Anatomy Exam 4: Head

Maxilla Bone

Contributes to the anterolateral walls of the nasal cavity and forms most of the boundary between the nasal and oral cavities.

How is the middle meningeal artery often damaged?

Following an impact to the side of the head, fracturing the skull in the area of the pterion. This artery runs in close proximity to the pterion, so a fracture of this weakened area of the lateral skull may lacerate the middle meningeal artery, which leads to an epidural hemorrhage as the blood pools between the endosteal layer of the dura mater and the calvaria.

A 27-year-old woman comes to her physician with noted asymmetry in her pupils. Her right pupil is abnormally dilated, and on examination, the right eye is slow to respond to light stimuli. Her visual acuity is not impaired, and no other signs and symptoms are noted. What structure is most likely affected in this patient?

Oculomotor nerve. The slowness of the right pupil to respond to light stimuli is the fi rst sign of compression of the oculomotor nerve (CN III).

An 18-year-old male skier is brought to the emergency room after a high-speed collision with a tree. His forehead absorbed much of the impact, resulting in multiple fractures and lacerations. His ER physician noted a clear nasal discharge, which tested positive for glucose. Given the patient's presentation, what cranial nerve was most likely damaged?

Olfactory nerve (CN I). These fibers descend into the nasal cavity via the foramina within the cribiform plate of the ethmoid bone, so when this bone is fractured the olfactory nerve is most likely damaged.

While participating in a bar fight, the orbit of a 25-year-old man is pierced by a broken pool cue stick, which extends back to the superior orbital fissure. Which of the following nerves is most likely damaged?

Ophthalmic division of trigeminal. The ophthalmic (first) division of trigeminal nerve (CN V1) supplies sensory (cutaneous) innervation to the skin of the upper eyelid, anterior aspect of the nose, forehead, and anterior scalp.

The Masseter Muscle

Primarily functions to close the jaw. Functions in protrusion, retrusion, elevation and lateral movements

The vagus nerve (CN X)

Serves as the efferent limb of the gag reflex, it gives motor innervation to a majority of muscles serving the soft palate, pharynx, and larynx. CN X provides sensory (afferent) innervation in the larynx

A (CT) scan shows a left crescent-shaped extraaxial hematoma, compressing the brain of a 17-year-old woman, who impacted the front of her head on the steering wheel during a head-on motor vehicular accident. Given the radiologic imaging results and the history of the accident, what blood vessel(s) is/are the most likely source for this cerebral hemorrhage?

Superior cerebral veins. Following traumatic impact to the front of the head, the superior cerebral veins may be torn as they drain into the superior sagittal sinus. Tearing of the superior cerebral veins leads to a subdural (or dural border) hemorrhage.

To test this eye muscle, have the patient adducting the eye and then look downward (depression). This muscle is:

Superior oblique. Failure of these step indicates possible damage to the trochlear nerve (CN IV), which supplies only the superior oblique muscle.

From the abducted position, asking the patient to look upward, which elevates the eye, tests which eye muscle?

Superior rectus, failure to accomplish this task is an indicator of possible damage to the oculomotor nerve, which supplies the superior rectus muscle.

A 59-year-old man went to his doctor unable to close his right eye. The physical examination also revealed asymmetry in his smile and an inability to wrinkle the right side of his forehead. What cranial nerve is affected in this patient?

The Facial nerve. The main trunk of the facial nerve (CN VII) exits the stylomastoid foramen and runs anteriorly in close relationship to (or within) the parotid gland. This nerve branches into five terminal branches: Temporal, Zygomatic, Buccal, Marginal mandibular, and Cervical. Damage to the main trunk of the facial nerve causes unilateral facial paralysis due to loss of innervation to these muscles.

A 59-year-old man with a herpes zoster infection within the mandibular division of the trigeminal nerve (CN V3) complains of weakness when opening his mouth. A comprehensive evaluation reveals that his problems are due to difficulty protruding the mandible, and when protrusion is accomplished the mandible deviates to the left side. What muscle is most likely weakened?

The Lateral pterygoid. The lateral pterygoid muscle acts on the temporomandibular joint (TMJ) to cause protrusion (or protraction) of the mandible, functions with depression (opening), protrusion and lateral movements

Ophthalamic nerve (CN V1)

The first division of the trigeminal nerve) supplies sensory (cutaneous) innervation to the skin of the upper eyelid, cornea, anterior aspect of the nose, forehead, and anterior scalp.

The greater palatine nerve

a branch off the maxillary (second) division of the trigeminal nerve (CN V2), supplies sensory innervation to the mucosa and gingivae of the hard palate.

Hair cells in the apex of the cochlea

detect low frequency sounds due to the further distance being traveled in the cochlea

The cervical branch of the facial nerve (CN VII) innervates the:

platysma muscle, which wrinkles the skin of the inferior face and neck, which is often seen when a person is under stress.

