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D injury to the hypoglossal n. in the periphery will weaken the IPSILATERAL genioglossus muscle, causing the tongue to deviate to that same side on protrusion

Following a cervical carotid endartectomy performed to remove a large atherosclerotic plaque it is noted that the patient's tongue deviates to the right when asked to protrude it. Which of the following nerves was most likely injured during the procedure? A. Left glossopharyngeal B. Right glossopharyngeal C. Left hypoglossal D. Right hypoglossal E. Left vagus F. Right vagus

A. The superior cerebellar artery arises near the termination of the basilar artery, passes immedi- ately below the oculomotor nerve, and eventually winds around the cerebral peduncle, close to the trochlear nerve, as it continues on toward the upper surface of the cerebellum where it will divide into branches that anastomose with the inferior cerebellar arteries. The trochlear nerve passes between the pos- terior cerebral artery and the superior cerebellar ar- tery, and therefore a hematoma of the superior cere- bellar artery can easily injure the trochlear nerve, which runs alongside the internal carotid artery and then enters the orbit through the superior orbital fis- sure. The facial and vestibulocochlear nerves both enter the skull via the internal acoustic meatus (or internal auditory meatus) in the temporal bone and do not have an intimate relationship with the superior cerebellar artery. The glossopharyngeal nerve passes through the jugular foramen, and as it exits from the skull it passes forward between the internal jugular vein and internal carotid artery. GAS 837, 838; GA 451-452, 454

131 A 64-year-old man is admitted to the hospital in an unconscious condition. A CT scan examination reveals that the patient has suffered a cerebral vascular accident (stroke), with a small hematoma produced by the superior cerebellar artery. Which of the following nerves will most likely be affected by the hematoma? ⃣ A. Trochlear nerve ⃣ B. Abducens nerve ⃣ C. Facial nerve ⃣ D. Vestibulocochlear nerve ⃣ E. Glossopharyngeal nerve

A. An injury to the left vagus nerve would cause the uvula to become deviated to the right. This is because of the innervation of the musculus uvulae muscle that makes up the core of the uvula. If only one side is effectively innervated, contraction of the active muscle will deviate the uvula to the contralateral side of the injury (ipsilateral side of the uninjured vagus nerve). In addition, the intact levator veli palatini will pull the uvula to the intact side. The right and left hypoglossal nerves innervate the tongue muscles and would not affect the uvula. The glossopharyngeal nerve supplies sensory innervation to the oropharynx and nasopharynx, but not motor innervation to these areas.

29 A 36-year-old woman is admitted to the hospital with severe head injuries after a car crash. During neurologic examination her uvula is deviated to the right. Which nerve is most likely affected to result in this deviation? HEAD AND NECK 215 ⃣ A. Left vagus ⃣ B. Right vagus ⃣ C. Right hypoglossal ⃣ D. Left glossopharyngeal ⃣ E. Right glossopharyngeal

E. The superior oblique muscle turns the pupil downward from the adducted position. Inability to perform this motion, in conjunction with diplopia when walking down stairs, indicates damage to the trochlear nerve. The abducens innervates the lateral rectus, resulting in abduction of the eye. The oculo- motor nerve supplies the superior, inferior, and me- dial rectus as well as the inferior oblique. Overall, innervation from the oculomotor nerve results in up- ward and downward movements of the eye. Damage to this nerve would not induce diplopia when an af- fected individual walks down stairs. In addition, in- ability to gaze downward in the adducted position does not indicate oculomotor nerve damage. In this position the oculomotor nerve would be responsible for upward movement. The nasociliary nerve is a sen- sory nerve originating from the ophthalmic branch of the trigeminal nerve. GAS 888-891; GA 464, 466

76 A 43-year-old male is admitted to the hospital complaining of diplopia (double vision) when walking down stairs. During physical examination of the extraocular muscles the patient experiences diplopia, and when he is asked to turn his right eye inward toward his nose and look down, he is able to look inward but not down. Which nerve is most likely involved? ⃣ A. Abducens ⃣ B. Nasociliary ⃣ C. Oculomotor, inferior division ⃣ D. Oculomotor, superior division ⃣ E. Trochlear

A: Greater petrosal nerve. Secretomotor con- trol of the lacrimal gland is provided by parasympathetic neu- rons derived from the facial nerve. These fibers branch from the facial nerve as the greater petrosal nerve at the geniculum of the facial canal, within the petrous part of the temporal bone. This parasympathetic nerve leaves the temporal bone and courses along the floor of the middle cranial fossa on its way to the foramen lacerum, pterygoid canal, and pterygo- palatine fossa. It is readily damaged in trauma to the floor of the middle cranial fossa. Lesion of the nerve will result in loss of emotional tearing plus reduced mucus secretion in the nasal cavity (dry nasal passages). Choice B (Lesser petrosal nerve) is incorrect. The lesser petrosal nerve is a parasympathetic bundle derived from the tympanic branch of the glossopha- ryngeal nerve in the middle ear. It is the presynaptic (pregan- glionic) element in the secretomotor pathway to the parotid gland via the otic ganglion. Choice C (Deep petrosal nerve) is incorrect. The deep petrosal nerve is a sympathetic bundle that branches off the carotid plexus at the exterior base of the skull. It joins with the greater petrosal nerve to form the nerve of the pterygoid canal that travels through the pterygoid canal into the pterygopalatine fossa. The deep petrosal nerve may be damaged in a fracture of the floor of the middle cranial fossa. However, it does not control lacrimation, and thus is not the element related to the deficit here. Obviously, you must take care to differentiate the three petrosal nerves in accounting for autonomic relations in the head. Choice D (Lacrimal nerve) is incorrect. The lacrimal nerve is a branch of the ophthalmic division of the trigeminal nerve within the orbit. It conveys general sensory fibers from the upper eyelid, conjunctiva, and lacrimal sac. Further, its distal portion carries the postsynap- tic parasympathetic secretomotor fibers to the lacrimal gland. However, the lacrimal nerve itself would not be damaged by a fracture within the middle cranial fossa. Choice E (Chorda tympani nerve) is incorrect. The chorda tympani nerve is a branch of the facial nerve that runs through the middle ear cavity and continues into the infratemporal fossa. It carries parasympathetic secretomotor fibers to two salivary glands, the submandibular and sublingual glands, via the submandib- ular ganglion. It also conveys taste sensation from the anterior part of the tongue.

A 12-year-old boy suffers a fracture of the floor of the right side of the middle cranial fossa during an automobile acci- dent. Subsequent physical examination reveals he is devoid of emotional tearing on the ipsilateral side. Which of the follow- ing nerves is most likely damaged? (A) Greater petrosal nerve (B) Lesser petrosal nerve (C) Deep petrosal nerve (D) Lacrimalnerve (E) Chorda tympani nerve

A, D A and D are both correct. With only the superior oblique and lateral rectus functional, the eye will be abducted (lateral rectus), and slightly depressed and medially rotated (superior oblique). However, medial rotation will not be evident on observation alone.

