A Rare Presentation of Wernicke's Encephalopathy With Internuclear Ophthalmoplegia.

Wernicke's encephalopathy (WE) is a neurological emergency caused by thiamine (vitamin B1) deficiency and classically presents with a triad of confusion, ophthalmoplegia, and ataxia. Although classically associated with chronic alcohol misuse, it may also occur in non-alcoholic individuals due to causes such as persistent vomiting, malnutrition, or gastrointestinal disorders. We present a rare case of WE in a 35-year-old woman who developed internuclear ophthalmoplegia (INO), a highly unusual manifestation in this context. She presented with a one-week history of blurred and double vision, gait unsteadiness, and persistent bilious vomiting, resulting in significant weight loss. Neurological examination revealed right INO with preserved convergence, positive Romberg's sign, and gait ataxia. Imaging revealed fibrous dysplasia of the left temporal bone, but no intracranial abnormalities were suggestive of WE. Based on clinical findings, a clinical diagnosis of WE secondary to persistent vomiting was made. Prompt intravenous thiamine led to a rapid resolution of symptoms. This case underscores the importance of early recognition of atypical WE manifestations, even in the absence of classic imaging findings. Timely thiamine replacement is critical, as delayed or inadequate treatment can result in up to 20% mortality, with approximately 85% of survivors developing Korsakoff's psychosis.