In clinical practice, there is no concept of how large an arachnoid cyst is normal. As long as there is an arachnoid cyst, it is an abnormal change and does not require special clarification as to how large it is, but it is important to note the size of the arachnoid cyst in terms of the degree of compression on the brain and the patient’s clinical symptoms, which are the criteria for deciding whether to take further treatment. If the arachnoid cyst is very small and there is no pressure on the brain tissue, and the clinical symptoms are relatively mild, no special treatment is needed at this time, and regular follow-up is sufficient. If the arachnoid cyst is relatively large and the compression of brain tissue is severe, and may even affect daily life, it is recommended to improve the relevant tests and give surgical treatment, such as puncture and drainage of the cyst or resection surgery, etc. Therefore, it must be combined with the actual situation to make a better evaluation.