Here, we report a case of a 64-year-old female with acute-onset vertigo, nausea, and vomiting. In an emergency imaging examination, the results of computed tomography (CT) and diffusion weighted imaging (DWI) were negative. However, on 1 day post-hospital admission, a small acute infarct in the posterolateral aspect of the left medulla was detected by DWI. Extra attention should be payed to the false-negative imaging results to avoid diagnosis and treatment delay.