The examination of cerebral infarction is mainly based on the patient’s age, onset and stroke risk factors to arrive at an impression diagnosis of cerebral infarction. The main tests include the following items: i. CT plain scan of the head, which is the most commonly used test and is meaningful for clinical suspicion of stroke. However, cerebral infarction usually takes 24 hours or even longer to show brain tissue density changes and is not sensitive to ultra-early ischemic lesions and small cortical or subcortical infarct foci, especially brainstem and cerebellar infarcts are more difficult to detect. Second, MRI, a non-invasive examination, can diagnose ischemic stroke at an early stage, showing the size and location of ischemic tissue at an early stage, and even small infarct foci in the subcortex, brainstem and cerebellum, with a diagnostic sensitivity of 80%-100% and specificity of 95%-100%. 2 hours after onset, it can show ischemic lesions, suggesting irreversible damage and providing time for early treatment.