COMLEX Level 1 Form 110 EXAM FOR COMSAE Exam
Questions and Correct Answers
Q1. A 54-year-old man presents with a hoarse voice and difficulty swallowing after a
thyroidectomy. Laryngoscopy reveals paralysis of the left vocal cord. Which structure was most
likely injured? A) Right recurrent laryngeal nerve B) Left recurrent laryngeal nerve C) Left
superior laryngeal nerve D) Glossopharyngeal nerve
Ans: B. Rationale: The left recurrent laryngeal nerve loops under the aortic arch and ascends in
the tracheoesophageal groove, making it highly susceptible to injury during thyroid surgery. It
innervates all intrinsic muscles of the larynx except the cricothyroid.
Q2. A patient presents with a "winged" scapula and inability to abduct the arm past 90 degrees.
Which nerve is damaged? A) Axillary B) Long thoracic C) Thoracodorsal D) Dorsal scapular
Ans: B. Rationale: The long thoracic nerve (C5-C7) innervates the serratus anterior, which
holds the scapula against the thoracic wall and upwardly rotates it to allow abduction >90
degrees. Injury causes medial scapular winging.
Q3. A newborn presents with an arm hanging by the side, internally rotated, with the forearm
extended and pronated. This is caused by damage to which nerve roots? A) C3-C4 B) C5-C6 C)
C7-C8 D) C8-T1
Ans: B. Rationale: Erb-Duchenne palsy (waiter's tip) results from upper trunk (C5-C6) injury,
often due to excessive lateral displacement of the neck during birth. It paralyzes the deltoid,
supraspinatus, infraspinatus, and biceps brachii.
Q4. A patient catches their hand in a closing car door and subsequently loses the ability to
adduct the fingers and flex the wrist. Which nerve is injured? A) Median B) Ulnar C) Radial D)
Musculocutaneous
Ans: B. Rationale: The ulnar nerve (C8-T1) innervates the intrinsic hand muscles
(adduction/abduction) and the flexor carpi ulnaris. Injury at the wrist or elbow causes these
deficits.
Q5. A 60-year-old woman experiences tingling in the lateral 3.5 digits and thenar atrophy. Which
structure is compressed? A) Ulnar nerve at Guyon's canal B) Median nerve at the carpal tunnel
C) Radial nerve in the spiral groove D) Median nerve at the ligament of Struthers
Ans: B. Rationale: Carpal tunnel syndrome involves compression of the median nerve under
the flexor retinaculum, causing sensory loss over the lateral 3.5 digits and motor weakness of
the LOAF muscles (Lumbricals 1-2, Opponens pollicis, Abductor pollicis brevis, Flexor pollicis
brevis).
,Q6. A 72-year-old woman falls on her hip. Her leg is shortened and externally rotated. Which
artery is most at risk of avascular necrosis if the femoral neck is fractured? A) Obturator artery
B) Medial circumflex femoral artery C) Lateral circumflex femoral artery D) Inferior gluteal artery
Ans: B. Rationale: The medial circumflex femoral artery provides the primary blood supply to
the femoral head. Intracapsular femoral neck fractures can tear this vessel, leading to avascular
necrosis.
Q7. A patient presents with foot drop and loss of sensation over the dorsum of the foot after a
fibular neck fracture. Which nerve is injured? A) Tibial B) Common fibular (peroneal) C) Sural D)
Deep fibular
Ans: B. Rationale: The common fibular nerve wraps around the fibular neck. Injury causes
paralysis of the anterior and lateral compartment muscles, resulting in foot drop (loss of
dorsiflexion and eversion) and sensory loss over the lateral leg and dorsum of the foot.
Q8. A 2-year-old boy has a cleft palate and recurrent respiratory infections. Which
embryological structure failed to fuse? A) Maxillary prominences B) Lateral palatine processes,
nasal septum, and median palatine process C) Mandibular prominences D) Frontonasal
prominence
Ans: B. Rationale: The secondary palate forms from the fusion of the lateral palatine processes
(maxillary prominences) with each other and with the nasal septum (frontonasal prominence)
during weeks 7-9.
