Wernicke encephalopathy is characterized by acute onset of confusion, nystagmus, partial ophthalmoplegia, and ataxia due to thiamin deficiency. Diagnosis is primarily clinical. The disorder may remit with treatment, persist, or degenerate into Korsakoff psychosis. Treatment consists of thiamin and supportive measures.
Wernicke encephalopathy results from inadequate intake or absorption of thiamin plus continued carbohydrate ingestion. Severe alcoholism
is a common underlying condition. Excessive alcohol intake interferes
with thiamin absorption from the gastrointestinal tract and hepatic
storage of thiamin; the poor nutrition associated with alcoholism often
precludes adequate thiamin intake.
Wernicke encephalopathy may also result from other conditions
that cause prolonged undernutrition or vitamin deficiency (eg, recurrent
dialysis, hyperemesis, starvation, gastric plication, cancer, AIDS).
Giving a carbohydrate load to patients with thiamin deficiency (ie,
refeeding after starvation or giving IV dextrose-containing solutions to
high-risk patients) can trigger Wernicke encephalopathy.
Not all thiamin-deficient alcohol abusers develop Wernicke
encephalopathy, suggesting that other factors may be involved. Genetic
abnormalities that result in a defective form of transketolase, an
enzyme that processes thiamin, may be involved.
Characteristically, central nervous system lesions are
symmetrically distributed around the 3rd ventricle, aqueduct, and 4th
ventricle. Changes in the mamillary bodies, dorsomedial thalamus, locus
ceruleus, periaqueductal gray matter, ocular motor nuclei, and
vestibular nuclei are common.
Symptoms and Signs
In patients with Wernicke encephalopathy, clinical changes occur suddenly.
Oculomotor abnormalities, including horizontal and vertical nystagmus and partial ophthalmoplegias (eg, lateral rectus palsy, conjugate gaze palsies), are common. Pupils may be abnormal; they are usually sluggish or unequal.
Vestibular dysfunction without hearing loss is common, and the
oculovestibular reflex may be impaired. Gait ataxia may result from
vestibular disturbances, cerebellar dysfunction, and/or polyneuropathy;
gait is wide-based and slow, with short-spaced steps.
Global confusion is often present; it is characterized by
profound disorientation, indifference, inattention, drowsiness, or
stupor. Peripheral nerve pain thresholds are often elevated, and many
patients develop severe autonomic dysfunction characterized by
sympathetic hyperactivity (eg, tremor, agitation) or hypoactivity (eg,
hypothermia, postural hypotension, syncope). In untreated patients,
stupor may progress to coma, then to death.
Diagnosis
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Clinical evaluation
There are no specific diagnostic studies. Diagnosis of Wernicke
encephalopathy is clinical and depends on recognition of underlying
undernutrition or vitamin deficiency. There are no characteristic
abnormalities in cerebrospinal fluid, evoked potentials, brain imaging,
or electroencephalogram. However, these tests, as well as laboratory
tests (eg, blood tests, glucose, complete blood count, liver tests,
arterial blood gas measurements, toxicology screening), should typically
be done to rule out other etiologies. Thiamin levels are not routinely
measured, because serum thiamin levels do not always reflect
cerebrospinal fluid levels and normal serum levels do not exclude the
diagnosis.
Prognosis
Prognosis depends on timely diagnosis of Wernicke encephalopathy.
If begun in time, treatment may correct all abnormalities. Ocular
symptoms usually begin to abate within 24 hours after early thiamin
administration. Ataxia and confusion may persist days to months. Memory
and learning impairment may not resolve completely. Untreated, the
disorder progresses; mortality is 10 to 20%. Of surviving patients, 80%
develop Korsakoff psychosis; the combination is called Wernicke–Korsakoff syndrome.
Treatment
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Parenteral thiamin
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Parenteral magnesium
Treatment of Wernicke encephalopathy consists of immediate
administration of thiamin 100 mg IV or IM, continued daily for at least 3
to 5 days. Magnesium is a necessary cofactor in thiamin-dependent
metabolism, and hypomagnesemia should be corrected using magnesium sulfate
1 to 2 g IM or IV every 6 to 8 hours or magnesium oxide 400 to 800 mg
orally once/day. Supportive treatment includes rehydration, correction
of electrolyte abnormalities, and general nutritional therapy, including
multivitamins. Patients with advanced disease require hospitalization.
Alcohol cessation is mandatory.
Because Wernicke encephalopathy is preventable, all
undernourished patients should be treated with parenteral thiamin
(typically 100 mg IM followed by 50 mg orally once/day) plus vitamin B12
and folate (1 mg orally once/day for both), particularly if IV dextrose
is necessary. Thiamin is also prudent before any treatment is begun in
patients who present with a reduced level of consciousness. Patients who
are undernourished should continue to receive thiamin as outpatients.
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