A 45-year-old female presents to her primary care physician with complaints of a droopy right eyelid, double vision, an increased sensitivity to light, and difficulty reading at a close distance. Her physician suspects a cranial nerve injury. In evaluating this patient the physician notes which of the following presentations of the affected eye when in primary position? (More than one answer possible) A The pupil of the eye is abducted B The pupil of the eye is adducted C The pupil of the eye is slightly elevated D The pupil of the eye is slightly depressed

B: Inferior oblique. Paralysis of one or more of the extraocular muscles causes a lack of coordinated eye movements, often resulting in diplopia (double vision). Clini- cal evaluation of the muscles includes step-wise positioning of the eye in such a way as to test each individual muscle at its position of greatest mechanical efficiency (relative to the visual axis) to determine if that muscle is functioning prop- erly. Testing begins from the rest position, with the patient looking straight ahead. In this case, the first step (looking inward; adduction) tests the action of the medial rectus, the primary adductor of the eye. At the adducted position, the superior and inferior oblique muscles are aligned along their primary lines of action. The second step (looking upward; elevation) tests for function of the inferior oblique, which elevates the eye. Failure of either step indicates possible dam- age to the oculomotor nerve (CN III), which supplies both of these muscles. The inferior oblique and inferior rectus muscles can be impinged in head trauma cases when the floor of the orbit is fractured. These orbital (blowout) frac- tures lead to the downward herniation of orbital contents into the maxillary sinus, leading to the potential entrapment of these two extraocular muscles. The integrity of the infe- rior oblique muscle was tested in this question. Choice A (Superior oblique) is incorrect. Testing the superior oblique includes the same first step as for the inferior oblique, that is, adducting the eye to test the medial rectus and to position the oblique muscles along their primary lines of action. In this case, the second step is to look downward (depression) to test the superior oblique, which depresses the eye. Failure of this step indicates possible damage to the trochlear nerve (CN IV), which supplies only the superior oblique muscle. Choice C (Lateral rectus) is incorrect. The lateral rectus is the primary abductor of the eye from the rest position. Asking the patient to look outward (away from the nose) tests the ability of the lateral rectus to abduct at its position of greatest efficiency. Failure of this test indicates possible damage to the abducent nerve (CN VI), which supplies only the lateral rectus. Fur- thermore, at the adducted position, the superior and inferior rectus muscles are aligned along their primary lines of action and are set in best testing position. Choice D (Inferior rectus) is incorrect. At the abducted position, asking the patient to look downward tests the function of the inferior rectus, which depresses the eye. Failure to accomplish this task indicates possible damage to the oculomotor nerve, which supplies the inferior rectus muscle. Choice E (Superior rectus) is incor- rect. From the abducted position, asking the patient to look upward tests the superior rectus, which elevates the eye. Fail- ure to accomplish this task is another indicator of possible damage to the oculomotor nerve, which supplies the superior rectus muscle.

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 ophthalmol gist 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? (A) Superioroblique (B) Inferior oblique (C) Lateralrectus (D) Inferiorrectus (E) Superior rectus

C: Inability to close the eyelids. The stylomas- toid foramen is located in a well-protected position between the styloid and mastoid processes, at the base of the skull. It is the terminal opening of the facial canal, transmitting the main branch of the facial nerve out of the petrous temporal bone to the exterior base of the skull. From there, the facial nerve sends sensory branches to the external ear, motor branches to small muscles in the upper neck (stylohyoid and posterior belly of the digastric), and terminal motor branches to the facial muscles (muscles of facial expression). However, the mastoid process is not developed at birth, leaving the stylomastoid foramen and the emerging facial nerve exposed. Undue pres- sure applied to the mastoid area (as from misapplied obstet- ric forceps) may entrap and damage the facial nerve. In this case, crush injury to the facial nerve would produce unilateral paralysis of the facial muscles, including the orbicularis oculi. This sphincter-like muscle surrounds the orbit, acting to close the eyelids. Choice A (Reduced blood flow to the inner ear) is incorrect. Vascular supply to the inner ear is provided by small labyrinthine vessels that accompany the facial and ves- tibulocochlear nerves through the internal acoustic meatus. Supply to the external ear is mainly from branches of the pos- terior auricular and superficial temporal arteries. The posterior auricular arterial branching is susceptible to damage in this scenario. Supply to the middle ear is mainly from branches of the maxillary artery. These vessels are unlikely to be affected by compression around the incipient mastoid process. Choice B (No sensation in the external acoustic meatus) is incorrect. The external ear receives afferent innervation from a plethora of cranial nerves, including trigeminal (CN V), facial (CN VII), vagus (CN X), and possibly even the glossopharyngeal (CN IX). The trigeminal and vagus are the major nerves, supplying most of the sensory fibers to this region, including the exter- nal acoustic meatus. The facial nerve provides relatively small contributions to the sensation of the external acoustic meatus because its sensory innervation is concentrated on the auricle. Choice D (Lack of taste on the body of the tongue) is incor- rect. The facial nerve provides taste fibers to the body (anterior two thirds) of the tongue and parasympathetic fibers to the oral floor via its chorda tympani branch. However, the chorda tympani nerve leaves the facial nerve within the facial canal, traverses the tympanic (middle ear) cavity, and exits the base of the skull near the temporomandibular joint (TMJ). Therefore, this forceps injury would not affect the taste or parasympathetic functions governed by the facial nerve. Choice E (Inability to tense the eardrum) is incorrect. The tensor tympani muscle attaches to the handle of the malleus, acting to pull this ear ossicle medially and tense the tympanic membrane (eardrum). This muscle is innervated by the mandibular division of the trigeminal nerve (CN V3). The stapedius muscle attaches to the stapes, acting to tighten the oval window. This muscle is controlled by the facial nerve, via a branch off the facial canal, proximal to the stylomastoid foramen.

During a difficult childbirth, a physician uses obstetric forceps to grip the infant's head as an aid to extracting her from the birth canal. However, the forceps are misapplied at the right stylomastoid foramen and crush its contents at the opening of the foramen. Which of the following ipsilateral deficits is the baby most likely to suffer? (A) Reduced blood flow to the inner ear (B) No sensation in the external acoustic meatus (C) Inability to close the eyelids (D) Lack of taste on the body of the tongue (E) Inability to tense the eardrum

