Wernicke's+Encephalopathy

=Wernicke's Encephalopathy=

What it is
Wernicke encephalopathy is a serious neurologic disorder caused by thiamine (vitamin B-1) deficiency

Long-term alcohol abuse is the most common cause of Wernicke encephalopathy. In long-term alcoholics, malnutrition can reduce intestinal thiamine absorption by 70%, decreasing serum levels of thiamine from between 30% and 98% below the lower level established for normal subjects.
 * Risk Factors**

Other less common etiologies are forced or self-imposed starvation, protein-energy malnutrition resulting from inadequate diet or malabsorption (from sprue), conditions associated with protracted vomiting (eg, hyperemesis gravidarum), chronic renal failure, carbohydrate loading in the presence of marginal thiamine stores (feeding after starvation), bariatric surgery and other gastric bypass surgeries, absence of thiamine from the diet (in the case of infants fed formula without the addition of thiamine), and congenital transketolase function abnormalities.

Iatrogenic exacerbation of Wernicke encephalopathy can occur with prolonged glucose or carbohydrate loading in the setting of thiamine deficiency. A single acute administration of glucose does not appear to cause this effect. Nutritionally deficient patients receiving glucose should also receive thiamine, but urgent administration of glucose should not be delayed pending thiamine administration

Symptoms
//The 3 components of the classic triad of Wernicke encephalopathy are encephalopathy, ataxic gait, and some variant of oculomotor dysfunction. All 3 features of the triad are recognized in only about one third of cases. In addition to ophthalmoplegia and ataxia, 80% of adults will have some degree of peripheral neuropathy, which may include weakness, foot drop, and decreased proprioception.//

__Encephalopathy__ - characterized by a global confusional state, disinterest, inattentiveness, or agitation - most constant symptoms of Wernicke encephalopathy are the mental status changes - stupor and coma are rare

__Ataxic gait__ - likely to be a combination of polyneuropathy, cerebellar damage, and vestibular paresis - vestibular dysfunction, usually without hearing loss, is universally impaired in the acute stages of Wernicke encephalopathy - in less severe cases, patients walk slowly with a broad-based gait. (gait and stance may be so impaired as to make walking impossible) - cerebellar testing in bed with finger-to-nose and heel-to-shin tests may not illicit any notable deficit; thus, it is important to test for truncal ataxia with the patient sitting or standing. - Other symptoms that may occur in addition to, or in place of, the classic triad include vestibular dysfunction, hypothermia, hypotension, and coma

__Oculomotor dysfunction__ //ocular abnormalities are the hallmarks of Wernicke encephalopathy// - oculomotor signs are nystagmus, bilateral lateral rectus palsies, and conjugate gaze palsies reflecting cranial nerve involvement of the oculomotor, abducens, and vestibular nuclei. - less frequently noted are pupillary abnormalities such as sluggishly reactive pupils, ptosis, scotomata, and anisocoria The most common ocular abnormality is nystagmus, not complete ophthalmoplegia

Of patients surviving Wernicke encephalopathy, a large percentage have Korsakoff psychosis, characterized by the following: retrograde amnesia (inability to recall information), anterograde amnesia (inability to assimilate new information), decreased spontaneity and initiative, and confabulation.

How to Treat
//Because patients with Wernicke encephalopathy present with altered mental status in the prehospital setting, focus prehospital care on stabilizing the airway, ensuring oxygenation, and maintaining blood pressure and euvolemia.// Although as little as 2 mg of thiamine may be enough to reverse symptoms, the dose of thiamine required to prevent or treat Wernicke encephalopathy in most alcoholic patients may be as high as greater than 500 mg given once or, preferably, twice or thrice daily parenterally. With a short half-life, multiple daily administrations may be necessary to replete levels and allow for optimal blood-brain diffusions. Thiamine solution should be fresh, since old solutions may be inactive. Ataxia and acute confusional state may resolve dramatically, although improvement may not be noted for days or months.
 * Treat all poorly nourished patients with large doses of parenteral thiamine, particularly if intravenous glucose administration is necessary, even in the absence of symptoms and signs of Wernicke encephalopathy. Administering dextrose in a thiamine-deficient state exacerbates the process of cell death by providing more substrate for biochemical pathways that lack sufficient amounts of coenzymes
 * Start thiamine prior to or concurrently with treatment of intravenous glucose solutions, and continue until the patient resumes a normal diet. The administration of dextrose or other carbohydrates in this setting can be hazardous, because glucose oxidation is a thiamine-intensive process that may drive the last reserves of circulating vitamin B-1 toward the intracellular compartment, thereby aggravating the neurologic damage.
 * Patients with Wernicke encephalopathy are likely hypomagnesemic and should be treated empirically with parenteral magnesium sulfate, as they may be unresponsive to parenteral thiamine in the presence of hypomagnesemia. After correction of hypomagnesemia in conjunction with thiamine repletion, the blood transketolase activity can return to normal and clearing of the clinical signs may occur.

Additional Resources
[|Medscape - Overview]