially just below the sixth cervical transverse process, then descends on longus colli to the lower border of the thyroid gland (Figs 28.7A, 28.17). It passes anterior to the vertebral vessels and posterior to the carotid sheath and its contents (and usually the sympathetic trunk, whose middle cervical ganglion frequently adjoins the vessel). On the left, near its origin, the artery is crossed anteriorly by the thoracic duct as the latter curves inferolaterally to its termination. Relations between the terminal branches of the artery and recurrent laryngeal nerve are very variable and of considerable surgical importance. The artery usually passes behind the nerve as it nears the gland. However, very close to the gland, the right nerve is equally likely to be anterior, posterior or amongst, the branches of the artery, and the left nerve is usually posterior. The artery is not accompanied by the inferior thyroid vein.

Fig. 28.17 Vessels and nerves of the neck, left lateral view. The left sternocleidomastoid, the greater part of the infrahyoid group of muscles and numerous vessels have been removed in order to expose deeper structures. Compare with Fig. 28.7A, which shows a more superficial level of dissection. V, VI, VII, VIII refer to the anterior primary rami of C5, C6, C7, and C8, respectively.

(From Sobotta 2006.)

Muscular branches

These supply the infrahyoid muscles, longus colli, scalenus anterior and the inferior pharyngeal constrictor.

Ascending cervical artery

The ascending cervical artery is a small branch which arises as the inferior thyroid turns medially behind the carotid sheath and ascends on the anterior tubercles of the cervical transverse processes between scalenus anterior and longus capitis. It supplies the adjacent muscles and gives off one or two spinal branches which enter the vertebral canal through the intervertebral foramina to supply the spinal cord and membranes and vertebral bodies, and thereby supplement the spinal branches of the vertebral artery. The ascending cervical artery anastomoses with the vertebral, ascending pharyngeal, occipital and deep cervical arteries.

Inferior laryngeal

The inferior laryngeal artery ascends on the trachea with the recurrent laryngeal nerve, enters the larynx at the lower border of the inferior constrictor and supplies the laryngeal muscles and mucosa. It anastomoses with its contralateral fellow, and with the superior laryngeal branch of the superior thyroid artery.

Pharyngeal branches

These supply the lower part of the pharynx. Tracheal branches supply the trachea and anastomose with the bronchial arteries; oesophageal branches supply the oesophagus and anastomose with the oesophageal branches of the thoracic aorta; inferior and ascending glandular branches supply the posterior and inferior regions of the thyroid gland, and anastomose with the contralateral inferior and ipsilateral superior thyroid arteries. The ascending branch also supplies the parathyroid glands.

Costocervical trunk

On the right, this short vessel arises posteriorly from the second part of the subclavian artery, and, on the left, from its first part. It arches back above the cervical pleura to the neck of the first rib, where it divides into superior intercostal and deep cervical branches.

Fig. 28.12 Variations in the origins of the inferior thyroid, suprascapular, transverse cervical and internal thoracic arteries.

(Redrawn with permission from Sobotta 2006.)

External jugular vein

The external jugular vein mainly drains the scalp and face, although it also drains some deeper parts. The vein is formed by the union of the posterior division of the retromandibular vein with the posterior auricular vein and begins near the mandibular angle just below or in the parotid gland (see Fig. 25.3). It descends from the angle to the midclavicle, running obliquely, superficial to sternocleidomastoid, to the root of the neck. Here it crosses the deep fascia and ends in the subclavian vein, lateral or anterior to scalenus anterior. There are valves at its entrance into the subclavian, but they do not prevent regurgitation. Its wall is adherent to the rim of the fascial opening. It is covered by platysma, superficial fascia and skin, and is separated from sternocleidomastoid by deep cervical fascia. The vein crosses the transverse cutaneous nerve and lies parallel with the great auricular nerve, posterior to its upper half. In size the external jugular vein is inversely proportional to the other veins in the neck, and may be double. Between the entrance into the subclavian vein and a point approximately 4 cm above the clavicle, the vein is often dilated, producing a so-called sinus.

