A left temporal arachnoid cyst mainly means that there is a membranous structure in the left temple, a membrane on the outside and a cerebrospinal fluid, or some other unknown fluid, inside the skull. This lesion is generally benign, and the effect on the brain is mainly gradual growth and compression of the brain tissue, and does not become malignant, and does not suddenly produce an unexpected situation. Patients need more timely observation, and if the pressure on the brain tissue is indeed very heavy, surgical treatment is required to remove the arachnoid cyst or drilling and drainage surgery, and the follow-up must be reviewed regularly, sometimes it is easy to recur, so timely improvement of the examination to be more meaningful.