Cranial Nerves (Gray's Anatomy Review, BRS, Lippincott)

KNOW THIS:

-Disruption of sympathetic fibers in the sympathetic chain causing Horner syndrome would greatly affect the deep petrosal nerve. -The marginal mandibular branch of the facial nerve (CN VII) is one of five terminal branches of the main trunk of CN VII that supply the muscles of facial expression. This nerve supplies muscles of the lower lip and chin.

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-The anterior communicating artery, the portion of the arterial circle (of Willis), is directly superior to the optic chiasm, and an aneurysm of this artery would likely compress the chiasm, as in this patient. -Vertebral artery aneurysm will likely affect the hypoglossal nerve. -Most times when you see a drooling mouth the issue is the facial nerve (passes through the internal acoustic meatus). -The oculomotor nerve innervates the extraocular muscles of the eye except the lateral rectus & superior oblique muscle.

KNOW THIS:

1) The arterial circle (of Willis) receives its blood supply from the internal carotid and vertebral arteries. 2) The actual circle is formed by the bifurcation of the basilar, posterior cerebral, posterior communicating, internal carotid, anterior cerebral, and anterior communicating arteries. 3) The middle cerebral artery is the lateral continuation of the internal carotid artery and therefore not part of the arterial circle. 4) Although it receives its blood supply from the arterial circle (of Willis), it does not actually form any part of the circle.

Compression of the oculomotor nerve would cause:

1) The eye to deviate "out and down" (paralysis of the four extraocular muscles innervated by this nerve) 2) Ptosis (paralysis of levator palpebrae) 3) Mydriasis (paralysis of constrictor pupillae)

Contents of the superior orbital fissure:

1) The oculomotor nerve (CN III) 2) Branches of the ophthalmic division of trigeminal nerve (CN V1) 3) Abducens nerve (CN VI) 4) Ophthalmic vein

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1) The trochlear nerve innervates the superior oblique muscle, which acts to move the pupil downward and laterally. 2) It is the only muscle that can depress the pupil when the eye is adducted. 3) When an individual walks down stairs, this eye motion is initiated, and diplopia results if it is not functioning properly. 4) The superior cerebellar artery/trochlear nerve are usually both affected as a unit.

A 55-year-old male farmer is admitted to the emergency department after falling from the hayloft in his barn. Radiographic examination reveals a small,depressed fracture of the skull vertex and thrombosis of the superior sagittal sinus. A day later the patient loses consciousness. What is the most likely cause of his loss of consciousness? A. Obstruction of CSF resorption B. Obstruction of the cerebral aqueduct (of Sylvius) C. Laceration of the middle meningeal artery D. Fracture of the cribriform plate with CSF rhinorrhea E. Aneurysm of the middle cerebral artery

A. A thrombus of the superior sagittal sinus can to lead to an obstruction of CSF (communicating hydrocephalus) in which all of the ventricles of the brain are enlarged and the intracranial pressure is increased

A 24-year-old man is admitted to the hospital after a street fight. Radiographic examination reveals an inferior blow-out fracture of the orbit. Which of the following nerves is particularly vulnerable with this type of injury? A. Infraorbital B. Supratrochlear C. Frontal D. Inferior alveolar E. Optic

A. An inferior fracture of the orbit would likely damage the infraorbital nerve. A blow-out fracture often results in a displaced orbital wall, and in this case, the inferior wall. The infraorbital nerve leaves the skull immediately inferior to the inferior aspect of the orbit, via the infraorbital foramen. Thus, this nerve is the most likely to be damaged.

A 2-month-old male infant is admitted to the hospital after falling from his stroller. During physical examination the infant shows signs of facial nerve injury. What is the most common place for facial nerve injury in an infant? A. At the stylomastoid foramen B. Posterior to the parotid gland C. Anterior to the parotid gland D. Proximal to the stylomastoid foramen E. Mandibular involvement of zygomatic and buccal branches

A. At the point where the facial nerve exits the stylomastoid foramen it is most susceptible to shearing forces. In the absence of a skull fracture whereby the facial nerve can be damaged within the facial canal, the nerve is most commonly injured as it exits the stylomastoid foramen. In infants, in whom the mastoid process has not yet developed, the facial nerve lies unprotected, just beneath the skin.

The goalkeeper of a soccer team accidentally hit his head against the goal post while trying to reach for the ball. He was confused for several minutes and later resumed playing. Four hours later, he was found unconscious and was immediately rushed to the emergency department. A CT scan of his head shows a hemorrhage (Fig. 7-19, arrows). The vessel that was ruptured to produce this hemorrhage enters the skull through which of the following openings? A. Foramen spinosum B. Foramen ovale C. Jugular foramen D. Hypoglossal canal E. Foramen lacerum

A. Extradural (epidural) hemorrhage is arterial in origin. Blood from torn branches of a middle meningeal artery (which passes through foramen spinosum) collects between the external periosteal layer of the dura and the calvaria. The extravasated blood strips the dura from the cranium. Usually this follows a hard blow to the head; an extradural (epidural) hematoma then forms.

A 9-year-old girl is admitted to the emergency department with painful swelling behind her ear. An MRI examination reveals mastoiditis (Fig. 7-12). Which of the following structures is most likely to be affected by the inflammation? A. Transverse sinus B. Petrous part of the temporal bone C. Inner ear D. Occipital sinus E. Internal carotid artery

A. Mastoiditis is an infection of the air cells within the mastoid process of the temporal bone, often caused by untreated acute otitis media. A known complication of mastoiditis is inflammation of the transverse sinus.

