Head and Neck Anatomy Flashcards

Question

An otherwise healthy term 6-month-old male infant is evaluated for a mobile, firm, well-circumscribed mass at the right lateral brow in the area of the zygomaticofrontal suture. Which of the following procedures is the most appropriate next step in management? A) CT scan B) Fine-needle aspiration of the mass C) MRI D) Surgical excision of the mass E) Ultrasonography

Answer 1

The correct response is Option D. Dermoid cysts are common in the lateral brow. They present as firm, well-circumscribed, slow-growing masses that have the potential for infection or continued growth. Surgical excision is recommended and no imaging is required. CT scan or MRI require sedation and are unnecessary risks for this patient with a lateral dermoid. Midline masses do require imaging because of the risk for intracranial excision.

Answer 2

The correct response is Option D. The first branchial arch is associated with the trigeminal nerve (V), second branchial arch with the facial nerve (VII), third branchial arch with the glossopharyngeal (IX), fourth branchial arch with the superior laryngeal (X), and sixth branchial arch with the recurrent laryngeal (X).

Answer 3

The correct response is Option B. The patient described has a persistent thyroglossal duct cyst. The thyroid gland is the first of the body’s endocrine glands to develop, at approximately 24 days’ gestation. The gland originates as a proliferation of endodermal epithelial cells on the median surface of the developing pharyngeal floor known as the foramen cecum. The foramen cecum originates from between the first and second pouches and represents the opening of the thyroglossal duct into the tongue. Descent of the thyroid gland carries it anterior to the hyoid bone and anterior to the laryngeal cartilages. As the thyroid gland descends, it forms its mature shape. The thyroid completes its descent in the seventh gestational week, coming to rest in its final location immediately anterior to the trachea. If the thyroglossal duct does not atrophy, then the remnant can manifest clinically as a thyroglossal duct cyst. While half of these generally midline cystic masses are located at or just below the level of the hyoid bone, they may be located and can track anywhere from the thyroid cartilage up the base of the tongue. Because the hyoid bone develops in an anterior direction and may surround the thyroglossal duct, the surgeon should resect the central portion on the hyoid bone along with the cyst. The thyroid gland is ensheathed by the visceral fascia, which attaches it firmly to the laryngoskeleton (i.e., Berry ligament). This firm attachment of the gland to the laryngoskeleton is responsible for movement of the thyroid gland and related structures during swallowing. This also causes a thyroglossal duct cyst to move on physical examination. Ectopic thyroid gland may occur anywhere along the path of initial descent of the thyroid, although it is most common at the base of the tongue, just posterior to the foramen cecum. Ectopic parathyroid glands occur in 15 to 20% of patients. The glands may be located anywhere near or even within the thyroid or thymus. For example, if parathyroid IVs do not descend entirely, they may be located as high as the bifurcation of the common carotid artery. Conversely, if parathyroid IVs do not release from the thymus, they may be located intrathoracically, as low as the aortopulmonary window. Other common ectopic locations include the anterior mediastinum, posterior mediastinum, and retroesophageal and prevertebral regions. However, even when the parathyroid glands are in an ectopic location, they still often are symmetrical from side to side, making localization somewhat easier. Ossification of cartilages from the second and third pharyngeal arches gives rise to the hyoid bone.

Answer 4

The correct response is Option B. Dermoid cyst is the correct answer and the most common cause of a lateral brow mass in an infant. If it were a hemangioma, its size would change during crying or any activity that increases blood flow. Lacrimal gland ptosis is unlikely in a child but can be seen in the adult population, and can be ruled out if the mass is above the orbital rim, as seen in the photograph. The mass is not in the distribution of any of the different types of branchial cleft cysts. Lymphatic malformations typically change in size during infections.

Answer 5

The correct response is Option C. The origin of the superior thyroid artery is predictable and most commonly it arises from the external carotid artery. It has, however, been described to arise from all three of the other options, just less frequently.

Answer 6

The correct response is Option D. The first branchial arch is associated with the trigeminal nerve (V), second branchial arch with the facial nerve (VII), third branchial arch with the glossopharyngeal (IX), fourth branchial arch with the superior laryngeal (X), and sixth branchial arch with the recurrent laryngeal (X).

Answer 7

The correct response is Option B. The parotid gland is the largest of the three paired salivary glands (parotid, submandibular, and sublingual). It has two lobes, the deep and superficial, each of which is enveloped in a fascial sheath (parotid sheath) and between which passes the facial vein and nerve. The superficial lobe lies lateral (superficial) to the masseter muscle, and the deep lobe lies between the mastoid process and the mandibular ramus. The parotid, or Stensen, duct arises from the deep lobe of the parotid gland and receives contributions from the superficial lobe as it travels anteriorly. After exiting the anterior edge of the superficial lobe, the duct passes directly over the masseter muscle, crosses over the anterior edge of the masseter, extends medially and anteriorly over and through the buccinator muscle, and enters into the mouth via the parotid papilla, typically located opposite the second maxillary molar. The course of the duct has classically been described as following a line connecting the tragus and the midportion of the upper lip, but there is significant variation, and some studies report that this line should end in the lower half of the upper lip. The laceration shown in the photograph is just at the anterior border of the parotid and, at this level, the duct should be passing over the masseter muscle and its fascia. The course of the duct is below the superficial lobe of the parotid and, therefore, well below the subcutaneous tissue and the submuscular aponeurotic system (SMAS), which is confluent with the platysma inferiorly and the temporoparietal fascial superiorly. Superficial parotid fascia defines the layer of fascia that invests the superficial lobe of the parotid gland.

Answer 8

The correct response is Option B. The lesion described is a mucocele, which is a type of cyst likely caused by minor salivary gland mucin seepage. They are most frequently on the lower lip mucosa away from the midline, but they can present anywhere there is oral mucosa. A minority of these resolve on their own, therefore, the majority of the time an excisional biopsy is recommended. Imaging is not indicated for this type of lesion. Fine-needle aspiration is not indicated.