Q9. During a vagal-sparing esophagectomy, the surgeon must identify the esophageal hiatus.
Which structure passes through the T10 opening of the diaphragm? A) Aorta B) Inferior vena
cava C) Esophagus and vagal trunks D) Thoracic duct
Ans: C. Rationale: "I ate (8) 10 eggs at 12". IVC at T8, Esophagus/Vagus at T10, Aorta/Thoracic
duct/Azygos at T12.
Q10. A patient with severe angina is found to have an occlusion of the artery that supplies the
SA node in 60% of the population. Which artery is occluded? A) Left anterior descending B)
Right coronary artery C) Circumflex artery D) Posterior descending artery
Ans: B. Rationale: The Right Coronary Artery (RCA) supplies the SA node in ~60% of people
(right-dominant or co-dominant) and the AV node in ~80% of people.
Q11. A patient presents with loss of pain and temperature on the right side of the body and loss
of pain and temperature on the left side of the face. Where is the lesion? A) Right medulla B)
Left medulla C) Right pons D) Left midbrain
,Ans: A. Rationale: Wallenberg syndrome (lateral medullary syndrome) on the right causes
ipsilateral (right) facial sensory loss (spinal trigeminal nucleus) and contralateral (left) body
sensory loss (spinothalamic tract, which has already crossed in the spinal cord).
Q12. A patient cannot dorsiflex the foot or evert the ankle, but can invert the foot. Which nerve
is intact? A) Deep fibular B) Superficial fibular C) Tibial D) Sural
Ans: C. Rationale: The tibial nerve innervates the posterior compartment (plantarflexion,
inversion). The common fibular nerve innervates the anterior (dorsiflexion) and lateral
(eversion) compartments.
Q13. A 30-year-old man suffers a stab wound to the posterior axillary fold. He later cannot
extend his wrist. Which nerve was damaged? A) Axillary B) Radial C) Ulnar D) Median
Ans: B. Rationale: The radial nerve runs through the posterior compartment of the arm and
the spiral groove. The posterior axillary fold contains the latissimus dorsi and teres major, near
the radial nerve's course. Radial nerve injury causes wrist drop.
Q14. A patient has a lesion in the right optic tract. What visual field deficit will they have? A)
Right homonymous hemianopia B) Left homonymous hemianopia C) Bitemporal hemianopia D)
Right anopia
Ans: B. Rationale: Fibers from the right optic tract carry information from the left visual field of
both eyes (nasal retina of left eye, temporal retina of right eye). Lesions posterior to the optic
chiasm cause contralateral homonymous hemianopia.
Q15. A newborn has a congenital diaphragmatic hernia. Which embryological failure caused
this? A) Failure of the pleuroperitoneal membranes to close B) Failure of the septum
transversum to form C) Failure of the esophageal mesentery to fuse D) Failure of the
pericardioperitoneal canals to close
Ans: A. Rationale: The pleuroperitoneal membranes close the pericardioperitoneal canals.
Failure (usually on the left, Bochdalek hernia) allows abdominal contents to herniate into the
pleural cavity, causing pulmonary hypoplasia.
Q16. A patient presents with a "popeye" deformity in the anterior arm after a lifting injury.
Which tendon ruptured? A) Long head of biceps brachii B) Short head of biceps brachii C)
Brachialis D) Coracobrachialis
Ans: A. Rationale: The long head of the biceps brachii tendon originates from the supraglenoid
tubercle. Rupture causes the muscle belly to bunch up distally, creating a "popeye" appearance.
Q17. A patient has a fracture of the surgical neck of the humerus. Which nerve and artery are
most at risk? A) Radial nerve and profunda brachii artery B) Axillary nerve and posterior
, circumflex humeral artery C) Ulnar nerve and superior ulnar collateral artery D) Median nerve
and brachial artery
Ans: B. Rationale: The axillary nerve and posterior circumflex humeral artery wrap around the
surgical neck of the humerus through the quadrangular space.
