21. An adult patient presents with persistent headaches. A CT scan of the head demonstrates a 2-cm spherical mass at the junction of the white and gray matter of the lateral aspect of the cerebral hemisphere. Which of the following would most likely produce this lesion?

(A)            Astrocytoma

(B)            Ependymoma

(C)            Glioblastoma multiforme

(D)            Meningioma

(E)            Metastatic carcinoma

21. The correct answer is E. Seventy percent of adult brain tumors occur above the tentorium (70% of childhood tumors occur below the tentorium). Statistically, metastases > astrocytomas (including glioblastoma) > meningioma > pituitary tumor. Location at the junction of cortical gray and white matter is also typical for metastatic disease, as is the round shape.

Astrocytomas (choice A) typically arise in the white matter and have an irregular shape.

Ependymomas (choice B) are uncommon and arise from the ependymal lining of the ventricles.

Glioblastoma multiforme (choice C) is an aggressive form of astrocytoma that can cause a “butterfly lesion,” crossing between the cerebral hemispheres.

Meningiomas (choice D) can cause spherical lesions and are usually located on the surface of the brain.

22. A 37-year-old woman presents to the emergency department with a fever. Chest x-ray film shows multiple patchy infiltrates in both lungs. Echocardiography and blood cultures suggest a diagnosis of acute bacterial endocarditis limited to the tricuspid valve. Which of the following is the most probable etiology?

(A)            Congenital heart disease

(B)       Illicit drug use

(C)            Rheumatic fever

(D)            Rheumatoid arthritis

(E)            Systemic lupus erythematosus

22. The correct answer is B. The most probable etiology of bacterial endocarditis involving the tricuspid valve is illicit IV drug use, which can introduce skin organisms into the venous system that then attack the tricuspid valve. Staphylococcus aureus accounts for between 60% and 90% of cases of endocarditis in IV drug users.

The endocarditis associated with congenital heart disease (choice A) typically involves either damaged valves or atrial or ventricular septal defects. The tricuspid valve is not particularly vulnerable.

Rheumatic fever (choice C) most commonly damages the mitral and aortic valves, and tricuspid damage is usually less severe and seen only when the mitral and aortic valves are heavily involved. Consequently, secondary bacterial endocarditis involving only the tricuspid valve in a patient with history of rheumatic fever would be unusual.

Rheumatoid arthritis (choice D) is not associated with bacterial endocarditis.

Systemic lupus erythematosus (choice E) can produce small, aseptic vegetations on valves, but is not associated with bacterial endocarditis.

23. A 5-year-old child, who has not had routine pediatric care, develops a febrile disease with cough and a blotchy rash and is brought to the emergency department. On physical examination, there is cervical and axillary lymphadenopathy. Also noted is an erythematous, maculopapular rash behind the ears and along the hairline, involving the neck and, to a lesser extent, the trunk. Examination of this patient’s oropharynx would most likely reveal which of the following lesions?

(A)            Adherent thin, whitish patch on gingiva

(B)       Cold sores on the lips

(C)       Curdy white material overlying an erythematous base on the oral mucosa

(D)       Large shallow ulcers on the oral mucosa

(E)            Multiple small white spots on the buccal mucosa

23. The correct answer is E. The question stem describes the typical presentation of measles (rubeola), which is caused by a Morbillivirus, an RNA virus belonging to the Paramyxovirus family. Koplik spots, which are pathognomonic for measles, are small, bluish-white spots on the buccal mucosa in the early stages of the disease. These lesions appear just before the onset of the characteristic rash (which can also involve the extremities) and fade as the rash develops.

Leukoplakia is a premalignant condition characterized by adherent whitish patches on the gingiva (choice A) and other sites in the oral cavity.

Cold sores of the lips (choice B) are due to infection with Herpes viruses.

Candida infection (thrush) produces curdy white material loosely attached to an erythematous base (choice C).

Aphthous ulcers are large shallow ulcers of the oral mucosa (choice D), commonly known as canker sores.

