Question
A 49-year-old man with long-standing alcohol misuse is brought to hospital because of worsening confusion. He is drowsy but rousable, walks with a broad-based unsteady gait, and has horizontal nystagmus. There is no history of head injury and no focal limb weakness.
Which brain MRI finding is most characteristic of the likely diagnosis?
a. Chronic frontal lobe volume loss
b. Communicating hydrocephalus
c. Enhancement of the mamillary bodies
d. Acute pontine infarction
e. Thin bilateral subdural collections
Answer
c. Enhancement of the mamillary bodies
Detailed explanation
This patient has Wernicke’s encephalopathy, caused by thiamine/vitamin B1 deficiency. The key clinical clues are:
- Alcohol misuse or alcoholic liver disease
- Confusion/encephalopathy
- Ataxia, especially gait ataxia
- Ocular signs, especially nystagmus or ophthalmoplegia
The classic triad is:
Confusion + ataxia + ophthalmoplegia/nystagmus
However, the full triad is not always present, so Wernicke’s encephalopathy must be suspected early in any malnourished or alcohol-dependent patient with acute confusion or gait/eye movement abnormalities.
The most specific MRI finding among the options is enhancement of the mamillary bodies. In Wernicke’s encephalopathy, thiamine deficiency causes brain lesions particularly around metabolically active periventricular structures, including:
- Mamillary bodies
- Medial thalami
- Periaqueductal grey matter
- Tectal plate
- Walls of the third and fourth ventricles
The mamillary bodies are classically involved. MRI may show high T2/FLAIR signal and/or contrast enhancement in these regions. Mamillary body enhancement is relatively specific, although MRI sensitivity is imperfect, so a normal MRI does not exclude Wernicke’s encephalopathy.
Why the other options are wrong
a. Chronic frontal lobe volume loss
Alcohol dependence may be associated with cerebral atrophy, but this is a chronic nonspecific finding. It does not explain the acute triad of confusion, ataxia, and nystagmus.
b. Communicating hydrocephalus
Hydrocephalus can cause gait disturbance and cognitive change, but the history here strongly points to thiamine deficiency. Nystagmus and acute encephalopathy in an alcohol-dependent patient are much more suggestive of Wernicke’s encephalopathy.
d. Acute pontine infarction
A brainstem stroke can cause eye movement problems and ataxia, but it would usually produce focal neurological signs such as diplopia, dysarthria, weakness, sensory loss, or cranial nerve findings. It would not classically cause the Wernicke triad in an alcoholic patient.
e. Thin bilateral subdural collections
Alcohol-dependent patients are at increased risk of subdural haematoma because of falls, trauma, and cerebral atrophy stretching bridging veins. However, the absence of trauma and the presence of confusion, broad-based gait, and nystagmus make Wernicke’s encephalopathy more likely.
Key exam point
In an alcoholic or malnourished patient with confusion + ataxia + nystagmus/ophthalmoplegia, think:
Wernicke’s encephalopathy → thiamine deficiency → mamillary body involvement → urgent IV thiamine.
Very important treatment point
Treat Wernicke’s encephalopathy immediately with parenteral thiamine.
In exams, remember:
Give thiamine before glucose.
Glucose can worsen Wernicke’s encephalopathy because carbohydrate metabolism consumes thiamine. In practice, if hypoglycaemia is life-threatening, glucose should not be delayed, but thiamine should be given urgently.
Wernicke’s encephalopathy versus Korsakoff syndrome
Wernicke’s encephalopathy is the acute, potentially reversible phase.
Main features:
- Confusion
- Ataxia
- Nystagmus/ophthalmoplegia
- Peripheral neuropathy may occur
Korsakoff syndrome is the chronic irreversible memory disorder that may follow untreated Wernicke’s encephalopathy.
Main features:
- Anterograde amnesia
- Retrograde amnesia
- Confabulation
- Poor insight
Together, they are called Wernicke-Korsakoff syndrome.
Cheat sheet for exam
Wernicke’s encephalopathy
Cause: Thiamine/vitamin B1 deficiency.
Commonest association: Chronic alcohol misuse.
