Background Wernicke's encephalopathy (WE) is a neurological emergency due to thiamine deficiency. The clinical triad of ophthalmoplegia, altered consciousness, and ataxia is uncommon. MRI is a powerful tool to help prompt diagnosis, as early treatment can result in complete recovery.

Case Report A 64-year-old man, who recently commenced chemotherapy for gastric cancer, was admitted with worsening vomiting by his oncology team. He had multiple vascular risk factors and a previous stroke. 4 days into admission, he developed sudden onset confusion, diplopia, ataxia and worsening right sided weakness. MRI brain was performed and a clinical diagnosis of acute stroke was suspected with referral to the stroke team. Examination revealed disorientatation, bilateral six nerve palsies, right arm weakness and ataxic gait. WE was suspected clinically and intravenous thiamine immediately administered. Neuroradiological review of the MRI confirmed radiological signs consistent with WE—signal abnormality in both inferior colliculi, periaqueductal gray matter, medial thalami and the hypothalamic region. His symptoms resolved within 2 days. Repeat MRI Brain 2 months later confirmed resolution of the WE associated signal changes.

Conclusion Our patient presented with the classical triad of WE. However, the case illustrates that WE can be a stroke mimic. Recognising the specific neuroradiological features on MRI brain can facilitate early diagnosis.