Pharm
A 19-year-old woman is found unresponsive at home next to an empty bottle of phenobarbital and brought to the emergency room. Which of the following clinical findings is expected?
(A) Hypertension
(B) Hyperthermia
(C) Hypoxemia
(D) Ventricular tachycardia
(E) Fixed, dilated pupils
Answer C (correct answer): Phenobarbital is a central nervous system depressant. Its use has largely been replaced by benzodiazepines but is still part of certain migraine-headache medications (e.g., fioricet) and is occasionally used as an anticonvulsant or sedative. Overdose of phenobarbital is associated with collapse of the central nervous system and cardiovascular system. Acute overdose is life-threatening due to respiratory depression (similar to opioids). Other overdose features include coma, pupillary constriction, hypotension, and hypothermia.
A 6-year-old boy is evaluated for increased sensitivity to noise. His mother also reports that he cannot close his right eye. He was seen four days ago by his pediatrician for fever and ear pain and diagnosed with otitis media. His vital signs are normal. Physical examination reveals an absent right-sided nasolabial fold. Visual acuity is normal, but he is unable to raise his right eyebrow. A lesion involving which of the following cranial nerves is the most likely explanation for this boy’s current symptoms?
(A) Oculomotor nerve
(B) Optic nerve
(C) Facial nerve
(D) Vestibulocochlear nerve
(E) Trigeminal nerve
Answer C (correct answer): This boy has facial nerve palsy (cranial nerve VII) caused by extension of otitis media to the facial canal, where the facial nerve passes through the temporal bone. Other causes of facial nerve palsy in children include Lyme disease and viral infections (varicella, herpes zoster, and coxsackie virus). Bell’s palsy is used to describe facial nerve palsy of unknown etiology. Symptoms of facial nerve palsy include lack of tearing, an inability to close the eye or move the forehead, sagging of the eyebrow, and an abnormal smile or frown. Facial creases and the nasolabial fold (also called “smile lines”) on the affected side may disappear due to muscle paralysis.
A 26-year-old man is evaluated for right shoulder pain and weakness. He is a martial arts instructor who recently fell on his shoulder during a competition. Physical examination reveals right shoulder droop and impaired abduction of the right shoulder. He also has weakness turning his head to the left. Damage to which of the following nerves most likely occurred in this man?
(A) Long thoracic nerve
(B) Accessory nerve
(C) Suprascapular nerve
(D) Upper subscapular nerve
(E) Axillary nerve
Answer B (correct answer): This man has accessory (cranial nerve XI) nerve damage secondary to trauma from a sports injury. The accessory nerve is a pure motor nerve. It innervates the trapezius and sternocleidomastoid muscles. Patients with accessory nerve damage present with shoulder droop, impaired shoulder abduction, and difficulty turning their head away from the affected side. They can also develop a winged scapula (scapular prominence that is most obvious with extension of the arms against a wall).
13. 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
13. 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.
19. A 31-year-old hockey player is hit in the head by a puck. His radiogram shows a fracture of the foramen rotundum. Which of the following nerves would be damaged by this event?
(A). Ophthalmic nerve
(B). Mandibular nerve
(C). Maxillary nerve
(D). Optic nerve
(E). Trochlear nerve
19. The answer is C. The maxillary nerve runs through the foramen rotundum; the ophthalmic nerve runs through the supraorbital fissure; the mandibular nerve passes through the foramen ovale; the optic nerve runs through the optic canal; and the trochlear nerve passes through the superior orbital fissure.
A 25-year-old man comes to the emergency department because of altered mental status. He was found at home by his girlfriend two hours after they had an argument. He has a history of depression. His girlfriend says he takes several daily psychiatric medications, but she does not know the names. Pulse is 88/min, respirations are 16/min, blood pressure is 110/60 mmHg, and oxygen saturation is 99% on non-rebreather mask. Physical examination shows a lethargic man who is arousable. His speech is slurred. He is oriented to person but not place or time. Pupils are non-dilated and reactive to light. Laboratory studies show blood glucose of 110 mg/dL (normal levels: 70 – 150 mg/dL). Overdose of which of the following is the most likely cause of this man’s presentation?
(A) Acetaminophen
(B) Alprazolam
(C) Metoprolol
(D) Sertraline
(E) Amitriptyline
Answer B (correct answer): This patient has classic signs of benzodiazepine (alprazolam) overdose, which consists of CNS depression with normal vitals. Typical CNS depression symptoms include slurred speech, ataxia, and altered mental status. The normal vital signs distinguish benzodiazepine overdose from ingestion of other substances.