Q18. A patient presents with a loss of the corneal reflex on the right side. When the right cornea
is touched, neither eye blinks. When the left cornea is touched, both eyes blink. Which nerve is
damaged? A) Right CN V1 B) Right CN VII C) Left CN V1 D) Left CN VII
Ans: A. Rationale: The afferent limb of the corneal reflex is CN V1 (ophthalmic). The efferent
limb is CN VII (facial). If touching the right eye causes no blink in either eye, the right afferent
(V1) is broken. Touching the left eye (intact V1) causes bilateral blinking (intact CN VII
bilaterally).
Q19. A 5-year-old boy has a persistent connection between the umbilicus and the bladder,
leaking urine from the umbilicus. What failed to obliterate? A) Urachus B) Vitelline duct C)
Umbilical vein D) Allantois
Ans: A. Rationale: The urachus connects the dome of the bladder to the umbilicus. Failure to
obliterate results in a urachal fistula (urine from umbilicus) or cyst. The vitelline duct connects
the midgut to the yolk sac.
Q20. A patient has a fracture of the medial epicondyle of the humerus. Which nerve is most
likely injured? A) Radial B) Median C) Ulnar D) Musculocutaneous
Ans: C. Rationale: The ulnar nerve passes directly posterior to the medial epicondyle (the
"funny bone"). Fractures here commonly injure the ulnar nerve, causing claw hand and sensory
loss over the medial 1.5 digits.
### Biochemistry & Genetics (21-40)
Q21. A 6-month-old infant presents with severe hypoglycemia, hepatomegaly, lactic acidosis,
and hyperuricemia. Liver biopsy shows normal glycogen structure but increased amounts.
Which enzyme is deficient? A) Debranching enzyme B) Glucose-6-phosphatase C) Branching
enzyme D) Muscle phosphorylase
Ans: B. Rationale: Von Gierke disease (Type I) is caused by glucose-6-phosphatase deficiency.
The liver cannot release free glucose from glycogen or gluconeogenesis, leading to severe
fasting hypoglycemia, lactic acidosis, and hyperuricemia (G6P shunts to purines).
Questions and Correct Answers
Q1. A 54-year-old man presents with a hoarse voice and difficulty swallowing after a
thyroidectomy. Laryngoscopy reveals paralysis of the left vocal cord. Which structure was most
likely injured? A) Right recurrent laryngeal nerve B) Left recurrent laryngeal nerve C) Left
superior laryngeal nerve D) Glossopharyngeal nerve
Ans: B. Rationale: The left recurrent laryngeal nerve loops under the aortic arch and ascends in
the tracheoesophageal groove, making it highly susceptible to injury during thyroid surgery. It
innervates all intrinsic muscles of the larynx except the cricothyroid.
Q2. A patient presents with a "winged" scapula and inability to abduct the arm past 90 degrees.
Which nerve is damaged? A) Axillary B) Long thoracic C) Thoracodorsal D) Dorsal scapular
Ans: B. Rationale: The long thoracic nerve (C5-C7) innervates the serratus anterior, which
holds the scapula against the thoracic wall and upwardly rotates it to allow abduction >90
degrees. Injury causes medial scapular winging.
Q3. A newborn presents with an arm hanging by the side, internally rotated, with the forearm
extended and pronated. This is caused by damage to which nerve roots? A) C3-C4 B) C5-C6 C)
C7-C8 D) C8-T1
Ans: B. Rationale: Erb-Duchenne palsy (waiter's tip) results from upper trunk (C5-C6) injury,
often due to excessive lateral displacement of the neck during birth. It paralyzes the deltoid,
supraspinatus, infraspinatus, and biceps brachii.
Q4. A patient catches their hand in a closing car door and subsequently loses the ability to
adduct the fingers and flex the wrist. Which nerve is injured? A) Median B) Ulnar C) Radial D)
Musculocutaneous
Ans: B. Rationale: The ulnar nerve (C8-T1) innervates the intrinsic hand muscles
(adduction/abduction) and the flexor carpi ulnaris. Injury at the wrist or elbow causes these
deficits.