B: 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. Its mental nerve branch enters the mandible through the mental foramen after supplying sensory (cutaneous) innervation to the skin overly- ing the mandible, including the lower lip. Due to its location within the mandible and close relation to the dental arcade, the inferior alveolar nerve may be damaged during dental extrac- tions, especially more complicated extractions of impacted third molars ("wisdom teeth"). Thus, paresthesia in the lower lip may result from such procedures. Choice A (Inability to compress the cheek) is incorrect. Compression of the cheek is an important action in all aspects of feeding and in other oral functions as well, and it is produced by the contraction of the buccinator muscle, one of the facial muscles. Being a muscle of facial expression, the buccinator is controlled by the facial nerve (CN VII), through its terminal facial branches. Choice C (Weakness in closing the jaw) is incorrect. Chew- ing is the result of the complex interactions of the muscles of mastication, which are controlled by the motor branches of the mandibular division of the trigeminal nerve (CN V3). Of these four mastication muscles, the masseter, temporalis, and medial pterygoid muscles act in closing the jaw. The lateral pterygoid and anterior belly of the digastric muscles act in the opening of the oral fissure by depressing the mandible. The inferior alveolar nerve gives rise to the mylohyoid nerve before it enters the mandible via the mandibular foramen. The mylohyoid nerve supplies the anterior belly of the digas- tric and mylohyoid muscles. Therefore, while damage to the proximal part of the inferior alveolar nerve may influence jaw opening by affecting the anterior digastric muscle, damage to its distal (intramandibular) part does not affect any muscles of mastication, sparing both opening and closing of the mandible. Choice D (Decreased salivary flow) is incorrect. Secretomotor control of the submandibular and sublingual salivary glands is governed by parasympathetic neurons that originate in the facial nerve through its chorda tympani branch and ultimately reach the oral floor via the lingual nerve, a branch of the mandibular division of the trigeminal nerve (CN V3). Control of the parotid salivary gland is conveyed through parasym- pathetic fibers that originate in the glossopharyngeal nerve, travel through its tympanic and lesser petrosal branches, and ultimately reach the parotid through the auriculotemporal nerve (another branch of CN V3). Choice E (Reduced taste in the body of the tongue) is incorrect. Taste fibers in the body (anterior two thirds) of the tongue are provided by the facial nerve via its chorda tympani branch. General sensory fibers to the same area are supplied by the lingual nerve, a branch of the mandibular division of the trigeminal nerve (CN V3). The chorda tympani nerve unites with the lingual nerve within the infratemporal fossa. Thus, whereas the taste and general sensory components to the body of the tongue arise from separate cranial nerve pathways, they share a final common pathway to their target region. Remember that the parasympa- thetic supply to the oral floor (submandibular and sublingual salivary glands; oral floor mucus glands) also shares most of the chorda tympani/lingual nerve pathway. However, the auto- nomic fibers leave the lingual nerve in the oral floor to synapse in the submandibular ganglion.

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? (A) Inability to compress the cheek (B) Paresthesia of the lower lip (C) Weakness in closing the jaw (D) Decreased salivary flow (E) Reduced taste in the body of the tongue

C the cells within the pterygopalatine ganglion innvervate the lacrimal gland and the mucus-producing glands of the nose and palate. the greater petrosal br. of the facial n. provides the preganglionic input to the cells in the pterygopalatine ganglion.

The cell bodies of the postganglionic parasympathetic neurons supplying the lacrimal gland are located in which of the following ganglia? A. Ciliary B. Otic C. Pterygopalatine D. Superior cervical E. Trigeminal

B the bridge and dorsum of the nose are part of the opthalmic dermatome of the face; the lateral aspects of the external nose are part of the maxillary dermatome

Two weeks following rhinoplasty (cosmetic surgery on the nose) a 24-year-old female states that she has numbness and tingling from the bridge to the tip of her nose. Branches of which of the following nerves were most likely injured in the rhinoplasty? A. Olfactory B. Ophthalmic C. Maxillary D. Mandibular E. Facial

B,D,F,G CN III, VII, IX, X CNs III, VII, IX, and X all emerge from the brainstem with preganglionic parasympathetic nerve fibers bundled within. Although most of these nerve fibers remain within their cranial nerve of origin, not all do. Some preganglionic nerve fibers will leave their cranial nerve of origin and join other cranial nerves (usually branches of the trigeminal nerve) to reach their effector organs in the periphery.

Which of the following cranial nerves have a parasympathetic visceral motor/efferent component? (select all that apply) A CN II B CN III C CN V D CN VII E CN VIII F CN IX G CN X H CN XI I CN XII

A,C,D,F

Which of the following ganglia houses the cell bodies of postganglionic parasympathetic neurons? (select all that apply) A Ciliary B Dorsal root C Otic D Pterygopalatine E Stellate F Submandibular

B Buccinator is a muscle of facial expression and is innervated by the facial nerve. The rest are muscles of mastication and are innervated by CNV3.

Which of the following muscles is NOT innervated by the trigeminal nerve? A medial pterygoid B buccinator C temporalis D masseter E lateral pterygoid

B,D,E B-glossopharyngeal- posterior 1/3 D- facial - anterior 2/3 E- vagus - root of tongue The facial nerve (CN VII) carries taste from the anterior 2/3 on the tongue, and glossopharyngeal nerve (CN IX) carries taste from the posterior 1/3 of the tongue, the vagus nerve (CN X) carries taste from the "root" of the tongue in the oropharynx.

Which of the following nerves carry taste sensation? (select all that apply) A Trigeminal B Glossopharyngeal C Hypoglossal D Facial E Vagus

B,C, E

Which of the following nerves have both sensory and motor components? (select all that apply) A CN II B CN V C CN VII D CN VIII E CN X F CN XI

C Look up and away from injured side Unilateral contraction of the sternocleidomastoid muscle rotates the chin in the opposite direction.

Which of the following statements best describes the physical presentation of an upright patient with torticollis due to excessive contraction of the right sternocleidomastoid muscle? A Head flexed forward in the midline B Neck flexed and chin rotated up and to the right C Neck flexed and chin rotated up and to the left D Head extended in the midline

D in the H-test, evaluation of the adducted -eye tests for function of the inferior oblique muscle; depression of the adducted eye tests for function of the SUPERIOR OBLIQUE MUSCLE. the superior oblique muscle is innervated by the TROCHLEAR N. (CNIV)

A 19-year-old student presented with a complaint of double vision whenever he attempted to read. When gazing toward the right, the patient could depress the abducted right eye but could not depress the adducted left eye. He could depress the abducted left eye when looking to the left. All other eye movements were normal. Which nerve has been injured? A. Left abducens B. Right abducens C. Left oculomotor D. Left trochlear E. Right trochlear

D In the H-test, adduction of the eye aligns the superior and inferior oblique muscles so as to maximize their ability to produce rotation along the transverse axis, while simultaneously minimizing the ability of the superior and inferior rectus muscles to act on this axis (See University of Toronto H-Test Simulator; https://www.bmc.med.utoronto.ca/anatomia/intro.swf). With the affected eye adducted, depression of the eye occurs through contraction of the superior oblique muscle; elevation of the eye is achieved by contraction of the inferior oblique muscle. An inability to elevate the adducted eye indicates an injury to the inferior oblique muscle.

