| Answers -
11-06-2007, 08:10 PM
1>The correct answer is A. An exudate results from leakage of protein-rich fluid from the plasma into the interstitium. It is usually the result of increased vascular permeability caused by inflammation. Exudates also contain numerous acute or chronic inflammatory cells, depending on the inciting event. Of the above choices, only bacterial pleuritis would produce an exudate. If pleuritis is caused by pyogenic organisms, the exudate is purulent (neutrophil-rich). If pleural inflammation is due to mycobacterial infection or neoplastic infiltration, the resulting exudate will contain chronic inflammatory cells.
In contrast, a transudate contains less protein and few inflammatory cells. There are two main mechanisms of transudate formation: 1) decreased oncotic pressure, such as that which occurs in cirrhosis of the liver, nephrotic syndrome, and protein-losing enteropathy (choices B, D, and E); and 2) increased hydrostatic pressure, which may result from congestive heart failure (choice C).
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2>The correct answer is B. Myxopapillary ependymoma is a variant of ependymoma, a tumor arising from ependymal cells. Histologically, myxopapillary ependymoma contains a myxoid (mucus-rich) intercellular matrix, in which spindly neoplastic ependymal cells are arranged in a fascicular and papillary pattern (hence its designation). It is a benign tumor that almost always occurs in the distal segment of the spinal cord, ie, the conus medullaris. Once excised, the patient is cured.
The cerebellum (choice A) is the favorite site for pilocytic astrocytomas, medulloblastomas, and hemangioblastomas, but not ependymomas.
In general, classic ependymomas occur in close proximity to the ventricular cavities, specifically, the 4th ventricle (choice C) in children and the lateral ventricles (choice D) in adults. The myxopapillary variant does not occur in either location.
A midbrain location (choice E) would be truly exceptional for any type of ependymoma.
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3>The correct answer is B. The disease is beta thalassemia major, which is a severe hemolytic anemia characterized by a failure to produce the beta chains of hemoglobin (some HbF, the fetal form of hemoglobin, is produced). The excess alpha chains are insoluble, leading to intra- and extravascular hemolysis. These patients require large numbers of transfusions, and iron overload with resulting secondary hemochromatosis can contribute to eventual cardiac failure. The heart is also damaged by the chronic high output state needed to compensate for the anemia.
Calcium (choice A) deposition is seen in damaged tissues and states with high serum calcium, such as hyperparathyroidism.
Magnesium (choice C), potassium (choice D), and sodium (choice E) are highly soluble and do not usually precipitate in tissues.
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4>The correct answer is A. The test described is the Ames test, which measures damage to DNA and correlates well with carcinogenicity in vitro. It is relatively inexpensive to perform, compared to other tests of carcinogenicity, and is frequently used as a screening test for potential carcinogens.
The nitroblue tetrazolium test (choice B) is used to examine the ability of neutrophils to undergo a respiratory burst, and is used in the diagnosis of hereditary immunodeficiencies.
The Watson-Schwartz test (choice C) detects porphobilinogen in urine, and is used in the The correct answer is C. Any tumor "filling the 4th ventricle" blocks the circulation of cerebrospinal fluid (CSF). This blockage leads to increased intracranial pressure, which manifests with nausea, vomiting, headache, nuchal rigidity, and mental status changes. If surgery is not performed promptly, cerebellar tonsillar herniation and rapid death will ensue. In children, medulloblastoma and ependymoma are the most frequent neoplasms presenting in this manner.
There is no evidence in this case suggesting that acute hemorrhage into the 4th ventricular cavity (choice A) has occurred, nor is medulloblastoma typically associated with this complication. CNS tumors that frequently bleed are metastases from melanoma, renal cell carcinoma, and choriocarcinoma.
Alterations in medullary function (choice B) lead to cardiorespiratory instability and may be caused by direct tumor compression or infiltration of the medulla, neither of which is supported by MRI findings in this case.
Infiltration of the cerebellar vermis (choice D) is certainly seen in many cases of medulloblastoma, a tumor that arises from this midline cerebellar structure. However, this would lead to truncal ataxia and gait instability, not symptoms of increased intracranial pressure.
Medulloblastoma characteristically spreads to the subarachnoid space (choice E), from which the neoplasm may metastasize to distant sites such as spinal cord. Plaques of medulloblastoma are often found on the cerebellar surface, creating a characteristic sugar coating, but this would not cause any significant blockage of CSF circulation.
The correct answer is C. Any tumor "filling the 4th ventricle" blocks the circulation of cerebrospinal fluid (CSF). This blockage leads to increased intracranial pressure, which manifests with nausea, vomiting, headache, nuchal rigidity, and mental status changes. If surgery is not performed promptly, cerebellar tonsillar herniation and rapid death will ensue. In children, medulloblastoma and ependymoma are the most frequent neoplasms presenting in this manner.
There is no evidence in this case suggesting that acute hemorrhage into the 4th ventricular cavity (choice A) has occurred, nor is medulloblastoma typically associated with this complication. CNS tumors that frequently bleed are metastases from melanoma, renal cell carcinoma, and choriocarcinoma.
Alterations in medullary function (choice B) lead to cardiorespiratory instability and may be caused by direct tumor compression or infiltration of the medulla, neither of which is supported by MRI findings in this case.
Infiltration of the cerebellar vermis (choice D) is certainly seen in many cases of medulloblastoma, a tumor that arises from this midline cerebellar structure. However, this would lead to truncal ataxia and gait instability, not symptoms of increased intracranial pressure.