A detached retina

separation of the retina from the choroid in the back of the eye; can be caused by injury, tumor, or hemorrhage, can lead to vision loss and blindness,

The trochlear nerve provides innervation to the __________, while the Abducent nerve provides innervation to the ____________.

superior oblique muscle, lateral rectus muscle.

The temporal branch of the facial nerve (CN VII) innervates muscles that move:

the auricle (ear) as well as the frontalis muscle and the superior part of the orbicularis oculi. The frontalis muscle raises the eyebrows and wrinkles the skin of the forehead.

What cranial nerve exits the cranium via the jugular foramen?

the glossopharyngeal (CN IX), vagus (CN X), and accessory (CN XI) nerves.

The foramen ovale (or oval foramen) is an opening in:

the greater wing of the sphenoid bone that enables the mandibular (third) division of the trigeminal nerve (CN V3) and a small meningeal artery to pass into the middle cranial fossa.

The zygomatic branch of the facial nerve (CN VII) innervates primarily:

the inferior part of the orbicularis oculi muscle to close the lower eyelid ipsilaterally.

The foramen spinosum conveys:

the middle meningeal artery and the meningeal branch (nervus spinosum) of the mandibular division of the trigeminal nerve (CN V3). This artery and nerve supply the dura mater in the cranial cavity.

The maxillary (second) division of the trigeminal nerve (CN V2) supplies sensory (cutaneous) innervation to:

the skin to the lower eyelid, cheek, upper lip, upper dentition and gingivae, and lateral aspects of the nose. CN V2 enters the middle cranial fossa through the foramen rotundum.

Damage to the hypoglossal nerve (CN XII) causes

ipsilateral deviation of the tongue during protrusion, dysarthria (difficulty speaking), and fasciculations (involuntary twitching of muscle fibers).

The superior orbital fissure is a:

large opening that conveys the oculomotor (CN III), trochlear (CN IV), ophthalmic division of the trigeminal (CN V1), and abducent (CN VI) nerves as well as the superior ophthalmic veins into the orbit.

The optic nerve (CN II)

leaves the orbit via the optic canal to relay vision from the retina to the brain.

The IX cranial nerve, Glossopharyngeal nerve:

supplies only one muscle, the stylopharyngeus, autonomic innervation to the parotid gland, swallowing, sensation from the tongue, sensation from the pharynx.

The inferior alveolar nerve

A branch off the mandibular division of the trigeminal nerve (CN V3), enters the mandibular foramen to supply the lower teeth, periosteum, and gingivae of the mandible. The mental nerve, a terminal branch of the inferior alveolar nerve, supplies the skin and mucosa of the lower lip and chin.

The Vestibulocochlear VIII cranial nerve?

A lesion can result in tinnitus (ringing in the ears), A lesion can result in vertigo, A lesion can result in hearing loss, It enters the internal acoustic meatus.

a woman with a lesion in which cranial nerve VI, Abducens would illustrate:

A paralyzed lateral rectus, would not be able to abduct the pupil on the affected side

The tympanic (middle ear) cavity

A small air-filled space within the petrous part of the temporal bone. It has six walls: the roof (tegmental), wall), floor (jugular wall), anterior (carotid) wall, posterior (mastoid) wall, medial (labyrinthine) wall, and lateral (membranous) wall. Each wall has a close relationship to one or more significant neighboring structures.

The lesser palatine nerve

a branch of the maxillary division of the trigeminal nerve (CN V2), supplies sensory innervation to the soft palate and aspects of the palatine tonsil.

Levator labii superioris

a muscle of facial expression, so it would be paralyzed in facial nerve palsy. It functions as a dilator of the oral fissure by retracting (elevating) the upper lip to show the upper teeth

Which of the following sets of cranial nerves all carry preganglionic parasympathetic (general visceral efferent) fibers?

CN III: Occulomotor CN VII: Facial CN IX: Glossopharyngeal CN X: Vagus

A 68-year-old man arrived at the ER with sudden onset of the worst headache of his life, lethargy, and nuchal rigidity. He quickly loses consciousness and dies. Autopsy reveals no traumatic injury; however, the man's subarachnoid space is filled with blood. Damage to what blood vessel most likely led to the death of this patient?

Cerebral arterial circle. The cerebral arterial circle (of Willis) is an anastomoses of arteries located on the inferior surface of the brain in the area of the interpeduncular fossa, optic chiasm, and hypothalamus. These vessels are prone to saccular (berry) aneurysm, particularly where the arteries join together. Upon rupturing, blood spills into the subarachnoid space, causing the subarachnoid hemorrhage.

The mandibular division of the trigeminal nerve (CN V3) controls:

Chewing, the complex interactions of the muscles of mastication, (the masseter, temporalis, and medial pterygoid muscles act in closing the jaw), taste and salivary flow of the tongue due to the branch of the lingual nerve

After asking a 47-year-old woman to open her mouth wide and say "Ah," the physician notes deviation of the uvula to the left side and asymmetry in the elevation of the soft palate, with the right side of the palate sagging. What specific nerve is most likely damaged?