A 22-year-old male presents at the emergency department following a late night bar brawl in which he was hit squarely in the right eye by a fist of one of the participants. The patient complains of eye pain and double vision, and his eye and surrounding tissues are swollen and bruised. Suspecting a blow-out fracture may have trapped one of the extra-ocular muscles, you manage to successfully complete an H-test on the affected eye. Results indicate that the patient cannot elevate the eye when adducted. Which of the following muscles is likely trapped by the bone fragments of the blow-out fracture? A Superior rectus B Inferior rectus Superior oblique Inferior oblique C Superior oblique D Inferior oblique

B: 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, and due to its location, this nerve is most likely damaged during the biopsy. Damage to the infraorbital nerve causes paresthesia and numbness in the areas of cutaneous (sensory) distribution for this nerve. Choice A (First division of trigeminal nerve) is incorrect. The first (oph- thalmic) division of the trigeminal nerve (CN V1) supplies the skin of the upper eyelid, forehead, and scalp. CN V1 enters the middle cranial fossa via the superior orbital fissure, and its branches are distributed within the orbit, anterior cranial fossa, and nasal cavity. CN V1 does not supply sensory innervation to the maxillary sinus, so it would be spared during this FESS. However, the ophthalmic division of the trigeminal nerve does innervate three other paranasal sinuses (ethmoidal, frontal, and sphenoidal). Choice C (Third division of trigeminal nerve) is incorrect. The third (mandibular) division of the trigeminal nerve (CN V3) supplies the skin of the lower lip, chin, cheek, anterior auricle, and aspects of the lateral scalp. CN V3 leaves the middle cranial fossa via the foramen ovale, and it does NOT have a significant branch, which courses through the superior aspect (roof) of the maxillary sinus. Therefore, it could not be damaged in this patient. Choice D (Zygomatic branch of facial nerve) is incorrect. The zygomatic branch of the facial nerve (CN VII) is a terminal branch of the main trunk of CN VII. This nerve has only motor innervation, supplying the inferior part of the orbicularis oculi and other muscles of facial expression located below the orbit. Because it does not pass through the maxillary sinus or supply cutaneous innervation to any region, the zygomatic nerve of CN VII could not cause the numbness and paresthesia seen in this patient. Choice E (Buccal branch of facial nerve) is incorrect. The buccal branch of the facial nerve (CN VII) is a terminal branch of the main trunk of CN VII. This nerve has only motor innervation, sup- plying the risorius and muscles of the upper lip. Because it does not pass through the maxillary sinus or supply cutaneous innervation to any region, the buccal nerve of CN VII could not cause the numbness and paresthesia seen in this patient.

A 24-year-old man came to his physician with a history of chronic maxillary sinusitis. A computed tomography (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? (A) First division of trigeminal nerve (B) Second division of trigeminal nerve (C) Third division of trigeminal nerve (D) Zygomatic branch of facial nerve (E) Buccal branch of facial nerve

A. The motor portion of the facial nerve (CNVII) innervates the orbicularis occuli muscle. The sphincter muscle of the eyelids is responsible for closing the eyelids- an action that sweeps lacrimal fluids cross the cornea from their origin at the superolateral aspect of the orbit to the lacrimal sac in the inferomedial aspect of the orbit.

A 33-year-old woman develops Bell palsy. She must be cautious because this can result in corneal inflammation and subsequent ulceration. This symptom results from which of the following conditions? A. Absence of the corneal blink reflex B. Absence of sweating on the face C. Inability to constrict the pupil D. Sensory loss of the cornea and conjunctiva

D: Presynaptic parasympathetic fibers. The nerve of the pterygoid (vidian) canal consists of presynaptic parasympathetic fibers from the greater petrosal nerve of the facial nerve (CN VII) and postsynaptic sympathetic fibers from the deep petrosal nerve, derived from the periarterial arterial plexus enveloping the internal carotid artery. The presynaptic parasympathetic fibers follow the greater pet- rosal nerve (of CN VII), traverse the pterygoid canal, enter the pterygopalatine fossa to synapse in the pterygopalatine ganglion, and carry the postsynaptic parasympathetic fibers to the lacrimal gland via branches of the first two divisions of the trigeminal nerve (CN V1 and CN V2). The parasympathetic fibers of CN VII produce emotional tears from the lacrimal glands. Choice A (Taste fibers to the anterior two thirds of the tongue) is incorrect. The chorda tympani, a branch of the facial nerve (CN VII), joins the lingual branch of the man- dibular nerve (CN V3) in the infratemporal fossa. The chorda tympani nerve conveys taste sensation from the anterior two thirds of the tongue and carries presynaptic parasympathetic fibers to the submandibular ganglion for innervation of the submandibular and sublingual salivary glands. However, the chorda tympani nerve is not associated with the pterygoid canal, so it would not be damaged by a facial nerve schwan- noma at this location. Choice B (Parasympathetic innervation to the submandibular and sublingual glands) is incorrect. The chorda tympani, a branch of the facial nerve (CN VII), joins the lingual branch of the mandibular nerve (CN V3) in the infratemporal fossa. The chorda tympani nerve conveys taste sensation to the anterior two thirds of the tongue and carries presynaptic parasympathetic fibers to the submandibular gan- glion for innervation of the submandibular and sublingual salivary glands. However, the chorda tympani nerve is not associated with the pterygoid canal, so it would not be dam- aged by a facial nerve schwannoma at this location. Choice C (Presynaptic sympathetic fibers) is incorrect. All sympathetic fibers in the head are postsynaptic because they synapse in the superior cervical ganglion before reaching their targets in the head. Therefore, the sympathetic fibers traveling in the pterygoid canal are postsynaptic. These postsynaptic sym- pathetic fibers control the smooth muscle tone (vasodilation and vasoconstriction) of the blood vessels lying underneath the nasal mucosa. Choice E (Postsynaptic parasympathetic fibers) is incorrect. The parasympathetic fibers derived from the greater petrosal nerve (of CN VII) do not synapse until after they have left the pterygoid (vidian) canal. After leaving this canal, these presynaptic parasympathetic fibers synapse in the pterygopalatine ganglion distal to the pterygoid canal. Therefore, the parasympathetic fibers in the pterygoid (vidian) canal are presynaptic. These fibers serve to increase emotional tearing of the lacrimal glands.

A 37-year-old man presented with decreased emotional tear- ing on the right side and intermittent headaches. Magnetic resonance images (MRIs) revealed a facial nerve schwannoma located within the right pterygoid (vidian) canal. What nerve fibers are most likely injured by this tumor? (A) Taste fibers to the anterior two thirds of the tongue (B) Parasympathetic innervation to the submandibular and sublingual glands (C) Presynaptic sympathetic fibers (D) Presynaptic parasympathetic fibers (E) Postsynaptic parasympathetic fibers

A Structures of the eye that receive parasympathetic include the ciliary muscles and the constrictor pupillae.