Posterior external jugular vein

The posterior external jugular vein begins in the occipital scalp, and drains the skin and the superficial muscles which lie posterosuperior in the neck. It usually joins the middle part of the external jugular vein.

Anterior jugular vein

The anterior jugular vein arises near the hyoid bone from the confluence of the superficial submandibular veins. It descends between the midline and the anterior border of sternocleidomastoid. Turning laterally, low in the neck, deep to sternocleidomastoid but superficial to the infrahyoid strap muscles, it joins either the end of the external jugular vein or may enter the subclavian vein directly. In size it is usually inverse to the external jugular vein. It communicates with the internal jugular vein, and receives the laryngeal veins and sometimes a small thyroid vein. There are usually two anterior jugular veins, united just above the manubrium by a large transverse jugular arch, receiving the inferior thyroid tributaries. They have no valves and may be replaced by a midline trunk.

Internal jugular vein

The internal jugular vein collects blood from the skull, brain, superficial parts of face and much of the neck. It begins at the cranial base in the posterior compartment of the jugular foramen, where it is continuous with the sigmoid sinus. At its origin it is dilated as the superior bulb, which lies below the posterior part of the tympanic floor. The internal jugular vein descends in the carotid sheath, and unites with the subclavian vein, posterior to the sternal end of the clavicle, to form the brachiocephalic vein (Fig. 28.14). Near its termination the vein dilates into the inferior bulb, above which is a pair of valves.

Inferior petrosal sinus

The inferior petrosal sinus leaves the skull through the anterior part of the jugular foramen, crosses lateral or medial to the ninth to eleventh cranial nerves and joins the superior jugular bulb.

Facial vein

The initial part of the facial vein as it lies on the face is described on page 492. From the face it passes over the surface of masseter, crosses the body of the mandible and enters the neck where it runs obliquely back under platysma. Here it lies superficial to the submandibular gland, digastric and stylohyoid (Fig. 28.14). Just anteroinferior to the mandibular angle it is joined by the anterior division of the retromandibular vein, and then descends superficial to the loop of the lingual artery, the hypoglossal nerve and external and internal carotid arteries, to enter the internal jugular near the greater cornu of the hyoid bone, i.e. in the upper angle of the carotid triangle. Near its end a large branch often descends along the anterior border of sternocleidomastoid to the anterior jugular vein. Its uppermost segment, above its junction with the superior labial vein, is often termed the angular vein.

Lingual vein

The lingual veins follow two routes. The dorsal lingual veins drain the dorsum and sides of the tongue, join the lingual veins accompanying the lingual artery between hyoglossus and genioglossus and enter the internal jugular near the greater cornu of the hyoid bone. The deep lingual vein begins near the tip of the tongue and runs back, lying near the mucous membrane on the inferior surface of the tongue. Near the anterior border of hyoglossus it joins a sublingual vein, from the sublingual salivary gland, to form the vena comitans nervi hypoglossi which runs back between mylohyoid and hyoglossus with the hypoglossal nerve to join the facial, internal jugular or lingual vein.

Pharyngeal veins

The pharyngeal veins begin in a pharyngeal plexus external to the pharynx. They receive meningeal veins and a vein from the pterygoid canal, and usually end in the internal jugular vein, but may sometimes end in the facial, lingual or superior thyroid vein.

Superior thyroid vein

The superior thyroid vein is formed by deep and superficial tributaries corresponding to the arterial branches in the upper part of the thyroid gland (Figs 28.13, 28.14). It accompanies the superior thyroid artery, receives the superior laryngeal and cricothyroid veins, and ends in the internal jugular or facial vein.

Middle thyroid vein

The middle thyroid vein drains the lower part of the gland and also receives veins from the larynx and trachea. It crosses anterior to the common carotid artery to join the internal jugular vein behind the superior belly of omohyoid.