Other causes:
- Prolonged vomiting
- Hyperemesis gravidarum
- Anorexia nervosa
- Malnutrition
- Bariatric surgery
- Gastric cancer
- Refeeding syndrome
- Prolonged IV glucose without thiamine
Classic triad:
- Confusion
- Ataxia
- Ophthalmoplegia/nystagmus
Most common ocular sign: Nystagmus.
Other ocular signs:
- Lateral rectus palsy
- Conjugate gaze palsy
- Ophthalmoplegia
MRI findings:
- Mamillary body enhancement
- Medial thalamic signal change
- Periaqueductal grey matter involvement
- Periventricular lesions
Most specific option in this question: Enhancement of the mamillary bodies.
Pathology: Petechial haemorrhages and neuronal injury in mamillary bodies and periventricular structures.
Investigation sometimes mentioned: Reduced red cell transketolase activity.
Treatment: Urgent IV thiamine.
Exam phrase: Thiamine before glucose.
Complication if untreated: Korsakoff syndrome.
Korsakoff syndrome features:
- Anterograde amnesia
- Retrograde amnesia
- Confabulation
Flash cards
Q: What vitamin deficiency causes Wernicke’s encephalopathy?
A: Thiamine, also called vitamin B1.
Explanation: Thiamine is essential for cerebral energy metabolism. Deficiency damages metabolically vulnerable brain regions such as the mamillary bodies and thalami.
Q: What is the classic triad of Wernicke’s encephalopathy?
A: Confusion, ataxia, and ophthalmoplegia/nystagmus.
Explanation: The full triad is not always present, but its presence in an alcoholic or malnourished patient is highly suggestive.
Q: What is the most common ocular sign in Wernicke’s encephalopathy?
A: Nystagmus.
Explanation: Ophthalmoplegia may occur, but nystagmus is the commonest eye movement abnormality.
Q: What MRI finding is most specific for Wernicke’s encephalopathy?
A: Enhancement of the mamillary bodies.
Explanation: The mamillary bodies are classically affected by thiamine deficiency.
Q: Which brain structures are commonly affected in Wernicke’s encephalopathy?
A: Mamillary bodies, medial thalami, periaqueductal grey matter, and periventricular regions.
Explanation: These areas are vulnerable because of high metabolic demand and dependence on thiamine-mediated pathways.
Q: What is the urgent treatment for suspected Wernicke’s encephalopathy?
A: Parenteral thiamine.
Explanation: Treatment should not wait for imaging confirmation because delay can lead to irreversible Korsakoff syndrome.
Q: Why should thiamine be given before glucose?
A: Glucose metabolism consumes thiamine and can worsen neurological injury in a thiamine-deficient patient.
Explanation: This is a classic exam principle, especially in alcohol-dependent or malnourished patients.
Q: What syndrome can follow untreated Wernicke’s encephalopathy?
A: Korsakoff syndrome.
Explanation: Korsakoff syndrome is characterised by severe memory impairment and confabulation.
Q: What is confabulation?
A: The production of fabricated or distorted memories without deliberate lying.
Explanation: It is a classic feature of Korsakoff syndrome.
Q: Does a normal MRI exclude Wernicke’s encephalopathy?
A: No.
Explanation: MRI is not fully sensitive; treatment should be clinical and urgent.
MCQs
MCQ 1
A 56-year-old man with alcohol dependence presents with confusion, unsteady gait, and nystagmus. Which diagnosis is most likely?
a. Normal pressure hydrocephalus
b. Wernicke’s encephalopathy
c. Multiple sclerosis
d. Cerebellar metastasis
e. Vestibular neuritis
Answer: b. Wernicke’s encephalopathy
Explanation: The combination of confusion, ataxia, and ocular signs in an alcohol-dependent patient is classic for Wernicke’s encephalopathy. Vestibular neuritis may cause vertigo and nystagmus but not encephalopathy. Normal pressure hydrocephalus causes gait disturbance, cognitive impairment, and urinary incontinence but is usually chronic.
MCQ 2
Which vitamin deficiency is responsible for Wernicke’s encephalopathy?
a. Vitamin B12
b. Vitamin C
c. Vitamin B1
d. Vitamin D
e. Vitamin K
Answer: c. Vitamin B1
Explanation: Wernicke’s encephalopathy is caused by thiamine, or vitamin B1, deficiency. Vitamin B12 deficiency causes subacute combined degeneration, neuropathy, macrocytic anaemia, and cognitive changes, but not the typical Wernicke triad.