A 41-year-old woman overdoses on some prescription medications that have a common side effect of autonomic nerve stimulation. Which of the following conditions or actions results from stimulation of the parasympathetic fibers to the eye? A Contraction of the ciliary muscles B Dilation of the pupil C Flattening of the lens D Vasoconstriction of the capillaries of the iris

A: Internal acoustic meatus. The loss of facial expression and drooping corner of the mouth indi- cate paralysis of the facial muscles and damage to the facial nerve (CN VII). The intact ability to clench the jaw and chew denotes proper functioning of the muscles of mastication and an intact mandibular division of the trigeminal nerve (CN V3). The hearing loss and unsteady balance indicate failure in the inner ear complex implicating the right ves- tibulocochlear 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 eye- lids, and this evidence reinforces a problem with the facial nerve. Normal cutaneous sensation across the face indicates the entire trigeminal pathway is intact. Therefore, the sus- pected tumor affects both CN VII and CN VIII, but not the trigeminal nerve (CN V). The only location where CN VII and CN VIII can be affected simultaneously is at the internal acoustic meatus (in the wall of the posterior cranial fossa), where the paired nerves leave the cranial cavity to enter the petrous part of the temporal bone. Very quickly thereafter, the nerves diverge and follow separate pathways to their target regions. The given contrast-enhanced T1-weighted MRI demonstrates a right-sided vestibular schwannoma (acoustic neuroma), located at the internal acoustic meatus and identified by the arrow, which confirms this diagnosis. This vestibular schwannoma, which is clearly seen in white due to the gadolinium-based intravenous contrast, resides at the cerebellopontine angle and affects the facial and ves- tibulocochlear nerves as they emerge from this location. This tumor would also increase intracranial pressure potentially causing pontomedullary brain stem compression. Choice B (Foramen ovale) is incorrect. The mandibular division of the trigeminal nerve (CN V3) passes through the foramen ovale in the floor of the middle cranial fossa. At this location, a tumor would affect the muscles of mastication and cutane- ous sensation over the mandibular region of the face, which is not evident in this patient. Choice C (Foramen rotundum) is incorrect. The maxillary division of the trigeminal nerve (CN V2) passes through this opening in the anterior wall of the middle cranial fossa. Nerve damage here would affect cutaneous sensation across the midfacial region, which is not evident in this patient. Choice D (Geniculum of the facial canal) is incorrect. The facial nerve travels through the facial canal within the petrous part of the temporal bone, including the knee-like bend (geniculum) of the canal. Thus, tumor growth in this location would affect the facial nerve and pro- duce the facial paralysis described in this case. However, the vestibulocochlear nerve would not be affected at this site, as it has already separated from the facial nerve. Choice E (Stylomastoid foramen) is incorrect. The main branch of the facial nerve exits the skull through the stylomastoid foramen at the base of the skull. Tumor growth here would affect the facial nerve, producing the described facial paralysis. How- ever, the vestibulocochlear nerve would not be affected by problems at this location.

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 dif- ficulty 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? (A) Internal acoustic meatus (B) Foramen ovale (C) Foramen rotundum (D) Geniculum of the facial canal (E) Stylomastoid foramen

C. The superior salivatory nucleus is the autonomic nucleus for the facial nerve. Parasympathetic fi bers carried by the greater petrosal branch of the facial nerve are responsible for supply of the lacrimal gland and sinuses, via the pterygopalatine ganglion. The geniculate ganglion contains the cell bodies for taste from the anterior two thirds of the tongue carried by the chorda tympani branch of the facial nerve. This branch also carries the parasympathetic supply for the submandibular and sublingual salivary glands. The auriculotemporal nerve provides sensory innervation to the temporal regions of the head, the TMJ, and general sensation from the ear. The inferior salivatory nucleus provides preganglionic parasympathetic fi bers carried by the glossopharyngeal nerve that synapse in the otic ganglion, providing parotid stimulation. The pterygopalatine ganglion includes fi bers that innervate only lacrimation and the nasal sinuses, but not taste on the anterior two thirds of the tongue.

A 45-year-old female is admitted to the hospital with severe headaches, dizziness, and vomiting. Radiographic examination reveals an intracranial tumor. Upon physical examination the patient has dryness of the nasal and paranasal sinuses, loss of lacrimation, and loss of taste from the anterior two thirds of the tongue. Which of the following structures is most likely involved with the tumor? A. Auriculotemporal nerve ⃣ B. Lesser petrosal nerve ⃣ C. Facial nerve ⃣ D. Inferior salivatory nucleus ⃣ E. Pterygopalatine ganglion

B,F B and F are both correct. In oculomotor nerve palsies the lateral rectus muscle is functional and the patient can abduct the affected eye. The superior oblique muscle is also intact, leading to a slight depression of the abducted eye (although its pull is minimized, the superior oblique muscle can still act on the transverse axis when the eye is abducted). When adducting the eye from the abducted position, the eye will rotate along the vertical axis to primary position as a consequence of inhibition of the lateral rectus muscle, but in the absence of contraction of the medial rectus muscle, it cannot rotate beyond that point.

A 45-year-old female presents to her primary care physician with complaints of a droopy right eyelid, double vision, an increased sensitivity to light, and difficulty reading at a close distance. Her physician suspects a cranial nerve injury. In performing an H-Test on this patient, which of the following findings are expected? (More than one answer possible) A The pupil of the affected eye is slightly elevated when abducted B The pupil of the affected eye is slightly depressed when abducted C The pupil of the affected eye is neither elevated nor depressed when abducted D The pupil of the affected eye is slightly elevated when adducted fully E The pupil of the affected eye is slightly depressed when adducted fully F The pupil of the affected eye cannot move past primary position when attempting adduction

B The oculomotor nerve is a "super" motor nerve; it carries both somatic efferent fibers to skeletal muscles in the orbit (levator palpebrae superioris, superior, medial and lateral rectus, and inferior oblique), and visceral efferent (parasympathetic) fibers to smooth muscles in the iris of the eye (ciliary muscle, constrictor pupillae). This patient's constellation of symptoms is consistent with an injury to the right oculomotor nerve. Common causes of oculomotor nerve injury include pressure on or compression of the oculomotor nerve, and inadequate blood flow to the nerve. Of these the former results from such life-threatening, emergent conditions as herniation of portions of the temporal lobes of the brain through the tentorial notch (transtentorial herniation - due to an enlarging tumor or intracranial bleed), or a growing aneurysm in an artery supplying the brain. Inadequate blood flow typically results from diabetes, high blood pressure (hypertension), and other disorders that affect blood vessels.

A 45-year-old female presents to her primary care physician with complaints of a droopy right eyelid, double vision, an increased sensitivity to light, and difficulty reading at a close distance. Her physician suspects a cranial nerve injury.Which cranial nerve is most likely affected in this patient? A Abducens B Oculomotor C Ophthalmic D Optic E Trochlear

C: Third division of trigeminal nerve. The third (mandibular) division of the trigeminal nerve (CN V3) sup- plies general sensation to the skin of the lower lip, chin, cheek, and even the anterior auricle and the lateral scalp. This sensory innervation is supplied via three cutaneous nerves: mental, buccal, and auriculotemporal. The mandibular divi- sion of the trigeminal nerve also supplies innervation to the mandibular teeth and gingivae via the inferior alveolar nerve. This patient is suffering from trigeminal neuralgia (or tic dou- loureux), often seen in patients suffering from demyelinating diseases such as multiple sclerosis, affecting CN V3. Trigeminal neuralgia is characterized by episodes of pain that occur sud- denly, and debilitating pain can often be triggered by stimuli within the distribution area of the nerve affected, which was seen following eating, talking, or brushing her teeth in this patient. Choice A (First division of the trigeminal nerve) is incorrect. 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 ante- rior scalp. The sensory distribution of the ophthalmic division of the trigeminal nerve does not correlate to the areas of the face affected in this patient, so this option can be eliminated. Choice B (Second division of trigeminal nerve) is incorrect. 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. The sensory distribution of the maxillary division of the trigeminal nerve does not correlate to the areas of the face affected in this patient, so this option can be eliminated. Choice D (Buccal branch of facial nerve) is incorrect. 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 buc- cinator muscle and muscles of the upper lip. It does not have a sensory component, so this nerve would not be the source of this patient's pain. Choice E (Marginal mandibular branch of the facial nerve) is incorrect. The marginal mandibular branch of the facial nerve (CN VII) is 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. It does not have a sensory component, so this nerve would not be the source of this patient's pain.