Medulloblastoma characteristically spreads to the subarachnoid space (choice E), from which the neoplasm may metastasize to distant sites such as spinal cord. Plaques of medulloblastoma are often found on the cerebellar surface, creating a characteristic sugar coating, but this would not cause any significant blockage of CSF circulation.
diagnosis of porphyrias.
The Widal test (choice D) is used to diagnose typhoid fever.
The Woellner enzyme test (choice E) detects heterophil antibodies in patients with Epstein-Barr virus infection, such as infectious mononucleosis.
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5>The correct answer is A. A good way to remember what goes through the superior orbital fissure is that everything that innervates the eye, other than the optic nerve, passes through this fissure. This includes the oculomotor nerve (CN III), the trochlear nerve (CN IV), the ophthalmic nerve (V1), and the abducens nerve (CN VI).
The facial nerve (CN VII; choice B) passes through the internal auditory meatus.
The mandibular nerve (V3; choice C) passes through the foramen ovale.
The maxillary nerve (V2; choice D) passes through the foramen rotundum.
The middle meningeal artery (choice E) passes through the foramen spinosum.
The ophthalmic artery (choice F) passes through the optic canal.
The optic nerve (choice G) passes through the optic canal.
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6>The correct answer is B. Cranial nerve IX is the glossopharyngeal nerve, which has a nucleus in the medulla and is necessary for the gag reflex. The gag reflex is elicited by touching either side of the posterior pharynx with a tongue blade, producing bilateral elevation of the palate and bilateral contraction of the pharyngeal muscles. The afferent of this reflex arc consists of the ipsilateral glossopharyngeal nerve, while the vagus nerve, bilaterally, supplies the efferent limb. While the glossopharyngeal nerve may seem to be one of the less important cranial nerves, you should remember to test for its function, as a loss of gag reflex can lead to the patient's death secondary to an aspiration pneumonia. This form of pneumonia can be difficult to treat, as it commonly is due to a mixed flora, which may include a variety of anaerobes.
Cranial nerve VII (choice A) is the facial nerve, which supplies motor function to the face, but does not supply the oropharynx.
Cranial nerve XII (choice C) is the hypoglossal nerve, which supplies the tongue. It is not involved in the gag reflex.
Cranial nerve XI (choice D) is the spinal accessory nerve, which supplies the trapezius and sternocleidomastoid.
Cranial nerve VIII (choice E) is the vestibulocochlear nerve, responsible for hearing and equilibrium.
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7>The correct answer is D. The rule of thumb is that the plasma concentration will reach 50% in one half-life, 75% in two half-lives, 87.5% in three half-lives, etc., so that the difference between the current drug level and 100% halves with each half-life. In this instance, it takes two half-lives to reach 75%. The half-live of this drug is 6 hours, so two half-lives is 12 hours.
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8>The correct answer is E. Herpes simplex can cause a necrotizing, hemorrhagic acute encephalitis that may rapidly produce death. The encephalitis characteristically involves the lower portions of the cerebral cortex, notably the temporal lobes and the base of the frontal lobes, possibly because the infection spreads from the oropharynx.
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9>The correct answer is D. The genetic condition is Marfan syndrome, which is characterized by skeletal, ocular, and cardiovascular abnormalities. Typically, Marfan patients are tall with very long legs and tapering fingers. Laxity of joints is present, so that the thumb can be extended back to the wrist. Chest and spinal column deformities may be present as well. The most frequent cardiovascular anomalies are incompetence of the aortic valve, aortic dissection, and mitral valve prolapse ("floppy valve"). The latter may give rise to mitral regurgitation with the typical auscultatory phenomenon of a systolic click followed by a murmur. The most characteristic ocular change is ectopia lentis, i.e., dislocation of the lens. Most deaths are due to rupture of aortic dissections. The gene mutated in Marfan syndrome encodes fibrillin, a 350-kD protein that serves as scaffolding for the deposition of elastin and formation of elastic fibers. Elastin (choice C) is a 70-kD protein that constitutes the central core of elastic fibers. Abundant elastin is found in the walls of large arteries, uterus, skin, and ligaments. Although elastic fibers are disrupted by mutations of the fibrillin gene, the structure of elastin protein is intact in Marfan syndrome.
Collagen (choice A) is affected in a different set of genetic diseases, including Ehlers-Danlos syndromes and osteogenesis imperfecta.
Dystrophin (choice B) is a large transmembrane protein whose function is essential in maintaining the structural integrity of striated muscle fibers. Mutations of the dystrophin gene, located on X chromosome, are responsible for muscular dystrophy.
Mutations of the gene for myosin b-chain (choice E) account for more than one third of cases of hypertrophic cardiomyopathy, a condition characterized by hypertrophy of the left ventricle. Hypertrophic cardiomyopathy is not associated with mitral valve prolapse.
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10>The correct answer is D. The disease is poliomyelitis, which is caused by the poliovirus, a picorna virus. The virus is spread via the fecal-oral route and can then cause paralysis by infecting the alpha-motor neurons of the anterior horn of the spinal cord. Early symptoms include malaise, headache, fever, nausea, abdominal pain, and sore throat.
Bacterial and fungal infections can be spread by dirt contact with an open wound (choice A).
AIDS is an example of a disease spread by injection (choice B) or exchange of body fluids.
Malaria is an example of a disease spread by mosquitoes (choice C).
Tetanus is the classic example of disease spread by a puncture wound of the foot (choice E).
11>The correct answer is A. This is a typical presentation of an abdominal aortic aneurysm, which is almost always due to severe atherosclerosis. The foci of calcification described occur within the atherosclerotic plaques, and indicate severe atherosclerotic disease.