24. A 57-year-old man is brought to the emergency room for a suspected myocardial infarction. An electrocardiogram indicates the appearance of a wide-complex ventricular tachycardia with a rate of 126 beats per minute. The physician prescribes a drug to decrease SA node automaticity, increase AV node refractoriness, and decrease AV node conduction velocity. Which of the following agents was most likely prescribed?

(A)            Amiodarone

(B)            Disopyramide

(C)            Lidocaine

(D)            Propranolol

(E)            Verapamil

24. The correct answer is D. The patient has a ventricular tachycardia as indicated by the electrocardiogram: the appearance of a wide-complex ventricular tachycardia with a rate of 126 beats per minute. Propranolol is a Type II antiarrhythmic agent that acts by decreasing SA node automaticity, increasing AV nodal refractoriness, and decreasing AV nodal conduction velocity. Propranolol is indicated for the treatment of ventricular tachycardias, supraventricular arrhythmias, and for slowing the ventricular rate during atrial fibrillation and atrial flutter.

Amiodarone (choice A) is a Type III antiarrhythmic that acts by prolonging the action potential duration in tissue with fast-response action potentials. Amiodarone is indicated for treatment of refractory ventricular arrhythmias that are unresponsive to other antiarrhythmics.

Disopyramide (choice B) is a Type IA antiarrhythmic that reduces the maximal velocity of phase 0 depolarization by blocking the inward sodium current in tissue with fast-response action potentials. It also increases the action potential duration. Disopyramide is indicated for the treatment of atrial and ventricular extrasystoles and atrial and ventricular tachyarrhythmias.

Lidocaine (choice C) is a Type IA antiarrhythmic that reduces the maximal velocity of phase 0 depolarization by blocking the inward sodium current in tissue with fast-response action potentials. Lidocaine is indicated for the treatment of atrial and ventricular extrasystoles, and atrial and ventricular tachyarrhythmias.

Verapamil (choice E), a Type IV antiarrhythmic agent, blocks calcium channels, thereby decreasing conduction velocity and increasing refractoriness in tissue with slow-response action potentials. Verapamil is indicated for the treatment of atrial fibrillation and flutter as well as other atrial tachycardias.

25. While performing a subtotal thyroidectomy, a surgeon inadvertently sections the recurrent laryngeal nerve. Which of the following muscles would retain its innervation subsequent to this injury?

(A) Cricothyroid

(B)       Lateral cricoarytenoid

(C) Posterior cricoarytenoid

(D) Thyroarytenoid

(E)       Vocalis

25. The correct answer is A. The recurrent laryngeal nerve is a branch of the vagus nerve, which innervates all the intrinsic laryngeal muscles except the cricothyroid muscle. The cricothyroid is attached to the cricoid cartilage and the thyroid cartilage; contraction of this muscle tends to stretch and adduct the vocal ligament. The cricothyroid is innervated by the external laryngeal nerve.

The lateral cricoarytenoid muscle (choice B) is innervated by the recurrent laryngeal nerve and is attached to the cricoid cartilage and the arytenoid cartilage. Its contraction causes adduction of the vocal ligament.

The posterior cricoarytenoid muscle (choice C) is innervated by the recurrent laryngeal nerve and is attached to the cricoid cartilage and the arytenoid cartilage. Its contraction causes abduction of the vocal ligament.

The thyroarytenoid muscle (choice D) is innervated by the recurrent laryngeal nerve and is attached to the thyroid cartilage and the arytenoid cartilage. Its contraction causes slackening of the vocal ligament.

The vocalis muscle (choice E) is the most medial part of the thyroarytenoid muscle. It attaches either to the thyroid cartilage and the vocal ligament, or to the arytenoid cartilage and the vocal ligament. It is innervated by the recurrent laryngeal nerve. Its contraction causes tension on segments of the vocal ligament.

26. A newborn infant who was apparently healthy at birth develops aspiration pneumonia in the first 2 days of life. All attempts to feed the infant cause it to cough and choke. Which of the following abnormalities is the most likely cause of the infant’s difficulties?