A 34-year-old woman is admitted to the emergency department after her right cheekbone and bony orbit hit the dashboard in an automobile crash. Physical examination reveals that the patient has lost the ability for the affected eye to be directed downward when the pupil is in the adducted position. An MRI examination reveals a torn nerve. What is the most common location at which this nerve will be injured? A. As it pierces the dura of the tentorium cerebelli in the tentorial notch B. At the cavernous sinus C. At the sella turcica D. At the inferior orbital fissure E. At the superior orbital fissure

A. Paralysis of the trochlear nerve results in loss of ability for the affected eye to be directed downward when the pupil is in the adducted position (the primary action of the superior oblique muscle). The delicate nerve is easily torn where it pierces the dura of the tentorium cerebelli in the tentorial notch because the brain and brainstem move forward and backward with the force of impact.

A 54-year-old man is admitted to the hospital due to severe headaches. A CT examination reveals an internal carotid artery aneurysm inside the cavernous sinus. Which of the following nerves would be typically affected first? A. Abducens nerve B. Oculomotor nerve C. Ophthalmic nerve D. Maxillary nerve E. Trochlear nerve

A. The abducens nerve would be affected first due to aneurysmal dilation of the internal carotid artery (ICA) because the nerve runs in closest proximity to the artery within the cavernous sinus

55-year-old man is admitted to the emergency department after slipping on wet pavement and falling. Physical examination reveals that the patient has a hematoma that formed in the danger zone of the scalp, spreading to the area of the eyelids. Which of the following layers is regarded as the "danger zone"? A. Loose, areolar layer B. Skin C. Galea aponeurotica D. Pericranium E. Subcutaneous layer

A. The loose areolar connective tissue layer is known as the "danger zone" because hematoma can spread easily from this layer into the skull by means of emissary veins that pass into and through the bones of the skull.

A 22-year-old man is admitted to the emergency department with a sinus infection. Radiographic examination reveals posterior ethmoidal cell infection. During history taking the patient complains of progressive loss of vision. Which of the following structures is most likely affected? A. Ophthalmic artery B. Nasociliary nerve C. Anterior ethmoidal nerve D. Trochlear nerve E. Abducens nerve

A. The ophthalmic artery is a branch of the internal carotid artery and provides origin to the ocular and orbital vessels, including the central artery of the retina, which supplies the retina.

A 2-month-old female infant is hospitalized with hydrocephalus. MRI reveals a ventricular system that is entirely dilated. Which of the following conditions will most likely lead to this type of clinical picture? A. Lack of absorption through arachnoid granulations into venous system B. Occlusion of cerebral aqueduct (of Sylvius) C. Blockage of the left foramina of Luschka D. Congenital absence of the cisterna magna E. Closure of the interventricular foramina of Monro

A. With all of the ventricles enlarged and no obvious single site of complete ventricular obstruction, the problem must be a condition of communicating hydrocephalus, with inadequate drainage through the arachnoid granulations into the superior sagittal sinus.

A 57-year-old man is admitted to the emergency department with dizziness and severe headaches. A CT scan evaluation reveals a tumor in the superior orbital fissure. Upon physical examination the patient's eyeball is fixed in an abducted position, slightly depressed, and the pupil is dilated. In addition, the upper lid is droopy. When the patient is asked to move the pupil toward the nose, the pupil rotates medially. Consensual corneal reflexes are normal. Which of the following nerves is most likely affected? A. Trochlear nerve B. Oculomotor nerve C. Abducens nerve and sympathetic nerve plexus accompanying the ophthalmic artery D. Ophthalmic nerve and short ciliary nerve E. Superior division of oculomotor nerve and the nasociliary nerve

B. A lesion of the oculomotor nerve will cause the eye to remain in a "down and out" position. This is due to the actions of the unopposed lateral rectus (supplied by the abducens nerve) and the superior oblique (supplied by the trochlear nerve). The tertiary function of the superior oblique is to cause intorsion (internal rotation) of the eyeball, a function that is not usually seen unless the oculomotor nerve is paralyzed.

A 32-year-old man is admitted to the emergency department with visual problems. Radiographic examination reveals a tumor of the adenohypophysis (anterior pituitary gland). Physical examination reveals a loss of the lateral halves of the fields of vision of both eyes (bitemporal hemianopia or "tunnel vision"). Which of the following structures was most likely compressed by the tumor? A. Optic nerve B. Optic chiasm C. Optic tract D. Oculomotor E. Abducens nerve

B. Compression of the optic chiasm can cause bitemporal hemianopia due to compression of nerve fibers coming from the nasal (medial) hemiretinas of both eyes. The optic chiasm is located in very close proximity above the pituitary gland. Compression of an optic nerve would cause complete blindness in the affected eye.

A 20-year-old construction worker presented to the emergency department with an occipital scalp laceration. The wound was closed. Three days later he presents at the clinic with a tender erythematous infected wound that has spread anteriorly on the scalp. Between which layers of the scalp has the infection spread? A. The periosteum and bone B. The aponeurosis and the periosteum C. The dense connective tissue and the aponeurosis D. The dense connective tissue and the skin E. The dermis and the epidermis

B. Each letter in the word SCALP serves as a mnemonic for one of its five layers, skin, connective tissue, aponeurosis, loose areolar tissue, and pericranium. The loose connective tissue layer (fourth layer) of the scalp is the danger area of the scalp because pus or blood spreads easily in it.