Damage to the right vagus nerve is causing asymmetry in soft palate elevation and contralateral deviation of the uvula of the soft palate to the left side. On examination, the arch of the soft palate droops on the affected side (right side) and the uvula deviates to the unaffected side (left side) as a result of the unopposed action of the intact muscles acting on the soft palate.

Startled by a loud noise while shaving his head with a straight razor, a young man accidentally cuts his scalp, severing branches of the supraorbital and superficial temporal vessels. The scalp wound appears modest but bleeds profusely. In what layer of the scalp do the severed vessels reside?

Dense connective tissue. This layer houses the main networks of nerves and vessels that enter the scalp from its periphery. The walls of the arteries within the scalp are tightly attached to the surrounding connective tissue bed. As a result, scalp lesions that penetrate the second layer tend to bleed profusely because the fibrous tissue holds apart the cut ends of the severed vessels.

The facial nerve

Enters the petrous temporal bone through the internal acoustic meatus, traveling through this foramen with the vestibulocochlear nerve (CN VII). It has three terminal branches (chorda tympani, greater petrosal, and the main branch of the facial nerve)

A 54-year-old man comes to his doctor complaining of an inability to open his left eye. When he physically pries open his affected eye with his fingers, the gaze of his left eye is directed inferiorly and laterally, causing diplopia. His left pupil is also dilated in comparison to the right one. What nerve is most likely affected in this patient?

Left oculomotor nerve. Damage to the left CN III leads to ptosis (or drooping) of the left upper eyelid due to loss of innervation to the levator palpebrae superioris muscle, Damage to the parasympathetic component of CN III causes pupillary dilation due to the unopposed sympathetic innervation to the dilator pupillae muscle of the iris.

The buccal branch of the facial nerve (CN VII) is one of five terminal branches of the main trunk of CN VII, which supplies the muscles of:

Facial expression and other muscles derived from mesoderm in the embryonic second pharyngeal arch. This buccal branch is entirely efferent (motor) in its innervation supplying the buccinator muscle and muscles of the upper lip. It does not have a sensory component.

The orbicularis oris is a muscle of

Facial expression that encircles the mouth to act as the sphincter of the oral fissure. It originates from the incisive fossae of the mandible and maxilla and contracts in a patient to close the oral fissure, protrude the lips (as in kissing, whistling, or sucking), and resists distension when blowing (as seen when playing the trumpet).

A 13-year-old girl visits her pediatrician complaining of loss of sensitivity in her lower eyelid, the skin below her right eye, and in her upper lip and teeth. Which of the following sites is the most likely location for the nerve lesion responsible for these signs and symptoms?

Foramen rotundum. The foramen rotundum is an opening in the greater wing of the sphenoid bone that enables the maxillary (second) division of the trigeminal nerve (CN V2) to pass into the middle cranial fossa. CN V2 supplies sensory (cutaneous) innervation to the skin to the lower eyelid, cheek, upper lip, upper dentition and gingivae, and lateral aspects of the nose.

A 10-year-old boy underwent surgery, a bilateral palatine tonsillectomy. During a postoperative examination, the doctor noted the boy did not possess a gag reflex on the right side on the posterior tongue. He also complained of abnormal taste sensations in the back of his oral cavity. The soft palate elevated symmetrically when the gag reflex was tested. No other signs or symptoms were noted. What cranial nerve was damaged during the tonsillectomy?

Glossopharyngeal nerve. The lingual and tonsillar branches of the glossopharyngeal nerve (CN IX) reside in the palatine tonsillar bed between the palatoglossal and palatopharyngeal folds. At this location, these branches of CN IX are susceptible to damage during a tonsillectomy, which would compromise taste and visceral sensation to the posterior portion of the tongue.

During a fight between two construction workers, one man strikes the other with a hammer at the pterion of the skull. Which of the following bones may be fractured?

Greater wing of the sphenoid bone.

A 78-year-old man presents with signs of reduced blood flow into the right side of his face. His physician wishes to take a pulse of the facial artery on both sides to help evaluate the situation. The pulse of the facial artery can be readily palpated at which of the following locations?

Inferior margin of the body of the mandible. After originating from external carotid artery, the facial artery ascends in the upper neck deep to the submandibular gland. The facial artery then crosses the body of the mandible anterior to the masseter muscle to enter the face. Its pulse can be readily palpated at the point where it crosses the inferior margin of the body of the mandible, at the anterior border of the masseter muscle. The artery continues ascending across the face, taking a winding path relatively close to the angle of the mouth. The folding of the vessel allows it to accommodate being stretched during wide opening of the mouth. It gives branches to the lips and side of the nose, finally terminating at the medial canthus of the eye.