Answer 9

The correct response is Option A. Although it is most commonly seen after parotidectomy, Frey syndrome has also been encountered after condylar fracture of the mandible and treatment. The syndrome is thought to result from damage to auriculotemporal parasympathetic nerve fibers with subsequent aberrant regeneration and innervation of sympathetic fibers to the sweat glands. The facial, inferior alveolar, greater auricular, and lingual nerves are not thought to be the underlying cause of Frey syndrome.

Answer 10

The correct response is Option E. When performing head and neck microsurgery, a strong background in the vascular anatomy of that region is imperative. As chemotherapy regimens have become commonplace for laryngopharyngeal cancers, so have the challenges of failures which generally require surgery. These cases have much higher complication rates, including fistulas, strictures, and carotid injury, among others. This case demonstrates another complexity that is increasingly observed, the “vascular or vessel-depleted neck.” The facial and occipital arteries are branches of the external system and would not be available. The subclavian is generally not a viable option due to its size, location, and potential complications through dissection. The internal mammary system has potential, but requires dissection through the ribs and has morbidities and the potential need of vein grafts. Generally speaking, even radical neck dissections do not sacrifice the transverse cervical vessels as they are usually used as the caudal margin. A number of reports have detailed the usefulness of these vessels as recipients in cases like the one described.

Answer 11

The correct response is Option D. Adenoid cystic carcinoma of the hard or soft palate is a slow-growing, insidious disease with a tendency to spread via a perineural mechanism along the palatine branches of the maxillary division of the trigeminal nerve. The facial nerve exits the skull base from the stylomastoid foramen. The foramen lacerum, foramen ovale, and the foramen rotundum contain the internal carotid artery, mandibular (V3) nerve, and maxillary (V2) nerve, respectively. The glossopharyngeal (IX), vagus (X), and spinal accessory (XI) nerves emerge from the jugular foramen.

Answer 12

The correct response is Option A. Auricular hillocks are ectodermal derivatives of the first pharyngeal groove and are responsible for the formation of external ear structures (e.g., auricle and external auditory canal [EAC]). Incomplete fusion of the auricular hillocks (defective closure of the dorsal 1st pharyngeal groove) results in preauricular sinus. This is the only answer choice that contributes to the development of the external ear. The meatal plug is an ectodermal derivative of the first pharyngeal groove (extends from the medial end of the EAC), which largely degenerates/canalizes, but is responsible for formation of the surface layer of the tympanic membrane. Persistence of the meatal plug results in conductive congenital deafness. The otic vesicle is an ectodermal derivative of the developing brain that is responsible for formation of inner ear structures (e.g., saccule, utricle, semicircular and cochlear ducts, and membranous cochlea including the spiral organ of Corti). Abnormal development of the membranous labyrinth results in sensorineural congenital deafness. The otic capsule is derived from mesenchyme of the first and second pharyngeal arches, surrounds/is induced by the otic vesicle, and is responsible for formation of inner ear structures (e.g., bony labyrinth). Abnormal development of the bony labyrinth results in sensorineural congenital deafness. The tubotympanic recess is an endodermal derivative of the first pharyngeal pouch, responsible for the formation of middle ear structures (e.g., auditory tube, tympanic cavity, etc.). Abnormal/under-development of the middle ear structures increases the risk for chronic otitis media and can have an effect on conductive hearing.

Answer 13

The correct response is Option A. Initial treatment of acute suppurative sialadenitis begins with aggressive medical management. This includes prompt fluid and electrolyte replacement, oral hygiene, reversal of salivary stasis, and antimicrobial therapy. Stimulation of salivary flow is done by use of sialogogues such as lemon drops. Warm soaks and massage promote secretion and drainage of the gland. Oral cultures are typically contaminated by oral flora and therefore do not direct antibiotic treatment. Needle aspiration is more accurate in isolating the cause of suppurative parotitis. Incision and drainage is reserved for cases resistant to medical management. Surgical removal of the gland is not recommended in the case of an actively infected gland.

Answer 14

The correct response is Option D. Avulsion of a permanent tooth is one of the most serious dental injuries that may be encountered by a plastic surgeon. Without prompt intervention, the tooth may be lost, committing the patient to a bone graft, an implant, or lifelong prosthodontic appliance. When a permanent tooth is fully avulsed, exposure of the periodontal ligament can lead to its desiccation and cell death within an hour of injury. The long-term viability of a tooth with a dry time of greater than 60 minutes is poor. If the tooth cannot be immediately replanted, it should be stored in a neutral medium such as milk, saliva (in the mouth), or Hanks balanced storage solution. Enamel and cementum make the hard outer layer of the tooth (enamel at the crown and cementum at the root) and are relatively resistant to damage with an avulsion. Dentin is the thick layer deep to the enamel/cementum, which makes up the bulk of the tooth and is not typically injured in a clean avulsion. The pulp contains the neurovascular supply of the tooth. In a complete avulsion, the pulp will become nonviable and will need to be removed with a root canal procedure after the tooth has become stable. However, with appropriate treatment, the tooth can survive after the pulp has been removed.