The arachnoid villi allow cerebrospinal fluid to pass between which two of the following spaces? A. Choroid plexus and subdural space B. Subarachnoid space and superior sagittal sinus C. Subdural space and cavernous sinus D. Superior sagittal sinus and jugular vein E. Epidural and subdural space

B. The arachnoid villi are extensions of the arachnoid mater into the superior sagittal sinus. The villi allow for proper drainage of the CSF into the venous bloodstream from the subarachnoid space in which the CSF circulates. These villi are a crucial element in maintaining proper intracranial pressure and circulation of the CSF

A 15-year-old boy was brought to the emergency department with complaints of right ear pain. While attempting to clean his itchy ear with a swab, his little brother bumped into his elbow, causing the stick to penetrate deeply into the ear. On examination with the otoscope, the tympanic membrane was pearly white and there was no cone of light visible. There was clotted blood in the external auditory meatus. Rinne's test was positive (bone conduction was better than air conduction). Which of the following best describes the nerves responsible for the perception of pain from the injured area? A. Auriculotemporal and great auricular nerves B. Facial, glossopharyngeal, and vagus nerves C. Lesser occipital and great auricular nerve D. Chorda tympani and glossopharyngeal nerve E. Tympanic plexus and lesser petrosal nerve

B. The area of damage is in the external acoustic meatus, which is supplied by the facial, glossopharyngeal, and vagus nerves. The auriculotemporal and great auricular nerves supply the TMJ and external ear, respectively. The lesser occipital nerves supply the skin on the posterior aspect of the skull. The chorda tympani is responsible for taste to the anterior two thirds of the tongue and sensation to the middle ear.

A 34-year-old man complains of hyperacusis (sensitivity to loud sounds). Injury to which of the following cranial nerves is most likely responsible? A. Hypoglossal B. Facial C. Accessory D. Vagus E. Glossopharyngeal

B. The facial nerve innervates the stapedius muscle, which is responsible for limiting movement of the stapes, thereby reducing the intensity of the sound entering the inner ear. A lesion of the facial nerve is likely to lead to the symptoms described (drooping mouth, unable to close right eye, and food collection in the oral vestibule) because the muscles of facial expression are paralyzed.

A 55-year-old woman is admitted to the hospital with severe hypertension. Examination reveals hypertension (190/110 mm Hg) and hypercholesterolemia (250 mg/dL). During physical examination she complains of headaches and dizziness. An arteriogram reveals 90% occlusion of both common carotid arteries. A carotid endarterectomy is performed and large atherosclerotic plaques are removed. During a postoperative physical examination on the right side, it was noted that her tongue deviated toward the right when she was asked to protrude it. Which of the following nerves was most likely injured during the procedure? A. Right glossopharyngeal B. Right hypoglossal C. Left hypoglossal D. Left lingual E. Left vagus

B. The hypoglossal nerve provides motor innervation to the muscles of the tongue, with the exception of the palatoglossus. Injury to the glossopharyngeal nerve would result in loss of taste in the posterior third of the tongue and a loss of soft palate sensation and gag reflex on the affected side. Injury to the hypoglossal nerve would result in deviation of the tongue toward the affected side when the tongue is protruded (in this case the right side).

A 75-year-old woman presents to the emergency department complaining of double vision. Physical examination reveals inability to abduct her right eye. In which of the locations indicated in the arteriogram (Fig. 7-25) would an aneurysm most likely be located to cause the nerve compression resulting in these symptoms/signs? A. PCA B. ICA C. External carotid artery D. Anterior cerebral artery E. Posterior communicating artery

B. The internal carotid is the artery that supplies the majority of the blood supply to the brain. The internal carotid artery and the abducens nerve run through the cavernous sinus. Damage to this part of the internal carotid would affect the abducens nerve and the patient's ability to abduct the eye.

A 27-year-old man is admitted to the hospital after a middleweight boxing match. During physical examination the strength and symmetry of strength in opening the jaws are tested. Which of the following muscles is the most important in jaw protrusion and depressing the mandible? A. Anterior portion of temporalis B. Lateral pterygoid C. Medial pterygoid D. Masseter E. Platysma

B. The lateral pterygoid muscle is a muscle of mastication innervated by the lateral pterygoid nerve of the mandibular division of the trigeminal nerve. The lateral pterygoid acts to protrude the mandible and open the jaw. The anterior portion of temporalis is a muscle of mastication innervated by the deep temporal nerves of the mandibular division of the trigeminal nerve that elevates the mandible when contracted. The medial pterygoid muscle is a muscle of mastication innervated by the mandibular division of the trigeminal nerve. The masseter muscle is a muscle of mastication innervated by the mandibular division of the trigeminal nerve that specifically assists in chewing.

A 34-year-old man complains of diplopia that becomes worse when reading a newspaper or walking down the stairs. Physical examination in the neurosurgery outpatient clinic reveals weakness of downward movement of the left eye. A CT scan reveals a large aneurysm in one of the arteries of the posterior cerebral circulation compressing the nerve resulting in the symptoms. In which artery in the diagram (Fig. 7-23) is the aneurysm? A. A B. B C. C D. D E. E

B. The superior cerebellar artery is the penultimate branch of the basilar artery. It originates from the basilar artery and runs laterally to supply the superior and medial parts of the cerebellum. In its course, it travels very close to the trochlear nerve.

A 36-year-old female racquetball player is admitted to the hospital after being struck in the orbital region. Radiographic examination reveals a blow-out fracture of the medial wall of the orbit. Physical examination also reveals that the pupil of the affected eye cannot be turned laterally. Which of the following muscles is most likely injured or trapped? A. Lateral rectus B. Medial and inferior recti C. Medial rectus D. Medial rectus and superior oblique E. Inferior rectus

C. A blow-out fracture of the medial wall of the orbit would likely render the medial rectus muscle nonfunctional by entrapment of the muscle between the fracture fragments of the cracked medial wall. The medial rectus is responsible for adduction of the eye, but in this case the muscle acts as a tether or anchor on the eyeball, preventing lateral excursion (abduction) of the eye.