A 47-year-old woman with a history of multiple sclerosis comes to her doctor complaining of sudden bursts (parox- ysms) 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? (A) First division of trigeminal nerve (B) Second division of trigeminal nerve (C) Third division of trigeminal nerve (D) Buccal branch of facial nerve (E) Marginal mandibular branch of facial nerve

C: Levator palpebrae superioris. The levator palpebrae superioris muscle attaches into the tarsal plate and skin of the upper eyelid and is the primary elevator of the eye- lid. Weakness in this muscle results in ptosis (drooping) of the upper eyelid and may reflect a problem with the oculomotor nerve (CN III). The oculomotor nerve provides the motor con- trol for the levator palpebrae superioris and most (4 of 6) of the extraocular muscles. The levator palpebrae superioris is assisted by the superior tarsal muscle, a thin smooth muscle sheet in the upper eyelid innervated by sympathetic fibers. Choice A (Orbicularis oculi) is incorrect. The orbicularis oculi is a muscle of facial expression that acts to close the eye, form- ing a sphincter-like arrangement around the orbit and extend- ing into the eyelids. Functional deficits of the orbicularis oculi muscle result in loss of the ability to blink, which endangers the health of the eye by hampering proper spread of tears across the eyeball. Choice B (Frontalis) is incorrect. The fron- talis muscle is the anterior component of the epicranius muscle in the scalp. It elevates the eyebrows and produces the hori- zontal wrinkles across the forehead, occurring when a person looks up (superior). Choice D (Superior rectus) is incorrect. The superior rectus muscle is one of the extraocular muscles. It attaches onto the sclera on the superior aspect of the eye and acts as the primary elevator of the eyeball. Choice E (Orbital muscle) is incorrect. The orbital muscle is a rudimentary smooth (nonstriated) muscle sling across the orbit that helps to support and position the eyeball within the orbit.

A 75-year-old man tells his physician he has been having pro- gressively more trouble opening his left eye because his upper eyelid tends to droop. Which of the following muscles is most likely weakened? (A) Orbicularis oculi (B) Frontalis (C) Levator palpebrae superioris (D) Superior rectus (E) Orbital muscle

E: Left oculomotor nerve. The left oculomotor nerve (CN III) is damaged in this patient. The physician is performing the pupillary light reflex, which tests the integrity of the sensory and motor functions of the eye. The afferent limb of the reflex is the optic nerve, and the efferent limb is the oculomotor nerve. In this patient, the constriction of the right pupil (a consensual response to the light) implies the affer- ent limb (left optic nerve) of the light reflex is intact because one of the pupils responded to the light. However, the effer- ent limb of the left eye is likely damaged due to the lack of a direct response (pupillary constriction) to the light. Under normal circumstances, both pupils constrict in response to increased light intensity due to a bilateral projection from the pretectal nucleus within the upper medulla to the Edinger- Westphal nucleus, which then projects its parasympathetic fibers along the oculomotor nerve causing pupillary constric- tion. Choice A (Right optic nerve) is incorrect. Because the physician did not direct the light into the right eye, the integ- rity of the right optic nerve was not tested. To test this afferent limb of the pupillary light reflex, the physician must shine the light directly into the right eye. Because there was no direct response (pupillary constriction) of the left eye, the physician did confirm damage to the left oculomotor nerve. Choice B (Left optic nerve) is incorrect. The left optic nerve is intact in this patient because the right pupil constricted (a consensual response), which implies the patient's left optic nerve recog- nized the increase in light intensity. Choice C (Right ophthal- mic nerve) is incorrect. The ophthalmic nerve (or first division of the trigeminal nerve) supplies sensory (cutaneous) innerva- tion to the skin of the upper eyelid, cornea, anterior aspect of the nose, forehead, and anterior scalp. This nerve did not participate in the pupillary light reflex, so this option can be eliminated. Choice D (Right oculomotor nerve) is incorrect. The right oculomotor nerve is intact because the right pupil constricted in response to the increased luminescence. The bilateral projections within the pupillary light response path- way enable this consensual response.

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? (A) Right optic nerve (B) Left optic nerve (C) Right ophthalmic nerve (D) Right oculomotor nerve (E) Left oculomotor nerve

F The hypoglossal nerve innervates the muscles of the tongue. Loss of function of the left genioglossus muscle of the tongue will result in the tongue deviating to the left upon protrusion.

A routine physical exam of a 39-year-old female patient reveals deviation of her tongue to the left on protrusion. Which of the following nerves is injured? A Right glossopharyngeal nerve (CN IX) B Left glossopharyngeal nerve (CN IX) C Right vagus nerve (CN X) D Left vagus nerve (CN X) E Right hypoglossal nerve (CN XII) F Left hypoglossal nerve (CN XII)

A. Horner's syndrome is a result of interruption of the sympathetic supply to the head. In this syndrome, the dilator pupilae is inactive, which results in unopposed action of the constrictor pupillae m.

An 8-year-old male is admitted to the hospital with a drooping right eyelid (ptosis). The initial diagnosis is Horner's syndrome. Which of the following additional signs on the right side would confirm the diagnosis? A. Constricted pupil B. Dry eye C. Exophthalmos D. Pale, blanched face E. Sweaty face

B: Abducent nerve. All of the listed nerves travel within the cavernous sinus; however, 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 internal carotid artery and abducent nerve are located medially as they traverse the cavernous sinus. In the given figure, the other nerves that travel through the cavern- ous sinus (CNs III, IV, V1, and V2) lie laterally. Therefore, the increased pressure, seen within the internal carotid artery due to the atherosclerotic plaque causing the stenosis and result- ing aneurysm, would most likely affect the abducent nerve. Choice A (Trochlear nerve) is incorrect. The trochlear nerve (CN IV) traverses the cavernous sinus; however, it lies along the lateral wall of the sinus. The abducent nerve, which paral- lels the internal carotid artery, would most likely be affected by increased pressure within this vessel due to the stenosis and subsequent aneurysm. Choice C (Maxillary nerve) is incor- rect. The maxillary nerve (or second division of the trigeminal nerve) traverses the cavernous sinus; however, it lies along the lateral wall of the sinus. The abducent nerve, which parallels the internal carotid artery, would most likely be affected by increased pressure within this vessel due to the stenosis and subsequent aneurysm. Choice D (Ophthalmic nerve) is incor- rect. The ophthalmic nerve (or first division of the trigeminal nerve) traverses the cavernous sinus; however, it lies along the lateral wall of the sinus. The abducent nerve, which paral- lels the internal carotid artery, would most likely be affected by increased pressure within this vessel due to the stenosis and subsequent aneurysm. Choice E (Oculomotor nerve) is incorrect. The oculomotor nerve (CN III) traverses the cavern- ous sinus; however, it lies along the lateral wall of the sinus. The abducent nerve, which parallels the internal carotid artery, would most likely be affected by increased pressure within this vessel due to the stenosis and subsequent aneurysm.