Q5. A 60-year-old woman experiences tingling in the lateral 3.5 digits and thenar atrophy. Which
structure is compressed? A) Ulnar nerve at Guyon's canal B) Median nerve at the carpal tunnel
C) Radial nerve in the spiral groove D) Median nerve at the ligament of Struthers
Ans: B. Rationale: Carpal tunnel syndrome involves compression of the median nerve under
the flexor retinaculum, causing sensory loss over the lateral 3.5 digits and motor weakness of
the LOAF muscles (Lumbricals 1-2, Opponens pollicis, Abductor pollicis brevis, Flexor pollicis
brevis).
,Q6. A 72-year-old woman falls on her hip. Her leg is shortened and externally rotated. Which
artery is most at risk of avascular necrosis if the femoral neck is fractured? A) Obturator artery
B) Medial circumflex femoral artery C) Lateral circumflex femoral artery D) Inferior gluteal artery
Ans: B. Rationale: The medial circumflex femoral artery provides the primary blood supply to
the femoral head. Intracapsular femoral neck fractures can tear this vessel, leading to avascular
necrosis.
Q7. A patient presents with foot drop and loss of sensation over the dorsum of the foot after a
fibular neck fracture. Which nerve is injured? A) Tibial B) Common fibular (peroneal) C) Sural D)
Deep fibular
Ans: B. Rationale: The common fibular nerve wraps around the fibular neck. Injury causes
paralysis of the anterior and lateral compartment muscles, resulting in foot drop (loss of
dorsiflexion and eversion) and sensory loss over the lateral leg and dorsum of the foot.
Q8. A 2-year-old boy has a cleft palate and recurrent respiratory infections. Which
embryological structure failed to fuse? A) Maxillary prominences B) Lateral palatine processes,
nasal septum, and median palatine process C) Mandibular prominences D) Frontonasal
prominence
Ans: B. Rationale: The secondary palate forms from the fusion of the lateral palatine processes
(maxillary prominences) with each other and with the nasal septum (frontonasal prominence)
during weeks 7-9.
Q9. During a vagal-sparing esophagectomy, the surgeon must identify the esophageal hiatus.
Which structure passes through the T10 opening of the diaphragm? A) Aorta B) Inferior vena
cava C) Esophagus and vagal trunks D) Thoracic duct
Ans: C. Rationale: "I ate (8) 10 eggs at 12". IVC at T8, Esophagus/Vagus at T10, Aorta/Thoracic
duct/Azygos at T12.
Q10. A patient with severe angina is found to have an occlusion of the artery that supplies the
SA node in 60% of the population. Which artery is occluded? A) Left anterior descending B)
Right coronary artery C) Circumflex artery D) Posterior descending artery
Ans: B. Rationale: The Right Coronary Artery (RCA) supplies the SA node in ~60% of people
(right-dominant or co-dominant) and the AV node in ~80% of people.
Q11. A patient presents with loss of pain and temperature on the right side of the body and loss
of pain and temperature on the left side of the face. Where is the lesion? A) Right medulla B)
Left medulla C) Right pons D) Left midbrain
,Ans: A. Rationale: Wallenberg syndrome (lateral medullary syndrome) on the right causes
ipsilateral (right) facial sensory loss (spinal trigeminal nucleus) and contralateral (left) body
sensory loss (spinothalamic tract, which has already crossed in the spinal cord).
Q12. A patient cannot dorsiflex the foot or evert the ankle, but can invert the foot. Which nerve
is intact? A) Deep fibular B) Superficial fibular C) Tibial D) Sural
Ans: C. Rationale: The tibial nerve innervates the posterior compartment (plantarflexion,
inversion). The common fibular nerve innervates the anterior (dorsiflexion) and lateral
(eversion) compartments.
Q13. A 30-year-old man suffers a stab wound to the posterior axillary fold. He later cannot
extend his wrist. Which nerve was damaged? A) Axillary B) Radial C) Ulnar D) Median
Ans: B. Rationale: The radial nerve runs through the posterior compartment of the arm and
the spiral groove. The posterior axillary fold contains the latissimus dorsi and teres major, near
the radial nerve's course. Radial nerve injury causes wrist drop.