A 58-year-old man is admitted to the ENT clinic with progressive unilateral hearing loss and ringing in the affected ear (tinnitus) of 4 months duration. MRI reveals a tumor at the cerebellopontine angle. Which of the following nerves is most likely affected? A. Vagus B. Hypoglossal C. Vestibulocochlear D. Glossopharyngeal E. Trigeminal

C. A tumor at the cerebellopontine angle, such as an acoustic schwannoma, is most likely to affect first the vestibulocochlear nerve and then the facial nerve.

A 20-year-old woman delivered an infant boy at term by cesarean section (C-section). During the third trimester an abdominal ultrasound revealed enlarged ventricles of the fetal brain. On examination, the circumference of the infant's head was 40 cm (normal range, 34 to 36 cm). He showed decreased movement of the limbs and seemed drowsy. A CT scan of the brain with contrast medium showed dilatation of all the ventricles. Which of the following is likely to be the cause of the infant's condition A. Narrowing of the median aperture B. Narrowing of the lateral aperture C. Abnormality of arachnoid granulations D. Lack of choroid plexus in the lateral ventricles E. Increased blood flow in the cerebral arteries

C. Hydrocephalus is an abnormal accumulation of cerebrospinal fluid in the ventricles of the brain. This can be due to abnormal flow (often blockage in the cerebral aqueduct of Sylvius), impaired reabsorption, or rarely, excessive production of CSF. Communicating hydrocephalus is caused by impaired reabsorption of CSF due to abnormal functioning of the arachnoid granulations, which are responsible for drainage of the CSF into the venous system.

A 55-year-old woman visits the outpatient clinic complaining of unilateral neck pain, sore throat, and ear pain. Radiographic examination reveals Eagle's syndrome, in which the styloid process and stylohyoid ligament are elongated and calcified. Which of the following nerves is most likely affected by Eagle's syndrome in this patient? A. Vagus B. Facial C. Glossopharyngeal D. Hypoglossal E. Vestibulocochlear

C. The glossopharyngeal nerve (CN IX) enters the posterior oropharynx by coursing between the stylohyoid ligament and the stylopharyngeus muscle. Calcification of the stylohyoid ligament can readily affect this nerve by irritation or compression.

A 26-year-old male boxer is brought to the emergency department after being knocked out by his rival. CT examination reveals severe trauma to the articular disc and fracture of the neck of the mandible. This could result in injury to a muscle that developed from which of the following embryonic structures? A. First pharyngeal pouch B. Second pharyngeal pouch C. First pharyngeal arch D. First pharyngeal cleft E. Second pharyngeal arch

C. The lateral pterygoid muscle attaches to the articular disc and capsule of the temporomandibular joint and as such any damage here will injure the muscle. The muscles of mastication including the lateral pterygoid muscle are derived from the first pharyngeal arch (aka mandibular arch) mesenchyme.

A 30-year-old man was brought to the emergency department after being involved in a head-on collision with another car. He did not wear a seat belt and was found unconscious in the driver's seat, from which he had to be extricated. Examination revealed a poorly responsive patient with a low BP, tachycardia, and several lacerations about his face and body. Examination revealed a bony deformity of the right mandible where abnormal mobility of the bone was palpated approximately along the ramus. Once the patient was stabilized, a CT of the skull was performed, revealing a displaced, transverse fracture of the ramus, just proximal to the angle of the mandible. Which of the following will most likely be affected? A. Elevation of the jaw B. Lateral deviation of the jaw to the left side C. Salivation; sensation and taste from the anterior tongue D. Sensation from skin over anterior cheek and tongue E. Salivation; sensation from posterior temporal skin and tragus of the ear

C. The signals that regulate these functions are carried by the chordae tympani nerve, which then joins the lingual nerve. As the lingual nerve makes its way to the tongue it passes between the medial pterygoid muscle and the ramus of the mandible, where it was likely affected by the fracture. The elevation of the jaw or mandible is a function performed by the masseter, temporalis, and medial pterygoid muscles. The lateral deviation is performed by the medial and lateral pterygoid muscles.

Physical examination of an 88-year-old man reveals inability to abduct his right eye and an absent corneal reflex on the same side. These symptoms might indicate a growth in which part of the skull? A. Inferior orbital fissure B. Optic canal C. Superior orbital fissure D. Foramen rotundum E. Foramen ovale

C. The superior orbital fissure is an opening in the skull found between the lesser and greater wings of the sphenoid bone. Abduction of the eye is done by the oculomotor nerve, and the ophthalmic nerve supplies sensation to the cornea and serves as the afferent limb of the corneal reflex. These functions were lost because of compression of these nerves.

A 48-year-old man complains of diplopia (double vision). On neurologic examination he is unable to adduct his left eye and lacks a corneal reflex on the left side. Where is the most likely location of the lesion resulting in the symptoms? A. Inferior orbital fissure B. Optic canal C. Superior orbital fissure D. Foramen rotundum E. Foramen ovale

C. The superior orbital fissure is the opening that allows the passage of the oculomotor nerve and the trochlear nerve HELP!