A 47-year-old man has trouble with double vision (diplopia) after striking his head on the steering wheel in a car accident. During a subsequent eye examination, his ophthalmologist asks him to first look inward (toward his nose) and then upward (toward the ceiling). The integrity of which of the following extraocular muscles is being tested?

Inferior oblique.

At the abducted position, asking the patient to look downward, to depress the eye, tests the function of which eye muscle?

Inferior rectus. Failure to accomplish this task indicates possible damage to the oculomotor nerve, which supplies the inferior rectus muscle.

Hypoglossal Nerve (XII)

Innervates the intrinsic and (most of the) extrinsic muscles of tongue

A 43-year-old man presents with loss of control of facial expression across the entire right side. The corner of his mouth droops on the right side, but he can clench his jaw and chew on demand. During examination, his physician also notes loss of hearing on the right side, and the patient has difficulty maintaining balance while standing on one foot. The patient's corneal (blink) reflex is absent in the right eye, but cutaneous sensation is normal on the entire face. The physician orders radiographic imaging in anticipation of finding a tumor. What is the most likely location of the tumor?

Internal acoustic meatus. The loss of facial expression and drooping corner of the mouth indicate paralysis of the facial muscles and damage to the facial nerve (CN VII: Facial). The hearing loss and unsteady balance indicate failure in the inner ear complex implicating the right vestibulocochlear nerve (CN VIII; auditory nerve). The absence of the blink reflex is related to loss of the orbicularis oculi muscle, the facial muscle responsible for closing the eyelids, and this evidence reinforces a problem with the facial nerve. The only location where CN VII and CN VIII can be affected simultaneously is at the internal acoustic meatus

A 57-year-old woman presents with right unilateral facial paralysis and dizziness. During an examination, the physician also notes a loss of hearing on the right side. An MRI of the patient's head reveals a brain tumor, where is the tumor located?

Internal acoustic meatus. This patient is displaying defi cits associated with the facial nerve (CN VII), explaining the unilateral facial paralysis, and the vestibulocochlear nerve (CN VIII), evident from the dizziness and hearing loss on her right side.

Damage to the Optic Nerve results in CN II

Ipsilateral blindness or other visual deficits of the affected eye.

Damage to the facial nerve (CN VII) causes the following sequelae of signs and symptoms:

Ipsilateral paralysis of the muscles of facial expression, hyperacusis (sensitivity to noise), loss of taste to the anterior two thirds of the tongue, loss of secretion from the submandibular and sublingual salivary glands, and loss of emotional tearing.

Damage to the abducent nerve (CN VI) causes

Ipsilateral paralysis to the lateral rectus muscle, which is the only extraocular muscle innervated by CN VI. When the abducent nerve is damaged, the patient displays diplopia, and the ipsilateral eye rests in the adducted position due to the unopposed action of the other extraocular muscle

the Trochlear Nerve (IV)

It emerges from the posterior aspect of the brainstem, Nerve injury is characterized by lack of coordination for the two eyes when looking downwards, It traverses the lateral wall of the cavernous sinus, It innervates the superior oblique in the orbit, traverses the cavernous sinus;

A 27-year-old man comes to his family physician complaining of double vision. While sitting face-to-face, the doctor notes the patient exhibits strabismus, especially esotropia of the left eye, which gives the patient a "cross-eyed" appearance. When asked to follow the doctor's index finger with only his eyes, the patient is unable to look laterally. No other visual deficits are noted. What specific nerve is most likely damaged?

Left abducent nerve. The only extraocular muscle innervated by the left abducent nerve, CN VI, is the left lateral rectus muscle, which enables the left globe to move laterally. Due to damage, the eye will be resting in an adducted position.

A physician directs a small light into only the left eye of a patient to test pupillary constriction. The left pupil does not respond to the light; however, the right pupil constricts. What nerve is most likely damaged in this patient?

Left oculomotor nerve. Performing the pupillary light reflex tests the integrity of the sensory and motor functions of the eye.

A 38-year-old woman comes to her family physician complaining of repeatedly tripping and double vision when descending stairs. While testing the eye movements in a cranial nerve examination, she was unable to move her left eye inferiorly when she followed the physician's finger to her right side. What specific nerve is most likely damaged?

Left trochlear nerve. Innervates only one muscle, the superior oblique. Test by asking patient to look inferiorly after placed in an adducted position. Damage to the left CN III leads to diplopia (due to the left pupil resting in an abducted and lateral position) and ptosis (drooping of the eyelid) associated with the left eye.

A lesion of the facial nerve CN VII may result in all of the following

Loss of taste from the anterior two-thirds of the tongue, partial sensory denervation of the auricle, increase in loudness of sound, loss of tear production.

A 46-year-old woman was cut on the right side of her face by a window that shattered. Her laceration was located at the anterior border of the inferior part of the masseter muscle. When she returns to her doctor to have the stitches removed, her physician notes asymmetry in her lower lip when she grimaces. Damage to what nerve would cause the facial asymmetry seen in this patient?

