As the name implies, the carotid artery and jugular vein may also be involved as part of the pathology. The carotid space is a paired space defined by the carotid sheath, a connective tissue boundary in the neck, that is made by the superficial, middle, and deep layers of the deep cervical fascia.
Extending from the jugular foramen at the skull base to the aortic arch at the thoracic inlet, the carotid space is divided craniocaudally into the supra- and infrahyoid regions. The suprahyoid carotid space is surrounded anteriorly by the masticator and parapharyngeal spaces, laterally by the parotid space, medially by the retropharyngeal space, and posteriorly by the perivertebral space.
The suprahyoid portion of the carotid space contains the internal carotid artery, the internal jugular vein, cranial nerves 9 through 12, the ansa cervicalis, the sympathetic plexus, and deep cervical lymph nodes [ 1 ]. The infrahyoid carotid space is surrounded anteriorly by the anterior cervical space, medially by the visceral and retropharyngeal spaces, and posteriorly by the perivertebral and posterior cervical spaces.
Below the level of the hyoid, the ansa cervicalis a loop of the first 3 cervical nerves and cranial nerves 9, 11, and 12 have exited, thus leaving only cranial nerve The internal jugular vein and the common carotid artery are also contained within the infrahyoid carotid space [ 2 ]. Knowledge of the location of particular structures within the carotid space can lead to the correct diagnosis, if not narrow, the differential to a few lesions.
The carotid artery is the center of the carotid space, and the jugular vein lies posterolateral to the carotid artery. The 10th cranial nerve lies in the posterior groove between these two vessels. The remaining cranial nerves 9, 11, and 12 all pierce the carotid sheath anteriorly. The ansa cervicalis is embedded in the anterior carotid sheath, and the sympathetic plexus is found posteriorly [ 3 ].
Lesions of the carotid space may arise from any of the above structures, and radiographic imaging is valuable in aiding diagnosis Fig. The carotid space. Paragangliomas, often referred to as glomus tumors, are rare neuroendocrine tumors that may occur anywhere in the body where healthy paraganglia occur. They are named for their location within the carotid sheath. These tumors tend to be well-marginated and highly vascular masses that are rubbery and firm on exam [ 4 ]. The majority of paragangliomas are nonfunctional.
While functional tumors are rare, they can be life-threatening and may present clinically with signs of catecholamine hypersecretion [ 7 ]. Nonfunctioning tumors grow insidiously and present as palpable masses or pain at the site of the tumor [ 8 ].
Due to the highly vascular nature of these masses, biopsy carries significant risk; thus, their diagnosis on imaging is the key [ 10 ]. Due to their hypervascularity, paragangliomas typically demonstrate arterial spectral waveforms on ultrasound imaging, and intense homogenous contrast enhancement on computed tomography CT and magnetic resonance imaging MRI.
Feeding and draining vessels can also be identified on angiography. The carotid body is the largest collection of paraganglia in the head and neck and is found on the medial aspect of the carotid bifurcation bilaterally.
Carotid body tumors are usually found in the fourth or fifth decade of life and are the most common head and neck paraganglioma. These tumors tend to grow slowly and painlessly and present as a lateral neck mass at the level of the carotid bifurcation.
Due to their location, and when large enough, they tend to splay the internal and external carotid arteries apart from each other [ 4 ] Fig. Carotid body tumor. There is mass effect on the internal jugular vein j.
The left carotid space dotted circle demonstrates the normal relationship of the carotid and jugular vessels. Again seen is splaying of the internal and external carotid arteries. These tumors have a predilection for females over males and typically present in the fifth or sixth decades of life.
Patients clinically present with pulsatile tinnitus, hearing loss or vertigo, and other symptoms related to the cranial nerves within the jugular foramen glossopharyngeal, vagus, and accessory [ 4 ]. These tumors can extend into the tympanic cavity glomus jugulotympanicum and may also involve the internal carotid artery or internal jugular vein. Glomus Jugulare. Sagittal a and axial b T1 post-contrast images demonstrate an enhancing mass white arrows centered at the jugular foramen arrowheads.
Note the prominent flow voids black arrows typical of a glomus tumor paraganglioma. The vagus nerve is the longest cranial nerve, and although paragangliomas may arise anywhere along its tract, they are most commonly found at the ganglion nodosum inferior ganglion at the level of the C1 lateral mass [ 12 ].
These tumors have a heavy predilection for females in the fifth or sixth decades of life, however they are less common than the carotid body tumor or glomus jugulare [ 13 ]. Clinically, these present as asymptomatic masses posterior to the angle of the mandible; however, symptoms of vagal nerve dysfunction such as dysphagia, hoarseness, and vocal cord paralysis may develop late in the course.
Although usually confined to the carotid space, these tumors can grow superiorly into the posterior fossa, entering via the jugular foramen, or inferiorly to the carotid bifurcation. As mentioned previously, the vagus nerve lies within the posterior aspect of the carotid space, and therefore, a large glomus vagale will anteriorly displace the carotid artery Figs.
