The common carotid artery runs through the neck and divides into internal and external carotid arteries on both sides near the upper thyroid cartilage. In emergency situations, carotid sinus massage is also used to diagnose or treat paroxysmal supraventricular tachycardia.

During the procedure, to maximize access to the carotid artery, the patient is put in a supine position with the neck extended (i.e. elevating the chin away from the chest). The carotid sinus is normally positioned inferior to the angle of the jaw, near the arterial impulse, at the level of the thyroid cartilage. For 5 to 10 seconds, pressure is administered to one carotid sinus.

Although pulsatile pressure applied in a vigorous circular motion may be more effective, continuous pressure is preferred since it is more reproducible. If the predicted reaction is not obtained, the operation is repeated on the opposite side after a one- to two-minute wait.

The anterior triangle is the triangular area of the neck found anteriorly to the sternocleidomastoid muscle. It is formed by the anterior border of sternocleidomastoid laterally, the median line of the neck medially and by the inferior border of the mandible superiorly. The apex of the anterior triangle extends towards the manubrium sterni. The anterior triangle contains:
Muscles: thyrohyoid, sternothyroid, sternohyoid muscles
Organs: thyroid gland, parathyroid glands, larynx, trachea, esophagus, submandibular gland, caudal part of the parotid gland
Arteries: superior and inferior thyroid, common carotid, external carotid, internal carotid artery (and sinus), facial, submental, lingual arteries
Veins: anterior jugular veins, internal jugular, common facial, lingual, superior thyroid, middle thyroid veins, facial vein, submental vein, lingual veins
Nerves: vagus nerve (CN X), hypoglossal nerve (CN XII), part of sympathetic trunk, mylohyoid nerve

The posterior triangle is a triangular area found posteriorly to the sternocleidomastoid muscle. It has three borders; anterior, posterior and inferior borders. The anterior border is the posterior margin of the sternocleidomastoid muscle. The posterior border is the anterior margin of the trapezius muscle, while the inferior border is the middle one-third of the clavicle. The investing layer of deep cervical fascia and integument forms the roof of the space, while the floor is covered with the prevertebral fascia along with levator scapulae, splenius capitis and the scalene muscles. The inferior belly of omohyoid subdivides the posterior triangle into a small supraclavicular, and a large occipital, triangle.
Contents:
Vessels: the third part of the subclavian artery, suprascapular and transverse cervical branches of the thyrocervical trunk, external jugular vein, lymph nodes
Nerves: accessory nerve (CN XI), the trunks of the brachial plexus, fibers of the cervical plexus

The anterior triangle is the triangular area of the neck found anteriorly to the sternocleidomastoid muscle. It is formed by the anterior border of sternocleidomastoid laterally, the median line of the neck medially and by the inferior border of the mandible superiorly. The apex of the anterior triangle extends towards the manubrium sterni. The anterior triangle contains:
Muscles: thyrohyoid, sternothyroid, sternohyoid muscles
Organs: thyroid gland, parathyroid glands, larynx, trachea, esophagus, submandibular gland, caudal part of the parotid gland
Arteries: superior and inferior thyroid, common carotid, external carotid, internal carotid artery (and sinus), facial, submental, lingual arteries
Veins: anterior jugular veins, internal jugular, common facial, lingual, superior thyroid, middle thyroid veins, facial vein, submental vein, lingual veins
Nerves: vagus nerve (CN X), hypoglossal nerve (CN XII), part of sympathetic trunk, mylohyoid nerve

The posterior triangle is a triangular area found posteriorly to the sternocleidomastoid muscle. It has three borders; anterior, posterior and inferior borders. The anterior border is the posterior margin of the sternocleidomastoid muscle. The posterior border is the anterior margin of the trapezius muscle, while the inferior border is the middle one-third of the clavicle. The investing layer of deep cervical fascia and integument forms the roof of the space, while the floor is covered with the prevertebral fascia along with levator scapulae, splenius capitis and the scalene muscles. The inferior belly of omohyoid subdivides the posterior triangle into a small supraclavicular, and a large occipital, triangle.
Contents:
Vessels: the third part of the subclavian artery, suprascapular and transverse cervical branches of the thyrocervical trunk, external jugular vein, lymph nodes
Nerves: accessory nerve (CN XI), the trunks of the brachial plexus, fibers of the cervical plexus

All lymphatics from the tongue ultimately drain into the deep cervical chain of nodes along the internal jugular vein, particularly the jugulo-omohyoid lymph node.

A blowout fracture is an isolated fracture of the orbital walls without compromise of the orbital rims. The common mechanisms are falls, high-velocity ball-related sports, traffic accidents, and interpersonal violence.