Answer 15

The correct response is Option C. Each of the six branchial arches gives rise to a branch of the aortic arch, a cranial nerve, muscular structures, and skeletal structures. The fourth branchial arch gives rise to the right proximal subclavian artery, the aortic arch, the vagus (X) nerve, the superior laryngeal nerve, the intrinsic muscles of the levator veli palatini, cricothyroid muscles, laryngeal cartilages, and the superior parathyroid glands. The styloid process is derived from the second branchial arch, along with the stapedial and hyoid arteries, the facial (VII) nerve, the muscles of facial expression, the stapes, the lesser horn of the hyoid bone, and the crypts of the palatine tonsils. The maxillary artery is derived from the first branchial arch, along with the trigeminal (V) nerve, the muscles of mastication, anterior belly of the digastric muscle, tensor tympani, tensor veli palatini, mylohyoid, mandible, incus and malleus, maxilla, vomer, zygoma, and temporal bone. The inferior parathyroid glands are derived from the third branchial arch, along with the common carotid artery, internal carotid artery, glossopharyngeal (IX) nerve, stylopharyngeus muscle, greater horn of the hyoid bone, and thymus. The lesser horn of the hyoid bone is derived from the second branchial arch.

Answer 16

The correct response is Option C. The ear development starts during the third month of gestation from six hillocks that arise on the first and second arches. The first pharyngeal cleft develops into the external auditory meatus. The second through fourth pharyngeal clefts are usually obliterated due to the expansion of the second pharyngeal arch. The first pharyngeal pouch develops into the auditory tube and middle ear cavity. The second through fourth pharyngeal pouches are not related to ear development, nor is the third pharyngeal arch. The second pouch becomes the palatine tonsils' crypts, while the third pouch forms parathyroid glands and thymus. The fourth pouch differentiates into parathyroid glands and parafollicular cells of the thyroid gland. The cartilaginous component of the third pharyngeal arch gives rise to part of the hyoid bone.

Answer 17

The correct response is Option C. Because 80% of a meal's flavor is a result of olfactory input, patients often interpret a loss of smell as a loss of taste. For most patients who complain of chemosensory loss, however, the sense of taste—biologically, the sensation of salt, bitter, sweet, sour, and umami (monosodium glutamate)— which is from cranial nerve V, is intact. In a large prospective study, 7 to 9% of individuals who have undergone various types of nasal surgery experienced a decrease in olfactory function. Gustatory rhinorrhea is an increasingly recognized complication of septoplasty and rhinoplasty that is associated with clear rhinorrhea postoperatively when the patient eats. This complication is not usually associated with changes in taste. It probably stems from inappropriate nerve regeneration, not dissimilar to gustatory sweating (Frey syndrome) after parotidectomy. Many drugs can affect taste, but usually antibiotics given for this type of surgery would be limited to a short course, and their side effects would almost certainly be resolved. Injury to the tongue and its nerves, including the lingual nerve, is possible, but rare; injury also would have been resolved in a period of 3 months.

Answer 18

The correct response is Option A. One of the determinants of beauty is facial shape. For a woman, a heart-shaped face is considered youthful and attractive. With a history of bruxism, masseter hypertrophy changes the face into a more square, masculine shape. Botulinum injections can reduce the facial bulk, redefine the lower facial width, and make the face more youthful and heart-shaped. The other surgical options are associated with significant morbidity and may not give the desired shape. Orthodontic care is used for patients whose malocclusion has altered the facial shape.

Answer 19

The correct response is Option D. The supraorbital nerve (SON) supplies sensation to the forehead skin (paramedian) and anterior scalp as well as the frontoparietal scalp. The latter scalp is supplied by the deep division of the nerve, whereas the rest is supplied by its superficial division. Medially passing through the corrugator supercilii muscle is the supratrochlear nerve, which supplies the medial skin of the forehead. The deep division of the SON travels initially (just medial to the superotemporal line) along the temporal periosteum and then more cephalad pierces the deep galea plane and enters the galea fat pat. This information is the key to avoid injury when performing a forehead lift. Also, when planning a bicoronal incision for craniofacial surgery, one can use this information to preserve the sensation of the related scalp. The superficial branch of the SON, on the other hand, travels superficial to the frontalis muscle in the paramedian forehead area.

Answer 20

The correct response is Option D. The trigeminal nerve (cranial nerve V) develops from the first branchial arch and gives rise to the malleus and incus. The ligaments associated with the first branchial arch are the anterior ligament of the malleus and the sphenomandibular ligament. The muscles of the first branchial arch include the muscles of mastication (masseter, temporalis, medial pterygoid, lateral pterygoid), tensor veli palatini, tensor tympani, mylohyoid, and the anterior belly of the digastric. The first pouch is associated with the external auditory canal and middle ear space. The facial nerve (cranial nerve VII) develops from the second branchial arch and gives rise to the stapes, styloid, and the upper body of the hyoid. It includes the stylohyoid ligament. The associated muscles are facial expression muscles, stapedius, stylohyoid, and the posterior belly of the digastric. The second pouch is associated with the tonsillar fossa. The glossopharyngeal nerve (cranial nerve IX) develops from the the third branchial arch and gives rise to the lower body of the hyoid. Its muscle is the stylopharyngeus, and the pouch is associated with the inferior parathyroid gland and the thymus. The fourth branchial arch is associated with the larynx. The muscles associated with this arch are the laryngeal, pharyngeal, and soft palate. The pouch is associated with the superior parathyroid gland and the thyroid gland.

Answer 21

The correct response is Option A. Aside from the third molars, the maxillary canines are typically the last teeth to erupt of the available options (around 11 to 12 years of age). It is important to give the tooth a large area of viable bone to traverse and become supported by, and alveolar bone grafting is typically performed well in advance of the eruption of the maxillary canine in order to preserve the native tooth. The maxillary central incisor is often the second permanent tooth a child will erupt, typically at age 7 to 8 years. The maxillary lateral incisor is often the third permanent tooth a child will erupt, typically at age 8 to 9 years. The maxillary first premolar is often the fourth permanent tooth a child will erupt, typically at age 10 to 12 years. The maxillary first molar is often the first permanent tooth a child will erupt, typically at age 6 to 7 years.

