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An Overview Of Wernicke-Korsakoff Syndrome

  • - Alcohol related dementia - Wernicke-Korsakoff Syndrome
  • Oct 30, 2011
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  • Viewed: 2663
Tags: | alcohol abuse | ataxia | karl wernicke | korsakoff's psychosis |

Definition
Wernicke-Korsakoff Syndrome (WKS) is a neurological disorder. Wernicke’s Encephalopathy and Korsakoff’s Psychosis are the acute and chronic phases, respectively, of the same disease.

WKS is caused by a deficiency in the B vitamin thiamine. Thiamine plays a role in metabolizing glucose to produce energy for the brain. An absence of thiamine therefore results in an inadequate supply of energy to the brain, particularly the hypothalamus (which regulates body temperature, growth and appetite and has a role in emotional response. It also controls pituitary functions including metabolism and hormones) and mammillary bodies (where neural pathways connect various parts of the brain involved in memory functions). The disease is typically associated with chronic alcoholism, but may be associated with malnutrition or other conditions which cause nutritional deficiencies.

Facts
WKS has a relatively low prevalence (0.4% to 2.8% of reported autopsies).  However, it is likely that the disease is under-reported and under-diagnosed. An estimated 25% of WKS cases were missed where the brains were not examined microscopically. Another study found that only 20% of clinical WKS diagnoses were made correctly in life when compared to autopsy results. Moreover, WKS appears to be only one distinct disease that causes alcohol-related dementia. Based on clinical research studies, between 22% to 29% of individuals with dementia were found to be heavy drinkers or alcoholics and 9% to 23% of elderly alcoholics in alcoholism treatment were found to also have dementia.

An estimated 1.1 to 2.3 million older Americans have problems with alcohol.  Medical researchers are still grappling with how to more fully define the association between heavy alcohol use and symptoms of dementia.

Symptoms
WKS symptoms may be long-lasting or permanent and should be distinguished from the acute affects of alcohol consumption or from a period of alcohol “withdrawal.”  The disease is characterized by mental confusion, amnesia (a permanent gap in memory) and impaired short-term memory.  An estimated 80% of persons with WKS continue to have a chronic memory disorder.  Individuals often appear apathetic and inattentive and some may experience agitation.  In addition, WKS tends to impair the person’s ability to learn new information or tasks.  Individuals with WKS are known to “confabulate” (make up or invent information to compensate for poor memory).  Other symptoms include ataxia (weakness in limbs or lack of muscle coordination, unsteady gait), slow walking, rapid, tremor-like eye movements or paralysis of eye muscles Fine motor function (e.g., hand or finger movements) may be diminished and sense of smell also may be affected.  In the advanced stages, coma can occur. Although treatable if caught early enough, the death rate from WKS is relatively high, about 10% to 20%.

Diagnosis
WKS is often missed as a diagnosis.  In the acute phase, a physical examination may reveal skin changes and a red “beefy” tongue.  In addition, blood count, electrolytes and liver function tests should be conducted. Even in the chronic phase, an MRI may show shrunken mammillary bodies and other changes in the brain.  CT scans have showed enlarged ventricles and diencephalic lesions.

Treatments

Nutritional
Individuals with signs of Wernicke’s encephalopathy should be treated with thiamin immediately. In many cases, prompt administration of thiamin reverses the symptoms and prevents amnesia from developing. Thiamin can be administered intravenously or directly into the digestive system. Unfortunately, thiamin is less effective in the chronic phase of the condition. Based on autopsy findings suggesting the presence of Wernicke-Korsakoff syndrome in people with milder cognitive problems who do not show the classic signs of the disorder, researchers have examined the usefulness of thiamin treatment in people with alcohol dependence who are at risk of developing the syndrome. Results suggest that thiamin treatment improves performance on memory tests in this group, and that higher thiamin doses are associated with better performance. These findings suggest that thiamin treatment can help prevent Wernicke-Korsakoff syndrome in heavy drinkers.

Medication
Recent reports suggest that donepezil and rivastigmine , drugs used to treat Alzheimer’s disease , may improve memory in patients with Wernicke-Korsakoff syndrome. Both drugs prevent the breakdown of the neurotransmitter acetylcholine, which is important for the formation of memories. Patients treated with these drugs showed improvements on memory tests and were more able to recognize hospital staff and family members. Although improvements appear to be rather modest, these drugs may be useful for patients who do not respond to thiamin. Antidepressants that increase levels of serotonin may also be helpful, although the reasons why are not clear since these drugs are not effective with other memory disorders.

Conditioning
The fact that implicit memory is not affected by Wernicke-Korsakoff syndrome has led some researchers to explore the use of classical conditioning procedures in helping patients to remember specific people. In classical conditioning, animals and people learn to associate a stimulus with an outcome. The most famous example is the pairing of a ringing bell with food. Dogs naturally salivate when given food. In a famous experiment, Ivan Pavlov rang a bell immediately before serving food to dogs. After doing this repeatedly, Pavlov found that the dogs salivated upon hearing the bell ring even when the food was not presented. This form of learning does not rely on the hippocampus and cortex but appears to involve neurons in other parts of the brain. Patients with Wernicke-Korsakoff syndrome who are given specific rewards for correctly choosing a picture of a face that matches a face they have seen previously are more able to choose the correct face than those who do not receive the rewards. Although these individuals do not explicitly remember the face they saw previously, they are still able to make the correct choice. Training patients in this way could enable them to recognize familiar people and differentiate them from strangers.

It is important that a full medical history include information about the person’s daily drinking habits, both present and past.  Family, friends and past medical records should be consulted to obtain the most complete information possible on the person’s history with alcohol.  Proposed criteria for diagnosing alcohol-related dementia (not strictly WKS) suggest that the diagnosis be made at least 60 days after the last exposure to alcohol and that a “significant” alcohol history would include an average of 35 drinks per week for men (28 for women) for at least five years.  Typically, the period of significant drinking must be within three years of the onset of dementia.

Recent medical research also suggests that the genetic marker APOE4 is a significant predictor of global intellectual deficits in people with WKS. Individuals with the ApoE genotype may experience a certain interaction with heavy alcohol use which could predispose them to WKS.  Concerns about an inherited susceptibility to WKS should be discussed with a genetic counselor.

In cases of suspected non-alcohol related WKS, the physician may investigate anorexia nervosa, hypermesis gravidarum, severe malnutrition and other disorders or surgical procedures which impair intestinal absorption of thiamine.

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