Tympanic body

The tympanic body (glomus jugulare) is ovoid, 0.5 mm long and 0.25 mm broad, and lies in the adventitia of the upper part of the superior bulb of the internal jugular vein. It is similar in structure to the carotid body and is presumed to have a similar function. The predominant cell type has morphological similarities to adrenal chromaffin cells, and is derived from the neural crest. Cells obtained from glomus jugulare paragangliomas show spontaneous neurite outgrowth in culture, and have vasoactive intestinal peptide (VIP)-like activity. The tympanic body may be present as two or more parts near the tympanic branch of the glossopharyngeal nerve or the auricular branch of the vagus as they lie within their canals in the petrous part of the temporal bone. Tumours of tympanic bodies may involve the adjacent cranial nerves and the middle ear.

Subclavian vein

The subclavian vein is a continuation of the axillary vein and extends from the outer border of the first rib to the medial border of scalenus anterior, where it joins the internal jugular vein to form the brachiocephalic vein (Fig. 28.14). The clavicle and subclavius lie anterior to it, the subclavian artery is posterosuperior, separated by scalenus anterior and the phrenic nerve, and the first rib and pleura are inferior. The vein usually has a pair of valves 2 cm from its end. Its tributaries are the external jugular, dorsal scapular and sometimes the anterior jugular vein. At its junction with the internal jugular, the left subclavian vein receives the thoracic duct, and the right subclavian vein receives the right lymphatic duct.

Vertebral vein

Numerous small tributaries from internal vertebral plexuses leave the vertebral canal above the posterior arch of the atlas and join small veins from local deep muscles in the suboccipital triangle. Their union produces a vessel which enters the foramen in the transverse process of the atlas and forms a plexus around the vertebral artery. It descends through successive transverse foramina and ends as the vertebral vein. The vein emerges from the sixth cervical transverse foramen, whence it descends, at first anterior, then anterolateral, to the vertebral artery, to open superoposteriorly into the brachiocephalic vein: the opening has a paired valve. As it descends it passes behind the internal jugular vein and in front of the first part of the subclavian artery. A small accessory vertebral vein usually descends from the vertebral plexus, traverses the seventh cervical transverse foramen and turns forwards between the subclavian artery and the cervical pleura to join the brachiocephalic vein.

Anterior vertebral vein

The anterior vertebral vein starts in a plexus around the upper cervical transverse processes, descends near the ascending cervical artery between attachments of scalenus anterior and longus capitis, and opens into the end of the vertebral vein.

Deep cervical vein

The deep cervical vein accompanies its artery between semispinales capitis and cervicis. It is formed in the suboccipital region by the union of communicating branches of the occipital vein; veins from suboccipital muscles; and veins from plexuses around the cervical spines. It passes forwards between the seventh cervical transverse process and the neck of the first rib to end in the lower part of the vertebral vein.

Central venous access

Central venous cannulation permits monitoring of the central venous pressure and the administration of drugs directly into the central circulation.

Deep branches – medial series

Deep branches – lateral series

Communicating branches

The glossopharyngeal nerve communicates with the sympathetic trunk, vagus and facial nerves. Its inferior ganglion is connected with the superior cervical sympathetic ganglion. Two filaments from the inferior ganglion pass to the vagus, one to its auricular branch and the other to its superior ganglion. A branch to the facial nerve arises from the glossopharyngeal nerve below the inferior ganglion, and perforates the posterior belly of digastric to join the facial nerve near the stylomastoid foramen.

Branches of distribution

The glossopharyngeal nerve has tympanic, carotid, pharyngeal, muscular, tonsillar and lingual branches.

Lesions of the glossopharyngeal nerve

Damage to the glossopharyngeal nerve rarely occurs without involvement of other lower cranial nerves. Transient or sustained hypertension may follow surgical section of the nerve, and indicates involvement of the carotid branch. Isolated lesions of the glossopharyngeal nerve lead to loss of sensation over the ipsilateral soft palate, fauces, pharynx and posterior third of the tongue, although this is difficult to assess clinically and confirmation requires galvanic stimulation. The palatal and pharyngeal (gag) reflexes are reduced or absent and salivary secretion from the parotid gland may also be reduced. Weakness of stylopharyngeus cannot be tested individually. Glossopharyngeal neuralgia consists of episodic brief but severe pain, often precipitated by swallowing, and experienced in the throat, behind the angle of the jaw and within the ear. Superior jugular bulb thromboses (e.g. in otitis media) and jugular foramen syndrome (associated with nasopharyngeal carcinoma or a glomus tumour) may cause lesions of the adjacent glossopharyngeal, vagus and accessory nerves, with associated weakness in the muscles supplied in the pharynx and larynx.

