Korsakoff syndrome
Korsakoff syndrome (KS)[1] is an amnestic condition induced by thiamine (vitamin B1) deficiency generally coupled with persistent use of alcohol. [2] The illness and psychosis are named after Sergei Korsakoff, the Russian neuropsychiatrist who identified it during the late 19th century.
This neurological condition is caused by a shortage of thiamine in the brain, and is also exacerbated by the neurotoxic effects of alcohol. When Wernicke encephalopathy accompanies Korsakoff disease the combination is called Wernicke–Korsakoff syndrome; however, an episode of Wernicke encephalopathy is not usually observed
Signs and symptoms
- Seven key symptoms of Korsakoff syndrome, an amnestic-confabulatory syndrome:
- Anterograde amnesia, memory loss after syndrome onset
- Retrograde amnesia, memory loss extends some time before symptoms starts
- Fixation amnesia called fixation amnesia (loss of immediate memory, a person being unable to remember events of the past few minutes)
- Confabulation, i.e. fabricated memories that are then considered true due to memory gaps, occasionally related with blackouts
- Minimum conversation content
- Missing insight
- Apathy - interest in things is rapidly lost, indifference to change
Benon R. and LeHuché R. (1920) reported the classic indications of Korsakoff syndrome with some additional symptoms including: confabulation (false memories), fixing amnesia, paragnosis or false location awareness, mental excitement, and euphoria.
Thiamine is needed for pyruvate decarboxylation, and shortage during this metabolic process is hypothesised to induce damage to the post-hypothalamus medial thalamus and mammary bodies as well as generalised cerebral atrophy.
These brain areas are all elements of the limbic system involved in emotion and memory.
KS involves neuronal loss, i.e. neuronal injury; gliosis resulting from injury to supporting central nervous system cells, and bleeding also occurs in mammary bodies. Damage to the thalamus medial dorsal nucleus (limbic-specific nuclei) is also related with this illness. Cortical dysfunction may result from thiamine shortage, alcohol neurotoxicity, and/or diencephalon structural damage. [8] [8]
Originally, a lack of initiative and a flat effect were regarded to be essential aspects of emotional presentation in sufferers. Studies questioned this, suggesting that neither is necessarily KS symptom. Research suggesting emotionally unimpaired people with Korsakoff syndrome made this a controversial topic. It might be argued that indifference, a common feature, shows a shortage of emotional expressiveness without impacting emotional experience or perception. [9] [9]
KS induces declarative memory loss in most people[10] but leaves implicit spatial, linguistic and procedural memory intact.
People with KS lack contextual information processing. Context memories refers to where and when experiences, and is a crucial aspect of memory. It impairs the ability to store and recall this information, such as geographical location or chronological order information.
Research has also revealed that persons with Korsakoff syndrome have poor executive functioning that might cause behavioural issues and impede with day-to-day activities. But it's unclear which executive functions are most affected.
However, IQ is usually not impaired by Korsakoff's syndrome-related brain injury.
Initially, it was considered that persons with KS used confabulation to fill memory gaps. Confabulation and amnesia, however, have not necessarily co-occurred. Studies showed dissociation between induced confabulation, spontaneous (unprovoked) confabulation, and false recollections. That is, persons affected could be induced to believe that certain things had happened that hadn't happened, but those without Korsakoff syndrome could
Causes
Thiamine deficiency and its symptoms include prolonged drunkenness and severe starvation. Alcoholism may co-occur with inadequate nutrition, causing thiamine deficiency in addition to stomach lining irritation. Other causes include nutritional deficits, persistent vomiting, eating problems, chemotherapy effects. It can also occur in pregnant women with intense morning sickness known as hyperemesis gravidarum. Mercury poisoning can potentially cause Korsakoff syndrome. Although it doesn't usually co-occur, it can frequently emerge as a consequence effect of Wernicke's encephalopathy.
PET scans demonstrate a reduction in glucose metabolism in brain frontal, parietal, and cingulated regions in people with Korsakoff syndrome. This may cause memory loss and amnesia. Structural neuroimaging also showed midline diencephalic lesions and cortical atrophy.
Structural central nervous system lesions, however rare, can also contribute to KS symptoms. Severe dorsal nucleus injury inevitably results in memory loss. Additionally, autopsies of persons with KS indicated midline and anterior thalamus lesions and thalamic infarctions. Bilateral thalamus infarctions can also cause Korsakoff-induced amnesia. These findings may result in disruptive memory impairment to anterior thalamic nuclei.
Risk factors
Many variables may raise a person's risk of developing Korsakoff syndrome. These elements often relate to overall health and diet.
- Age
- Alcoholism
- Chemotherapy
- Dialysis
- Extreme dieting
- Genetic factors
Diagnosis
KS is primarily a clinical diagnosis; imaging and lab tests are not necessary.
Prevention
The most effective way to prevent AKS is to avoid vitamin/thiamine deficiency B. In Western nations, the most common causes are drinking and eating problems. Because they are causes of behaviour, Korsakoff syndrome is essentially considered a preventable condition. Thus, strengthening thiamine foods, or requiring corporations selling alcoholic beverages to enhance them with B vitamins in general or thiamine in particular, could avert many cases.
Treatment
Once expected that someone with KS would eventually need full-time care. This is still frequently the case, though rehabilitation can help restore some, if often limited, independence. Treatment requires replacing or supplementing intravenous or intramuscular thiamine with sufficient nutrition and hydration. However, disease-caused amnesia and brain damage does not usually respond to thiamine replacement therapy.
Drug therapy is sometimes advised. Treatment normally needs 3-12 months of oral thiamine, however only approximately 20 percent of cases are recoverable. If treatment is successful, improvements will emerge within two years, although recovery is sluggish and generally incomplete.
As an urgent form of treatment, a pairing of IV or IM thiamine with high concentration of B-complex vitamins can be given three times daily for 2-3 days. In most cases, an effective reaction is observed. A dose of 1 gramme thiamine may also be given for clinical response. In those who are very malnourished, the rapid availability of glucose without sufficient thiamine levels to digest is thought to induce cell damage. Thus, thiamine supplementation and intravenous glucose are often effective practise.
KS memory aspect treatment may also include domain-specific learning, which, when applied for rehabilitation, is called the vanishing signs approach. They try to use intact memory processes as the basis for rehabilitation. Those who used therapy's method of disappearing signs were shown to absorb and retain material more quickly.
People diagnosed with KS have normal life expectancy, assuming they refrain from alcohol and follow a balanced diet. Empirical evidence suggests that health behaviours have beneficial impact on Korsakoff syndrome.
Epidemiology
Tariffs vary across countries, but an estimated 12.5% of strong drinkers are affected.
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