MCQ 3
Which MRI finding is most characteristic of Wernicke’s encephalopathy?
a. Enhancement of the mamillary bodies
b. Pituitary enlargement
c. Temporal lobe ring-enhancing lesion
d. Diffuse subarachnoid blood
e. Frontal extradural haematoma
Answer: a. Enhancement of the mamillary bodies
Explanation: Mamillary body involvement is classically associated with Wernicke’s encephalopathy. Other affected regions include the medial thalami, periaqueductal grey, and periventricular areas.
MCQ 4
Which of the following is false regarding Wernicke’s encephalopathy?
a. It is commonly associated with alcohol misuse
b. It may occur after prolonged vomiting
c. MRI is perfectly sensitive and excludes the diagnosis if normal
d. It may progress to Korsakoff syndrome
e. Nystagmus is a common ocular finding
Answer: c. MRI is perfectly sensitive and excludes the diagnosis if normal
Explanation: This is false. MRI can support the diagnosis but does not exclude it if normal. Wernicke’s encephalopathy is a clinical emergency, and thiamine should be given urgently when suspected.
MCQ 5
A malnourished patient is brought to hospital with reduced consciousness. Blood glucose is low. Which principle is most important in relation to Wernicke’s encephalopathy?
a. Avoid thiamine because it worsens hypoglycaemia
b. Give oral folate only
c. Give thiamine urgently, ideally before or with glucose
d. Delay glucose until MRI is available
e. Treat only if mamillary body enhancement is seen
Answer: c. Give thiamine urgently, ideally before or with glucose
Explanation: Glucose metabolism can worsen thiamine depletion. In suspected Wernicke’s encephalopathy, thiamine should be given urgently. Life-threatening hypoglycaemia should still be treated immediately, but thiamine must not be forgotten.
MCQ 6
Which clinical feature best suggests progression from Wernicke’s encephalopathy to Korsakoff syndrome?
a. Limb weakness
b. Confabulation
c. Papilloedema
d. Chorea
e. Hyperreflexia
Answer: b. Confabulation
Explanation: Korsakoff syndrome is characterised by profound memory impairment, especially anterograde amnesia, with confabulation. Confabulation means filling memory gaps with invented but sincerely believed explanations.
MCQ 7
Which of the following is the best description of Wernicke’s encephalopathy?
a. Acute thiamine deficiency causing confusion, ataxia, and ocular abnormalities
b. Chronic vitamin B12 deficiency causing dorsal column degeneration
c. Acute autoimmune demyelination causing ascending paralysis
d. Chronic alcohol-related cerebellar degeneration without confusion
e. A prion disease causing rapidly progressive dementia
Answer: a. Acute thiamine deficiency causing confusion, ataxia, and ocular abnormalities
Explanation: Wernicke’s encephalopathy is an acute neuropsychiatric emergency caused by thiamine deficiency. Alcohol-related cerebellar degeneration may cause gait ataxia but not the acute encephalopathy and eye signs typical of Wernicke’s.
MCQ 8
A patient with Wernicke’s encephalopathy has abnormal eye movements. Which ocular sign is most commonly described?
a. Papilloedema
b. Ptosis
c. Nystagmus
d. Complete blindness
e. Argyll Robertson pupil
Answer: c. Nystagmus
Explanation: Nystagmus is the most common ocular sign in Wernicke’s encephalopathy. Ophthalmoplegia can occur, including lateral rectus palsy or conjugate gaze palsy.
MCQ 9
Which of the following is least likely to cause Wernicke’s encephalopathy?
a. Alcohol dependence
b. Hyperemesis gravidarum
c. Bariatric surgery
d. Prolonged malnutrition
e. Hypervitaminosis D
Answer: e. Hypervitaminosis D
Explanation: Wernicke’s encephalopathy results from thiamine deficiency. Alcohol dependence, persistent vomiting, bariatric surgery, malnutrition, anorexia nervosa, and refeeding states are recognised causes. Hypervitaminosis D is unrelated.