An MRI of the right internal carotid artery reveals atheroscle- rotic 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? (A) Trochlearnerve (B) Abducent nerve (C) Maxillary nerve (D) Ophthalmic nerve (E) Oculomotor nerve

D: Orbicularis oris. The orbicularis oris is a muscle of facial expression (mimetic muscle), and these mus- cles insert or originate in the subcutaneous tissue of the skin, which enables them to convey mood via facial expressions as well as alter the form of the facial orifices. All the muscles of facial expression are derived from the mesoderm of the second pharyngeal (hyoid) arch and innervated by the facial nerve (CN VII). Most of these muscles are located within the face; however, a few extend into the scalp (e.g., epicranius) or the neck (platysma). The most important, and therefore most clin- ically relevant, role of the facial muscles is to control and oper- ate the facial orifices, that is, the eyes, nose, mouth, and ears. Facial expression is a secondary byproduct of the ability to finely control the facial orifices. The mouth is controlled by an extensive, interweaving array of facial muscles that influence feeding, respiration, and articulate speech. The orbicularis oris is a broad, very complex muscle that encircles the mouth in a sphincter-like fashion. It interacts with the other orofacial muscles to modify the form and tension of the lips and their margins. By itself, it acts to close the mouth by bringing the lips together tightly. Choice A (Zygomaticus major) is incor- rect. The zygomaticus major is an elongated muscle of facial expression that originates on the lateral aspect of the zygomatic bone and attaches into the angle of the mouth. It contracts to dilate oral fissure, but it also elevates the labial commissures bilaterally to smile (show happiness) or unilaterally to sneer (show disdain). Choice B (Buccinator) is incorrect. The buc- cinator (L: trumpeter) muscle is a wide, thin muscle of facial expression that lies relatively deep in the cheek, coursing from the pterygopalatine raphe and the alveolar ridges of maxil- lary and mandibular molar teeth to insert into the orbicularis oris at the angle of the mouth. The buccinator compresses the cheeks and lips against the teeth and gums, provides resis- tance to keep the teeth from tilting laterally, and prevents patients from looking like a hamster when they chew food. This muscle is important in all phases of feeding. During mas- tication, it assists in positioning food between the occlusal surfaces of the teeth. In suckling, it creates pressure within the oral cavity. This pressure also serves in blowing air, as when playing a wind instrument. Choice C (Levator labii superio- ris) is incorrect. The levator labii superioris is a relatively large muscle of facial expression that runs from the infraorbital margin of the maxilla into the upper lip. Acting in concert with its neighbors, it dilates the oral fissure by elevating and everting the upper lip to show the upper (maxillary) teeth. It also deepens nasolabial sulcus to show sadness. Please note that this muscle covers the infraorbital foramen, lying over the emerging infraorbital nerve and vessels. Choice E (Mentalis) is incorrect. The mentalis is a small, conical muscle of facial expression that originates on the incisive fossa of the mandible and inserts into the skin of the chin and the base of the lower lip. When pouting, this muscle raises, protrudes, and everts the lower lip. This muscle also elevates the skin of the chin to show doubt.

As a result of facial injuries suffered in an automobile accident, a 17-year-old girl is unable to close her lips together tightly. Which of the following muscles is paralyzed? (A) Zygomaticus major (B) Buccinator (C) Levator labii superioris (D) Orbicularis oris (E) Mentalis

E Tilting of the head is seen in patients with an injury of the trochlear nerve and the associated weakness or paralysis of the superior oblique muscle it innervates. Dysfunction of the superior oblique muscle results in unopposed contraction of the inferior oblique muscle, its primary antagonist, and lateral rotation of the affected eye. Tilting the head away from the side of the nerve deficit medially rotates the unaffected eye to bring the two eyes into better alignment. Grandfather's tilting of his head towards his right shoulder indicates the lesion is on the left side.

At Thanksgiving dinner you notice for the first time that your grandfather always holds his head at a slight angle when looking directly at you. Suspecting an extra-ocular muscle deficit of some kind, you seize this opportunity to apply your newly-gained knowledge of eye movements and clinical testing to diagnose his condition. In your initial observation of your "patient" you notice that when looking straight ahead your grandfather's head is tilted towards his right shoulder. Assuming this is a cranial nerve injury, which of the following cranial nerves is likely affected? A Left abducens B Right abducens C Left oculomotor D Right oculomotor E Left trochlear F Right trochlear

A,F A and F are both correct. Unopposed contraction of the inferior oblique muscle will result in a slight elevation of the affected eye when in primary position (A). Weakness of depression of the eye in individuals with trochlear nerve damage results in diplopia when looking down and is most often noticed when walking down the stairs. The patient's tilting of the head is done to rotate the pupil in the unaffected eye and bring it into alignment with the laterally rotated pupil of the affected eye. Straightening of the head will result in rotational changes in the unaffected eye, but not the affected eye (F).

At Thanksgiving dinner you notice for the first time that your grandfather always holds his head at a slight angle when looking directly at you. Suspecting an extra-ocular muscle deficit of some kind, you seize this opportunity to apply your newly-gained knowledge of eye movements and clinical testing to diagnose his condition. In your initial observation of your "patient" you notice that when looking straight ahead your grandfather's head is tilted towards his right shoulder. To rule out some other explanation for your grandfather's head posture (e.g., torticollis), you ask him to straighten his head while you observe his eyes. Which of the following observations do you expect ? (More than one answer possible) A The pupil of the affected eye elevates slightly as he straightens his head B The pupil of the affected eye depresses slightly as he straightens his head C The pupil of the affected eye neither elevates nor depresses as he straightens his head D The pupil of the affected eye rotates medially as he straightens his head E The pupil of the affected eye rotates laterally as he straightens his head F The pupil of the affected eye does not rotate in either direction as he straightens his head

A,B,C A, B and C are all correct. In the H-test, abduction of the eye aligns the superior and inferior rectus muscles so as to maximize their ability to rotate the eye in the transverse axis, while simultaneously minimizing the ability of the superior and inferior oblique muscles to act on this axis (See University of Toronto H-Test Simulator; https://www.bmc.med.utoronto.ca/anatomia/intro.swf). In this individual elevation and depression of the abducted eye will be normal. Adduction of the eye in the H-test aligns the superior and inferior oblique muscles so as to maximize their ability to produce rotation in the transverse axis, while simultaneously minimizing the ability of the superior and inferior rectus muscles to act on this axis. In an individual with a trochlear nerve injury, the adducted eye can be elevated (inferior oblique muscle), not be depressed (superior oblique muscle). Note that in trochlear nerve injuries, elevation of the affected eye is maximized when the eye is adducted.