Congenital weakness of vessels (choice B) can produce berry aneurysms, especially in cerebral vessels in the circle of Willis.
Cystic medial necrosis (choice C) can produce dissecting aneurysms, especially in Marfan's syndrome.
Syphilitic aneurysms (choice D) typically involve the aortic root as it leaves the heart.
Vasculitis (choice E) can produce aneurysms in small arteries.
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12>The correct answer is A. This scenario is classic for "dependent" personality. Look for reliance on others, subordination of own needs, and fear of abandonment. Note that in real life, patients may show symptoms of more than one personality disorder.
Histrionic personality disorder (choice B) is characterized by theatricality, suggestibility, a strong desire for attention, and shallowness.
Obsessive-compulsive personality disorder (choice C), also called anancastic personality disorder, is characterized by obsessions, perfectionism, rigidity, and self-doubt.
Paranoid personality disorder (choice D) is characterized by suspiciousness, oversensitivity, querulousness, and an unforgiving character.
Schizoid personality disorder (choice E) is characterized by emotional coldness, solitude, and social insensitivity.
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13>The correct answer is A. The point of this question is that sometimes the obvious explanation is the correct one. Occlusion of the central retinal artery rapidly causes irreversible blindness with loss of the inner retinal layers. (The photoreceptor rod and cone cells are maintained by the pigment epithelium.) The site of occlusion is typically just posterior to the cribriform plate. A garden-variety atheroma or embolism is overwhelmingly the most common cause of central retinal artery occlusion.
Despite all of the teaching about the risk of blindness in temporal arteritis (choice B), this disorder causes only 10% of central retinal artery occlusions.
Hypertension (choice C) is more apt to cause bleeding than thrombosis.
Polycythemia vera (choice D) could (rarely) cause occlusion because of increased blood viscosity and a tendency for thrombosis.
Tumor (choice E) might also cause retinal artery thrombosis, but this would be far rarer than atheroma.
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14>B
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15>C
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16>The correct answer is A. The facial nerve and the vestibulocochlear nerve emerge from the brain stem at the cerebellopontine angle. These are the two nerves which will be initially affected by a tumor in this region.
The glossopharyngeal nerve and vagus nerve (choices B and E) emerge from the brain stem at the post-olivary sulcus. This is caudal to the cerebellopontine angle.
The optic nerve (choice C) exits from the optic chiasm on the ventral surface of the diencephalon. This is rostral to the cerebellopontine angle.
The trigeminal nerve (choice D) emerges from the brain stem at the anterolateral surface of the pons. This is rostral and ventral to the cerebellopontine angle.
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17>The correct answer is B. This patient has gout, characterized by painful joints due to the precipitation of uric acid crystals caused by excessive production of uric acid (a minority of cases are associated with underexcretion of uric acid). Kidney disease is also seen due to accumulation of uric acid in the tubules. The disease mostly affects males, and is frequently treated with allopurinol, an inhibitor of xanthine oxidase. Xanthine oxidase catalyzes the sequential oxidation of hypoxanthine to xanthine to uric acid.
A defect in urea synthesis (choice A) would result in the accumulation of ammonia.
Phenylketonuria is a disease in which tyrosine cannot be produced from phenylalanine (choice C). It is characterized by a musty body odor and mental retardation.
Defective topoisomerases (choice D) would affect DNA unwinding, and therefore replication.
Leukotrienes (choice E) are potent constrictors of smooth muscle and would more likely lead to bronchoconstriction.
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18>The correct answer is C. Any tumor "filling the 4th ventricle" blocks the circulation of cerebrospinal fluid (CSF). This blockage leads to increased intracranial pressure, which manifests with nausea, vomiting, headache, nuchal rigidity, and mental status changes. If surgery is not performed promptly, cerebellar tonsillar herniation and rapid death will ensue. In children, medulloblastoma and ependymoma are the most frequent neoplasms presenting in this manner.
There is no evidence in this case suggesting that acute hemorrhage into the 4th ventricular cavity (choice A) has occurred, nor is medulloblastoma typically associated with this complication. CNS tumors that frequently bleed are metastases from melanoma, renal cell carcinoma, and choriocarcinoma.
Alterations in medullary function (choice B) lead to cardiorespiratory instability and may be caused by direct tumor compression or infiltration of the medulla, neither of which is supported by MRI findings in this case.
Infiltration of the cerebellar vermis (choice D) is certainly seen in many cases of medulloblastoma, a tumor that arises from this midline cerebellar structure. However, this would lead to truncal ataxia and gait instability, not symptoms of increased intracranial pressure.
Medulloblastoma characteristically spreads to the subarachnoid space (choice E), from which the neoplasm may metastasize to distant sites such as spinal cord. Plaques of medulloblastoma are often found on the cerebellar surface, creating a characteristic sugar coating, but this would not cause any significant blockage of CSF circulation.
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19The correct answer is E. Maternal diabetes is best known for causing large but immature-for-age babies. There is also a specific association between maternal diabetes and transposition of the great vessels. In transposition of the great vessels, the aorta takes off from the anterior part of the right ventricle and the pulmonary trunk takes off from the posterior part of the left ventricle. This produces a complete separation of the systemic and pulmonary circulations. Without surgical correction, most affected infants die within the first months of life, although a patent ductus arteriosus, patent foramen ovale, or ventricular septal defect may allow enough mixing of blood to temporarily sustain life.
In atrial septal defect (choice A) blood can pass from one atrium to the other.
Associate coarctation of the aorta (choice B) with Turner syndrome.
Eisenmenger's syndrome (choice C) is a shift from a left-to-right shunt to a right-to-left shunt secondary to developing pulmonary hypertension.
