Psychiatric-Predominant Wernicke Encephalopathy With Normal Blood Thiamine Levels: A Case Report.

Wernicke encephalopathy (WE), caused by thiamine deficiency in patients with chronic alcohol use, may progress to Korsakoff syndrome if untreated. Diagnosis is challenging and often missed because the classic triad can be incomplete and blood thiamine levels can be normal. A 56-year-old woman with 40-60 g of pure alcohol consumption daily since her 20s and a previous psychiatric hospitalization for alcohol dependence at the age of 50 years developed hallucinations, delusions, agitation, and cognitive decline. One month later, she fractured her left femoral neck at home, for which she underwent hemiarthroplasty at a general hospital. Although no clear alcohol withdrawal symptoms were observed, the patient was unable to engage in meaningful conversations and was diagnosed with alcohol-related dementia. Antipsychotic treatment was ineffective, and she was transferred to our hospital. Upon admission, her Hasegawa Dementia Scale-Revised (HDS-R) score was 1. Neurological examination, brain computed tomography (CT), and laboratory tests, including blood thiamine levels, appeared normal. Based on the patient's clinical course, WE was suspected. High-dose intravenous thiamine (400 mg/day) was administered for five days, followed by oral thiamine. Her psychiatric symptoms and cognitive function rapidly improved, and the HDS-R score increased to 27 by day 17. The patient was diagnosed with WE. WE diagnosis can be difficult, particularly in patients with alcohol use disorder and atypical presentations. High-dose intravenous thiamine is safe and may serve as an intervention with diagnostic value when WE cannot be excluded.