Clinical Nutrition & Vitamin Deficiency Neurology –
Comprehensive 300 MCQ Bank with Rationales
This resource provides high-yield multiple-choice questions on vitamin deficiencies in
neurology, focused on Wernicke’s encephalopathy from thiamine depletion in chronic
alcoholism. Perfect for USMLE, COMLEX, or clinical rotations. Each answer includes
bold italic correct options with italicized rationales explaining pathophysiology, classic
triads, and prevention. Master the association between nystagmus, confusion, gait ataxia,
and early thiamine replacement. Ideal for self-testing and last-minute review.
,Question 1
A 50-year-old alcoholic presents with confusion, nystagmus, and unsteady gait. What is the
most likely diagnosis?
a) Hepatic encephalopathy
b) Wernicke encephalopathy
c) Delirium tremens
d) Cerebellar stroke
*Rationale: The classic triad of confusion, ophthalmoplegia/nystagmus, and ataxia defines
Wernicke encephalopathy, caused by thiamine (B1) deficiency in chronic alcoholism. *
Question 2
Which vitamin deficiency causes pellagra, characterized by dementia, diarrhea, and dermatitis?
a) Vitamin B1
b) Vitamin B3 (Niacin)
c) Vitamin B6
d) Vitamin B12
Rationale: Pellagra results from niacin (B3) deficiency, presenting with the "3 D's" – dementia,
diarrhea, dermatitis. It is seen in malnutrition, alcoholism, and Hartnup disease.
Question 3
A vegan presents with paresthesias, loss of vibration sense, and a positive Romberg sign. What
is the most likely deficiency?
a) Folate
b) Vitamin B12
c) Iron
d) Vitamin B6
*Rationale: Subacute combined degeneration from B12 deficiency damages the posterior
columns (vibration/proprioception loss) and lateral corticospinal tracts, causing sensory ataxia
and a positive Romberg sign. *
,Question 4
A patient with Crohn's disease develops progressive ataxia and areflexia. MRI shows dorsal
column T2 hyperintensity. Which deficiency is most likely?
a) Vitamin B1
b) Vitamin B3
c) Vitamin E
d) Vitamin C
Rationale: Vitamin E deficiency (fat malabsorption in Crohn's) causes spinocerebellar
degeneration, mimicking Friedreich ataxia. Dorsal column involvement is characteristic on MRI.
Question 5
A patient on isoniazid for tuberculosis reports tingling in both feet. What is the best preventive
measure?
a) Increase INH dose
b) Pyridoxine (Vitamin B6) supplementation
c) Thiamine injection
d) Folic acid
*Rationale: INH inhibits pyridoxal phosphate, causing functional B6 deficiency and peripheral
neuropathy. Prophylactic pyridoxine (25–50 mg/day) prevents this complication. *
Question 6
Which of the following is NOT associated with vitamin B12 deficiency?
a) Macrocytic anemia
b) Subacute combined degeneration
c) Flapping tremor (asterixis)
d) Optic atrophy
Rationale: Asterixis is classically seen in hepatic or uremic encephalopathy, not B12 deficiency.
B12 causes posterior column signs, neuropathy, myelopathy, and optic atrophy.
Question 7
A newborn has intractable seizures that fail to respond to phenobarbital. Which vitamin should
be administered emergently?
a) Vitamin K
b) Pyridoxine (Vitamin B6)
, c) Thiamine
d) Vitamin D
*Rationale: Pyridoxine-dependent seizures result from B6 deficiency (cofactor for GABA
synthesis). IV pyridoxine typically stops seizures within minutes. *
Question 8
A chronic alcoholic is brought to the ER with confusion. Before giving IV glucose, what must be
administered?
a) Naloxone
b) IV Thiamine
c) Folic acid
d) Magnesium
Rationale: Glucose can precipitate or worsen Wernicke encephalopathy if thiamine is not given
first. Always administer high-dose IV thiamine before glucose in at-risk patients.
Question 9
A patient presents with glossitis, angular stomatitis, and a seborrheic dermatitis-like rash. Which
deficiency is most likely?
a) Riboflavin (Vitamin B2)
b) Biotin
c) Vitamin B12
d) Vitamin A
Rationale: Riboflavin deficiency causes cheilosis, angular stomatitis, glossitis, and seborrheic
dermatitis. Common in vegans, alcoholics, and malabsorption syndromes.
Question 10
Dry beriberi primarily affects which system?
a) Cardiovascular
b) Peripheral nervous system
c) Central nervous system
d) Hematologic
Rationale: Dry beriberi is a symmetric peripheral neuropathy from thiamine deficiency. Wet
beriberi affects the heart (high-output failure).