The frontal, ethmoidal, sphenoid, zygomatic, and lacrimal bones form the bony structures of the orbit. Medially, the maxillary and the lacrimal bone form the lacrimal fossa. Together with the lamina papyracea of the ethmoid bone, they form the medial wall. The sphenoid bone forms the posterior wall and houses the orbital canal. Lateral to the orbital canal lies the superior orbital fissure housing cranial nerves III, IV, V, and VI. The zygomatic bone forms the lateral wall. Superior and inferior borders are the frontal and maxillary bones. Located around the globe of the eye and attached to it are 6 extraocular muscles; the 4 rectus muscles and the superior and inferior oblique muscles. The fat and connective tissue around the globe help to reduce the pressure exerted by the extraocular muscles.

The goal of treatment is to restore aesthetics and physiological function. The problem with orbital blowout fractures is that the volume of the orbit can be increased, resulting in enophthalmos and hypoglobus. In addition, the orbital tissue and inferior rectus muscle can become trapped by the bony fragments leading to diplopia, limitation of gaze, and tethering. Finally, the orbital injury can lead to retinal oedema, hyphema, and significant loss of vision.

While some cases may be managed with conservative care, others may require some type of surgical intervention.

The anterior triangle is the triangular area of the neck found anteriorly to the sternocleidomastoid muscle. It is formed by the anterior border of sternocleidomastoid laterally, the median line of the neck medially and by the inferior border of the mandible superiorly. The apex of the anterior triangle extends towards the manubrium sterni. The anterior triangle contains:
Muscles: thyrohyoid, sternothyroid, sternohyoid muscles
Organs: thyroid gland, parathyroid glands, larynx, trachea, esophagus, submandibular gland, caudal part of the parotid gland
Arteries: superior and inferior thyroid, common carotid, external carotid, internal carotid artery (and sinus), facial, submental, lingual arteries
Veins: anterior jugular veins, internal jugular, common facial, lingual, superior thyroid, middle thyroid veins, facial vein, submental vein, lingual veins
Nerves: vagus nerve (CN X), hypoglossal nerve (CN XII), part of sympathetic trunk, mylohyoid nerve

The posterior triangle is a triangular area found posteriorly to the sternocleidomastoid muscle. It has three borders; anterior, posterior and inferior borders. The anterior border is the posterior margin of the sternocleidomastoid muscle. The posterior border is the anterior margin of the trapezius muscle, while the inferior border is the middle one-third of the clavicle. The investing layer of deep cervical fascia and integument forms the roof of the space, while the floor is covered with the prevertebral fascia along with levator scapulae, splenius capitis and the scalene muscles. The inferior belly of omohyoid subdivides the posterior triangle into a small supraclavicular, and a large occipital, triangle.
Contents:
Vessels: the third part of the subclavian artery, suprascapular and transverse cervical branches of the thyrocervical trunk, external jugular vein, lymph nodes
Nerves: accessory nerve (CN XI), the trunks of the brachial plexus, fibers of the cervical plexus

Hutchinson sign relates to involvement of the tip of the nose from facial herpes zoster. It implies involvement of the external nasal branch of the nasociliary nerve which is a branch of the ophthalmic division of the trigeminal nerve.

The nasociliary branch of the trigeminal nerve innervates the apex and lateral aspect of the nose, as well as the cornea. Therefore, lesions on the side or tip of the nose should raise suspicion of ocular involvement.

Sensory innervation to the external ear is supplied by both cranial and spinal nerves. Branches of the trigeminal, facial, and vagus nerves (CN V, VII, X) are the cranial nerve components, while the lesser occipital (C2, C3) and greater auricular (C2, C3) nerves are the spinal nerve components involved. The lateral surface of the tympanic membrane, the external auditory canal, and the external acoustic meatus are all innervated by nervus intermedius (a branch of CN VII), the auriculotemporal nerve (CN V3), and the auricular branch of the vagus nerve. The concha receives split innervation from nervus intermedius, the auricular branch of the vagus nerve, and the greater auricular (spinal) nerve. Beyond the concha, the anteromedial and anterosuperior parts of the pinna are innervated by the auriculotemporal nerve, and a portion of the lateral helix by the lesser occipital nerve. The greater auricular nerve provides innervation to the area of the pinna inferolateral to the lobule.

Mastoiditis is the inflammation of a portion of the temporal bone referred to as the mastoid air cells. The mastoid air cells are epithelium lined bone septations that are continuous with the middle ear cavity.

The temporal bone is composed of four parts: the mastoid process, the petrous pyramid, the squamous, and tympanic portions. The mastoid process and the petrous pyramid are the portions of particular interest because of the prevalence of suppurations within these parts of the temporal bone.

In adults, there are 32 teeth, 16 in the upper jaw and 16 in the lower jaw. On each side in both upper and lower arches, there are two incisors, one canine, two premolars and three molar teeth.