A 30-year-old woman is evaluated for blurry vision and left-sided eye pain. Physical examination reveals decreased visual acuity in her left eye. She also has a left-sided afferent pupillary defect and central vision loss on visual field testing. A lesion involving which of the following cranial nerves is the most likely explanation for this woman’s current symptoms?
(A) Oculomotor nerve
(B) Trochlear nerve
(C) Optic nerve
(D) Abducens nerve
(E) Trigeminal nerve
Answer C (correct answer): This woman has optic neuritis, an inflammatory, demyelinating condition that commonly occurs as a component of multiple sclerosis (seen in 50% of patients). While this woman does not have a history of multiple sclerosis, this presentation of optic neuritis may represent the first evidence of the disease. Optic neuritis is an immune-mediated condition that develops in response to an unknown trigger. T-cell activation and release of inflammatory cytokines leads to inflammation and demyelination of the optic nerve.
A 65-year-old man is evaluated on hospital day 2 following a carotid endarterectomy. His incisional pain is well controlled, and he is eating and drinking normally. His vital signs are normal. Physical examination reveals right tongue deviation. Damage to which of the following nerves most likely occurred in this man?
(A) Left hypoglossal nerve
(B) Right hypoglossal nerve
(C) Left glossopharyngeal nerve
(D) Right glossopharyngeal nerve
(E) Left facial nerve
Answer B (correct answer): This man has right-sided hypoglossal (cranial nerve XII) nerve injury caused by carotid endarterectomy. The hypoglossal nerve is the most commonly damaged nerve during this surgery. The hypoglossal nerve (cranial nerve XII) innervates all but one of the tongue muscles (the vagus nerve innervates the palatoglossal muscle). Patients with hypoglossal lesions present with protrusion of the tongue toward the affected side. This man’s tongue deviates to the right side, indicating right hypoglossal nerve injury.
10. A patient can move his eyeballs normally and see distant objects clearly but cannot focus on near objects. This condition may indicate damage to which of the following structures?
(A). Ciliary ganglion and oculomotor nerve
(B). Oculomotor nerve and long ciliary nerve
(C). Short ciliary nerves and ciliary ganglion
(D). Superior cervical ganglion and long ciliary nerve
(E). Oculomotor, trochlear, and abducens nerves
10. The answer is C. Damage to the parasympathetic ciliary ganglion and parasympathetic fibers in the short ciliary nerve impairs the ability to focus on close objects (accommodation). Because the patient can move his eyeballs normally, the oculomotor nerve is not damaged even if this nerve contains preganglionic parasympathetic fibers. The patient is able to see distant objects clearly because the long ciliary nerve also carries sympathetic fibers to the dilator pupillae. The ability to move the eyeball normally indicates that the oculomotor, trochlear, and abducens nerves are intact.
12. Following a penetrated injury in the submandibular triangle, the tongue of a 45-year-old patient deviates to the left on protrusion. Which of the following nerves is injured?
(A). Right lingual nerve
(B). Left lingual nerve
(C). Right hypoglossal nerve
(D). Left hypoglossal nerve
(E). Left glossopharyngeal nerve
12. The answer is D. A lesion of the hypoglossal nerve causes deviation of the tongue toward the injured side on protrusion. The lingual and glossopharyngeal nerves do not supply the tongue muscles.
A 29-year-old man has epilepsy treated with phenytoin. He confuses his medications and accidentally takes four times his normal dose of phenytoin. Which of the following may occur in this man as the earliest sign of phenytoin toxicity?
(A) Megaloblastic anemia
(B) Unsteady gait
(C) Hirsutism
(D) Gingival hyperplasia
(E) Purple discoloration of the hand
Answer B (correct answer): Phenytoin is an antiepileptic medication that inactivates sodium channels in the central nervous system. Because of a narrow therapeutic range, the serum level must be carefully monitored to avoid excessive phenytoin levels. When serum phenytoin levels are elevated, the earliest evidence of toxicity is unsteady gait and worsening coordination. On physical exam, patients may have horizontal nystagmus. Severe toxicity may cause an alteration in mental status and eventually coma. These effects occur due to excessive blockade of sodium channels leading to motor incoordination.