Tetralogy of Fallot (choice D) consists of a ventricular septal defect, an overriding aorta, pulmonic stenosis, and right ventricular hypertrophy. It is the most common cause of early cyanosis.
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20The correct answer is A. This is an example of displacement. In this defense mechanism, there is a transfer of emotion from a person, object, or situation with which it is appropriately associated to another that causes less distress. Displacement is common and often destructive to other individuals, such as when a man is fired from his job and subsequently beats his wife or children. In the medical setting, the hospital staff is a frequent target of displacement when family members react to their own feelings of guilt about someone's death.
Projection (choice B) occurs when someone attributes his or her own thoughts to a different person.
Reaction formation (choice C) is the unconscious adoption of behavior opposite to one's true feelings.
Regression (choice D) is the adoption of behavior more appropriate to a younger age.
Repression (choice E) is the deeply subconscious blocking of memories or emotions.
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21The correct answer is B. This item tests your knowledge of neurocutaneous syndromes, a group of hereditary conditions characterized by concomitant neoplastic or hamartomatous lesions predominantly affecting the skin and nervous system. Subependymal giant cell astrocytoma is a peculiar astrocytic tumor that grows from the walls of the lateral ventricles. It is pathognomonic of tuberous sclerosis, which is caused by mutations of TS1 or TS2 genes. Tuberous sclerosis manifests with multiple hamartomatous lesions in the skin, CNS, and visceral organs. Cortical tubers are malformed (hamartomatous) nodules of the cortex, probably resulting from faulty cortical development. Other lesions include shagreen patches and ash-leaf spots on the skin, cardiac myomas, and renal angiomyolipomas.
Café-au-lait spots (choice A) are found in both types of neurofibromatosis. Lisch nodules (choice D) are small pigmented nodular lesions of hamartomatous nature that are present in the iris of patients with neurofibromatosis type 1. Schwannomas of the 8th cranial nerve (choice E), especially when bilateral, are typically associated with neurofibromatosis type 2.
Hemangioblastoma (choice C) is a vascular tumor of unknown histologic origin that frequently develops in the cerebellum of patients with von Hippel-Lindau syndrome. Renal cell carcinomas are also common in this disease. Von Hippel-Lindau syndrome is caused by autosomal dominant mutations of the VHL gene, a tumor suppressor gene. You may recall that mutations of VHL gene are also found in the majority of sporadic renal cell carcinomas
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22The correct answer is A. This is a typical presentation of an abdominal aortic aneurysm, which is almost always due to severe atherosclerosis. The foci of calcification described occur within the atherosclerotic plaques, and indicate severe atherosclerotic disease.
Congenital weakness of vessels (choice B) can produce berry aneurysms.
Cystic medial necrosis (choice C) can produce dissecting aneurysms (e.g., in Marfan's syndrome).
Syphilitic aneurysms (choice D) typically involve the aortic root as it leaves the heart.
Vasculitis (choice E) can produce aneurysms in small arteries.
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23The correct answer is C. The physician should obtain an emergency order of detention, regardless of her threats of a lawsuit. The woman clearly still has suicidal intent, demonstrated by her expressed verbalizations, and is therefore a danger to herself.
Choices A, B, and D clearly place her in a position where she can carry out her plans to terminate her life.
Sedating her (choice E) is the second best choice since it will prevent her from taking her life; however, sedation does not give therapists the opportunity to address the underlying motivations for her suicidal ideation.
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24The correct answer is B. Blocking antibody is generally an IgG antibody against the allergen. It is induced in the allergic patient by administering small amounts of allergen over a period of time. When the person is again exposed to the allergen, the IgG reacts with the allergen before it can reach the IgE-coated mast cell.
Antihistamines (choice A) would block histamine receptors but would not react with the allergen before it could reach the IgE-coated mast cell.
Cromolyn sodium (choice C) is a drug that stabilizes mast cell membranes, thus inhibiting degranulation, but would have no effect on allergen binding to IgE on mast cells.
Epinephrine (choice D) is the mainstay of therapy in severe cases of immediate hypersensitivity (anaphylaxis). It increases intracellular cyclic AMP, thus decreasing mast cell degranulation, and causes smooth muscle dilation in the airways. Epinephrine would have no effect on the binding of the allergen to IgE on mast cells.
Cyclic AMP is degraded in cells by the enzyme phosphodiesterase. Theophylline (choice E) inhibits this enzyme, thereby increasing mast cell cyclic AMP levels and making degranulation less likely without affecting the binding of the allergen to IgE on mast cells.
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25The correct answer is E. At this level, the lateral portion of the dorsal columns (funiculus) is comprised of the fasciculus cuneatus. Axons carrying tactile, proprioceptive, and vibratory information from the ipsilateral arm enter the spinal cord via the dorsal root, ascend the cord in the fasciculus cuneatus, and synapse in the nucleus cuneatus of the caudal medulla. Secondary neurons from this nucleus give rise to internal arcuate fibers, which decussate and ascend to the thalamus (ventral posterolateral nucleus, VPL) as the medial lemniscus. Tertiary neurons from the VPL project to the ipsilateral somatosensory cortex. Therefore, damage to the fasciculus cuneatus would result in a deficit in tactile, proprioceptive, and vibratory sense in the ipsilateral arm, because the fibers that carry this information do not cross until they reach the medulla.
Fine motor control of the fingers (choice A) would be carried principally by the ipsilateral lateral corticospinal tract in the lateral funiculus of the cord.
Motor control of the contralateral foot (choice B) is carried by the ipsilateral corticospinal tract in the lateral funiculus of the cord.
