Thiamine and WE

Q; 44 year homeless patient is brought to ED by paramedics with mental status change. The patient is known to ED as a 'frequent flyer' and known to have Wernick's encephalopathy (WE). ED's resident reported that serum thiamine level was in the normal range. A normal thiamine blood level rules out WE?

A) True

B) False

Answer: B

WE is a clinical diagnosis. The sensitivity and specificity of blood tests are unreliable as blood levels do not accurately reflect brain thiamine levels. 

For academic purposes, thiamine deficiency can be reliably detected by measuring erythrocyte thiaminе transketolase activity (ETKA) before and after adding thiamine pyrophosphate (ТΡP). A low ETKA, along with more than 25 percent stimulation, establishes diagnosis of thiаmiոе deficiency. Also, serum thiamine or TΡР level requires high-performance liquid chromatography. These are special, time-consuming, and expensive tests, and the utility for such tests is not established. 

The best maneuver is to administer thiamine if WE is suspected.

To rule out WE, one approach is to perform a lumbar puncture (LP). Pleocytosis or protein >100 mg/dL suggests alternative diagnoses. 

If differential diagnosis is needed to rule out nonconvulsive seizure, an electroencephalogram (EEG) should be applied, as only approximately half of WE patients have EEG abnormalities with diffuse mild to moderate slow wave activity.

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References:

1. Victor M, Adams RA, Collins GH. The Wernicke-Korsakoff syndrome and related disorders due to alcoholism and malnutrition, FA Davis, Philadelphia 1989.

2. Leigh D. Erythrocyte transketolase activity in the Wernicke-Korsakoff syndrome. Br J Psychol 1981; 138:153.

3. Lu J, Frank EL. Rapid HPLC measurement of thiamine and its phosphate esters in whole blood. Clin Chem 2008; 54:901.

4. Davies SB, Joshua FF, Zagami AS. Wernicke's encephalopathy in a non-alcoholic patient with a normal blood thiamine level. Med J Aust 2011; 194:483.