Marginal mandibular branch of facial nerve.

The masseter is a muscle of

Mastication that primarily works to close the jaw, but its superficial fibers also play a limited role in protrusion of the mandible

A cleft palate is is related to failure of fusion of what craniofacial processes?

Maxillary and medial nasal processes.

A 7-year-old boy was kicked in the right side of his head during a sledding accident. He arrived at the ER with no loss of consciousness but complained of a severe headache and vomiting. A (CT) scan revealed a biconvex hyperdense extraaxial collection of blood. What blood vessel is the most likely source of the bleed?

Middle meningeal artery. The middle meningeal artery is often torn following impact to the side of the head, fracturing the skull in the area of the pterion. The pterion, an osteological feature on the side of the head that marks the junction of the parietal, frontal, squamous temporal, and sphenoid bones, is prone to fracture following traumatic impact to the side of the head.

A 35-year-old man complains to his physician that he feels congested, has trouble with nasal breathing, and is experiencing a yellowish nasal mucus discharge. He also mentions that his right side upper molar teeth ache terribly. A thorough physical examination reveals maxillary sinusitis. The discharge from this sinus initially drains into the nasal cavity at which region?

Middle nasal meatus. The maxillary sinus opens into the most posterior part of the semilunar hiatus in the middle meatus. The maxillary sinus is the largest paranasal sinus, occupying much of the maxillary bone. Infections there may affect the upper teeth, causing a toothache, because the sinus cavity is separated from the roots of the teeth by only a very thin layer of bone.

The Temporalis Muscle

Muscle of the side of the head that moves the mandible upward and backward. Elevation, Retrussion, and lateral movements

A 32-year-old man presents with unilateral paralysis of the muscles of mastication on the right side. This condition has resulted in facial asymmetry. Though he is uncomfortable with his appearance and has difficulty when chewing his food, his chief complaint is his difficulty swallowing (dysphagia). What muscle is most likely involved in his dysphagia?

Mylohyoid.

A 25-year-old professional boxer loses a fight when he is rendered unconscious by his opponent. After he regains consciousness, the ringside physician notes the boxer has a severe headache, nausea, and even vomiting. Being concerned about intracranial trauma, what cranial nerve can be observed by the physician, without the aid of radiographic imaging, to gain more information on whether the boxer has increased intracranial pressure?

Optic nerve (CN II) develops as an anterior extension of the diencephalon, part of the forebrain. Due to this unique embryological origin, the optic nerve is enveloped with extension of the cranial meninges (dura, arachnoid, and pia mater) and contains cerebrospinal (CSF) fluid in its subarachnoid space.

During extraction of her impacted wisdom teeth, a 22-year-old woman suffers damage to her right inferior alveolar nerve. Which of the following conditions is most likely to result?

Paresthesia of the lower lip. The inferior alveolar nerve, a branch of the mandibular division of the trigeminal nerve (CN V3), leaves the ramus of the mandible after traveling through the extent of that bone, conveying afferent fibers from the mandibular teeth.

The mastoid process of the temporal bone

a breast-like projection extending inferior from the temporal bone behind the external acoustic meatus. It forms part of the posterior boundary of the infratemporal fossa. Additionally, it is the attachment site for certain neck muscles

A 45-year-old man goes to his physician complaining of having trouble with his speech (dysarthria) and involuntary contractions (fasciculations) within his tongue muscles. The doctor notes that his tongue deviates to the right when the patient attempts to protrude his tongue. What nerve is most likely damaged in this patient?

Right hypoglossal nerve.

A 24-year-old man came to his physician with a history of chronic maxillary sinusitis. A (CT) scan reveals a soft-tissue mass in the superior aspect (or roof) of the right maxillary sinus. Functional endoscopic sinus surgery (FESS) was performed to biopsy the mass. Postoperatively, the patient experiences paresthesia and numbness of the skin of the right inferior eyelid and upper lip. Which nerve was most likely damaged during the surgery?

Second division of trigeminal nerve. The second (maxillary) division of the trigeminal nerve (CN V2) supplies the skin of the inferior eyelid and upper lip through the infraorbital nerve that courses through the superior aspect (roof) of the maxillary sinus.

Middle cerebral artery

Supplies entire lateral cortex, Largest branch of internal carotid artery, travels deep within the brain in between the frontal and temporal lobes, If compromised, it would lead to a subarachnoid hemorrhage.

Vagus Nerve (CN X)

Supplies muscles of the larynx as well as most of the muscles of soft palate (exception = tensor veli palatini of CN V3) and pharynx (exception = stylopharyngeus of CN IX). Provides taste sensations in the area of the epiglottis and serves as the efferent limb of the gag reflex;

A 17-year-old woman presents with an anterior dislocation of her temporomandibular joint (TMJ). With her mandible stuck in the protruded (protracted) position, her dentist pulls the mandible inferiorly to enable the tone of a muscle to retrude (retract) the mandible to its normal position. Which muscle returns the mandibular condyle back into its normal position after it clears the articular eminence?