Hemianhidrosis (lack of sweating) over half of the face (choice C) could be produced by interruption of sympathetic innervation to the face. The hypothalamospinal tract projects from the hypothalamus to the intermediolateral cell column at levels T-1 to T-2. It descends in the lateral funiculus of the cord. Interruption of this tract results in Horner's syndrome (miosis, ptosis, hemianhidrosis).
Proprioception from the ipsilateral leg (choice D) is carried by the fasciculus gracilis in the medial part of the dorsal columns.
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26The correct answer is A. While it is hard to develop a deficiency in oil-soluble vitamins (A, D, E, K) because the liver stores these substances, deficiency states can be seen in chronic malnutrition (specifically chronic fat deprivation) and chronic malabsorption. Vitamin A is necessary for formation of retinal pigments (deficiency can cause night blindness) and for appropriate differentiation of epithelial tissues (including hair follicles, mucous membranes, skin, bone, and adrenal cortex).
Vitamin C (choice B), which is water soluble rather than oil soluble, is necessary for collagen synthesis.
Vitamin D (choice C) is important in calcium absorption and metabolism.
Vitamin E (choice D) is a lipid antioxidant that is important in the stabilization of cell membranes.
Vitamin K (choice E) is necessary for normal blood coagulation.
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27The correct answer is C. The most likely diagnosis is an intracranial meningioma. Meningiomas are slow-growing, benign tumors comprising 15% of intracranial tumors; they are most common in the elderly. They originate from either dura mater or arachnoid and are sharply demarcated from brain tissue. Meningiomas often incite an osteoblastic reaction in the overlying cranial bones. Microscopically, the meningioma cells have a tendency to encircle one another, forming whorls and psammoma bodies. Clinically, they present as mass lesions; seizures may occur. The superior parasagittal surface of the frontal lobes is a favorite site of origin. This can often produce leg weakness, since the leg motor fibers that pass down through the internal capsule originate in parasagittal cortical regions. Treatment of meningiomas is usually surgical.
Arachnoid cysts (choice A) are formed by splitting of the arachnoid membrane; most arachnoid cysts arise near the Sylvian fissure. They may present with mass effect, but would be unlikely to produce seizures, prominent focal signs, or reactive hyperostosis.
Glioblastoma multiforme (choice B) is an aggressive malignant astrocytoma that would likely have killed the patient long before 5 years had elapsed.
Metastatic breast cancer (choice D) would generally look different microscopically (the whorling cell pattern is characteristic of meningioma). It would be unlikely for metastatic cancer to cause a reaction in the overlying bone, or to be present long enough to cause symptoms for 5 years.
Oligodendrogliomas (choice E) are glial tumors that could produce the described clinical picture, but usually do not cause hyperostosis of the calvarium or exhibit the characteristic whorling cell pattern microscopically
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28The correct answer is D. The two most common causes of aortic dissection are hypertension and atherosclerosis. An important distinction between the two is that hypertensive dissections generally originate in the ascending aorta, at an intimal surface free of atherosclerosis.
Dissection secondary to atherosclerosis is typically the consequence of a ruptured aortic aneurysm, which originates in the abdominal aorta at the iliac bifurcation. Dissections due to both hypertension and atherosclerosis generally course through the wall within the media (choice B). They both can involve the entire length of the aorta, and may rupture anywhere along its course (choices A and C). Well recognized sequelae of dissections include rupture through the adventitia, compromise of major arterial branches or the aortic valve, cardiac tamponade, and rapid exsanguination (choice E).
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29The correct answer is D. Although rare now because of advances in treatment, syphilitic aortitis and aneurysm are still seen, especially in underserved populations. This complication generally occurs 10 to 40 years after initial infection. The vasa vasorum of the aorta undergoes obliterative endarteritis, leading to atrophy of the muscularis and elastic tissues of the aorta and dilatation. Linear calcifications are often seen in the ascending aorta by x-ray. The intimal wrinkling or "tree barking" is also a common feature. Syphilitic aneurysm can be associated with respiratory distress, cough, congestive heart failure and rarely, rupture.
Atherosclerosis (choice A) is the most common cause of aortic aneurysms. These are most often located in the abdominal aorta, distal to the renal arteries. Intimal wrinkling and linear calcifications are not seen.
Hypertension (choice B) is usually responsible for dissecting aneurysms located within 10 cm of the aortic valve. Patients present with sudden chest pain, which is usually severe and tearing in nature. The chronic hypertension causes a cystic medial necrosis, allowing the separation of vessel layers.
Marfan's syndrome, an autosomal dominant connective tissue disorder (choice C) is also associated with dissecting aneurysms, usually of the ascending aorta. The patients are often very tall with arachnodactyly and ligamentous laxity. Their life-span is generally shortened. This patient's description and age are not consistent with this diagnosis.
Takayasu's arter itis (choice E) is a syndrome characterized by ocular disturbances and weak pulses in the arms. It occurs most frequently in young females. It is considered a giant cell arteritis, and does not cause aneurysms.
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30The correct answer is E. The disease is progressive supranuclear palsy, a degenerative disorder characterized by ophthalmoplegia, pseudobulbar palsy, axial dystonia, and bradykinesia. The presentation described in the question is typical. The pathologic changes consist of widespread neuronal loss and gliosis in subcortical sites with sparing of the cerebral and cerebellar cortices.
Pigmented neurons in the substantia nigra (pars compacta) and locus ceruleus (choice A) selectively degenerate in Parkinson's disease.
In Alzheimer's disease, there is diffuse cortical atrophy (choice B), especially over the association cortex of frontal, temporal, and parietal lobes, with relative sparing of primary sensory and motor areas.