Superior (jugular) ganglion

The superior ganglion is greyish, spherical and approximately 4 mm in diameter. It is connected to the cranial root of the accessory nerve, the inferior glossopharyngeal ganglion, and the sympathetic trunk, the latter by a filament from the superior cervical ganglion. The significance of these connections is not entirely clear, but the first probably contains aberrant motor fibres from the nucleus ambiguus which issue in the accessory nerve, to be distributed to the palatal, pharyngeal, laryngeal and upper oesophageal musculature via the vagus.

Inferior (nodose) ganglion

The inferior or nodose ganglion is larger than the superior ganglion, and is elongated and cylindrical in shape with a length of 25 mm and a maximum breadth of 5 mm. It is connected with the hypoglossal nerve, the loop between the first and second cervical spinal nerves, and with the superior cervical sympathetic ganglion. Just above the ganglion the cranial accessory blends with the vagus nerve, its fibres being distributed mainly in pharyngeal and recurrent laryngeal vagal branches. Most visceral afferent fibres have their cell bodies in the nodose ganglion.

Both vagal ganglia are exclusively sensory, and contain somatic, special visceral and general visceral afferent neurones. The superior ganglion is chiefly somatic, and most of its neurones enter the auricular nerve, whilst neurones in the inferior ganglion are concerned with visceral sensation from the heart, larynx, lungs and the alimentary tract from the pharynx to the transverse colon. Some fibres transmit impulses from taste endings in the vallecula and epiglottis. Large afferent fibres are derived from muscle spindles in the laryngeal muscles. Vagal sensory neurones in the nodose ganglion may show some somatotopic organization. Both ganglia are traversed by parasympathetic, and perhaps some sympathetic fibres, but there is no evidence that vagal parasympathetic components relay in the inferior ganglion. Preganglionic motor fibres from the dorsal vagal nucleus and the special visceral efferents from the nucleus ambiguus, which descend to the inferior vagal ganglion, commonly form a visible band, skirting the ganglion in some mammals. These larger fibres probably provide motor innervation to the larynx in the recurrent laryngeal nerve, together with some contribution to the superior laryngeal nerve supplying cricothyroid.

Branches in the neck

The branches of the vagus in the neck are the meningeal, auricular, pharyngeal, carotid body, superior and recurrent laryngeal nerves and cardiac branches.

Cranial root

The cranial root of the accessory nerve is smaller than the spinal root. It exits the skull through the jugular foramen, and unites for a short distance with the spinal root. It is also connected to the superior vagal ganglion. After traversing the foramen, the cranial root separates from the spinal part and immediately joins the vagus nerve superior to the inferior vagal ganglion. Those of its fibres that are distributed in the pharyngeal branches of the vagus are derived from the nucleus ambiguus, and probably innervate the pharyngeal and palatal muscles except tensor veli palatini. Other fibres enter the recurrent laryngeal nerve to supply the adductor muscles of the vocal cords, thyroarytenoid and lateral cricoarytenoid.

The status of the cranial root of the accessory nerve continues to excite debate. Cadaveric dissection studies have revealed wide variation in the patterns of anastomosis between the intracranial branches of the lower four cranial nerves (glossopharyngeal, vagus, accessory and hypoglossal) in the posterior cranial fossa: a separate cranial root of the accessory cannot always be demonstrated.

