A septum pellucidum cyst, also called fifth ventricle, is a congenital anomaly. Since Dandy reported the first case of septal cyst (septum pellucidum cyst,SPC) in 1931, similar reports are not uncommon, and with the application and popularity of CT and MR, related reports have increased significantly both at home and abroad. It is generally believed that septum pellucidum cyst is a benign, isolated cystic lesion that does not communicate with the ventricles or subarachnoid space, and the cyst fluid is similar in composition to cerebrospinal fluid, which may arise from the cyst wall. The cyst wall is thick and histological analysis of the ultrastructure of the cyst wall by electron microscopy observed that the cyst wall is composed of many protofibrous and fibrous structures and that the cyst wall appears to originate from the septum pellucidum rather than the choroid plexus and arachnoid membrane. On CT or MR examination, the hyaline septum was shown to be widened and expanded in an arc to the sides, containing cystic fluid with the same density or signal as the cerebrospinal fluid. on CT-enhanced scans, the cyst wall was not enhanced. It is generally believed that septal cysts (SPC) can be divided into two categories: asymptomatic septal cysts (ASPC) and symptomatic septal cysts (SSPC), which are also known as dilated septal cysts (ESPC); ASPC are usually found incidentally during physical examination; ESPC may cause blockage of interventricular foramen, distorted displacement of deep cerebral vessels, and compression of hypothalamus and optic chiasm with corresponding clinical symptoms. ASPC usually requires no treatment, but periodic examinations and dynamic observation are sufficient; once diagnosed, ESPC requires surgical treatment. There are many methods of surgical treatment, such as craniotomy, cyst wall opening, cyst|lateral ventricular shunt, lateral ventricular|abdominal shunt, etc., which have been widely used, but they need to be improved because of the large surgical trauma, heavy postoperative reaction and many complications. The development of microinvasive neurosurgery, especially the advancement of stereotactic techniques, has made the surgical treatment of this disease easier, more accurate and safer. The concept and diagnosis of septal cysts In the past, the septal cavity, Verga cavity, septal cysts and Verga cavity cysts were collectively referred to as the “septal cavity. Shaw noted that the cavity between the two walls of the septum pellucidum must be at least 1 mm wide to be called a septal cavity. A septal cavity is a normal variant and is usually asymptomatic. The diagnosis of a septal cyst is established if both walls of the fluid-containing structure between the lateral ventricles on either side are curved and bulging to the sides, not in a normal parallel state, and the distance between the lateral walls is greater than or equal to 10 mm. This artificially defined diagnostic criterion is clinically important because if the size of a cyst exceeds this criterion, it may cause narrowing of the interventricular foramen leading to hydrocephalus or neurological damage due to compression of peripheral nerve structures with clinical symptoms. In contrast, cysts less than or equal to 5 mm in width are mostly asymptomatic. Therefore, if on axial images (CT or MRI), the two walls of the hyaline septum are aligned anterior-posteriorly parallel to each other, with a diameter of less than 10 mm, and is clinically asymptomatic, it is called a hyaline septal cavity. There may be a traffic opening between the septal cavity and the lateral ventricle. On axial images (CT or MRI), the two walls of the septum pellucidum are curved and bulging to the sides, convex to the lateral ventricles on both sides, and the diameter between the two walls is greater than or equal to 10 mm, with clinical symptoms that can be explained by the lesion, called septal cyst. There is no traffic between the septal cysts and the lateral ventricles. The septum pellucidum is the septum between the two lateral ventricles, which, if not fully fused, creates a potential gap (the septal cavity, the fifth ventricle), which expands posteriorly to form the Vergae’s cavity, the sixth ventricle. It has been found that the incidence of septal cavity is 10% under one year of age. The incidence decreases with age. A hyaline septal cyst can be considered when the walls of both sides of the hyaline septal cavity protrude and the spacing is greater than 0.5 cm. A hyaloid septal cyst is a relatively common intracranial lesion of a congenital, benign process. Most patients are found incidentally during head CT or MRI examinations and are mostly asymptomatic and do not require surgical management. However, some septal cysts grow in size with age and are associated with obvious clinical symptoms, such as headache, dizziness, poor memory, epilepsy, syncope, etc. The septal cyst is the interval between the two ventricles, a film containing nerve fibers and gray matter cells, located in the anterior midline of the brain, with the corpus callosum above it and the dome below it, closely connected to the midline structures of the brain and generally not connected to the ventricles. In adults, only 15-20% of them exist, and 93% of them have not been closed by a certain age or are reopened by trauma or inflammation, and are filled with cerebrospinal fluid both to form hyaline septal cysts. Most of the hyaline septal cysts are small in size and have no clinical symptoms, only when the cyst is huge and affects the midline limbic system or interventricular foramen does it cause a series of neuropsychiatric symptoms, at which time it is treated surgically