A 50-year-old woman is evaluated for blurry vision. Her husband has noticed that her left eyelid is droopy. She has hypertension and type 2 diabetes. Physical examination reveals left-sided ptosis. She also has impaired adduction and elevation of her left eye. A lesion involving which of the following cranial nerves is the most likely explanation for this woman’s current symptoms?
(A) Oculomotor nerve
(B) Abducens nerve
(C) Trochlear nerve
(D) Optic nerve
(E) Facial nerve
Answer A (correct answer): This woman has oculomotor (cranial nerve III) nerve palsy. In patients with diabetes, microvascular dysfunction can impair blood flow to the third cranial nerve, leading to nerve ischemia. Parasympathetic fibers that travel with cranial nerve III are not affected, so the pupil is “spared” (i.e., pupil size is normal and not dilated). The oculomotor nerve innervates the levator palpebrae muscle of the eyelid, along with several ocular muscles, including the medial rectus, superior rectus, inferior rectus, and inferior oblique muscles. Patients with oculomotor neuropathy present with ptosis and eyes that are abducted and depressed (“down and out”).
A 39-year-old woman is evaluated for hoarseness. She was diagnosed with papillary thyroid cancer and had a total thyroidectomy two weeks ago. She is otherwise healthy, and her only medication is levothyroxine. Physical examination reveals a surgical scar on her anterior neck. Laryngoscopy demonstrates right-sided vocal cord paralysis. A lesion involving which of the following cranial nerves is the most likely explanation for this woman’s current symptoms?
(A) Glossopharyngeal nerve
(B) Accessory nerve
(C) Facial nerve
(D) Hypoglossal nerve
(E) Vagus nerve
Answer E (correct answer): This woman has unilateral vocal cord paralysis caused by damage to the recurrent laryngeal nerve. Damage to this nerve may develop following thyroidectomy. The recurrent laryngeal nerve is a branch of the vagus nerve (cranial nerve X). It ascends to the larynx through the tracheoesophageal groove. Patients with recurrent laryngeal nerve lesions present with hoarseness, and can also develop dyspnea, ineffective coughing, and aspiration pneumonia.
A 56-year-old man is evaluated for double vision. The double vision disappears when he closes his left eye and worsens when he looks to his left. He denies eye trauma or pain. He has a history of hypertension and type II diabetes. Physical examination reveals left-sided esotropia and impaired left eye abduction. A lesion involving a cranial nerve that supplies which of the following is the most likely cause of this man’s current symptoms?
(A) Superior oblique muscle
(B) Medial rectus muscle
(C) Superior rectus muscle
(D) Lateral rectus muscle
(E) Inferior oblique muscle
Answer D (correct answer): This man has abducens (cranial nerve VI) nerve palsy (also called lateral rectus palsy) caused by ischemia. Microvascular ischemia leading to abducens nerve palsy often occurs in association with poorly-controlled diabetes or hypertension. Raised intracranial pressure can also compress the abducens nerves, leading to unilateral or bilateral abducens nerve palsy. The abducens nerve innervates the lateral rectus muscle, which abducts the eye. Patients with abducens nerve lesions present with horizontal diplopia that improves with closing the affected eye. They also develop an inability to move the affected eye laterally (look outward). This will cause diplopia when the patient looks toward the side with the lesion. An inward deviation of the affected eye may also occur (esotropia).
9. A 53-year-old woman is diagnosed as having a pituitary tumor. If the tumor is large enough, she could exhibit which of the following disorders?
(A). Blindness
(B). Bitemporal (heteronymous) hemianopia
(C). Right nasal hemianopia
(D). Left homonymous hemianopia
(E). Binasal hemianopia
9. The answer is B. Lesion of the optic chiasma by a pituitary tumor results in bitemporal hemianopia resulting from loss in the nasal field of vision of both eyes. Lesion of the optic nerve causes blindness. A right perichiasmal lesion by an aneurysm of the internal carotid artery leads to right nasal hemianopia because of loss of vision in the nasal field of the right eye. Lesion of the right optic tract or optic radiation causes left homonymous hemianopia resulting from loss of the left half of the visual fields of both eyes. Aneurysms of both internal carotid arteries cause right and left perichiasmal lesions, leading to binasal hemianopia (loss of vision in the nasal fields of both eyes).
A 6-year-old girl presents after having “episodes” at school. During these episodes, she stares into space and does not respond to verbal or tactile stimuli. The episodes last for a few seconds. She has no confusion after these events. A drug with which of the following mechanisms of action is recommended for the treatment of her condition?