Spinal root

The spinal root arises from an elongated nucleus of motor cells situated in the lateral aspect of the ventral horn which extends from the junction of the spinal cord and medulla to the sixth cervical segment (Fig. 28.11). Some rootlets emerge directly, others turn cranially before exiting. Their line of exit is irregular rather than linear, and the spinal root usually passes through the first cervical dorsal root ganglion. The rootlets form a trunk which ascends between the ligamentum denticulatum and the dorsal roots of the spinal nerves and enters the skull via the foramen magnum, behind the vertebral artery. It then turns upwards and passes laterally to reach the jugular foramen, which it traverses in a common dural sheath with the vagus, but separated from that nerve by a fold of arachnoid mater. As the spinal root exits the jugular foramen it runs posterolaterally and passes either medial or lateral to the internal jugular vein. Occasionally it passes through the vein. The nerve then crosses the transverse process of the atlas and is itself crossed by the occipital artery. It descends obliquely, medial to the styloid process, stylohyoid and the posterior belly of the digastric. Running with the superior sternocleidomastoid branch of the occipital artery, it reaches the upper part of sternocleidomastoid and enters its deep surface, to form an anastomosis with fibres from C2 alone, C3 alone, or C2 and C3, the ansa of Maubrac. It may also communicate with the anterior root of the first cervical nerve (McKenzie branch).

The accessory nerve occasionally terminates in sternocleidomastoid. More commonly it emerges a little above the midpoint of the posterior border of sternocleidomastoid, generally above the emergence of the great auricular nerve (usually within 2 cm of it) and between 4–6 cm from the tip of the mastoid process. However, the point of emergence is very variable. The nerve then crosses the posterior triangle on levator scapulae (Fig. 28.7A), separated from it by the prevertebral layer of deep cervical fascia and adipose tissue. Here the nerve is relatively superficial and related to the superficial cervical lymph nodes. About 3–5 cm above the clavicle it passes behind the anterior border of trapezius, often dividing to form a plexus on its deep surface which receives contributions from C3 and C4, or C4 alone. It then enters the deep surface of the muscle.

The cervical course of the nerve follows a line from the lower anterior part of the tragus to the tip of the transverse process of the atlas and then across the sternocleidomastoid and the posterior triangle to a point on the anterior border of the trapezius 3–5 cm above the clavicle.

Conventionally, the spinal root is thought to provide the sole motor supply to sternocleidomastoid, and the second and third cervical nerves are believed to carry proprioceptive fibres from it. The supranuclear pathway of fibres destined for sternocleidomastoid is not simple: fibres may undergo a double decussation in the brainstem and/or there may be a bilateral projection to the muscle from each hemisphere. The motor supply to the upper and middle portions of trapezius is primarily from the spinal accessory nerve. However, the lower two-thirds of the muscle, in 75% of subjects, receives an innervation from the cervical plexus. On the basis of the incomplete denervation of the muscle that sometimes occurs following sacrifice of both the accessory nerve and the cervical plexus, it has been suggested that the trapezius receives a partial motor supply from other sources, possibly via thoracic roots. In addition to their motor contribution, C3 and 4 carry proprioceptive fibres from trapezius. In 25% of subjects the spinal accessory nerve receives no fibres from the cervical plexus. (For a detailed review of the applied surgical anatomy of the spinal accessory nerve plexus, see Brown 2002.)

Sensory ganglia have been described along the course of the spinal root.

Lesions affecting the accessory nerve

Lesions of the accessory nerve may occur centrally; at its exit from the skull; in the neck. The supranuclear fibres which influence motor neurones innervating sternocleidomastoid decussate twice, therefore a lesion of the pyramidal system above the pons produces weakness of the ipsilateral sternocleidomastoid and contralateral trapezius. Episodic contraction of sternocleidomastoid and trapezius, often accompanied by contraction of other muscle groups, e.g. splenius capitis, occurs in spasmodic torticollis, a focal dystonia. In jugular foramen syndrome, caused by pathologies including nasopharyngeal carcinoma or a glomus tumour, lesions of the glossopharyngeal, vagus and accessory nerves coexist. The accessory nerve can be injured more distally in the neck by trauma or by surgical exploration in the posterior triangle. If the accessory nerve is sacrificed as part of a radical neck dissection, and the innervation of trapezius is lost, the patient develops intractable neuralgia due to traction on the brachial plexus caused by the unsupported weight of the shoulder and arm.