Temporalis. The posterior fibers of the temporalis muscle run in a horizontal plane, and during contraction, enable retrusion (or retraction) of the mandible allowing it to return to its normal position in the TMJ. By pulling the mandible down, the dentist frees the mandibular condyle from its stuck position on the articular eminence of the temporal bone. The temporalis muscle is also involved with closing of the mouth (elevation of the mandible); however, its posterior, horizontally oriented fibers are the primary retractors of the mandible.

The superficial temporal artery and occipital artery are

Terminal branchs of the external carotid artery and lies outside of the skull. If this artery were lacerated, bleeding of the scalp would be profuse.

A tumor is discovered embedded in the posterior wall of the tympanic cavity in a 45-year-old man. If the tumor erodes through this wall, which of the following structures will it first encounter?

The Facial nerve. CN VII

Most senior citizens dislike the bass audio frequencies augmented by a large subwoofer in a teenager's car. But, one 68-year-old man came to his doctor complaining of hyperacusis, or heightened sensitivity to these loud, low-frequency sounds. The results from an audiometer hearing test reveal normal hearing for a man of his age. Given the presentation, what cranial nerve is most likely involved with his hyperacusis?

The Facial nerve. It also innervates the stapedius muscle, which contracts to pull the stapes away from the oval window of the cochlea. This action lowers the amplitude of sounds waves and decreases the transmission of vibrations to the ear.

An MRI of the right internal carotid artery reveals atherosclerotic plaques causing stenosis of the vessel's lumen within the cavernous sinus. The stenosis is causing increased pressure within the internal carotid artery as it courses through the cavernous sinus, resulting in an aneurysm. Given its location, what cranial nerve would most likely be damaged?

The abducent nerve (CN VI) parallels the course of the internal carotid artery within the cavernous sinus, which makes it the most likely nerve to be damaged.

The superficial temporal artery:

a continuation of the external carotid artery and supplies blood to the muscles of the front, side, and top of the head, the terminal branch of the external carotid artery, lies outside of the skull. If this artery were lacerated, bleeding of the scalp would be profuse.

A 36-year-old man flips over the handlebars of his motorcycle and falls on the asphalt pavement, striking his head. He was not wearing a helmet. Although alert after the fall, he has a clear nasal discharge that tests positive for glucose (CSF leakage). The patient most likely has a fracture of which of the following bones?

The ethmoid bone. A fracture of the ethmoid bone, specifically its cribiform plate, which separates the nasal cavity from the anterior cranial fossa, would enable cerebrospinal fluid (CSF), the clear discharge that tests positive for glucose, to leak from the nose.

A 10-year-old boy was admitted to the hospital with a sore throat, earache, and high fever. On examination, he had severely swollen palatine tonsils (tonsillitis). What nerve carries the sensory input for most of the patient's symptoms?

The glossopharyngeal nerve (CN IX) is responsible for visceral sensation to the posterior one third of the tongue, palatine tonsils, soft palate, pharyngotympanic tube, tympanic (or middle ear) cavity, and pharynx. CN IX is responsible for the pain associated with an earache and sore throat.

The mentalis muscle is

a muscle of facial expression located on the chin that elevates and protrudes the lower lip or elevates the skin of the chin. It originates from the incisive fossa of the mandible and contracts to show doubt in a patient.

A 35-year-old woman comes to her dentist complaining of tenderness and pain in her cheek near the parotid gland, as well as bad breath and a foul-tasting mouth at meal times. A radiopaque fluid is injected into the parotid duct system which confirms blockage by a calculus. What muscle, through which the parotid duct passes, is most likely causing the blocking of drainage of the parotid duct?

The buccinator muscle. This muscle is pierced by the duct of the parotid gland as it passes toward the oral cavity to drain in the oral vestibule via a small opening opposite the second maxillary molar teeth. The muscular tone of the buccinator muscle can create a stenosis of the parotid duct, and it is the most likely site for calculus of the parotid duct.

During preparation to extract the right maxillary (upper) canine tooth, a dentist has difficulty anesthetizing this tooth and its associated gingivae. Therefore, the dentist administers a regional nerve block, in which the anesthetic syringe needle penetrates the oral mucosa at the apex of the maxillary vestibule and is pushed beyond the roots of the teeth. Due to this injection, the patient experiences numbness and paresthesia within the upper canine and neighboring teeth, as well as the skin of the right inferior eyelid, cheek, lateral nose, and upper lip. What nerve was blocked and produced the described numbness?

The infraorbital nerve, a terminal branch of the maxillary (second) division of the trigeminal nerve (CN V2). This nerve passes through the superior aspect (roof) of the maxillary sinus and emerges from the infraorbital foramen. It supplies the maxillary incisor, canine, and premolar teeth via its anterior and middle superior alveolar branches in the roof of the maxillary sinus. Ultimately, it supplies the inferior eyelid, cheek, lateral nose, and upper lip via its terminal branches in the face.