Comprehensive 300 MCQ Bank with Rationales
This resource provides high-yield multiple-choice questions on vitamin deficiencies in
neurology, focused on Wernicke’s encephalopathy from thiamine depletion in chronic
alcoholism. Perfect for USMLE, COMLEX, or clinical rotations. Each answer includes
bold italic correct options with italicized rationales explaining pathophysiology, classic
triads, and prevention. Master the association between nystagmus, confusion, gait ataxia,
and early thiamine replacement. Ideal for self-testing and last-minute review.
,Question 1
A 50-year-old alcoholic presents with confusion, nystagmus, and unsteady gait. What is the
most likely diagnosis?
a) Hepatic encephalopathy
b) Wernicke encephalopathy
c) Delirium tremens
d) Cerebellar stroke
*Rationale: The classic triad of confusion, ophthalmoplegia/nystagmus, and ataxia defines
Wernicke encephalopathy, caused by thiamine (B1) deficiency in chronic alcoholism. *
Question 2
Which vitamin deficiency causes pellagra, characterized by dementia, diarrhea, and dermatitis?
a) Vitamin B1
b) Vitamin B3 (Niacin)
c) Vitamin B6
d) Vitamin B12
Rationale: Pellagra results from niacin (B3) deficiency, presenting with the "3 D's" – dementia,
diarrhea, dermatitis. It is seen in malnutrition, alcoholism, and Hartnup disease.
Question 3
A vegan presents with paresthesias, loss of vibration sense, and a positive Romberg sign. What
is the most likely deficiency?
a) Folate
b) Vitamin B12
c) Iron
d) Vitamin B6
*Rationale: Subacute combined degeneration from B12 deficiency damages the posterior
columns (vibration/proprioception loss) and lateral corticospinal tracts, causing sensory ataxia
and a positive Romberg sign. *
,Question 4
A patient with Crohn's disease develops progressive ataxia and areflexia. MRI shows dorsal
column T2 hyperintensity. Which deficiency is most likely?
a) Vitamin B1
b) Vitamin B3
c) Vitamin E
d) Vitamin C
Rationale: Vitamin E deficiency (fat malabsorption in Crohn's) causes spinocerebellar
degeneration, mimicking Friedreich ataxia. Dorsal column involvement is characteristic on MRI.
Question 5
A patient on isoniazid for tuberculosis reports tingling in both feet. What is the best preventive
measure?
a) Increase INH dose
b) Pyridoxine (Vitamin B6) supplementation
c) Thiamine injection
d) Folic acid
*Rationale: INH inhibits pyridoxal phosphate, causing functional B6 deficiency and peripheral
neuropathy. Prophylactic pyridoxine (25–50 mg/day) prevents this complication. *
Question 6
Which of the following is NOT associated with vitamin B12 deficiency?
a) Macrocytic anemia
b) Subacute combined degeneration
c) Flapping tremor (asterixis)
d) Optic atrophy
Rationale: Asterixis is classically seen in hepatic or uremic encephalopathy, not B12 deficiency.
B12 causes posterior column signs, neuropathy, myelopathy, and optic atrophy.
Question 7
A newborn has intractable seizures that fail to respond to phenobarbital. Which vitamin should
be administered emergently?
a) Vitamin K
b) Pyridoxine (Vitamin B6)
, c) Thiamine
d) Vitamin D
*Rationale: Pyridoxine-dependent seizures result from B6 deficiency (cofactor for GABA
synthesis). IV pyridoxine typically stops seizures within minutes. *
Question 8
A chronic alcoholic is brought to the ER with confusion. Before giving IV glucose, what must be
administered?
a) Naloxone
b) IV Thiamine
c) Folic acid
d) Magnesium
Rationale: Glucose can precipitate or worsen Wernicke encephalopathy if thiamine is not given
first. Always administer high-dose IV thiamine before glucose in at-risk patients.
Question 9
A patient presents with glossitis, angular stomatitis, and a seborrheic dermatitis-like rash. Which
deficiency is most likely?
a) Riboflavin (Vitamin B2)
b) Biotin
c) Vitamin B12
d) Vitamin A
Rationale: Riboflavin deficiency causes cheilosis, angular stomatitis, glossitis, and seborrheic
dermatitis. Common in vegans, alcoholics, and malabsorption syndromes.
Question 10
Dry beriberi primarily affects which system?
a) Cardiovascular
b) Peripheral nervous system
c) Central nervous system
d) Hematologic
Rationale: Dry beriberi is a symmetric peripheral neuropathy from thiamine deficiency. Wet
beriberi affects the heart (high-output failure).
