With the widespread use of CT and MRI, there has been an increasing trend in the discovery of asymptomatic arachnoid cysts in recent years, which are in fact benign cysts that occur in the brain and spinal cord. Closely related to the arachnoid subarachnoid space brain pool, the cyst fluid is colorless and clear like cerebrospinal fluid. The most common primary, also known as congenital arachnoid cyst, is related to an abnormality that occurs in the embryo. Clinical manifestations Arachnoid cysts are most commonly seen in the supratentorial area, accounting for about 80% of cases, with the lateral fissure area accounting for 30 ∽ 50%, the saddle area and supratentorial area accounting for 10%, and the infratentorial area accounting for 20%. They are more common in males, accounting for more than 2/3 of the cases. Some cysts are asymptomatic for life, while others develop symptoms years later after detection. Progressive enlargement of cysts that compress peripheral nerve structures or obstruct normal cerebrospinal fluid circulation pathways may result in the following signs and symptoms. Increased intracranial pressure, epilepsy, and limited neurological deficits; children may also have increased head circumference, mental retardation, and limited skull expansion. Different sites may have different clinical manifestations such as visual field changes and endocrine symptoms in the saddle area. CT and MRI can be clarified, and CT brain pool imaging can understand the relationship between cyst and normal cerebrospinal fluid circulation pathway. If the cyst is in good communication with the subarachnoid space, surgery is of little significance. Treatment Conservative treatment for those without symptoms of increased intracranial pressure or focal neurological symptoms. Surgery should be performed if the cyst is enlarged and combined with hydrocephalus or causes symptoms of increased intracranial pressure or focal neurological symptoms or epilepsy. Surgery includes craniotomy or endoscopic surgery to remove the cyst wall or to communicate the cyst with the subarachnoid space or the ventricles, and shunt surgery using a shunt to divert cyst fluid into the abdominal cavity. Each has advantages and disadvantages, and all have acceptable results.