The lack of knowledge, careless observation of patient's condition, and incomplete understanding of the results of laboratory tests and examinations make the clinical diagnosis and treatment of some cases in our daily practice full of twists and turns. In this article, a detailed description and analysis was provided on the diagnosis and treatment of one case of occult malignant tumor with cerebral infarction as the first manifestation and two cases of neuromyelitis optica spectrum disorders, with an attempt to explore the significance of in-depth study of these special cases in training clinical thinking mode and accumulating experience. By studying the clinical diagnosis and treatment of these cases, we can grasp the latest knowledge and progress, learn to pay attention to the details of disease evolution, laboratory tests, and examinations, and rearrange the logical thinking process in order to train our clinical thinking ability, constantly sum up experience and lessons, and infer other cases from one instance.