A 54-year-old man was admitted to the emergency department after he was struck by an automobile. Radiographic examination revealed a fracture through the crista galli of the anterior cranial fossa, resulting in slow, local bleeding. Which of the following is the most likely source of bleeding? A. Middle meningeal artery B. The great cerebral vein of Galen C. Superior sagittal sinus D. Straight sinus E. Superior ophthalmic vein

C. The superior sagittal sinus would most likely be the source of the bleeding because it attaches anteriorly to the crista galli and because of the slow nature of the bleed. ----------------------------------------------- The superior ophthalmic vein drains from the orbit to the cavernous sinus; further, it is located inferiorly to the crista galli and is not directly related to the superior sagittal sinus.

A 73-year-old man visits the outpatient clinic with a complaint of progressive, painless loss of vision. Radiographic examination reveals thrombophlebitis of the cavernous sinus. Through which of the following structures must a thrombus pass to cause the symptoms of this patient? A. Subarachnoid space B. Central artery of the retina C. Central vein of the retina D. Optic chiasm E. Ciliary ganglion

C. The thrombus may pass through the central vein of the retina to reach the cavernous sinus. The patient would suffer blindness because the central vein is the only vein draining the retina and if it is occluded, blindness will ensue.

A 63-year-old man with hearing loss in his left ear complains of a loss of taste and drooling from the left side of his mouth. A CT scan shows a tumor compressing the nerve exiting the skull through which of the following openings? A. Foramen ovale B. Foramen rotundum C. Internal acoustic meatus D. Jugular foramen E. Superior orbital fissure

C. The tumor is compressing the facial nerve, which runs through the internal acoustic meatus along with the vestibulocochlear nerve.

Lesion of the facial nerve:

Causes Bell's palsy, which is marked by characteristic distortion of the face such as no wrinkles on the forehead, drooping of the eyebrow, inability to close or blink the eye, sagging corner of the mouth, and inability to smile, whistle, or blow

Lesion of the abducens nerve:

Causes weakness/paralysis of the lateral gaze due to loss of the rectus muscle of the eye. The patient will present with a medial deviation of the affected eye (internal strabismus) or diplopia on lateral. It may result from a sepsis or thrombosis in the cavernous sinus. If the opposite side of the body is affected, there is a brain stem tumor or midline pontine stroke.

An 84-year-old man presents to the emergency department complaining of double vision. Physical examination reveals inability to abduct his right eye. In which of the locations indicated in the arteriogram (Fig. 7-20) will an aneurysm most likely be located to cause the nerve compression resulting in these symptoms/signs? A. A B. B C. C D. D E. E

D. Aneurysms of AICA cause direct impingement on the abducens nerve as it emerges from the brainstem at the pontomedullary junction between the labyrinthine artery above and the AICA below. Impingement of this nerve leads to loss of function to the lateral rectus muscle ipsilaterally, resulting in the inability to abduct the eye.

A 16-year-old boy is admitted to the hospital with fever, a confused mental state, and drowsiness. During physical examination it is noted that the boy suffers from severe acne. Radiologic examination reveals cavernous sinus thrombosis. Which of the following routes of entry to the cavernous sinus would most likely be responsible for the infection and thrombosis? A. Carotid artery B. Mastoid emissary vein C. Middle meningeal artery D. Ophthalmic vein E. Parietal emissary vein

D. Cavernous sinus thrombosis can often result from squeezing pimples or other infectious processes located around the danger area of the face, which includes the area of the face directly surrounding the nose.

A 59-year-old man is admitted to the emergency department with acute pain on his mandible. An MRI examination reveals an acute inflammation of the temporomandibular joint due to arthritis. Which of the following muscles will most likely be affected by the inflammatory process of this joint? A. Temporalis B. Medial pterygoid C. Masseter D. Lateral pterygoid E. Buccinator

D. Part of the lateral pterygoid muscle has its insertion on the articular disc within the TMJ and would be most affected by the inflammation of this joint. The temporalis muscle inserts upon the coronoid process and retracts the jaw. The medial pterygoid muscle extends from the medial surface of the lateral pterygoid plate to the mandible and functions in elevation of the jaw. The masseter extends from the zygomatic arch to the lateral ramus of the mandible and elevates the jaw. The buccinator pulls back the angle of the mouth and flattens the cheek

A 65-year-old man is admitted to the hospital 3 weeks after a "small bump of his head," according to his narrative. He suffered the accidental bump from a low-hanging branch while driving his tractor through the apple orchard during harvesting season. During physical examination the patient displays mental confusion and poor physical coordination. Radiologic examination reveals an intracranial thrombus probably due to leakage from a cerebral vein over the right cerebral hemisphere. From what type of bleeding is the patient most likely suffering? A. Subarachnoid bleeding B. Epidural bleeding C. Intracerebral bleeding into the brain parenchyma D. Subdural bleeding E. Bleeding into the cerebral ventricular system

D. Subdural bleeding usually results from tears in veins that cross the subdural space, between the dura and the arachnoid. This bleeding may cause a gradual increase in intracranial pressure and may result in leakage of venous blood over the right cerebral hemisphere with a variable rate of progression.

A 25-year-old man sustains a blow to the back of the head during a fight and is brought to the emergency department unconscious. A CT scan of the head reveals a fracture in the occipital bone extending superiorly from the foramen magnum. Which of the following is transmitted through the foramen magnum? A. Cranial nerve I B. Cranial nerve IX C. Cranial nerve X D. Cranial nerve XI E. Cranial nerve XII

D. The area behind the foramen magnum consists of the squamous part of the occipital bone. The foramen magnum is in the basilar part of the occipital bone (basiocciput). The dura mater is attached to the margins of the foramen as it sweeps down from the posterior cranial fossa. Within the tube of dura mater, the lower medulla with the vertebral and spinal arteries and the spinal roots of the accessory nerves traverse the foramen in the subarachnoid space.