Answer 22

The correct response is Option A. A deformity upon facial animation characterized by descent of the nasal tip, shortening of the upper lip, and a transverse crease in the mid philtral area may be created or accentuated by the action of the depressor septi nasi muscles. These are small, paired muscles located on each side of the nasal septum, which originate at the medial crura foot plates and insert either on the incisive fossa of the maxilla or into the fibers of the orbicularis oris muscle. Physical examination upon facial animation should be part of the routine preoperative evaluation of the rhinoplasty patient. Those who present with the dynamic deformity as described may benefit from excision or transection of the depressor septi nasi muscles. Several surgical techniques have been described, as well as the use of botulinum toxin type A. The nasalis muscle compresses the cartilaginous part of the nose and draws the ala toward the septum. Although this may generate some depression of the tip of the nose, it should not cause shortening of the upper lip. The procerus muscle depresses the medial angle of the eyebrows, creating transverse rhytides over the bridge of the nose. The risorius muscles retract the angles of the mouth, as in a grinning expression. The zygomaticus major muscles draw the angles of the mouth posteriorly and superiorly, as in laughing. These muscles do not cause depression of the tip of the nose.

Answer 23

The correct response is Option E. The answer is uvulopalatopharyngoplasty (UP3). The mainstay of UP3 surgery is to remove the uvula and lateral oropharyngeal tissues. The most common site of obstruction in obstructive sleep apnea (OSA) patients is the retropalatal area, including the lateral pharyngeal walls. This latter anatomic area is even more important if the patient has never had a tonsillectomy; in this case, the tonsils are removed in continuity with UP3. UP3 generally decreases the various indexes documented during a sleep study, such as the apnea-hypopnea index, by about 50%. Thus, those at the border of severe and moderate sleep apnea can see their reported indexes go to a level that can be managed by lifestyle changes without the need for a continuous positive airway pressure (CPAP) machine. On the other hand, in patients with very high indexes, these procedures merely make the disease less severe and may allow for a lower setting on the CPAP machine. Although the CPAP machine which applies positive pressure transnasally to patients can “cure” OSA, their compliance rates are low. There are other procedures that can help with OSA, such as a septoplasty or those that deal with the tongue base (e.g., geniohyoid advancement), but neither directly treats the most common site of obstruction. A tracheostomy is a curative treatment for OSA, but it completely bypasses all of the obstructive points without addressing them. A tracheostomy has much morbidity, including a measurable mortality rate, and is reserved for life-threatening cases of OSA. A sagittal split operation of the mandible is used for occlusion, not OSA.

Answer 24

The correct response is Option D. In patients with abnormal or excessive scar tissue formation, treatment and prognosis will be driven by the correct diagnosis of a keloid versus a hypertrophic scar. This patient presents with a recurrent keloid of the chest. His clinical history supports this diagnosis by recurrence after resection, growth extending beyond the original border of the lesion, late recurrence after several years, and continued growth over several years without regression or improvement. Hypertrophic scars are less likely to recur, contained within the original boundaries of the lesion, often regress somewhat within a year, and recur earlier in the postoperative period if they are to recur. Both hypertrophic scars and keloid scars can be pruritic. Pathologic analysis of keloids reveals more type I collagen than type III collagen, similar to normal skin. Hypertrophic scars will exhibit increased type III collagen and pro-fibrotic collagen cross-linking. Keloid growth is thought to be impacted by cell-signaling between keratinocytes and fibroblasts, but hypertrophic scar production requires an abundance of myofibroblasts expressing smooth muscle actin. While hypertrophic scars have parallel collagen fibrils and bundles, keloids are characterized histologically by thick, randomly oriented collagen fibrils that are not organized into bundles.

Answer 25

The correct response is Option A. Knowledge of the innervation of the external ear is critical to the understanding of its embryologic development, as well as in the delivery of adequate local anesthesia for minor surgical procedures. Sensation to the external ear is derived from several cranial and extracranial nerve branches. The great auricular (C2 to C3) and lesser occipital (C2) are cranial nerves which innervate the posterior aspect of the auricle and lobule. While the distribution is variable, in most cases the lesser occipital supplies the superior ear and mastoid region while the great auricular nerve supplies the inferior ear and a portion of the preauricular area. The anterior surface of the ear, including the helix, scapha, and concha, is supplied by the auriculotemporal nerve (V3 trigeminal) and is most likely to be injured in a microvascular decompression for the treatment of trigeminal neuralgia. Branches of the vagus (X) and glossopharyngeal (IX) nerve innervate the external auditory meatus. The innervation to the external ear follows its embryologic branchial arch origins with the great auricular nerve innervating first branchial arch structures and the auriculotemporal nerve innervating second branchial arch structures. An auriculotemporal nerve block provides anesthesia to the helix and tragus and is approached by injecting 2 to 4 mL of anesthesia superiorly and anteriorly to the tragus. The great auricular nerves and lesser occipital nerves are blocked by injecting 2 to 4 mL of anesthetic to the posterior sulcus from the inferior aspect of the earlobe. This will provide anesthesia to the earlobe and lateral helix.

Answer 26

The correct response is Option B. The stage of mixed dentition is defined as the age range in which there are both deciduous (primary) and permanent (secondary) teeth erupted in the oral cavity at the same time. Normally, the mandibular and maxillary teeth erupt in a slightly different pattern. This usually occurs at age 6 to 7 years and is completed by age 11 to 12 years. In the maxilla, the order of eruption is as follows: first molar, central incisor, lateral incisor, first premolar, second premolar, canine, second molar, and third molar. In the mandible, the order is slightly different and is as follows: first molar, central incisor, lateral incisor, canine, first premolar, second premolar, and second molar. The permanent first molars erupt between ages 6 and 7 years, the central and lateral incisors erupt between ages 6 and 8 years, and the first premolars erupt between ages 8 and 9 years. The first tooth to erupt is the permanent mandibular first molar, which erupts first in a position posterior to the deciduous second molar. There are no premolars in deciduous teeth.