Selective frontal and temporal lobe atrophy (choice C) is characteristic of Pick's disease.
The caudate nucleus and putamen undergo severe atrophy (choice D) in Huntington's disease. Cortical atrophy occurs to a lesser extent.
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31The correct answer is B. Collagen formation begins with transcription of mRNA from appropriate DNA genes in the nucleus. While still within the nucleus, the mRNA is spliced. It is then transported through the cytoplasm to the ribosomes on the rough endoplasmic reticulum. Individual chains are translated on the ribosomes, with the ends feeding into the endoplasmic reticulum lumen. Within the lumen, glycosylation of the individual chains occurs. The material then moves toward the Golgi bodies (whose lumens are connected to the endoplasmic reticulum) where the triple helices of procollagen form. The procollagen is then secreted into the extracellular space, where cleavage of pro-peptides and cross- linking of different triple helices occurs, maturing the collagen.
The extracellular space (choice A) is the site of procollagen cleavage and cross- linking.
The nucleus (choice C) is the site of mRNA transcription and splicing.
The rough endoplasmic reticulum (choice D) is the site of chain translation and glycosylation.
The smooth endoplasmic reticulum (choice E) does not participate in collagen synthesis
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32The correct answer is A. The uncus, which is the medial protrusion of the parahippocampal gyrus, is an external structure seen on the ventral surface of the temporal lobe. The amygdala is a collection of nuclei that lies directly beneath the uncus.
The caudate nucleus (choice B) is a deep nuclear structure that lies lateral to the lateral ventricles.
The claustrum (choice C) is a thin and elongated nucleus that lies just medial to the insular cortex.
The hippocampus (choice D) is a nuclear structure that lies in the interior of the parahippocampal gyrus.
The putamen (choice E) is a nuclear structure that resides lateral to the caudate, and medial to the claustrum.
The thalamus (choice F) is a deep nuclear structure, caudal to the caudate nucleus.
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33The correct answer is A. A third heart sound (S3) is a low-pitched sound occurring at the termination of rapid filling. In patients over 40 years of age, the appearance of a third heart sound strongly suggests congestive heart failure. It also occurs in patients with atrioventricular valve incompetence and can be a normal finding in some young athletes.
A fourth heart sound (S4; choice B) can be a normal finding in some older patients who do not have congestive heart failure.
Ascites (choice C) can also occur in patients with renal, hepatic, or local conditions not associated with cardiac factors.
Both orthopnea (choice D) and pulmonary rales (choice E) often occur secondary to heart failure, however, they both are associated with noncardiac disorders as well.
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34The correct answer is A. Several immunodeficiency disorders have X-linked genetics, including Bruton's agammaglobulinemia, Wiskott-Aldrich syndrome, and some cases of severe combined immunodeficiency diseases. Bruton's agammaglobulinemia is characterized by recurrent respiratory infections caused by pyogenic organisms.
Common variable immunodeficiency (choice B) is a relatively common, but probably heterogeneous, group of acquired and familial diseases. It is distinct from X-linked (Bruton's) agammaglobulinemia.
DiGeorge syndrome (choice C) is due to a developmental malformation of the third and fourth pharyngeal pouches leading to failure of the thymus, and sometimes the parathyroids, to develop. Defective cellular immunity and abnormalities of calcium metabolism are typical.
Hereditary angioedema (choice D) is a usually recessive genetic disease caused by deficiency of C1 esterase inhibitor.
Isolated IgA deficiency (choice E) can be acquired or genetic, but is not usually X-linked.
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35>The correct answer is E. The capacity for cooperative play generally does not begin much before the age of 4. Prior to this time (24-30 months), children may play in a parallel fashion, but without real interaction.
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36>The correct answer is C. Anticipation is a phenomenon in which the phenotype of a disease worsens over successive generations. This has been observed in families affected by a hereditary disorder because of an expansion of unstable sequences of nucleotide repeats (triplet repeat expansion). Clinical features worsen with each successive generation as the number of triplet repeats increases. Huntington disease is caused by expansion of an unstable CAG repeat in a gene encoding a protein called huntingtin, of unknown function. All the unstable triplet-repeat disorders identified so far are associated with neurodegenerative conditions. Other examples are fragile X syndrome, myotonic dystrophy, and Friedreich ataxia.
FAD (choice A) comprises 5% to 10% of all cases of Alzheimer disease and is due to autosomal dominant mutations of three different genes: amyloid precursor protein (APP) gene, presenilin-1 gene, and presenilin-2 gene. The e4 allele of the gene encoding apolipoprotein E increases the risk for FAD. Unstable repeat expansion is not a cause of FAD.
The great majority of cases of ALS (choice B)are sporadic. A small subset of familial ALS is caused by mutations in the gene coding for superoxide dismutase on chromosome 21.
Pick disease (choice D) and progressive supranuclear palsy (choice E) are usually sporadic. The genetic alterations of the very few familial cases reported have not been elucidated.
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38>The correct answer is E. Terfenadine is the only drug listed that does not cross the blood-brain barrier and therefore does not cause sedation (a bad thing for someone flying an airplane). Other drugs from the same class (piperidines) include astemizole and loratadine.
All of the other choices have some degree of sedation as a side effect and therefore would not be recommended for someone who is flying an airplane or operating any kind of machinery.
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39>The correct answer is D. Deficiency of vitamin K produces a clotting disorder characterized by an elevated prothrombin time and easy bleeding, particularly in neonates (hemorrhagic disease of the newborn). The biochemical basis for this hemorrhagic tendency is that glutamate residues on Factors II (Thrombin), VII, IX, and X must be converted to gamma-carboxyglutamate residues (in a vitamin K-requiring reaction) for optimal activity.