An 8-year-old boy suffers a fracture at the base of the skull from the impact of a terrorist bomb explosion. The skull trauma includes a lesion of the vagus nerve. Damage at which of the indicated openings would injure the vagus nerve?

The jugular foramen which is a large opening that connects the posterior cranial fossa with the exterior base of the skull. The anterior compartment transmits a bundle of three cranial nerves out of the cranial cavity: the glossopharyngeal nerve (CN IX), the vagus nerve (CN X), and the (spinal) accessory nerve (CN XI).

Asking the patient to look outward (away from the nose) tests the ability of what eye muscle?

The lateral rectus is the primary abductor of the eye from the rest position. Failure of this test indicates possible damage to the abducent nerve (CN VI), which supplies only the lateral rectus.

A 23-year-old man has an impacted left third mandibular molar (or wisdom) tooth extracted. Following the surgery, the patient reports numbness in the anterior aspect of his tongue. Which of the following nerves is damaged?

The lingual nerve is a branch of the mandibular division of the trigeminal nerve (CN V3), and is at risk during extraction of an impacted third mandibular molar tooth.

The trigeminal nerve (CN V)

The main sensory nerve for the face and scalp, and it has three divisions, namely, the ophthalmic (CN V1), maxillary (CN V2), and mandibular (CN V3). CN V3 is the only division of the trigeminal nerve (CN V) that supplies motor innervation. Provides general sensation to the anterior two thirds of the tongue via the lingual nerve.

A 21-year-old professional boxer receives a series of powerful punches to the side of his face, which fractures the left mandible slightly superior to the mandibular angle. Resultant muscle spasticity causes his jaw to close, making it difficult to remove his mouthpiece. Which of the following muscles is acting to close the jaw?

The masseter muscle which is one of four muscles of mastication, is a powerful elevator (adductor) of the mandible, acting to close the mouth and approximate the occlusal surfaces of the teeth.

As part of an initial oral examination of a new patient, a dental hygienist inspects the vestibule of the mouth. Which of the following structures is encountered in this area?

The opening of the parotid duct can be visualized in an oral examination and readily located by the tongue.

The first (ophthalmic) division of the trigeminal nerve (CN V1) supplies sensory (cutaneous) innervation to

The skin of the upper eyelid, anterior aspect of the nose, forehead, and anterior scalp.

The second (maxillary) division of the trigeminal nerve (CN V2) supplies sensory (cutaneous) innervation to

The skin to the lower eyelid, cheek, and upper lip, upper dentition and gingivae, maxillary sinus, and lateral aspect of the nose.

A 47-year-old woman with a history of multiple sclerosis comes to her doctor complaining of sudden bursts (paroxysms) of pain in her mandible, especially in the lower lip, mandibular teeth and gingivae, and cheek on her right side. This debilitating pain is often triggered by eating, talking, or brushing her teeth and often gets worse as the day progresses. Which nerve is the source of her pain?

The third (mandibular) division of the trigeminal nerve (CN V3) which supplies general sensation to the skin of the lower lip, chin, cheek, and even the anterior auricle and the lateral scalp.

The motor fibers of the trigeminal nerve (CN V)

They pass through foramen ovale, They are distributed entirely with the mandibular division, They innervate the muscles of mastication, They innervate the tensor tympani muscle.

Foramen ovale

This large, oval-shaped opening connects the middle cranial fossa with the exterior base of the skull. The mandibular division of the trigeminal nerve (CN V3) passes through here. At this location, a tumor would affect the muscles of mastication and cutaneous sensation.

Paralysis of superior oblique muscle

This muscle of the orbit is the only muscle innervated by the trochlear nerve (CN IV). This muscle would pull the eye inferolaterally, and is clinically tested by asking the patient to look down after the eye is placed in an adducted position. Paralysis of the superior oblique muscle would lead to diplopia (blurred vision) as well as clumsiness when descending stairs.

The anterior superior alveolar nerve

This nerve branches off the infraorbital nerve in the superior aspect (roof) of the maxillary sinus. It descends in a canal in the anterior wall of the maxillary sinus to supply the maxillary incisor and canine teeth.

Damage to infraorbital nerve

This nerve, is a branch of the second (maxillary) division of trigeminal nerve (CN V2), and due to its location, it would be the most likely damaged nerve during the blowout fracture of the inferior floor of the orbit. This nerve supplies sensory innervation to the maxillary sinus as well as the skin of the inferior eyelid, lateral nose, and upper lip. Damage here would caus paresthesia and numbness in the areas of cutaneous (sensory) distribution for this nerve.