(A) Binds post-synaptic GABA receptors
(B) Blocks T-type calcium channels
(C) Increases activity of GABA
(D) Binds to a voltage-dependent calcium channel
(E) Inactivates sodium channels
Answer B (correct answer): This girl has childhood absence epilepsy. Her “episodes” are brief seizures that cause a sudden impairment in consciousness. The treatment of choice for this condition is ethosuximide, a drug that blocks thalamic T-type calcium channels. This results in an increase in the seizure threshold and reduces nerve transmission in the cerebral cortex, making seizures less likely to occur.
A 58-year-old woman is evaluated for headaches. She has recurrent, brief episodes of pain located on the right side of the face that feel like an electric shock. Cold air, laughing, and chewing reproduce the pain. Physical examination reveals decreased sensation to her right forehead. Which of the following additional physical examination findings is most likely in this woman?
(A) Dilated pupil
(B) Absent corneal reflex
(C) Central vision loss
(D) Ptosis
(E) Uvula deviation
Answer B (correct answer): This woman has trigeminal neuralgia, also known as tic douloureux, caused by compression of the trigeminal nerve root where it enters the pons. The most common reason for compression is an aberrant artery or vein. This causes demyelination in the compressed portion of the nerve. Other rare causes of trigeminal neuralgia include acoustic neuromas, meningiomas, or arteriovenous malformations (AVMs). Patients with trigeminal neuralgia present with recurrent episodes of intense facial pain that usually last seconds to minutes. These episodes often feel like an electric shock.
The trigeminal nerve (cranial nerve V) is the largest cranial nerve. It is sensory to the face and provides motor innervation to the muscles of mastication (chewing). The V1 branch of the trigeminal nerve also functions as the afferent (sensory) limb of the corneal reflex, ensuring the eye blinks when the cornea is touched by a Q-tip.
Patients with a trigeminal neuropathy may present with decreased sensation (pain, touch, and temperature) to the face, and jaw weakness (deviation of jaw toward the affected side). These features are not usually seen in trigeminal neuralgia, however.
2. A 16-year-old boy presents with double vision. Further examination reveals that he has difficulty in turning his eye inferolaterally and trouble going downstairs. Which of the following nerves is most likely damaged?
(A). Oculomotor nerve
(B). Optic nerve
(C). Ophthalmic nerve
(D). Trochlear nerve
(E). Abducens nerve
2. The answer is D. 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.
7. A 34-year-old man in a bar fight suffers a knife wound that severs the abducens nerve proximal to its entrance into the orbit. Which of the following conditions results from this injury?
(A). Ptosis of the upper eyelid
(B). Loss of the ability to dilate the pupil
(C). External strabismus (lateral deviation)
(D). Loss of visual accommodation
(E). Internal strabismus (medial deviation)
7. The answer is E. 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). Ptosis of the upper eyelid is caused by lesions of the oculomotor nerve or sympathetic nerve to the levator palpebrae superioris. Inability to dilate the pupil is caused by a lesion of the sympathetic nerve to the dilator pupillae. External strabismus (lateral deviation) is caused by paralysis of the medial rectus muscle, which is innervated by the oculomotor nerve. Loss of visual accommodation is due to a lesion of parasympathetic nerve fibers to the ciliary muscle.
4. A 23-year-old woman suffers from a fracture of the jugular foramen by car accident. Which of the following nerves is/are most likely damaged?
(A). Cranial nerve V2
(B). Cranial nerve VI
(C). Cranial nerves VII and VIII
(D). Cranial nerves IX, X, and XI
(E). Cranial nerve XII
4. The answer is D. The jugular foramen transmits cranial nerves, IX, X, and XI, along with the internal jugular vein. The cranial nerve V2 runs through the foramen rotundum. The cranial nerve VI passes through the superior orbital fissure. The cranial nerves VII and VIII courses through the internal auditory meatus. The cranial nerve XII passes through the hypoglossal canal.
A 74-year-old man with a mechanical mitral valve who is on warfarin develops a seizure and is treated with an antiepileptic medication. Three weeks later he develops weakness of his left arm due to an ischemic stroke. Laboratory evaluation shows a serum international normalized ratio of 1.0 (normal 0.8 to 1.2). Which of the following medications was most likely used for treatment of his seizures?