(A)            Bronchogenic cysts

(B)            Congenital pulmonary cysts

(C)            Posterior deviation of the tracheoesophageal septum

(D)            Pulmonary immaturity

(E)            Pulmonary sequestration

26. The correct answer is C. The infant probably has esophageal atresia, which is typically caused by posterior deviation of the tracheoesophageal septum. Attempts at feeding cause fluid to spill into the trachea, and secondarily cause aspiration pneumonia. Emergent surgical correction is usually required.

Bronchogenic cysts (choice A) are centrally located cysts that are often asymptomatic and may be associated with cysts of other organs.

Congenital pulmonary cysts (choice B) are often multiple and located in the lung periphery without connection to the bronchi; they are vulnerable to infection and rupture complicated by pneumothorax and/or hemoptysis.

Pulmonary immaturity (choice D) produces progressive difficulty in breathing beginning in the first few hours of life.

Pulmonary sequestration (choice E) represents extrapulmonary lung tissue supplied by systemic blood vessels rather than by pulmonary arteries.

27. A 46-year-old man sustains a spider bite on his upper eyelid, and an infection develops. The physician is very concerned about spread of the infection to the dural venous sinuses of the brain via emissary veins. With which of the following dural venous sinuses does the superior ophthalmic vein directly communicate?

(A)            Cavernous sinus

(B)            Occipital sinus

(C)            Sigmoid sinus

(D)       Straight sinus

(E)            Superior petrosal sinus

27. The correct answer is A. The anterior continuation of the cavernous sinus, the superior ophthalmic vein, passes through the superior orbital fissure to enter the orbit. Veins of the face communicate with the superior ophthalmic vein. Because of the absence of valves in emissary veins, venous flow may occur in either direction. Cutaneous infections may be carried into the cavernous sinus and result in a cavernous sinus infection, which may lead to an infected cavernous sinus thrombosis. The cavernous sinus is lateral to the pituitary gland and contains portions of cranial nerves III, IV, V1, V2 and VI, and the internal carotid artery.

The occipital sinus (choice B) is at the base of the falx cerebelli in the posterior cranial fossa. It drains into the confluence of sinuses.

The sigmoid sinus (choice C) is the anterior continuation of the transverse sinus in the middle cranial fossa. The sigmoid sinus passes through the jugular foramen and drains into the internal jugular vein.

The straight sinus (choice D) is at the intersection of the falx cerebri and the falx cerebelli in the posterior cranial fossa. The straight sinus connects the inferior sagittal sinus with the confluence of sinuses.

The superior petrosal sinus (choice E) is at the apex of the petrous portion of the temporal bone and is a posterior continuation of the cavernous sinus. The superior petrosal sinus connects the cavernous sinus with the sigmoid sinus.

28. A 15-year-old high school student and several of her friends ate lunch at a local Chinese restaurant. They all were served the daily luncheon special, which consisted of sweet and sour pork with vegetables and fried rice. All the girls developed nausea, vomiting, abdominal pain, and diarrhea within 6 hours of eating lunch. Which of the following is the most likely cause of these symptoms?

(A)            Bacillus cereus

(B)            Clostridium botulinum

(C)            Clostridium perfringens

(D)       EHEC (Enterohemorrhagic Escherichia coli)

(E)            Staphylococcus aureus

(F)       Vibrio cholerae

28. The correct answer is A. Bacillus cereusproduces a self-limited diarrhea due to ingestion of the preformed enterotoxin in contaminated fried rice and seafood. The incubation period is typically around 4 hours. The degree of vomiting is greater than the diarrhea. B. cereus is also associated with keratitis, producing a corneal ring abscess.

Clostridium botulinum (choice B) produces a neurotoxin that blocks the release of acetylcholine, resulting in a symmetric descending paralysis that may lead to respiratory complications causing death. Symptoms include blurred vision, photophobia, dysphagia, nausea, vomiting, and dysphonia. Most cases are associated with the ingestion of contaminated home-canned food.

Clostridium perfringens (choice C) produces a severe diarrhea with abdominal pain and cramping (sometimes called “church picnic” diarrhea). The incubation period is 8-24 hours after ingesting contaminated meat, meat products, or poultry. The meats have usually been cooked, allowed to cool, and then warmed, which causes germination of the clostridial spores.

