Korsakoff’s syndrome is a manifestation of Wernicke’s encephalopathy, also called Wernicke’s disease. It happens in Wernicke’s disease in almost all alcohol abusers. It is rare among the other patients, but, for example, some cases have been observed after bariatric surgeries, when deficiency was not prevented by use of nutritional supplements. This neurological disorder is caused by a lack of thiamine (vitamin B1) in the brain, and is also often exacerbated by the neurotoxic effects of alcohol. When Wernicke’s encephalopathy accompanies Korsakoff’s syndrome, the combination is called the Wernicke–Korsakoff syndrome. Korsakoff’s is a continuum of Wernicke’s encephalopathy or disease, though a recognized episode of Wernicke’s is not always obvious. The syndrome is named after Sergei Korsakoff, a Russian neuropsychiatrist who discovered the syndrome during the late 19th century.
There are six major symptoms of Korsakoff’s syndrome:
- anterograde amnesia
- retrograde amnesia, severe memory loss
- confabulation, that is, invented memories which are then taken by the patient as true due to gaps in memory, with such gaps sometimes associated with blackouts
- minimal content in conversation
- lack of insight
- apathy — the patients lose interest in things quickly, and generally appear indifferent to change.
Thiamine is essential for the decarboxylation of pyruvate, and deficiency during this metabolic process is thought to cause damage to the medial thalamus and mammillary bodies of the posterior hypothalamus, as well as generalized cerebral atrophy. These brain regions are all parts of the limbic system, which is heavily involved in emotion and memory.
Korsakoff’s involves neuronal loss, that is, damage to neurons; gliosis, which is a result of damage to supporting cells of the central nervous system, and hemorrhage or bleeding also occurs in mammillary bodies. Damage to the dorsomedial nucleus or anterior group of the thalamus (limbic-specific nuclei) is also associated with this disorder. Cortical dysfunction may have arisen from thiamine deficiency, alcohol neurotoxicity, and/or structural damage in the diencephalon.
Originally, it was thought that a lack of initiative and a flat affect were important characteristics of emotional presentation in sufferers. Studies have questioned this, proposing that neither is necessarily a symptom of Korsakoff’s. Research suggesting that Korsakoff’s patients are emotionally unimpaired has made this a controversial topic. It can be argued that apathy, which usually characterizes Korsakoff’s patients, reflects a deficit of emotional expressions, without affecting the experience or perception of emotion.
Korsakoff’s Syndrome causes deficits in declarative memory in most patients, but leaves implicit spatial, verbal, and procedural memory functioning intact. People who have Korsakoff’s syndrome have deficits in the processing of contextual information. Context memories refers to the where and when of experiences, and is an essential part of recollection. The ability to store and retrieve this information, such as spatial location or temporal order information, is impaired. Research has also suggested that Korsakoff patients have impaired executive functions, which can lead to behavioral problems and interfere with daily activities. It is unclear, however, which executive functions are affected most.[ Nonetheless, IQ is usually not affected by the brain damage associated with Korsakoff’s syndrome.
At first it was thought that Korsakoff’s patients used confabulation to fill in memory gaps. However, it has been found that confabulation and amnesia do not necessarily co-occur. Studies have shown that there is dissociation between provoked confabulation, spontaneous confabulation (which is unprovoked), and false memories. That is, patients could be led to believe certain things had happened which actually had not, but so could people without Korsakoff’s syndrome.