The conversion of homocysteine to methionine (choice A) requires vitamin B1.
Conversion of methylmalonyl CoA to succinyl CoA (choice B) requires vitamin B12.
Degradation of cystathionine (choice C) requires vitamin B6.
Hydroxylation of proline (choice E) requires vitamin C. Vitamin C deficiency can cause easy bruising, but will not prolong the prothrombin time.
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40>The correct answer is D. Massive dilation of the aortic root with an absence of atherosclerotic vessel lesions strongly suggests a syphilitic aneurysm. These aneurysms are a manifestation of tertiary syphilis and have become very uncommon now, probably due to a combination of deliberate therapy and therapy of undiagnosed disease when antibiotics are given for some other condition. The histologic hallmark of the syphilitic aneurysm is a plasma cell lesion of the small blood vessels (the vasa vasorum) that supply the aorta, and eventually obliterate the small vessel lumina.
Choice A is a feature of Churg-Strauss syndrome, which is a variant of polyarteritis nodosa that involves vessels smaller than the aorta.
Choice B is a feature of polyarteritis nodosa, which involves vessels smaller than the aorta.
Choice C is a feature of cystic medial necrosis, which can cause aortic dissection.
Choice E is a feature of M?nckeberg's arteriosclerosis, which involves vessels smaller than the aorta.
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41>The correct answer is D. The patient is not eating well, as mentioned by her parents, and her weight loss (over 15% of baseline), as well as her school performance and activity level, is consistent with anorexia nervosa. Metatarsal stress fracture is a complication of rigorous prolonged walking or running in this population. While she is malnourished and underweight, she has poor insight and continues to decrease her input and increase her output with prolonged physical activity. The fracture is a complication of increased output beyond the patient's physical limitation.
Conversion disorder (choice A) is manifested by chronic neurologic pain or deficit without any objective organic cause. This patient's chief complaint is acute pain without any sign of another neurologic deficit.
Diffuse muscle and joint aches, in conjunction with lack of energy and reduced physical activity, is characteristic of depression (choice B). This patient's pain is localized and she is very active.
Ruptured or injured tendon of the ankle is a common injury, but the patient does not recall any recent injury, and localization of the pain is not consistent with medial ankle injury (choice C).
The girl's daily walking in the nearby forest raises suspicion for tick bite (choice E)and Lyme disease with secondary joint pain. Arthritis associated with Lyme disease is generally centered around joints, and does not present as acutely as in this patient.
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42>The correct answer is C. APGAR is an acronym for appearance, pulse, grimace, activity, and respiration; the APGAR score is taken at 1 minute and 5 minutes after birth. On each parameter, a maximum score of 2 is possible. In this case, one point was taken off for cyanosis of the hands and feet; one point was taken off for irregular respirations. The neonate received the maximum score of 2 for all of the other parameters, leading to an APGAR of 8.
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43>The correct answer is B. This question requires two logical steps: first, you need to appreciate that the hydrophilic amino acids are more likely to appear on the surface of a protein molecule, while hydrophobic amino acids are most likely be found in its interior. Next, you need to figure out which of the amino acids listed is hydrophilic. If you recall that arginine is a basic amino acid that is positively charged at physiologic pH, you should be able to answer this question right away.
All of the other choices have neutral side chains and are uncharged at physiologic pH. They would most likely be found in the hydrophobic core of the protein structure. Alanine (choice A), isoleucine (choice C), and leucine (choice D) all have aliphatic side chains; phenylalanine (choice E) and tryptophan (choice F) have aromatic side chains.
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44>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 superior petrosal sinus (choice D) 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.
The straight sinus (choice E) 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
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45.The correct answer is E. The baby is probably a victim of sudden infant death syndrome (SIDS). The etiology remains unknown. Rare cases have been witnessed, and some of the SIDS babies give a single small cry, as described in the question stem. Some of these babies were premature at birth and some have upper respiratory infections in the preceding few days before death. Findings at autopsy are subtle and may be absent. The cardiovascular system may show right ventricular hypertrophy, which is possibly secondary to smooth muscle hypertrophy in small pulmonary arteries, and possibly cardiac conduction system abnormalities. Other features include brainstem gliosis (suggesting chronic hypoxia), extramedullary hematopoiesis, and retained periadrenal brown fat.
A baby with endocarditis (choice A) would be very obviously ill.
A serious congenital heart defect, such as failure of development of the endocardial cushion (choice B), large interventricular septal defect (choice C), or a mitral value stenosis (choice D) would have been picked up in the comprehensive physical examination at the child's birth.
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46>The correct answer is C. Patients with AIDS develop a number of neurologic complications, including opportunistic infections, lymphomas, polyneuropathies, and a form of subacute encephalitis. HIV gains access to the CNS through incoming macrophages and may cause a subacute inflammation of the brain parenchyma known as HIV encephalitis. Typical clinical manifestations and histopathologic features of HIV encephalitis are mentioned in the clinical case. The presence of multinucleated giant cells should be emphasized since this is typical of HIV encephalitis. All the other histologic features can be seen in any other form of viral encephalitis.
Aspergillosis (choice A) is an opportunistic infection caused by Aspergillus species, a ubiquitous fungus found in the environment. Aspergillosis is frequent not only in AIDS, but in many immunocompromised patients. Aspergillus has a specific tropism for blood vessels, causing damage to vessel walls and producing hemorrhagic infarcts in the brain and other organs. The MRI and histopathologic findings rule out Aspergillus infection as the cause of this patient's neurologic condition.