Answer 27

The correct response is Option B. The pharyngeal, or branchial, arches are developmental structures derived from all three germ layers and also contain neural crest cells. These arches give rise to bony, cartilaginous, vascular, muscular, and neural structures of the head and neck. The second pharyngeal arch gives rise to the muscles of facial expression, posterior belly of the digastric muscle, and the stapedius muscle. These muscles are innervated by the facial nerve (VII), which also arises from this arch. The first pharyngeal arch gives rise to the muscles of mastication, anterior belly of the digastric, mylohyoid, tensor tympani, and tensor veli palatini muscles as well as the trigeminal nerve (V). The third pharyngeal arch gives rise to the stylopharyngeus muscle as well as the glossopharyngeal nerve (IX). The fourth pharyngeal arch gives rise to the cricothyroid muscle and all intrinsic muscles of the soft palate except the tensor veli palatini, as well as the superior laryngeal nerve (X). The sixth pharyngeal arch gives rise to the intrinsic muscles of the larynx except the cricothyroid muscle as well as the recurrent laryngeal nerve (X). The fifth pharyngeal arch does not give rise to structures in humans.

Answer 28

The correct response is Option D. Effective treatment of penetrating neck injuries depends on a thorough understanding of neck anatomy. The neck houses vital structures from six organ systems: The vascular system includes the innominate, subclavian, axillary, carotid, jugular, and vertebral vessels. The respiratory system includes the larynx, trachea, and the lung. The digestive system includes the pharynx and esophagus. The neurologic system includes the spinal cord, brachial plexus, cranial nerves, and the sympathetic chain. The endocrine system includes the thyroid and parathyroid. The skeletal system includes the cervical spine. Anatomy of the neck may be considered using two anatomical paradigms: the concept of “triangles” and the concept of “zones.” The triangles are divided into anterior and posterior, while the zones are divided in a cranial/caudal orientation anterior to the sternocleidomastoid muscle. An understanding of both is important when considering penetrating injuries. The neck may be divided into two triangles, anterior and posterior to the sternocleidomastoid muscle. The anterior triangle is bordered anteriorly by the midline, posteriorly by the sternocleidomastoid muscle, and superiorly by the lower edge of the mandible. Most vital structures are located in the anterior triangle. The posterior triangle is located within the boundaries of the sternocleidomastoid muscle anteriorly, inferiorly by the clavicle, and the anterior border of the trapezius muscle posteriorly. Trauma to the posterior triangle, excluding the spine, carries a much lower likelihood of significant injury. Zone I is in the inferior neck and includes the base of the neck and thoracic inlet. It extends from the sternal notch and clavicles to the cricoid cartilage. Zone I contains the thoracic outlet vasculature, vertebral and proximal carotid arteries, apices of the lungs, trachea, esophagus, spinal cord, and thoracic duct. Zone II is in the mid-neck and continues cephalad from the cricoid cartilage to the angle of the mandible, and contains the jugular veins, vertebral and common carotid arteries, and internal and external branches of the carotid arteries. It also includes nonvascular structures including the trachea, esophagus, larynx, and spinal cord. Zone III (upper neck) includes the region above the angle of the mandible up to the base of the skull and contains the pharynx along with the jugular veins, vertebral arteries, and the distal portion of the internal carotid arteries. Its caudal border is distal to the common carotid arteries. Portions of the jugular vein are located in all three zones. Only Zone III is located above the angle of the mandible.

Answer 29

The correct response is Option B. The pharyngeal muscles are all innervated by the vagus (X) nerve, except the stylopharyngeus muscle, which is innervated by the glossopharyngeal nerve (IX). The trigeminal nerve (V) is responsible for facial and oral sensation. The maxillary branch (V2) is responsible for sensation of the upper teeth, upper lip, hard palate, cheeks, and nasopharyngeal mucosa. The mandibular branch (V2) provides sensory fibers for the lower teeth, lower mucosa of the mouth and the anterior two-thirds of the tongue. The facial nerve (VII) provides motor innervation of the muscles of facial expression and the posterior bellies of the stylohyoid and digastric muscles. The vagus nerve (X) provides motor innervation to all of the pharyngeal muscles except the stylopharyngeus muscle. The hypoglossal nerve (XII) provides motor innervation to the intrinsic and extrinsic tongue muscles and also provides motor innervation to the geniohyoid muscle through the ansa cervicalis.

Answer 30

The correct response is Option B. Benign masseteric hypertrophy may present as a bilateral or a unilateral condition. When unilateral, it is associated with repetitive unilateral clenching of the teeth. Both the masseter and temporalis muscles of the affected side show varying degrees of enlargement. When mild, medical management may be offered first and can include muscle relaxants, anxiolytics, antiepileptic drugs, and botulinum toxin type A. Surgical resection of a portion of the masseter and/or bone contouring are appropriate surgical procedures for correction of the resulting cosmetic deformity. Unilateral masseteric hypertrophy must be distinguished from unilateral condylar hyperplasia, the latter consisting of the enlargement or overgrowth of the mandibular condyle. Condylar hyperplasia may also present with unilateral facial enlargement (type IB or type II), deviation of the mandibular midpoint toward the unaffected side, class III occlusion on the ipsilateral side, and a crossbite on the contralateral side. Condylar resection is the mainstay of treatment. Condylar reduction is appropriate for cases of condylar dislocation. This condition can occur unilaterally in patients with a hypermobile or stretched temporomandibular joint, or in patients with dystonia (hyperfunction of the lateral pterygoid muscle). Condylar dislocation occurs suddenly, and causes pain and a class III occlusion on the involved side. Condylar reduction is performed with the aid of muscle relaxants. Eminence surgery may be necessary (eminectomy, eminoplasty). Orthodontics are unnecessary for someone with bruxism, which is a typical feature of masseteric hypertrophy. However, a mouth guard is appropriate. Radiation is inappropriate for benign masseteric hypertrophy. It does not correct the underlying cause or the deformity associated with this condition. Sagittal split osteotomy is indicated in cases of class II or III malocclusion in which reduction or lengthening of the anteroposterior length of the mandible will achieve dental harmony. This procedure is not appropriate for class I occlusion or flaring of the mandibular angle.