A 40-year-old man was brought to the emergency department after falling through a glass window to the ground 5 feet below. He complained of pain from multiple lacerations across his body, particularly from a laceration to the left cheek. On examination, he was comfortable with stable vital signs. There were multiple superficial lacerations on his upper and lower limbs but no deformities of bones or joints were evident. There was a 5-cm longitudinal laceration over the left jaw. Gentle exploration of the wound revealed that it was deep and a foreign body was present. A CT scan of the head confirmed that a 3 × 2 cm foreign body, possibly glass, was lodged between the two heads of the lateral pterygoid muscle. Which of the following clinical findings are most likely to be found in this patient? A. Weak elevation of the jaw B. Weak deviation of the jaw to the right side C. Numbness over the skin of the tragus and helix of the left ear D. Numbness over the skin and mucosa of the anterior cheek E. Decreased volume of saliva

D. The nerves involved are the lingual and buccal nerves, which are branches of the mandibular branch of the trigeminal nerve. These branches provide sensation to mucosa of the anterior two thirds of the tongue (general sensation), adjacent gums, cheek mucosa, and overlying skin.

A patient with a brain tumor near the crista galli and cribriform plate of the ethmoid bone most likely experiences which of the following symptoms? A. Paralysis of facial muscles B. Loss of vision C. Difficulty swallowing D. Loss of smell E. Loss of hearing

D. The olfactory nerves arise from cells in the superior part of the lateral and septal walls of the nasal cavity. The processes of these cells (forming the olfactory nerve) pass through the cribriform plate and end in the olfactory bulbs, which lie on either side of the crista galli. Therefore a tumor here compresses the nerves, and the sense of smell will be affected.

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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.

A 45-year-old woman is admitted to the hospital for severe ear pain. Physical examination reveals chronic infection of the mastoid air cells (mastoiditis). The infection can erode the thin layer of the bone between the mastoid air cells and the posterior cranial fossa and spread most commonly into which of the following venous structures? A. Superior sagittal sinus B. Inferior sagittal sinus C. Straight sinus D. Cavernous sinus E. Sigmoid sinus

E. The sigmoid venous sinus empties into the internal jugular vein and drains the cranial vault. It runs along the posterior cranial fossa near the suture between the temporal and occipital bones just lateral to the mastoid air cells. The inferior sagittal sinus runs inferior to the superior sagittal sinus within the falx cerebri and joins the great cerebral vein (of Galen) to form the straight sinus. The straight sinus drains the great cerebral vein (of Galen) into the confluence of sinuses.

A 68-year-old man is admitted to the emergency department after an acute cerebral vascular accident (stroke). Radiologic studies reveal that the primary damage was to the anterior inferior cerebellar artery, resulting in a small hemorrhage of the artery at its origin from the main trunk. Which of the following nerves will most likely be immediately affected by the hemorrhage? A. Optic nerve B. Oculomotor nerve C. Trochlear nerve D. Trigeminal nerve E. Abducens nerve

E.The trigeminal nerve is situated in the pons and is thus located too far rostrally to be affected. The abducens nerve is situated at the pontomedullary junction and is therefore most likely to be damaged following hemorrhage of the AICA.

KNOW THIS:

If the trochlear nerve is injured, the patient is unable to turn the eyeball inferolaterally and has trouble going downstairs due to paralysis of the superior oblique muscle. Lesion of the oculomotor nerve causes ptosis due to paralysis of the levator palpebrae superioris, dilation of the pupil due to paralysis of the sphincter pupillae, loss of accommodation due to paralysis of ciliary muscles, and loss of pupillary light reflex due to loss of the efferent limb of the pupillary light reflex. Lesion of the optic nerve causes blindness. Lesion of the ophthalmic nerve causes loss of cutaneous sensation on the face above the upper eyelid. Lesion of the abducens nerve causes internal strabismus in which the eyeball turns medially

Lesion of the olfactory nerve

May occur as a result of ethmoidal bone fracture and cause anosmia, or loss of olfactory sensation. Many people with anosmia may complain of loss or alteration of taste since these senses are connected. Also, one may have a runny nose from CSF loss from fracture of the ethmoid bone.

Compression of the abducens nerve would cause:

Paralysis of the lateral rectus muscle, leading to medial deviation (adduction) of the eye

Epidural bleeding:

Results in most cases from tearing of the middle meningeal artery, and this rapidly expanding, space-occupying lesion can cause death within 12 hours.

A 17-year-old boy is involved in a gang fight and receives a penetrating injury to the neck. Which of the following conditions is most likely exhibited by this misadventure? (A) Internal strabismus (B) Trouble going down the stairs (C) Constricted pupil (D) Inability close the eye (E) Deviation of tongue toward lesion side

The Answer is C. Lesion of sympathetic nerves in the cervical region results in a constricted pupil due to paralysis of the dilator pupillae. Internal strabismus is caused by a lesion of the abducens nerve. Lesion of the trochlear nerve results in difficulty going downstairs. Inability to close the eye is due to a lesion of the facial nerve. Lesion of the hypoglossal nerve causes deviation of the tongue toward the lesion side.

A 27-year-old man came to his physician with drooping of the upper eyelid (ptosis), a dilated pupil, and a difficulty in focusing on close objects. Furthermore, he has an internal strabismus (medial deviation of the eye) and inability to look inferiorly when the eye is adducted. Which of the following is the most likely cause? (A) Lesion in the medulla (B) Tumor in the optic canal (C) Thrombosis in the cavernous sinus (D) Lesion of the olfactory nerve (E) Fracture of the foramen spinosum

The Answer is C. *Thrombosis in the cavernous sinus might damage all three CNs (III, IV, VI):* Lesion of CN III causes ptosis, a dilated pupil, and loss of accommodation; lesion of CN IV causes inability to look inferiorly when adducted; and lesion of CN VI causes the eyeball deviates medially (internal strabismus).