At Thanksgiving dinner you notice for the first time that your grandfather always holds his head at a slight angle when looking directly at you. Suspecting an extra-ocular muscle deficit of some kind, you seize this opportunity to apply your newly-gained knowledge of eye movements and clinical testing to diagnose his condition. In your initial observation of your "patient" you notice that when looking straight ahead your grandfather's head is tilted towards his right shoulder. You perform an H-test on your grandfather. Which of the following findings are expected? (More than one answer possible) A The pupil of the affected eye elevates as expected when abducted B The pupil of the affected eye depresses as expected when abducted C The pupil of the affected eye elevates as expected when adducted D The pupil of the affected eye depresses as expected when adducted

A the lingual br. of the mandibular n. (CNV-3) provides general SENSATION (not taste) to the mucosa of the anterior 2/3 of the tongue

Following radical resection of a primary tongue tumor, a 72-year-old patient has lost general sensation to the anterior portion of his tongue. This is probably due to injury to branches of which of the following nerves? A. Mandibular B. Chorda Tympani C. Glossopharyngeal D. Hypoglossal E. Vagus

B When in primary position the resting tone (contraction) of the medial rectus muscle is unopposed and results in adduction of the eye.

In performing an H-test on a patient you find that when asking the patient to abduct an eye from an adducted position, the pupil does not move beyond primary position. How will the affected eye in the patient above present when in primary position? A Abducted pupil B Adducted pupil C Laterally rotated pupil D Medially rotated pupil

A Abduction of the eye occurs through the combination of increased activity of the lateral rectus muscle, and decreased activity (inhibition) of the medial rectus muscle. In the patient described here, abducting the eye beyond primary position is not possible due to injury to the abducens nerve and absence of activation of the lateral rectus muscle. The affected eye successfully abducted to primary position due to inhibition of medial rectus muscle contraction, which is controlled by the intact oculomotor nerve.

In performing an H-test on a patient you find that when asking the patient to abduct an eye from an adducted position, the pupil does not move beyond primary position. Which of the following cranial nerves may be injured in this patient? A Abducens B Oculomotor C Ophthalmic D Optic E Trochlear

A. facial nerve. Along with the muscles of facial expression, posterior belly of the digastric, and sty- lohyoid muscles, the facial nerve 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 cochlea. Paralysis of the stapedius results in hyperacusis due to heightened reaction of the stapes to sound vibration. Therefore, a person would be more sensitive to loud sounds, particular low-frequency sounds, like the bass emitted from a subwoofer. The stapedius muscle contracts involuntarily, along the tensor tympani muscle innervated by CN V3, in response to high intensity sound waves, forming the acous- tic reflex. Choice B (Vestibulocochlear nerve) is incorrect. Because of the normal results from the audiometer hear- ing examination, the vestibulocochlear nerve (CN VIII) has not been damaged. However, the stapedius muscle, which decreases the impact of the footplate of the stapes on the oval window of the cochlea, has been injured. Given this patient's loss of the acoustic reflex, extended exposure to loud sounds could damage the cochlea in the future. Choice C (Glossopharyngeal nerve) is incorrect. The glossopharyngeal nerve (CN IX) supplies only one muscle, the stylopharyn- geus, and it is not involved with the acoustic reflex or sound transduction. So, the hyperacusis seen in this patient is not due to CN IX. Choice D (Vagus nerve) is incorrect. The vagus nerve (CN X) supplies all the 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). Despite its extensive motor innervation, the vagus nerve does not play a role in the acoustic reflex or sound conduction. Choice E (Hypoglossal nerve) is incorrect. The hypoglossal nerve (CN XII) innervates the intrinsic and (most of the) extrinsic muscles of tongue (exception = palatoglossus muscle of CN X). Losing innervation to the muscles of the tongue would cause ipsilateral tongue deviation, but would not cause hyperacusis.

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? (A) Facial nerve (B) Vestibulocochlear nerve (C) Glossopharyngeal nerve (D) Vagus nerve (E) Hypoglossal nerve

A Cell bodies of all preganglionic autonomic neurons (sympathetic and parasympathetic) are located in the CNS. The cell bodies of the preganglionic parasympathetic neurons that innervate head structures are located in various nuclei in the brainstem.

The cell bodies of the preganglionic parasympathetic neurons that innervate effector organs in the head are located in which of the following structures? A Brainstem B Superior cervical ganglion C Dorsal root ganglion D pterygoapalatine ganglion

E: Parasympathetic fibers via the chorda tym- pani nerve. All the salivary glands receive their secretomotor innervation from the parasympathetic nervous system. Both the submandibular and sublingual salivary glands are sup- plied by the facial nerve by way of its chorda tympani branch.The chorda tympani nerve originates from the distal part of the main trunk of the facial nerve and runs across the middle ear cavity. It earns its name at this location by its thread-like form lying across the deep surface of the tympanic mem- brane and the handle of the malleus. The nerve then enters the infratemporal fossa and merges with the lingual nerve (a branch of the mandibular division of the trigeminal nerve, or CN V3). The parasympathetic fibers synapse in the sub- mandibular ganglion, with the postsynaptic fibers passing to the submandibular and sublingual salivary glands and to mucus glands in the oral floor. Remember, the chorda tympani nerve also carries taste fibers from the anterior two thirds of the tongue. The remaining salivary gland, the parotid, is sup- plied by the glossopharyngeal nerve, by way of the following pathway: tympanic nerve/lesser petrosal nerve/otic ganglion/ auriculotemporal nerve. Choice A (Parasympathetic fibers via the inferior alveolar nerve) is incorrect. The inferior alveolar nerve is a branch of the mandibular division of the trigeminal nerve (CN V3) within the infratemporal fossa. It gives off the mylohyoid nerve, which innervates the mylohyoid and ante- rior digastric muscles, and then enters the mandible traversing the mandibular foramen. Most of its distribution is concerned with general sensation in the lower jaw (including the teeth and gums) and the skin overlying the mandible, including the lower lip. It has no direct role in secretion of any salivary gland. Choice B (Sympathetic fibers via the lingual nerve) is incorrect. Sympathetic neurons do not supply the salivary glands. The lingual nerve does carry autonomic fibers to the submandibular and sublingual salivary glands. However, this autonomic innervation is derived from parasympathetic fibers of the facial nerve/chorda tympani nerve pathway. Choice C (Parasympathetic fibers via the mandibular branch of the facial nerve) is incorrect. The (marginal) mandibular branch of the facial nerve is one of the five terminal branches of the main trunk of the facial nerve innervating the muscles of facial expression. The (marginal) mandibular branch of the facial nerve does not carry autonomic fibers to any salivary glands despite the fact that this nerve transverses the parotid gland. Choice D (Sympathetic fibers via the hypoglossal nerve) is incorrect. Again, the sympathetic division does not supply the salivary glands. The hypoglossal nerve may carry a small hitchhiking sympathetic bundle for part of its course. How- ever, its dominant content is motor fibers to the intrinsic and most of the extrinsic skeletal muscles of the tongue.

While planning a delicious dinner for his former anatomy professors, a doctor finds himself salivating at the thought of the feast. What description accurately describes the secretomotor pathway for innervation of the submandibular gland? (A) Parasympathetic fibers via the inferior alveolar nerve (B) Sympathetic fibers via the lingual nerve (C) Parasympathetic fibers via the mandibular branch of the facial nerve (D) Sympathetic fibers via the hypoglossal nerve (E) Parasympathetic fibers via the chorda tympani nerve