CMV encephalitis (choice B) is a frequent opportunistic infection affecting AIDS patients. CMV's tropism for epithelial and ependymal cells explains why this virus is found in ependymal and periventricular locations. Typical cytomegalic cells, which contain large purple intranuclear inclusions and granular cytoplasmic inclusions, represent important clues to the diagnosis. The accompanying tissue reaction is similar to that of any viral infection of the brain: lymphocytic infiltration (perivascular cuffing), microglial nodules, and neuronophagia (degenerating neurons surrounded by lymphocytes).
Mycobacterial infections (choice D), including infections by Mycobacterium tuberculosis and Mycobacterium avium-intracellulare complex, frequently affect AIDS patients. Because of the AIDS epidemic and the emergence of multidrug resistance, the incidence of mycobacterial infections has been increasing in the U.S. Mycobacteria can cause a chronic meningoencephalitis involving the basal surface of the brain or a tuberculoma (a circumscribed lesion consisting of confluent caseating granulomas). Acid-fast bacilli can be demonstrated in these lesions.
Vacuolar myelopathy (choice E) is a noninfectious complication of obscure pathogenesis involving the spinal cord. It is very similar to subacute combined degeneration pathologically. Vacuolar myelopathy, like subacute combined degeneration, may be related to vitamin B12 deficiency. In this condition, ascending (sensory) tracts in the posterior columns and descending (pyramidal-motor) tracts in the lateral columns degenerate, leading to sensory loss, ataxia, and spastic paraplegia.
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47>The correct answer is A. Glucose-6-phosphate dehydrogenase (G6PD) deficiency (choice A) is an X-linked recessive disorder that affects the pentose phosphate pathway. The hallmark of X-linked recessive inheritance is an abundance of affected males and an absence of affected females. Males are hemizygous for the X chromosome, so the phenotype is expressed with only one dose of the gene. Females have two copies of the X chromosome, so they appear phenotypically normal although they may carry the recessive allele. Since a male inherits his X chromosome from his mother, if he is affected, she must carry the trait. Other X-linked recessives include Lesch-Nyhan disease, hemophilia A, and Duchenne's muscular dystrophy.
Leber's hereditary optic neuropathy (choice B) is a relatively common cause of acute or subacute vision loss, especially in young men. It exhibits a mitochondrial inheritance pattern. The hallmark of this pattern is matrilineal inheritance. All of the children of an affected woman will be affected since they receive mitochondrial genes only from the female parent. Affected males do not contribute mitochondria to progeny, so their children will not receive the trait.
Neurofibromatosis (choice C) shows an autosomal dominant inheritance pattern, so the phenotype will be expressed if the allele is present in one dose. Deleterious autosomal dominants occur at very low frequencies, so affected individuals are almost always heterozygous for the trait. Since the gene is located on an autosome, both male and female progeny can be affected. Other autosomal dominants include Ehlers-Danlos syndrome, Huntington's disease, and osteogenesis imperfecta.
Sickle cell anemia (choice D) and Tay Sachs disease (choice E) are both inherited as autosomal recessives. For the phenotype of the autosomal recessive to be expressed, the recessive allele must be present in two doses. Both male and female children can be affected. The hallmark feature is that unaffected parents have affected children of both sexes.
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48>The correct answer is B. Brain herniation can occur either with generalized increased intracranial pressure or as a consequence of a mass lesion of the cranium. Subfalcine herniation occurs when part of one cerebral hemisphere herniates under the falx membrane, which separates the two cerebral hemispheres along the midline of the skull. The gyrus most affected is the cingulate gyrus, which runs along the medial aspect of the cerebral hemisphere, just above the corpus callosum.
The cerebellar tonsils (choice A) can herniate into the foramen magnum, in a tonsillar herniation. The medulla (choice D) can be compressed by the herniating cerebellar tonsils, producing damage to this structure.
The medial temporal lobe (choice C) can be damaged in uncal herniation.
The midbrain (choice E) can be damaged in the course of a uncal herniation.
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49>The correct answer is D. The tip off for oligodendroglioma is "fried egg" cells, which are tumor cells with round nuclei (the "yolk") and cleared cytoplasm (the "white"). These tumors may contain areas of calcification, hemorrhage, or cysts. They tend to occur in the cerebral hemispheres of middle-aged patients of both sexes, and have a better prognosis (average survival 5 years) than astrocytomas.
The usual tip-off for choroid plexus papilloma (choice A) is a papillary growth in a ventricle.
The usual tip-offs for ependymoma (choice B) are pseudorosettes and structures resembling ependymal canals.
The usual tip-offs for glioblastoma multiforme (choice C) are extreme pleomorphism, necrosis, and hemorrhage.
The usual tip-offs for pilocytic astrocytoma (choice E) are bipolar cells, and location in the cerebellum of young children.
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50>The correct answer is B. The ear has a complex sensory nerve supply, which includes all of the nerves listed. A consequence of this complexity is that pain actually originating in other sites (teeth and sinuses are notorious) may be misinterpreted as ear pain or (less commonly) pain originating in the ear may be misinterpreted as arising from other sites. The anterior half of the external ear canal is supplied by the auriculotemporal nerve, which also supplies the facial surface of the upper part of the auricle.
The auricular branch of the vagus (choice A) supplies the posterior half of the external ear canal.
The greater auricular nerve (choice C) supplies both surfaces of the lower part of the auricle.
The lesser occipital nerve (choice D) supplies the cranial surface of the upper part of the auricle.
The vestibulocochlear nerve (choice E) supplies hearing and motion sense. |