Q14. A patient has a lesion in the right optic tract. What visual field deficit will they have? A)
Right homonymous hemianopia B) Left homonymous hemianopia C) Bitemporal hemianopia D)
Right anopia
Ans: B. Rationale: Fibers from the right optic tract carry information from the left visual field of
both eyes (nasal retina of left eye, temporal retina of right eye). Lesions posterior to the optic
chiasm cause contralateral homonymous hemianopia.
Q15. A newborn has a congenital diaphragmatic hernia. Which embryological failure caused
this? A) Failure of the pleuroperitoneal membranes to close B) Failure of the septum
transversum to form C) Failure of the esophageal mesentery to fuse D) Failure of the
pericardioperitoneal canals to close
Ans: A. Rationale: The pleuroperitoneal membranes close the pericardioperitoneal canals.
Failure (usually on the left, Bochdalek hernia) allows abdominal contents to herniate into the
pleural cavity, causing pulmonary hypoplasia.
Q16. A patient presents with a "popeye" deformity in the anterior arm after a lifting injury.
Which tendon ruptured? A) Long head of biceps brachii B) Short head of biceps brachii C)
Brachialis D) Coracobrachialis
Ans: A. Rationale: The long head of the biceps brachii tendon originates from the supraglenoid
tubercle. Rupture causes the muscle belly to bunch up distally, creating a "popeye" appearance.
Q17. A patient has a fracture of the surgical neck of the humerus. Which nerve and artery are
most at risk? A) Radial nerve and profunda brachii artery B) Axillary nerve and posterior
, circumflex humeral artery C) Ulnar nerve and superior ulnar collateral artery D) Median nerve
and brachial artery
Ans: B. Rationale: The axillary nerve and posterior circumflex humeral artery wrap around the
surgical neck of the humerus through the quadrangular space.
Q18. A patient presents with a loss of the corneal reflex on the right side. When the right cornea
is touched, neither eye blinks. When the left cornea is touched, both eyes blink. Which nerve is
damaged? A) Right CN V1 B) Right CN VII C) Left CN V1 D) Left CN VII
Ans: A. Rationale: The afferent limb of the corneal reflex is CN V1 (ophthalmic). The efferent
limb is CN VII (facial). If touching the right eye causes no blink in either eye, the right afferent
(V1) is broken. Touching the left eye (intact V1) causes bilateral blinking (intact CN VII
bilaterally).
Q19. A 5-year-old boy has a persistent connection between the umbilicus and the bladder,
leaking urine from the umbilicus. What failed to obliterate? A) Urachus B) Vitelline duct C)
Umbilical vein D) Allantois
Ans: A. Rationale: The urachus connects the dome of the bladder to the umbilicus. Failure to
obliterate results in a urachal fistula (urine from umbilicus) or cyst. The vitelline duct connects
the midgut to the yolk sac.
Q20. A patient has a fracture of the medial epicondyle of the humerus. Which nerve is most
likely injured? A) Radial B) Median C) Ulnar D) Musculocutaneous
Ans: C. Rationale: The ulnar nerve passes directly posterior to the medial epicondyle (the
"funny bone"). Fractures here commonly injure the ulnar nerve, causing claw hand and sensory
loss over the medial 1.5 digits.
### Biochemistry & Genetics (21-40)
Q21. A 6-month-old infant presents with severe hypoglycemia, hepatomegaly, lactic acidosis,
and hyperuricemia. Liver biopsy shows normal glycogen structure but increased amounts.
Which enzyme is deficient? A) Debranching enzyme B) Glucose-6-phosphatase C) Branching
enzyme D) Muscle phosphorylase
Ans: B. Rationale: Von Gierke disease (Type I) is caused by glucose-6-phosphatase deficiency.
The liver cannot release free glucose from glycogen or gluconeogenesis, leading to severe
fasting hypoglycemia, lactic acidosis, and hyperuricemia (G6P shunts to purines).