KNOW THIS:

The abducens (sixth) cranial nerve controls the lateral rectus muscle, which abducts the eye. A lesion of the abducens nerve results in internal strabismus (medial deviation).

KNOW THIS:

The abducens nerve (CN VI) innervates the lateral rectus muscle, which abducts the eyeball. A lesion of the abducens nerve results in internal strabismus (medial deviation) and diplopia (double vision). External strabismus (lateral deviation) is caused by paralysis of the medial rectus muscle, which is innervated by the oculomotor nerve.

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

The answer is A: Facial nerve. Along with the muscles of facial expression, posterior belly of the digastric, and stylohyoid 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. (Vestibulocochlear nerve) is incorrect. Because of the normal results from the audiometer hearing examination, the vestibulocochlear nerve (CN VIII) has not been damaged.

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

The answer is A: Greater petrosal nerve. Secretomotor control of the lacrimal gland is provided by parasympathetic neurons derived from the facial nerve. These fi bers 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. (GREATER PAIN MAKES YOU CRY) The lesser petrosal nerve carries secretomotor (preganglionic parasympathetic) fibers to the parotid gland.

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 fi ngers (see photo), 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? (A) Left oculomotor nerve (B) Right oculomotor nerve (C) Left abducent nerve (D) Right abducent nerve (E) Left trochlear nerve

The answer is A: Left oculomotor nerve. The left oculomotor nerve, CN III, innervates four (of six) extraocular eye muscles and the levator palpebrae superioris in the ipsilateral (left) eye. 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, which is why the patient is having trouble opening his left eye without assistance from his fingers.

A 47-year-old man cannot move his eyeball laterally. Which of the following conditions would cause such a clinical sign? (A) Tumor of the pituitary gland (B) Occlusion of the posterior cerebral artery (C) Infection in the maxillary sinus (D) Infection in the cavernous sinus (E) Tumor in the anterior cranial fossa

The answer is D. The abducens nerve, which innervates the lateral rectus muscle, runs through the middle of the cavernous sinus. *Deep facial veins and trochlear nerve also communicate with the cavernous sinus*

A 25-year-old professional boxer loses a fi ght 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? (A) Optic nerve (B) Oculomotor nerve (C) Olfactory nerve (D) Trigeminal nerve (E) Trochlear nerve

The answer is A: Optic nerve. Unlike other cranial nerves, the 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. The optic nerve is formed when the axons of the retinal ganglion cells coalescence at the optic disc. A physician can view the optic disc by performing a fundoscopic examination of the back of the eye (or fundus) with an ophthalmoscope. This boxer exhibits signs of increased intracranial pressure (ICP), such as headache, nausea, and vomiting, so the physician can look at the optic disc to look for papilledema, or swelling of the optic disc, which is another sign of increased ICP.

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? (A) Trochlear nerve (B) Abducent nerve (C) Maxillary nerve (D) Ophthalmic nerve (E) Oculomotor nerve

The answer is 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.

A 42-year-old woman noticed that her right upper eyelid was drooping and her right pupil was constricted (see the given photo). She goes to her physician where a thorough examination revealed ptosis, miosis, anhydrosis, fl ushing of her face, and narrowing of the palpebral fi ssure (the slit between the upper and lower eyelids) on the right side of the patient. Which of the following structure is most likely damaged in this patient? (A) Superior division of the oculomotor nerve (B) Superior cervical ganglion (C) Nerve of the pterygoid canal (D) Ciliary ganglion (E) Ophthalmic division of trigeminal nerve

The answer is B: Superior cervical ganglion. The family of deficits described in this patient comprises a classic generalized sympathetic innervation deficit known as Horner syndrome. the superior cervical ganglion is the only choice involved in sympathetic innervation. *In Horner's Syndrome (partial ptosis) you will see loss of sympathethic innervation to the superior tarsal muscle*

A 32-year-old woman has hoarseness in her voice, and her uvula is deviated to the left on phonation. Which of the following nerve is most likely damaged? (A) Right trigeminal nerve (B) Left trigeminal nerve (C) Right vagus nerve (D) Left vagus nerve (E) Left glosopharyngeal nerve

The answer is C. The vagus nerve innervates the musculus uvulae. A lesion of the vagus nerve causes deviation of the uvula toward the opposite side of the injury. Because her uvula deviates to the left on phonation, the right vagus nerve is damaged. *Hoarseness is caused by a paralysis of the laryngeal muscles resulting from damage to skeletal motor fibers in the recurrent laryngeal branch of the vagus nerve.*

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, as noted by the asterisk in the figure. Based upon the patient's presentation and MRI, where is the tumor located? (A) Foramen rotundum (B) Foramen ovale (C) Internal acoustic meatus (D) Facial canal (E) Stylomastoid foramen

The answer is C: Internal acoustic meatus. This patient is displaying deficits 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. The internal acoustic meatus is the only location where both CN VII and CN VIII travel together.

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, as illustrated in the figure. No other visual deficits are noted. What specific nerve is most likely damaged? (A) Left oculomotor nerve (B) Right oculomotor nerve (C) Left abducent nerve (D) Right abducent nerve (E) Left trochlear nerve

The answer is C: 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 following the doctor's index finger. When the left abducent nerve is damaged, the patient would display strabismus, causing diplopia, because the left pupil would rest in the adducted position, termed esotropia, due to the unopposed action of the medial rectus muscle.