(A) Topiramate
(B) Valproic Acid
(C) Carbamazepine
(D) Levetiracetam
(E) Ethosuximide
Answer C (correct answer): This man had a stroke after treatment with an antiepileptic medication while taking warfarin for anticoagulation. Warfarin is used in patients with mechanical heart valves to prevent thrombus formation on the valve. Warfarin normally increases the international normalized ratio (INR), but this man’s INR is normal despite the drug. This occurred because his new anti-seizure medication reduced the efficacy of the warfarin. Warfarin is metabolized by the cytochrome P450 system (CYP450), a group of liver enzymes that metabolize many drugs. The action of these enzymes can be inhibited or induced by certain medications. The anti-seizure medication, carbamazepine, is a famous inducer of CYP450 enzymes, which may lead to increased metabolism of warfarin. The increased metabolism of warfarin results in a reduced blood thinning effect and a normal (rather than increased) INR. Patients on warfarin for prevention of stroke in the setting of mechanical valves should have an INR greater than 2.0. Patients who take warfarin require dose adjustments when they begin new medications like carbamazepine to prevent loss of warfarin’s anticoagulant effect.
A 14-year-old girl is evaluated for double vision. Her mother reports she frequently tilts her head to the right to avoid blurry vision. She also complains of difficulty going down the stairs. She is otherwise healthy and is not taking any medications. Physical examination reveals left eye hypertropia and a right-sided head tilt. A lesion involving which of the following cranial nerves is the most likely explanation for this girl’s current symptoms?
(A) Oculomotor nerve
(B) Optic nerve
(C) Facial nerve
(D) Abducens nerve
(E) Trochlear nerve
Answer E (correct answer): This girl has a congenital trochlear (cranial nerve IV) palsy. Congenital fourth nerve palsy is the most common cause of isolated trochlear nerve palsy. The cause is unknown. Children can compensate with head tilt for many years during childhood. As they grow, it becomes increasingly difficult to compensate and diplopia develops. For this reason, the initial presentation occurs later in childhood despite the disorder being present at birth.
The trochlear nerve has the longest intracranial course of the cranial nerves. It is a motor nerve that innervates only the superior oblique muscle. This muscle turns the eye down and in.
Patients with trochlear nerve lesions present with diplopia (double vision) and eyes tilted outward and upward. Patients frequently tilt their head away from the affected side to compensate for diplopia. These patients often have difficulty reading and going down the stairs, since both activities require the eyes to turn down and in. An upward deviation of the affected eye may also develop (hypertropia).
A 56-year-old man is evaluated for difficulty swallowing. He had a bronchoscopy one week ago and his symptoms started after that. He has also noticed difficulty tasting spicy and sour foods and decreased saliva production. His temperature is 37°C (98.6°F), heart rate is 105/min, and blood pressure is 150/95 mmHg. Physical examination reveals decreased sensation in the tonsils and posterior tongue. The tongue and buccal mucosa are dry. A lesion involving which of the following cranial nerves is the most likely explanation for this man’s current symptoms?
(A) Vagus nerve
(B) Facial nerve
(C) Hypoglossal nerve
(D) Glossopharyngeal nerve
(E) Trigeminal nerve
Answer D (correct answer): This man has a glossopharyngeal (cranial nerve IX) nerve lesion caused by nerve damage during a bronchoscopy. The glossopharyngeal nerve enters the pharynx where it can be damaged during oropharyngeal procedures like bronchoscopy or intubation. The glossopharyngeal nerve innervates the stylopharyngeus muscle, which elevates the palate. Branches of the nerve also control salivary gland secretion, provide sensation to the tonsils and posterior pharynx, and function as the afferent (sensory) limb of the gag reflex.
1. A 50-year-old family physician has vertical diplopia; the man feels unsure when descending stairs. He can eliminate the double vision by tilting his chin toward the paretic side. Which of the following extraocular muscles is responsible for the ocular malalignment?
(A) Inferior rectus
(B) Inferior oblique
(C) Lateral rectus
(D) Superior oblique
(E) Superior rectus
1. D. The superior oblique depresses, abducts, and intorts the eye. Paralysis of this muscle results in extorsion and weakness of downward gaze. Head tilting compensates for extorsion.
1. 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
1. 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). Lesion in the medulla may damage CNs IX, X, and XII. Tumor in the optic canal injures the optic nerve and ophthalmic artery. Lesion of the olfactory nerve causes anosmia (loss of smell). Fracture of the foramen spinosum damages the middle meningeal artery.