Answer 31

The correct response is Option E. The sphenopalatine nerve arises from the incisive foramen and provides sensation to the anterior hard palate. Blockade of this nerve is essential for adequate blockade of the palatal mucosa for laceration repair. The anterior superior alveolar nerve arises from the second branch of the trigeminal nerve before it exits the infraorbital foramen. The nerve supplies the maxillary anterior teeth and is part of the superior dental plexus of nerves that also includes the middle superior alveolar and the posterior superior alveolar nerves. The infraorbital nerve provides sensation to the ipsilateral lateral nose, upper lip, and cheek. The lesser palatine descends through the greater palatine foramen and provides innervation to the soft palate and uvula.

Answer 32

The correct response is Option D. The pharyngeal arches are created during embryological development by the migration of the neural crest cells and the surrounding pharyngeal endoderm and mesoderm. The first four pharyngeal arches are the most prominent and have unique nervous, arterial, muscular, and bony components. The muscular components of the first pharyngeal arch are innervated by the trigeminal nerve (cranial nerve V) and include the muscles of mastication, as well as the anterior digastric, mylohyoid, tensor tympani, and tensor veli palatini. The maxillary artery supplies blood to the components of the first pharyngeal arch. The greater wing of the sphenoid, as well as the incus, the malleus, maxilla, zygomatic, mandible, and temporal bones comprise the bony components of the first pharyngeal arch. The second pharyngeal arch is innervated by the facial nerve (cranial nerve VII) and receives blood supply from the stapedial artery. The bony components of the second pharyngeal arch include the stapes, styloid process, stylohyoid ligament, lesser horn, and upper body of the hyoid. The muscular components of the second pharyngeal arch include the muscles of facial expression, as well as the posterior digastric, stylohyoid, and stapedius. During embryological development of the external ear, the antihelix, antitragus, and lobule are derived from the three posterior hillocks of the second pharyngeal arch, while the tragus, the root of the helix, and the superior helix are derived from the three anterior hillocks of the first pharyngeal arch.

Answer 33

The correct response is Option B. The first branchial cleft develops into the external auditory canal. The second, third, and fourth branchial clefts merge to form the sinus of His, which will normally become involuted. When a branchial cleft is not properly involuted, a branchial cleft cyst forms. Occasionally, both the branchial pouch and branchial cleft fail to become involuted, and a complete fistula forms between the pharynx and skin. First branchial cleft cysts are divided into type I and type II. Type I cysts are located near the external auditory canal. Most commonly, they are inferior and posterior to the tragus (base of the ear), but they may also be in the parotid gland. Type II cysts appear at the angle of the mandible and may involve the submandibular gland. The second branchial cleft accounts for 95% of branchial anomalies, and they are most frequently identified along the anterior border of the upper third of the sternocleidomastoid muscle and adjacent to the muscle. However, these cysts may present anywhere along the course of a second branchial fistula, which proceeds from the skin of the lateral neck, between the internal and external carotid arteries, and into the palatine tonsil. Therefore, a second branchial cleft cyst is part of the differential diagnosis of a parapharyngeal mass. Third branchial cleft cysts are rare. A third branchial fistula extends from the same skin location as a second branchial fistula (recall that the clefts merge during development); however, a third branchial fistula courses posterior to the carotid arteries and pierces the thyrohyoid membrane to enter the larynx, terminating on the lateral aspect of the pyriform sinus. Third branchial cleft cysts occur anywhere along that course (eg, inside the larynx), but they are characteristically located deep to the sternocleidomastoid muscle. Congenital dermoid cysts of the face typically occur at the lateral orbit overlying the ZF suture, and vascular cyst lesions can be located anywhere on the face but do not present with sinus tracts into the EAC.

Answer 34

The correct response is Option D. During embryologic development, the thyroid gland descends from the foramen caecum to the midline of the neck. The tract in descent is typically absorbed but sometimes remains. This can be secondarily infected from infections of the head and neck. Rarely, the thyroid gland does not fully descend into its position in the midline neck. Diagnosis of this mass over other types of midline mass include elevation of the mass on tongue protrusion. This is because of the remaining attachment to the base of the tongue. Lymph nodes can present in the midline, but they are infrequent at the level of the hyoid and typically do not drain percutaneously. A type II branchial cleft cyst presents laterally, not in the midline. Infected sebaceous cysts can drain in any hair-bearing area, but do not move with protrusion of the tongue.

Answer 35

The correct response is Option E. Surgical exploration is most likely to show the ascending course of this pharyngeal fistula to be superficial to the stylopharyngeal muscle. Second pharyngeal cleft and pouch anomalies (including cysts, fistulas, and sinuses) account for 67 to 95% of the total anomalies of the pharyngeal apparatus. Cysts are the most common finding, occurring three times more often than fistulas. Fistulas usually present at birth. They derive from the ventral portion of the second pharyngeal cleft and pouch. The external opening is usually found along the anterior border of the sternocleidomastoid muscle, between the hyoid bone superiorly and the suprasternal notch inferiorly. Fistulas have a muscular coat, which is continuous superficially with the platysma and internally with the palatopharyngeal muscle. If this muscle coat is well developed, swallowing causes a pull on the fistulous opening, resulting in puckering. The anatomical relations between a second pharyngeal cleft and pouch fistula and the surrounding cervical structures are dictated by the embryogenesis of the pharyngeal apparatus. As an anomaly of the second cleft and pouch, the fistula is expected to course deeply to the second arch structures and superficially to the structures derived from the third to sixth arches. Therefore, the described fistula is expected to course deep to the stylohyoid muscle and posterior belly of the digastric muscle (derived from the second pharyngeal arch), and superficial to the internal carotid artery and stylopharyngeal muscle (derived from the third pharyngeal arch). The hypoglossal nerve and associated infrahyoid muscles do not develop in the mesenchyme of the pharyngeal apparatus, instead being derived from occipital somites in the paraxial mesoderm. All pharyngeal anomalies derived from ectoderm (e.g., fistulas) will be found superficial to the hypoglossal nerve and the infrahyoid strap muscles. Other cervical structures not mentioned in this scenario but which are relevant to the course of the described fistula include the external carotid artery (second pharyngeal arch) and the glossopharyngeal nerve (third pharyngeal arch). The expected fistula course is deep to the former and superficial to the latter.