EHEC, enterohemorrhagic Escherichia coli (choice D), produces a bloody, noninvasive diarrhea due to the ingestion of verotoxin found in undercooked hamburger at fast food restaurants. The 0157:H7 serotype typically produces this syndrome. Some patients develop a life-threatening complication called hemolytic-uremic syndrome.

Staphylococcus aureus (choice E) produces a self-limited food poisoning syndrome with nausea, vomiting, and abdominal pain followed by diarrhea beginning 1-6 hours after ingestion of the enterotoxin. The organism is found in foods such as potato salad, custard, milk shakes, and mayonnaise.

Vibrio cholerae (choice F) typically produces a watery, nonbloody diarrhea with flecks of mucus (rice-water stools). Abdominal pain is not a feature. Massive fluid loss and electrolyte imbalance are complications. In the U.S., cases of cholera (El Tor 01 strain) are associated with the Gulf coast and ingestion of poorly cooked or poorly stored crabs, shrimp, or oysters. A strain of V. cholerae, called non-01, is also found along the Gulf coast. Patients who ingest contaminated shellfish experience fever, copious watery diarrhea, and abdominal cramps within 48 hours after eating.

29. A 24-year-old woman with a history of allergic rhinitis is involved in an automobile accident and sustains a splenic laceration. She undergoes abdominal surgery and is then transfused with four units of blood of the appropriate ABO and Rh type. As the transfusion progresses, she becomes rapidly hypotensive and develops airway edema, consistent with anaphylaxis. Which of the following pre-existing conditions best accounts for these symptoms?

(A)       AIDS

(B)       C1 esterase inhibitor deficiency

(C)            DiGeorge syndrome

(D)            Selective IgA deficiency

(E)            Wiskott-Aldrich syndrome

29. The correct answer is D. Patients with selective IgA deficiency may have circulating antibodies to IgA. Fatal anaphylaxis may ensue if they are transfused with blood products with serum containing IgA, although many patients with selective IgA deficiency are asymptomatic and never diagnosed. Symptomatic patients may have recurrent sinopulmonary infections and diarrhea, as well as an increased incidence of autoimmune and allergic diseases.

AIDS (choice A) predisposes for infections and neoplasms, but not anaphylaxis.

C1 esterase inhibitor deficiency (choice B) is an autosomal dominant disease characterized by recurrent attacks of colic and episodes of laryngeal edema, without pruritus or urticarial lesions. This disorder is also known as hereditary angioedema.

DiGeorge syndrome (choice C) is characterized by thymic aplasia and, sometimes, hypoparathyroidism. The disorder is due to abnormal development of the third and fourth pharyngeal arches.

Wiskott-Aldrich syndrome (choice E) is a form of immunodeficiency associated with thrombocytopenia and eczema.

30. A couple presents to a clinic for workup of infertility after 5 years of unprotected intercourse. The wife denies any medical problems and notes regular menstrual cycles. The husband states that he has had chronic sinusitis and lower respiratory tract infections. Physical examination of the woman is unremarkable. Examination of the man is remarkable for dextrocardia. Further workup of the husband will most likely reveal

(A)            azoospermia

(B)            germinal cell aplasia

(C)            immotile sperm

(D)       isolated gonadotropin deficiency

(E)            varicocele

30. The correct answer is C. The husband is suffering from Kartagener syndrome, an autosomal recessive disorder characterized by infertility, situs inversus, chronic sinusitis, and bronchiectasis. The underlying cause of these varied manifestations is a defect in the dynein arms, which are spokes of microtubule doublets of cilia in the airways and the reproductive tract. Since sperm motility is dependent on the functioning of cilia, infertility frequently accompanies this disorder. Situs inversus occurs because ciliary function is necessary for cell migration during embryonic development.

Azoospermia (choice A) is not a feature of Kartagener syndrome, as sperm production or survival is not affected in this disorder.

Germinal cell aplasia (choice B), also known as Sertoli-only syndrome, is characterized by oligospermia or azoospermia.

Isolated gonadotropin deficiency (choice D) is characterized by delayed or incomplete pubertal maturation.

Varicocele (choice E) results in an increased testicular temperature, decreasing the count of normal, viable sperm.

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