Communications

The hypoglossal nerve communicates with the sympathetic trunk, vagus, first and second cervical nerves and lingual nerve. Near the atlas it is joined by branches from the superior cervical sympathetic ganglion and by a filament from the loop between the first and second cervical nerves which leaves the hypoglossal as the upper root of the ansa cervicalis. The vagal connections occur close to the skull, and numerous filaments pass between the hypoglossal nerve and the inferior vagal ganglion in the connective tissue uniting them. As the hypoglossal nerve curves round the occipital artery it receives the ramus lingualis vagi from the pharyngeal plexus. Near the anterior border of hyoglossus it is connected with the lingual nerve by many filaments which ascend on the muscle.

Branches of distribution

The branches of distribution of the hypoglossal nerve are meningeal, descending, thyrohyoid and muscular nerves.

Lesions of the hypoglossal nerve

The hypoglossal nerve may be damaged during neck dissection. Complete hypoglossal division causes unilateral lingual paralysis and eventual hemiatrophy; the protruded tongue deviates to the paralysed side, and, on retraction, the wasted and paralysed side rises higher than the unaffected side. The larynx may deviate towards the active side in swallowing, due to unilateral paralysis of the hyoid depressors associated with loss of the first cervical spinal nerve which runs with the hypoglossal nerve. If paralysis is bilateral, the tongue is motionless. Taste and tactile sensibility are unaffected but articulation is slow and swallowing very difficult.

Inferior (or cervicothoracic/stellate) ganglion

The inferior cervical ganglion (cervicothoracic/stellate) is irregular in shape and much larger than the middle cervical ganglion (Fig. 28.18). It is probably formed by a fusion of the lower two cervical and first thoracic segmental ganglia, sometimes including the second and even third and fourth thoracic ganglia. The first thoracic ganglion may be separate, leaving an inferior cervical ganglion above it. The sympathetic trunk turns backwards at the junction of the neck and thorax and so the long axis of the cervicothoracic ganglion becomes almost anteroposterior. The ganglion lies on or just lateral to the lateral border of longus colli between the base of the seventh cervical transverse process and the neck of the first rib (which are both posterior to it). The vertebral vessels are anterior, and the ganglion is separated from the posterior aspect of the cervical pleura inferiorly by the suprapleural membrane. The costocervical trunk of the subclavian artery branches near the lower pole of the ganglion, and the superior intercostal artery is lateral.

A small vertebral ganglion may be present on the sympathetic trunk anterior or anteromedial to the origin of the vertebral artery and directly above the subclavian artery. When present, it may provide the ansa subclavia and is also joined to the inferior cervical ganglion by fibres enclosing the vertebral artery. It is usually regarded as a detached part of the middle cervical or inferior cervical ganglion. Like the middle cervical ganglion it may supply grey rami communicantes to the fourth and fifth cervical spinal nerves. The inferior cervical ganglion sends grey rami communicantes to the seventh and eighth cervical and first thoracic spinal nerves, and gives off a cardiac branch, branches to nearby vessels and sometimes a branch to the vagus nerve.

The grey rami communicantes to the seventh cervical spinal nerve vary from one to five (two being the usual number). A third often ascends medial to the vertebral artery in front of the seventh cervical transverse process. It connects with the seventh cervical nerve, and sends a filament upwards through the sixth cervical transverse foramen in company with the vertebral vessels to join the sixth cervical spinal nerve as it emerges from the intervertebral foramen. An inconstant ramus may traverse the seventh cervical transverse foramen. Grey rami to the eighth cervical spinal nerve vary from three to six in number.

The cardiac branch descends behind the subclavian artery and along the front of the trachea to the deep cardiac plexus. Behind the artery it connects with the recurrent laryngeal nerve and the cardiac branch of the middle cervical ganglion (the latter is often replaced by fine branches of the inferior cervical ganglion and ansa subclavia).

The branches to blood vessels form plexuses on the subclavian artery and its branches. The subclavian supply is derived from the inferior cervical ganglion and ansa subclavia, and typically extends to the first part of the axillary artery, although a few fibres may extend further. An extension of the subclavian plexus to the internal thoracic artery may be joined by a branch of the phrenic nerve.