MCQ 10
Which of the following statements about the mamillary bodies is most relevant to Wernicke-Korsakoff syndrome?
a. They are commonly involved in thiamine-deficiency brain injury
b. They are the main site of dopamine production
c. They are located in the cerebellar cortex
d. They are primarily responsible for CSF production
e. They are usually spared in alcohol-related neurological disease
Answer: a. They are commonly involved in thiamine-deficiency brain injury
Explanation: The mamillary bodies are part of memory circuitry and are classically damaged in Wernicke-Korsakoff syndrome. This explains why chronic cases may develop prominent memory disturbance.
MCQ 11
A patient with alcohol dependence presents with acute confusion and ataxia. CT head shows no acute haemorrhage. Which is the best next step?
a. Wait for red cell transketolase level before treating
b. Start urgent parenteral thiamine
c. Start long-term oral vitamin D
d. Discharge if CT is normal
e. Treat only with benzodiazepines
Answer: b. Start urgent parenteral thiamine
Explanation: Wernicke’s encephalopathy is a clinical diagnosis and treatment should not be delayed for investigations. Parenteral thiamine is required because absorption may be unreliable and urgent replacement is needed.
MCQ 12
Which of the following is false about Korsakoff syndrome?
a. It can follow untreated Wernicke’s encephalopathy
b. It is associated with anterograde amnesia
c. It may involve confabulation
d. It is usually more reversible than acute Wernicke’s encephalopathy
e. It may include retrograde amnesia
Answer: d. It is usually more reversible than acute Wernicke’s encephalopathy
Explanation: This is false. Wernicke’s encephalopathy is the acute potentially reversible stage. Korsakoff syndrome is often chronic and may be irreversible, especially if treatment is delayed.
MCQ 13
A 38-year-old woman with hyperemesis gravidarum develops confusion, diplopia, and unsteady gait. Which diagnosis should be considered urgently?
a. Wernicke’s encephalopathy
b. Migraine aura
c. Myasthenia gravis only
d. Benign positional vertigo
e. Idiopathic intracranial hypertension
Answer: a. Wernicke’s encephalopathy
Explanation: Wernicke’s encephalopathy is not limited to alcohol misuse. Persistent vomiting, including hyperemesis gravidarum, can cause thiamine depletion and acute neurological injury.
MCQ 14
Which biochemical test may be reduced in Wernicke’s encephalopathy?
a. Serum caeruloplasmin
b. Red cell transketolase activity
c. Serum acetylcholine receptor antibody
d. Plasma ammonia only
e. Serum angiotensin-converting enzyme
Answer: b. Red cell transketolase activity
Explanation: Thiamine is a cofactor for transketolase. Reduced red cell transketolase activity may support thiamine deficiency, but treatment should never wait for this result.
MCQ 15
A patient with chronic alcohol misuse has confusion and ataxia. Which additional sign would most strongly complete the classical triad of Wernicke’s encephalopathy?
a. Nystagmus
b. Urinary retention
c. Hemiballismus
d. Resting tremor
e. Expressive dysphasia
Answer: a. Nystagmus
Explanation: The classic triad is encephalopathy, ataxia, and ocular dysfunction. Nystagmus is the commonest ocular feature.
Summary for quick exam revision
Wernicke’s encephalopathy is an acute neurological emergency caused by thiamine, or vitamin B1, deficiency. It is classically seen in alcohol misuse but can also occur with prolonged vomiting, hyperemesis gravidarum, anorexia nervosa, gastric malignancy, bariatric surgery, malnutrition, and refeeding. The classic triad is confusion, ataxia, and ophthalmoplegia or nystagmus, although all three features are not always present. Nystagmus is the most common ocular sign. The brain regions typically affected are the mamillary bodies, medial thalami, periaqueductal grey matter, and periventricular structures. The most specific MRI finding in this question is enhancement of the mamillary bodies. MRI can support the diagnosis but is not sensitive enough to exclude it. The pathology involves neuronal injury and petechial haemorrhages in vulnerable brain regions. The key treatment is urgent parenteral thiamine. In exams, always remember to give thiamine before glucose, because glucose metabolism can worsen thiamine depletion. If untreated, Wernicke’s encephalopathy can progress to Korsakoff syndrome. Korsakoff syndrome is characterised by anterograde amnesia, retrograde amnesia, and confabulation. Wernicke’s is the acute potentially reversible stage, while Korsakoff is the chronic memory disorder that may become irreversible. In any confused alcoholic or malnourished patient with gait disturbance or eye signs, treat first and investigate later.