USMLE step 1 :20-22:Answers

Question Number 20

Correct Answer: D

Explanation:
While the above the above clinical features are suggestive of systemic lupus the presence of positive antinuclear antibody (ANA) in the absence of a better diagnosis often represents the most practical way to make a clinical diagnosis. In patients with signs of nephritis (e.g. edema, oliguria, hypertension, dysmorphic RBCs/RBC casts, or significant proteinuria) a prompt evaluation of renal function is indicated. This should include electrolytes, throat culture, antistreptococcal antibodies, complement studies (C3 /C4 ), and anti-nuclear antibodies (ANA). Further evaluation and treatment depend on the results of these studies. Features of systemic lupus include Malar (butterfly) rash Discoid rash Photosensitivity Oral/nasopharyngeal ulcers Nonerosive arthritis Pleuritis pericarditis Renal disorder - proteinuria or cylindruria Neurologic disorder - psychosis or seizures Hematologic disorder - hemolytic anemia, leukopenia (less than 4,000), lymphopenia (less than 1,500), thrombocytopenia (less than 100,000) Immunologic disorder Positive antinuclear antibody (ANA) in absence of drugs known to cause positive ANA

 

 

Question Number 21

Correct Answer: D

Explanation:
The hypoglossal nerve is the main motor nerve to the tongue. The palatoglossus muscle, however, is supplied by the pharyngeal plexus of nerves, the motor branch of which is the pharyngeal branch of the vagus. Unilateral injury to the nucleus results in atrophy and paralysis of the muscles of half of the tongue. When the tongue is protruded, it deviates toward the paralyzed side, and while protruded, movement toward the normal side is absent. The nerve passes through the anterior condyloid foramen (the the hypoglossal canal which lies just medial to the jugular foramen) after it emerges from the medulla oblongata between the pyramid and olive.

 

Question Number 22

Correct Answer: B

Explanation:
The long thoracic nerve arises from the fifth, sixth, and seventh cervical roots. It is the motor nerve to the serratus anterior muscle.Lesions of the long thoracic nerve are most common in men who do heavy labor. The nerve may be injured by continued muscular effort with the arm extended or by carrying heavy sharp-cornered objects on the shoulder. Injury of the nerve following acute or chronic trauma is characterized by weakness in elevation of the arm above the horizontal plane. Winging of the scapula is a constant sign when the arm is fully abducted or elevated anteriorly. Winging is usually absent when the arm is held at the side.