LECTURIO USMLE |STEP 1


Гео и язык канала: Весь мир, Английский


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Гео и язык канала
Весь мир, Английский
Статистика
Фильтр публикаций


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Educational objective: Tay-Sachs disease is an autosomal recessive disorder caused by [3-hexosaminidase A deficiency, which results in GM2 ganglioside accumulation. Key clinical features include progressive neurodegeneration and a cherry-red macular spot. In contrast to patients with Niemann-Pick disease, those with Tay Sachs disease have no hepatosplenomegaly.


Accumulation of which of the following metabolites is most likely present in this patient's tissues?
Опрос
  •   A. Galactocerebroside
  •   B. Globotriaosylceramide
  •   C. Glucocerebroside
  •   D.Glycogen
  •   E. GM2 ganglioside
  •   F. Heparan sulfate
  •   G .Sphingomyelin
484 голосов


An 8-month-old girl is brought to the office for evaluation of irritability and regression of motor skills. Her birth was unremarkable and she appeared to develop normally, but she can no longer sit or roll over. Her parents have also noticed that she startles easily with loud noises. Head circumference measurement is consistent with macrocephaly. Bilateral funduscopic evaluation shows a bright red fovea centralis that is surrounded by a contrasting white macula. Peripheral vision is decreased. Abdominal examination is normal.


Educational objective: Neisseria meningitidis can cause sepsis and circulatory collapse in previously healthy young individuals. Lipooligosaccharide, a virulence factor in the pathogens outer membrane, is the major underlying cause of disease severity.


Which of the following microbial components is directly responsible for the severity of disease in this patient?
Опрос
  •   A. Capsular polysaccharide
  •   B. lmmunoglobulin protease
  •   C. Lipo-oligosaccharide
  •   D.Lipoteichoic acid
  •   E. Superantigen exotoxin
323 голосов


A 16-year-old girl is brought to the emergency department after she became unresponsive. Temperature is 39.7 C (103.5 F), blood pressure is 70/40 mm Hg, and pulse is 130/min and thready. There is a diffuse petechial and ecchymotic skin rash. Laboratory testing reveals leukocytosis with left shift and evidence of disseminated intravascular coagulation and multiorgan failure. Despite aggressive interventions, the patient dies several hours after admission. Autopsy reveals hemorrhagic necrosis of many internal organs, including the bilateral adrenal glands.


Educational objective: Amyotrophic lateral sclerosis (ALS) causes both upper and lower motor neuron lesions. Loss of neurons of the anterior horns of the spinal cord (LMN lesion) causes muscle weakness and atrophy. Demyelination of the lateral corticospinal tract (UMN lesion) leads to spasticity and hyperretlexia.


The patient most likely suffered from which of the following?
Опрос
  •   A. Amyotrophic lateral sclerosis
  •   B. Poliomyelitis
  •   C.Rabies
  •   D.Huntington disease
  •   E. Friedreich ataxia
  •   F. Vitamin 812 deficiency
332 голосов


A Caucasian male who suffers from a severe neurological disease dies of an overwhelming respiratory infection. Autopsy shows an atrophic precentral gyrus and thin anterior roots of the spinal cord. Light microscopy reveals a severe loss of neurons in the anterior horn of the spinal cord and in the hypoglossal and ambiguous cranial nerve nuclei; corticospinal tracts stain only faintly, indicating demyelinization.


Educational objective: Critical illness can lead to weakness due to both myopathy (eg, atrophy of muscles) and polyneuropathy (eg, axonal degeneration, decreased nerve excitability). This can lead to both extremity weakness and difficulty breathing due to chest wall weakness.


Which of the following is the most likely cause of this patient's current condition?
Опрос
  •   A. Corticospinal tract demyelination
  •   B. Motor cortex ischemic injury
  •   C.Motor endplate receptor loss
  •   D.Myofiber lymphocytic inflammation
  •   E. Peripheral nerve axonal degeneration
200 голосов


A 62-year-old hospitalized woman is evaluated for muscle weakness. The patient was admitted 2 weeks ago due to septic shock from acute pyelonephritis. She was treated in the intensive care unit with intravenous fluids, vasopressors, and broad-spectrum antibiotics. The patient was also mechanically ventilated due to respiratory failure. Her hemodynamic status and infection gradually improved, but she has had difficulty being taken off the ventilator due to respiratory muscle weakness. She is also noted to have significant extremity weakness. Physical examination shows diffuse mild atrophy of the extremity muscles. Bilateral upper and lower extremity deep tendon reflexes are decreased.


Educational objective: The posterior cerebral artery branches off the basilar artery and supplies cranial nerves Ill and IV and other structures in the midbrain.
It also supplies the thalamus, medial temporal lobe, splenium of the corpus
callosum, and occipital lobe. The most common finding with posterior cerebral artery stroke is contralateral homonymous hemianopia, often with macular sparing.


Which of the following cerebral arteries is most likely to be compromised in this patient?
Опрос
  •   A. Anterior cerebral artery
  •   B.Anterior choroidal artery
  •   C.Artery of Percheron
  •   D.Basilar artery
  •   E. Middle cerebral artery
  •   F. Posterior cerebral artery
230 голосов


A 70-year-old right-handed woman comes to the emergency department with left-sided visual loss that she noticed on awakening in the morning. She has no headache, slurred speech, difficulty swallowing, weakness, or difficulty walking. Her other medical problems include hypertension, atrial fibrillation, and hyperlipidemia. Blood pressure is 170/102 mm Hg and pulse is 90/min and irregular. On neurologic examination, she is alert and oriented to person, place, and time. Her speech is fluent, and she follows complex commands. Examination of her visual fields shows left homonymous hemianopia with macular sparing. There is decreased sensation over the left side of her body. The remainder of the neurologic examination is within normal limits. Non-contrast head CT demonstrates an area of focal parenchymal hypoattenuation, as shown in the image below.


Educational objective: In addition to unilateral facial paralysis, patients with Bell's palsy may experience decreased tearing, hyperacusis, and/or loss of taste sensation over the anterior two-thirds of the tongue.


Which of the following additional findings is most likely associated with this patient's condition?
Опрос
  •   A. Attenuated sense of touch on the right side of face
  •   B. Decreased tearing from the right eye
  •   C.Failure to elevate the palate when saying "ah"
  •   D.lnability to sweat on the right side of face
  •   E. Loss of taste sensation from the posterior 1 /3 of the tongue
164 голосов


A 51-year-old woman comes to the physician complaining that the right side of her face has felt "funny" for the past 12 hours. Her past medical history is significant for type 2 diabetes mellitus. Physical examination reveals asymmetry of her face when she smiles, puffs out her cheeks, and closes her eyes tightly. There is also effacement of the right nasolabial fold, and her mouth is drawn toward the left side.

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