Answer 36

The correct response is Option D. The periodontal ligament is responsible for keeping the tooth anchored. Enamel is the outer protective layer of the tooth. Dentine, enamel, cementum, and pulp are the four major components of the tooth but none are responsible for anchoring the tooth.

Answer 37

The correct response is Option E. Oral mucosal sensation is important in many stomatognathic functions. Mastication, oral hygiene, phonation, and swallowing can all influence patient quality of life. A proportionally worsening functional impact with an increasing area of anesthesia has been noted. Therefore, restoration of sensibility should be one of the important components of the functional rehabilitation of glossectomy defects. Although spontaneous reinnervation does occur in noninnervated flaps, it takes a longer period of time to develop, and it may not restore adequate functional sensation, nor does it provide useful tactile sensation or two-point discrimination. These sensory modalities are important in a patient's ability to handle oral secretions and food boluses. Microsurgical anastomoses of the lateral femoral cutaneous nerve is most commonly performed to the lingual nerve stump left after tumor extirpation. The cervical branch is the lowest division of facial motor nerve and would not provide sensory recovery to the freely transferred thigh tissue. The great auricular nerve provides sensation to the earlobe and can serve as an ideal donor for segmental nerve grafting, if required. Bioprosthetic conduits (nerve tubes) or vein grafts have also been described for this purpose. The hypoglossal nerve is commonly identified and preserved in selective cervical lymphadenectomy, and, if divided, causes a motor paralysis of the ipsilateral tongue. The inferior alveolar nerve is part of the trigeminal system (V3) and is not divided during a floor-of-mouth resection and/or glossectomy, unless a segmental mandibulectomy is also performed.

Answer 38

The correct response is Option A. Although it is most commonly seen after parotidectomy, Frey syndrome has also been encountered after condylar fracture of the mandible and treatment. The syndrome is thought to result from damage to auriculotemporal parasympathetic nerve fibers with subsequent aberrant regeneration and innervation of sympathetic fibers to the sweat glands. The facial, inferior alveolar, greater auricular, and lingual nerves are not thought to be the underlying cause of Frey syndrome.

Answer 39

The correct response is Option B. "Penetrating neck injury represents 5-10% of all trauma cases. It is important for clinicians to be familiar with management principles, as mortality rates can be as high as 10%." Penetrating neck injury describes trauma to the neck that has breached the platysma muscle. The most common mechanism of injury worldwide is a stab wound from violent assault, followed by gunshot wounds, self harm, road traffic accidents, and other high velocity objects. The neck is a complex anatomical region containing important vascular, aerodigestive, and neurological structures that are relatively unprotected. Arterial injury occurs in approximately 25% of penetrating neck injuries; carotid artery involvement is seen in approximately 80% and vertebral artery in 43%. Hard signs indicating immediate explorative surgery in penetrating neck injury: Shock Pulsatile bleeding or expanding hematoma Audible bruit or palpable thrill Airway compromise Wound bubbling Subcutaneous emphysema Stridor Hoarseness Difficulty or pain when swallowing secretions Neurological deficits The assessment and management of penetrating trauma to the neck has traditionally centered on the anatomical zone-based classification first described by Monson et al. in 1969 Zone 1 extends from clavicles to cricoid, zone 2 from cricoid to angle of mandible, and zone 3 from angle of mandible to skull base. There are only 3 zones in penetrating neck injuries.

Answer 40

The correct response is Option D. The hypoglossal (XII) nerve emerges from the hypoglossal canal in the skull base and runs deep and roughly parallel to the posterior belly of the digastric in the upper neck, eventually innervating the intrinsic and extrinsic muscles of the tongue (except for the palatoglossus, which is innervated by the vagus [X] nerve). Division of the nerve results in ipsilateral tongue paralysis. The posterior belly of the digastric muscle is known as the "resident’s friend" because it acts as a useful anatomic landmark for several critical structures in the neck. It lies directly superficial to the branches of the external carotid artery, the internal carotid artery, jugular vein, and hypoglossal (XII) nerve. The marginal mandibular nerve, a branch of the facial (VII) nerve, innervates the depressor anguli oris and depressor labii inferioris, which are the facial mimetic muscles responsible for frowning. It runs superficial to the posterior belly of the digastric muscle but deep to the platysma muscle. It is often injured in surgery of the neck region. The vagus (X) nerve exits the cranium via the jugular foramen and courses from superior to inferior within the carotid sheath between the internal jugular vein and common carotid artery. It has diverse functions including supplying the larynx, pharynx, heart, esophagus, stomach, and small and large intestines. Transection of the vagus (X) nerve in the neck can result in vocal cord paralysis, among other dysfunctions. The spinal accessory (XI) nerve innervates the sternocleidomastoid and trapezius muscles. Therefore, its division results in impaired shoulder mobility. Although it lies deep to the posterior belly of the digastric muscle, it courses inferiorly and posteriorly, crossing the internal jugular vein, rather than parallel to the muscle, to enter the posterior triangle of the neck. The phrenic nerve originates from cervical spinal nerves (C3-C5) and is found in the floor of the posterior triangle of the neck and is not found deep to the posterior belly of the digastric.

