Amnestic syndromes: Korsakoff and other causes
- Disorder
Losing the ability to form or recall memories while attention and thinking are largely kept, from brain damage or a psychological cause.
What it is
An amnestic syndrome is a disproportionate memory disorder: the person cannot learn new information (anterograde amnesia) and often loses some past memories (retrograde amnesia), while alertness, attention and general intellect are relatively spared. Memory depends on the hippocampus and its links with the mammillary bodies and the thalamus. The classic cause is Korsakoff syndrome after thiamine deficiency, usually in alcohol use disorder or severe undernutrition; others are herpes simplex encephalitis, head injury, strokes, seizures and transient global amnesia.
Key facts
- The core is a new-learning deficit out of proportion to other cognitive problems; consciousness is clear, unlike delirium.
- Korsakoff patients are often disoriented in time and apathetic; confabulation is often a striking early feature.
- Wernicke encephalopathy is the acute, partly reversible stage; by the time Korsakoff amnesia is established the brain damage is often permanent, so early thiamine is essential.
- Non-alcoholic thiamine deficiency (bariatric surgery, hyperemesis gravidarum, malnutrition, cancer) can also lead to Korsakoff syndrome.
- Herpes simplex encephalitis can leave amnesia that treatment may or may not lessen.
- After head injury, moderate or severe trauma affects wider areas of memory storage and recall.
Amnestic syndromes compared: the clue that separates each
| Syndrome | Onset and course | Memory pattern | Key clue |
|---|---|---|---|
| Korsakoff syndrome | After Wernicke encephalopathy; chronic | Anterograde and retrograde; recent memories worse than remote ones | Alcohol use or undernutrition, confabulation, mammillary body and thalamic damage |
| Transient global amnesia | Sudden; usually resolves within 24 hours | Anterograde and retrograde during the episode | Age 50 to 70, repeated questions, identity kept; sometimes after exertion, cold water or emotion |
| Herpes simplex encephalitis | Acute infection | Amnesia that may or may not improve with treatment | Signs of encephalitis: fever, confusion, seizures |
| Traumatic brain injury | At the injury | Post-traumatic amnesia, wider with more severe trauma | Head trauma |
| Transient epileptic amnesia | Episodes | Amnestic spells caused by seizure activity | EEG shows seizure activity; excluded before diagnosing transient global amnesia |
| Dissociative amnesia | After extreme stress or trauma | Memory loss with a psychological cause | Psychological trigger |
Clinical notes
- Any patient at risk of thiamine deficiency with confusion, eye-movement problems or unsteady gait is treated at once as Wernicke encephalopathy, with thiamine (see the Wernicke page).
- Rule out delirium, dementia and depression first; bedside tests of recall after a delay show the anterograde deficit.
- Workup aims at the cause: thiamine status, brain MRI, EEG if spells recur, spinal fluid when encephalitis is suspected.
- Korsakoff care adds abstinence, nutrition and rehabilitation with memory compensation techniques (diaries, phones, alarms) and errorless learning.
Test yourself
Think of the answer, then tap the question to see it.
What separates Korsakoff syndrome from Wernicke encephalopathy?
Wernicke is the acute stage (confusion, eye signs, ataxia) and can reverse with thiamine; Korsakoff is the chronic amnestic stage, usually permanent.
Which brain structures are classically damaged in Korsakoff syndrome?
The mammillary bodies and the thalamus, parts of the memory circuit.
A 62-year-old asks the same questions over and over for some hours after swimming in cold water, but knows who she is. What is the likely diagnosis?
Transient global amnesia: sudden amnesia with preserved identity that usually resolves within 24 hours.
How does dissociative amnesia differ from organic amnesia?
It is caused by extreme psychological trauma or stress rather than by brain damage.
Elsewhere in DurgiPedia
- Thiamine (vitamin B1)
- Thiamine and B12 deficiency in the CNS
- Herpesvirus encephalitis
- Learning and memory
Connections
In Pharmacology2
Educational content on behavior and the clinical relationship; not a diagnostic or treatment guide and no substitute for assessment by a health professional. If you or someone near you is at risk, seek help now from an emergency service or a mental-health helpline.
Sources: Korsakoff syndrome: An overlook (Review) (Experimental and Therapeutic Medicine (PubMed Central), 2021); Korsakoff Psychosis (MSD Manual Professional Edition, 2025); Transient Global Amnesia (MSD Manual Professional Edition, 2025); Amnesias (MSD Manual Professional Edition, 2025).
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Representative model, for educational purposes only.