The buccinator

a muscle of facial expression, so it would be paralyzed in facial nerve palsy. It originates on the alveolar ridges of maxillary and mandibular molar teeth and contracts to give tension to the cheek to keep food between the occlusal surfaces of the teeth. Controlled by the facial nerve (CN VII)

The temporalis muscle is

a muscle of mastication that elevates the mandible in closing of the mouth, and its posterior, horizontally-oriented fibers serve as the primary means of retruding (retracting) the mandible when it is in a protruded (protracted) position.

The lateral pterygoid

a muscle of mastication which acts to protract (or protrude) the mandible. It plays a significant role in opening of the mouth and medial-lateral excursion.

The pterion

a significant craniometric landmark point in the temporal fossa on the lateral aspect of the skull. Junction of four bones: greater wing of the sphenoid, frontal, parietal, and squamous parts of the temporal.

Coronoid process of the mandible

a thin, blade-like, superior projection from the anterior aspect of the ramus of the mandible. It serves as the insertion area for the large temporalis muscle, a muscle of mastication.

The lingual frenulum

a thin, midline fold of tissue that anchors the underside of the tongue to the floor of the oral cavity proper. Abnormal shortening of the frenulum results in ankyloglossia (tongue-tie).

The lateral pterygoid plate

a thin, winglike, inferior extension of the sphenoid bone. It forms the medial (deep) boundary of the infratemporal fossa and provides attachment for portions of the medial and lateral pterygoid muscles.

A complete lesion of the oculomotor nerve would produce all of the following signs:

abducted and laterally directed eyeball, absence of accommodation reflex, ptosis (drooping eye), absence of pupillary light reflex.

The cerebral arterial circle (of Willis) is an

anastomoses of arteries located on the ventral surface of the brain in the area of the interpeduncular fossa, optic chiasm, and hypothalamus. These vessels are prone to saccular (berry) aneurysm, particularly where the arteries join together. Upon rupturing, blood spills into the subarachnoid space because all major vessels of the brain travel within the subarachnoid space. Subarachnoid hemorrhages are often seen in the absence of trauma, and the three cardinal signs and symptoms of a subarachnoid hemorrhage are (1) loss of consciousness (lethargy), (2) nuchal rigidity (stiff neck), and (3) a sudden onset of the "worst headache of your life,"

The temporalis muscle

another muscle of mastication, runs from the temporal, fossa to the coronoid process and anterior edge of the ramus of the mandible. It also acts as an elevator (adductor) of the mandible, to close the mouth.

The marginal mandibular branch of the facial nerve (CN VII)

another one of five terminal branches of the main trunk of CN VII. This nerve only has an efferent (motor) component supplying the muscles of lower lip and chin.

A 62-year-old male factory worker went to his doctor complaining of a progressive hearing loss. Audiometric tests reveal an inability to detect high-frequency sound waves, but the rest of his hearing scores within the normal range. What is the most likely location of injury for this sensorineural hearing loss?

damage to the hair cells in the base of the cochlea.

The Medial Pterygoid

elevates mandible and moves it from side to side, functions to elevate the mandible, elevation, protrude and lateral movements

The spinal accessory Nerve CN XI:

provides motor innervation to the trapezius (major muscles of the back) and sternocleidomastoid (SCM) muscle (located behind ears and on either side of neck and helps rotate your head from side to side)

Following an automobile accident resulting in a cranial base fracture, a patient's tongue deviates to the right when protruded and he has moderate dysarthria (unclear speech) . You suspect damage to the:

right hypoglossal nerve CN XII (solely motor function, innervates all the extrinsic and intrinsic muscles of the tongue)

The olfactory nerve, CN I, provides:

sense of smell to the patient. Damage to this nerve causes anosmia, or loss of olfaction, which is frequently seen in patients with severe head trauma due to the delicate olfactory nerves traversing the cribiform plate of the ethmoid bone to enter the olfactory bulb.

A 23-year-old female professional student wakes up with a facial nerve (CN VII or Bell) palsy. What muscle will continue to function despite this affliction?

the masseter muscle, a muscle of mastication will continue to function. The mandibular (third) division of the trigeminal nerve (CN V3) supplies the four muscles of mastication, so this nerve is unaffected.

The mandibular (third) division of the trigeminal nerve (CN V3) supplies general sensation to:

the skin of the lower lip, chin, cheek, and even the anterior auricular and lateral scalp. This sensory innervation is supplied via three cutaneous nerves: mental, buccal, and auriculotemporal. The mandibular division of the trigeminal nerve also supplies innervation to the mandibular teeth and gingivae via the inferior alveolar nerve, and it is the only division of CN V that supplies motor innervation.

The uvula

the soft midline extension of the soft palate that is most often identified as "that thing that hangs down in the back of the mouth." It serves to assist in sealing off the nasopharynx during swallowing so that food does not regurgitate into the nasal passages.

The glossopharyngeal nerve (CN IX) supplies only one muscle:

the stylopharyngeus, a muscle of the pharynx