Glomus vagale. Note the anterior displacement of the right internal i and external e carotid arteries, and lateral displacement of the right internal jugular vein j. The vessels are labeled in their normal configuration on the left. The normal position of the right internal carotid artery cr is also seen. Primary neurogenic tumors that arise from nerve sheaths outside of the central nervous system are termed peripheral nerve sheath tumors.
The overwhelming majority of these tumors are benign; however, malignant nerve sheath tumors can occur. Although major nerve trunks are most commonly affected, almost any peripheral nerve can be involved. Typically, peripheral nerve sheath tumors are categorized as either schwannoma or neurofibroma, both of which are associated with neurofibromatosis.
Both categories of nerve sheath tumors have similar imaging findings; however, they can be differentiated by their configuration relative to the affected nerve Fig. On CT imaging, they tend to be hypoattenuating relative to muscle and enhance with contrast administration.
On MRI, nerve sheath tumors present as low T1 signal and high T2 signal lesions which have avid contrast enhancement [ 14 ]. Nerve sheath tumors. Ten percent of these neurofibromas are associated with neurofibromatosis and can be categorized as localized, plexiform, or diffuse.
Diffuse neurofibromas are a subcutaneous lesion that do not present within the carotid space. Localized neurofibroma appear similar to solitary lesions but tend to be larger, multiple, and deeper in location. A characteristic target sign or fish-eye appearance of the lesion referring to a central hypointense region has also been described [ 15 ].
Plexiform neurofibromas are pathognomic for neurofibromatosis type I Fig. Plexiform neurofibroma. The left internal carotid artery i is displaced posterolaterally. This patient had neurofibromatosis, and extensive trans-spatial neurofibromas can be seen in other portions of the neck arrowheads.
Most schwannomas are solitary; however, they are associated with neurofibromatosis, in which case they can be multifocal and plexiform as well. Schwannomas are also typically asymptomatic until late in the disease course, where neurologic symptoms associated with compression of the associated nerve may present.
As mentioned previously, enhancement pattern of schwannoma can be similar to neurofibroma, and therefore, a salient differentiating imaging finding between the two is the eccentric position relative to the parent nerve in schwannoma Figs.
Schwannomas are also more likely to be heterogeneous in appearance with areas of degeneration and cystic cavitation when large [ 15 ].
It is important to remember that in addition to schwannomas involving the cranial nerves, they may also be found within the sympathetic chain. These lesions will be located anteriorly or medially within the carotid space, displacing the carotid vessels laterally Fig.
Sympathetic plexus schwannoma. The left parapharyngeal fat is medially displaced black arrow. Note the normal configuration of the right carotid space and parapharyngeal fat dotted circle. Note the anteromedial location of the lesion relative to the carotid vessels, indicating sympathetic plexus origin.
Lipomas are common, benign, well-circumscribed, and encapsulated soft masses comprised of mature adipocytes. Although these are most commonly found as subcutaneous nodules, they can be found anywhere in the body. These tumors demonstrate characteristic low fat attenuation on CT imaging and follow subcutaneous fat signal on all MRI sequences. Persistent areas of high T2 signal after fat saturation are a worrisome feature. Meningiomas are the most common extra-axial neoplasms of the central nervous system.
Most meningiomas occur intracranially and are by definition closely associated with the dura. Tumors in the region of the skull base, in particular at the jugular foramen, can extend inferiorly and into the carotid space Fig. Primary extradural meningiomas are very rare, but have also been described, and are thought to originate from embryologic arachnoid rests. The bone overlying meningioma is also often affected, most commonly with reactive hyperostosis.
On MRI, meningiomas typically demonstrate iso- to hypointensity relative to gray matter on T1-weighted images and iso- to hyperintensity on T2-weighted images. MRI can also detect sequelae of the mass effect such as venous sinus thrombosis and invasion, as well as parenchymal edema [ 17 ].
An enhancing dural tail is seen arrowhead. The normal position of the left internal carotid artery is also seen. Note the thickness of the normal left mastoid bone cortex black arrow. The vascular components of the carotid space are also subject to a variety of pathologies. These may be congenital or acquired. Arterial dissection occurs when the innermost and least elastic layer of an arterial wall, the tunica intima, tears and allows the blood to enter, and form hematoma, in the tunica media Figs.
An intimal tear can occur spontaneously, or may be related to trauma or iatrogenic causes. Regardless of the cause, it usually results in narrowing of the true vessel lumen. In stenosis of the coronary arteries , the internal thoracic artery can be used as a natural coronary artery bypass graft.
A stenosis of the subclavian artery proximal to the origin of the vertebral artery may result in subclavian steal syndrome. The common carotid arteries bi four cate at the level of C4. An increased carotid sinus sensitivity can result in syncopes due to low systolic blood pressure when pressure is applied to the carotid sinus. It is frequently associated with arteriosclerotic changes in the carotid sinus.