Answer 41

The correct response is Option D. Innervation of the parotid gland comes from parasympathetic fibers that travel with the glossopharyngeal nerve (cranial nerve IX). It also receives taste sensation (afferent) from the posterior one-third of the tongue. The maxillary nerve of cranial nerve V (V2) is a sensory nerve and receives sensation from the mid face. Parasympathetic fibers (efferent) innervate the submandibular and sublingual glands via the chorda tympani. Afferent fibers, via the chorda tympani, send taste sensation of the anterior two-thirds of the tongue. The vestibulocochlear nerve (cranial nerve VIII) supplies sound and equilibrium to the brain. The auricular branch of the vagus nerve (cranial nerve X), innervates the external acoustic meatus. Stimulation of the vagus nerve can lead to reflex coughing (Arnold reflex).

Answer 42

The correct response is Option A. The dental root is covered by a mineralized layer called cementum. This is anchored to the surrounding alveolar bone by the periodontal ligament (periodontal membrane), which includes Sharpey fibers, to firmly anchor the tooth to the bone as well as sensory fibers. This facilitates the periodontal ligament’s functions of stabilizing the tooth, serving as a shock absorber, and allowing proprioception. The bulk of the dental root is composed of dentin, but it does not directly attach to the surrounding bone. The neurovascular bundles enter the tooth at the root apex and provide sensation and blood supply, but they are not a strong mechanical source of attachment. The enamel is the mineralized cover of the dental crown. It is not attached to the free gingiva, which attaches to the periodontal ligament at the cementoenamel junction. The gingiva does not directly attach to the bone.

Answer 43

The correct response is Option A. The first branchial arch contributes to the formation of the tragus and anterior helix. The first branchial cleft is incorrect. It gives rise to the external auditory canal. The second branchial arch is incorrect. It contributes to the formation of the majority of the external ear – the antitragus, remainder of the helix, antihelix, and crura all arise from the second branchial arch. The second branchial cleft is incorrect. It is typically obliterated during development, but may persist in the form of a second branchial cleft cyst.

Answer 44

Correct Answer: C. Levator veli palatini muscle The levator veli palatini is derived from the fourth pharyngeal arch during embryologic development, along with the uvula, palatopharyngeus muscle, palatoglossus muscle, pharyngeal constrictors, cricothyroid, salpingopharyngeus, laryngeal cartilages, vagus (X) nerve, aortic arch, and right subclavian artery. The common carotid artery is derived from the third pharyngeal arch, along with the stylopharyngeus muscle, glossopharyngeal (IX) nerve, and portions of the hyoid bone (greater cornu and lower body). The ductus arteriosus is derived from the sixth pharyngeal arch, along with the arytenoid muscles, epiglottis, aorta, and pulmonary artery. The malleus bone and mylohyoid are derived from the first pharyngeal arch, along with the anterior digastric muscle, tensor veli palatini muscle, squamous portion of the temporal bone, zygoma, maxilla, premaxilla, Meckel cartilage, trigeminal (V) nerve, and first aortic arch artery. References: Adams A, Mankad K, Offiah C, Childs L. Branchial cleft anomalies: a pictorial review of embryological development and spectrum of imaging findings. Insights Imaging. 2016;7(1):69-76. doi:10.1007/s13244-015-0454-5 Cohen MM Jr. Malformations of the craniofacial region: evolutionary, embryonic, genetic, and clinical perspectives. Am J Med Genet. 2002;115(4):245-268. doi:10.1002/ajmg.10982 Law HZ, Parker TH III. Head and neck embryology. In: Janis JE, ed. Essentials of Plastic Surgery. 3rd ed. Thieme; 2022:309-311.

Answer 45

The correct answer is option E. The nasopalatine nerve is a branch of the maxillary nerve (cranial nerve V2) and travels through the incisive foramen. It innervates the anterior hard palate behind the incisive foramen and the internal nasal cavity. The nasopalatine nerve travels from the pterygopalatine ganglion across the nasal septum towards the incisive canal. In this clinical scenario, the patient's symptoms of numbness and tingling in the anterior hard palate are consistent with injury or irritation of the nasopalatine nerve, which is commonly affected during dental procedures involving the incisive foramen or anterior palate. The anterior ethmoidal nerve is a branch of the ophthalmic nerve (cranial nerve V1) and supplies sensation to the roof of the nasal cavity, anterior nasal septum, anterior and middle ethmoid air cells, and parts of the meninges. It is involved in the diving reflex. The greater palatine nerve carries both sensory fibers from the maxillary nerve and parasympathetic fibers from the nerve of the pterygoid canal (vidian nerve). It supplies sensation to the gums, mucous membrane, and glands of the hard palate. The lesser palatine nerve is a branch of the maxillary nerve (cranial nerve V2). It descends through the greater palatine canal alongside the greater palatine nerve, emerges separately through the lesser palatine foramen posteriorly, and supplies sensation to the soft palate, tonsil, and uvula. The buccal nerve is the only sensory branch of the anterior mandibular division of the trigeminal nerve. It innervates a major part of the buccal mucosa, the inferior buccal gingiva in the molar area, and the skin above the anterior part of the buccinator muscle. Langford RJ. The contribution of the nasopalatine nerve to sensation of the hard palate. Br J Oral Maxillofac Surg. 1989;27(5):379-386. doi:10.1016/0266-4356(89)90077-6 Chandra RK, Rohman GT, Walsh WE. Anterior palate sensory impairment after septal surgery. Am J Rhinol. 2008;22(1):86-88. doi:10.2500/ajr.2008.22.3114

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