Within the foramina transversaria and intertransverse spaces, the cervical grey rami communicantes form intersegmental arcades as they communicate with one another and the ventral rami of the upper five or six cervical spinal nerves. These arcades accompany the second part of the vertebral artery and create the appearance of a long nerve known as the vertebral nerve. Fine filaments from this nerve and the grey rami communicantes form the vertebral plexus on the surface of the vertebral artery. This plexus contains not only sympathetic efferent fibres but also somatic sensory fibres from the adventitia of the artery, whose cell bodies are located in the cervical dorsal root ganglia. The vertebral nerve sends filaments to the posterolateral corners of the cervical intervertebral discs (Bogduk et al 1988), and gives rise to the meningeal branches (sinuvertebral nerves) at each cervical segment. The vertebral plexus, which contains some neuronal cell bodies, continues into the skull along the vertebral and basilar arteries and their branches as far as the posterior cerebral artery, where it meets a plexus from the internal carotid artery. The plexus on the inferior thyroid artery reaches the thyroid gland, and connects with the recurrent and external laryngeal nerves, the cardiac branch of the superior cervical ganglion, and the common carotid plexus.

Horner’s syndrome

Any condition or injury that destroys the sympathetic trunk ascending from the thorax through the neck into the face results in Horner’s syndrome, characterized by a drooping eyelid (ptosis), sunken globe (enophthalmos), narrow palpebral fissure, contracted pupil (meiosis), vasodilatation and lack of thermal sweating (anhydrosis) on the affected side. This occurs classically when a bronchial carcinoma invades the sympathetic trunk. It also occurs as a complication of cervical sympathectomy or a radical neck dissection. Avulsion of the first thoracic nerve from the spinal cord may be diagnosed by development of the syndrome after closed traction lesion of the supraclavicular brachial plexus.

Arteries

The thyroid gland is supplied by the superior and inferior thyroid arteries and sometimes by an arteria thyroidea ima from the brachiocephalic trunk or aortic arch (Figs 28.14, 28.17). The arteries are large and their branches anastomose frequently both on and in the gland, ipsilaterally and contralaterally. The superior thyroid artery, which is closely related to the external laryngeal nerve, pierces the thyroid fascia and then divides into anterior and posterior branches. The anterior branch supplies the anterior surface of the gland, and the posterior branch supplies the lateral and medial surfaces. The inferior thyroid artery approaches the base of the thyroid gland and divides into superior (ascending) and inferior thyroid branches to supply the inferior and posterior surfaces of the gland. The superior branch also supplies the parathyroid glands. The relationship between the inferior thyroid artery and the recurrent laryngeal nerve is highly variable and of considerable clinical importance: iatrogenic injury to the nerves that supply the larynx represents a major complication of thyroid surgery (Yalcxin 2006). The recurrent laryngeal nerve is usually related to the posterior branch of the inferior thyroid artery, which may be replaced by a vascular network (Moreau et al 1998).

Veins

The venous drainage of the thyroid gland is usually via superior, middle, and inferior thyroid veins (Figs 28.13, 28.14). The superior thyroid vein emerges from the upper part of the gland and runs with the superior thyroid artery towards the carotid sheath: it drains into the internal jugular vein. The middle thyroid vein collects blood from the lower part of the gland: it emerges from the lateral surface of the gland and drains into the internal jugular vein. The inferior thyroid veins arise in a glandular venous plexus, which also connects with the middle and superior thyroid veins. These veins form a pretracheal plexus, from which the left inferior vein descends to join the left brachiocephalic vein and the right descends obliquely across the brachiocephalic artery to join the right brachiocephalic vein at its junction with the superior vena cava. The inferior thyroid veins often open via a common trunk into the superior vena cava or left brachiocephalic vein. They drain the oesophageal, tracheal and inferior laryngeal veins and have valves at their terminations.

Cervical rib

A small extra rib (cervical rib) may develop in the root of the neck in association with the seventh cervical vertebra. It is often fibrous in nature, although in some cases it may have undergone ossification. A cervical rib may cause compression of the subclavian artery and the lower roots of the brachial plexus. Should this occur, affected individuals will complain of pain, paraesthesia and even pallor of the affected upper limb, a condition known as thoracic outlet syndrome.