The temporal artery is involved in giant cell arteritis. A branch of the maxillary artery is the middle meningeal artery. It enters the skull through the foramen spinosum and mostly supplies the meninges and the skull. A craniocerebral injury can result in rupture or laceration of the middle meningeal artery , leading to the life-threatening condition of an epidural hematoma.
Description : A nerve plexus composed of the anterior rami of the cervical nerve roots , which provides motor and sensory innervation to most neck muscles and the area over the anterior and lateral neck. Posterior branches of cervical nerves. Phrenic nerve : C3, C4, C5 — keep the diaphragm alive!
A mediastinal tumor can present with shortness of breath , shoulder pain , and hiccups due to irritation of the phrenic nerve. Many structures in the head and neck have their origin in the pharyngeal arches , pharyngeal pouches , and pharyngeal grooves.
For a detailed description of these see branchial apparatus. Expand all sections Register Log in. Trusted medical expertise in seconds. Find answers fast with the high-powered search feature and clinical tools. Try free for 5 days Evidence-based content, created and peer-reviewed by physicians. Read the disclaimer. Overview of the head and neck region. Summary This chapter gives an overview of the important structures, muscles, fasciae , and vessels arteries , veins , lymph , nerves of the head and neck region.
Organs Organs of the head Eye and orbit The ear Nose and sinuses Skull , the cerebral cortex, meninges, basal ganglia, and ventricular system , vertebral column , brainstem , cerebrovascular system Oral cavity structures e. The hyoid bone can be palpated between the laryngeal prominence and the chin. Muscle Function Anterior auricular muscle Pulls the ear to the front Superior auricular muscle Pulls the ear cranially Posterior auricular muscle Pulls the ear backward.
Muscle Function Orbicularis oculi Eyelid closure Squeezing the eyes shut Blinking Animation of the lacrimal sac Corrugator supercilii Draw eyebrows together creating vertical fold frown line.
Muscle Function Nasalis Has two parts with opposing functions: tightening and widening of the nostrils Draws the tip of the nose caudal Depressor septi nasi Pulls the nose inferiorly; opening the nostrils Procerus Pulls the skin between the eyebrows caudal. Muscle Function Orbicularis oris Closes the mouth Purses the lips Buccinator Pulls cheeks inwards against the teeth while chewing Upper group Levator labii superioris , levator labii superioris alaeque nasi muscle , risorius , levator anguli oris , zygomaticus major , zygomaticus minor Lift upper lip and draw the corners of the mouth upwards smiling Lower group Depressor anguli oris , depressor labii inferioris , mentalis Draw down the lower lip and the corners of the mouth Mentalis : raises lower lip and chin of the skin pouting muscle.
Muscle Function Innervation Suprahyoid muscles Digastric , stylohyoid , mylohyoid, geniohyoid Form the bottom of the mouth Elevate the hyoid bone during swallowing Support the opening of the jaw Inferior alveolar nerve mylohyoid and anterior belly of digastric Facial nerve stylohyoid and posterior belly of digastric Anterior ramus of the spinal nerve C1 via the hypoglossal nerve Infrahyoid muscles Sternohyoid, infrahyoid, sternothyroid, thyrohyoid, omohyoid Depress the larynx and hyoid bone after swallowing Ansa cervicalis from the cervical plexus C1—C3 , except the thyrohyoid muscle that is innervated by a branch of the anterior rami of the C1 spinal nerve.
Muscle Characteristics Function Innervation Sternocleidomastoid Prominent muscle on the sides of the neck Arises from sternum and clavicle and inserts into the mastoid process Unilateral contraction Flexes the head laterally on the ipsilateral side Rotates the head to the contralateral side Bilateral contraction: flexes neck dorsally Accessory respiratory muscle Motor: accessory nerve XI Sensation: cervical plexus C2—C3 Platysma Broad superficial muscle that runs subcutaneously from the upper chest area to the lower jawbone mandible Reinforces the skin of the neck Pulls lips to the sides and down Opens jaw Cervical branch of the facial nerve.
Characteristics Superficial cervical lymph nodes Accompany the External jugular vein posterior cervical triangle Anterior jugular vein anterior cervical triangle Drain into the deep cervical lymph nodes Deep cervical lymph nodes Superior Accompany the internal jugular vein carotid triangle Form the jugular trunk that ends on the Right side: into the venous angle junction of internal jugular vein and subclavian vein Left side: into the thoracic duct Inferior Located on the internal jugular vein close to the subclavian vein.
References Panchbhavi VK. Neck Anatomy. Thus, it is best to name lymph node groups outside of the established levels I-VI. If "level VII" is used for superior mediastinal lymph nodes, it should refer to the extension of the paratracheal chain below the suprasternal notch but above the level of the brachiocephalic artery 4.
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