A 27-year-old woman with green eyes comes to her physician with noted asymmetry in her pupils (as seen in the figure). 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? (A) Superior cervical ganglion (B) Optic nerve (C) Oculomotor nerve (D) Trochlear nerve (E) Abducent nerve

The answer is C: Oculomotor nerve. The slowness of the right pupil to respond to light stimuli is the first sign of compression of the oculomotor nerve (CN III). In this patient, it is the parasympathetic component of the right oculomotor nerve that is affected due to the loss of the sphincter pupillae muscle, which results in dilation of her right pupil.

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? (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

The answer is C: Third division of trigeminal nerve. The third (mandibular) division of the trigeminal nerve (CN V3) supplies 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. IMPORTANT!

A 47-year-old man cannot move his eyeball laterally. Which of the following conditions would cause such a clinical sign? (A) Tumor of the pituitary gland (B) Occlusion of the posterior cerebral artery (C) Infection in the maxillary sinus (D) Infection in the cavernous sinus (E) Tumor in the anterior cranial fossa

The answer is D. The abducens nerve, which innervates the lateral rectus muscle, runs through the middle of the cavernous sinus. The other conditions listed do not injure the abducens nerve. A tumor in the pituitary gland may injure the optic chiasma, causing bitemporal hemianopsia.

A knife wound has severed the oculomotor nerve in a 45-year-old man. Which of the following conditions will occur because of this injury? (A) Constricted pupil (B) Abduction of the eyeball (C) Complete ptosis (D) Impaired lacrimal secretion (E) Paralysis of the ciliary muscle

The answer is E. The oculomotor nerve carries parasympathetic fibers to the ciliary and sphincter pupillae ciliary muscles; thus, a lesion of the oculomotor nerve leads to ciliary muscle paralysis and a dilated pupil. The abducens nerve supplies the lateral rectus, which is an abductor of the eye. The levator palpebrae superioris inserts on the tarsal plate in the upper eyelid, which is innervated by sympathetic fibers. Thus, a lesion of the oculomotor nerve does not cause complete ptosis.

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, as seen in the given figure. What specific nerve is most likely damaged? (A) Left oculomotor nerve (B) Right oculomotor nerve (C) Left abducent nerve (D) Right abducent nerve (E) Left trochlear nerve

The answer is E: *Left trochlear nerve. The left trochlear nerve innervates only one muscle, the superior oblique, located in the orbit.* Acting individually, this muscle pulls the eye inferolaterally, but it would be hard to distinguish this movement from the combined movements of the inferior rectus muscle (innervated by the oculomotor nerve) and the lateral rectus muscle (innervated by the abducent nerve), which also move the globe inferior and lateral, respectively. *Therefore, the left trochlear nerve is clinically tested by asking the patient to look inferiorly after the left eye is placed 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? (A) Right optic nerve (B) Left optic nerve (C) Right ophthalmic nerve (D) Right oculomotor nerve (E) Left oculomotor nerve

The answer is 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.

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 as noted in the figure. 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? (A) Sternohyoid (B) Stylohyoid (C) Cricothyroid (D) Stylopharyngeus (E) Mylohyoid

The answer is E: Mylohyoid. The mylohyoid muscle is innervated by the mandibular division of the trigeminal nerve (CN V3), and this nerve is damaged in this patient due to the right-sided paralysis of the muscles of mastication, facial asymmetry (noted in the figure), and dysphagia.

What are the different innervations of the tongue?

The anterior two-thirds of the tongue is innervated by the lingual nerve, a branch of the mandibular division of the trigeminal nerve (CN V). The posterior one-third of the tongue is innervated by the glossopharyngeal nerve (CN IX) for general and taste sensations.

What are the five motor branches of the facial nerve?

The facial nerve then passes through the parotid gland, which it does not innervate, to form the parotid plexus, which splits into five branches innervating the muscles of facial expression: (temporal, zygomatic, buccal, marginal mandibular, cervical).

KNOW THIS:

The foramen ovale (oval foramen), which transmits the mandibular (third) division of the trigeminal nerve (CN V3) and aids in mastication. This nerve provides cutaneous (general) sensation to the skin of the lower lip, chin, cheek, anterior auricle, and lateral scalp.

KNOW THIS:

The lesser petrosal nerve carries secretomotor (preganglionic parasympathetic) fibers to the parotid gland.

KNOW THIS:

The oculomotor nerve carries parasympathetic fibers to the ciliary and sphincter pupillae ciliary muscles; thus, a lesion of the oculomotor nerve leads to ciliary muscle paralysis and a dilated pupil. The abducens nerve supplies the lateral rectus, which is an abductor of the eye.

KNOW THIS:

The parasympathetic fibers of CN VII produce emotional tears from the lacrimal glands

Damage to the oculomotor nerve:

The pupil would be directed "down and out"

Branches of the trigeminal nerve:

The three major branches of the trigeminal nerve: 1) the ophthalmic nerve (V1) 2) the maxillary nerve (V2) 3) the mandibular nerve (V3)

Injury to the trochlear nerve:

The trochlear nerve supplies the superior oblique muscle, which if injured would cause the patient to lose the ability to turn the pupil downward when it is in the adducted position. As an example, the affected patient could not turn the pupil to look downward to the left if the right trochlear nerve were paralyzed.

Crista galli (Latin: "crest of the rooster")

The upper part of the perpendicular plate of the ethmoid bone, which rises above the cribriform plate. The falx cerebri (fold of the dura mater) attaches to the crista galli.