Sporadic Creutzfeldt-Jakob disease (sCJD) is a rare, rapidly progressive human prion disease that often presents with nonspecific early symptoms. Its clinical manifestations may mimic common neurological conditions, including cerebrovascular disease and autoimmune encephalitis, contributing to diagnostic challenges. We retrospectively reviewed the diagnostic and therapeutic course of a 74-year-old man with sCJD. The patient initially presented with dizziness, blurred vision, and diplopia and was treated for acute cerebral infarction at another hospital, without symptomatic improvement. Over the following two months, his condition progressively deteriorated. He developed psychiatric and behavioral abnormalities, including incoherent speech, accompanied by a rapid decline in cognitive function, eventually progressing to akinetic mutism and impaired consciousness. Cranial diffusion-weighted imaging (DWI) revealed characteristic band-like cortical hyperintensities, known as the cortical ribbon sign. Although electroencephalography (EEG) showed abnormal electrical activity, typical periodic sharp wave complexes (PSWCs) were not observed. A planned lumbar puncture to obtain cerebrospinal fluid (CSF) for diagnostic tests, including 14-3-3 protein analysis and real-time quaking-induced conversion (RT-QuIC), was not performed because the patient developed acute delirium and could no longer cooperate. Based on the rapidly progressive clinical course and characteristic DWI findings, the patient was diagnosed with probable sCJD according to the applicable diagnostic criteria. This case highlights the importance of maintaining clinical suspicion for prion disease in older adults presenting with unexplained rapidly progressive cognitive decline, behavioral changes, or ataxia over a period of weeks to months. Early MRI with DWI is essential for diagnostic evaluation, alongside the systematic exclusion of infectious, metabolic, and autoimmune disorders.