We often find intracranial arachnoid cysts in the course of our clinical work, so what exactly is an intracranial arachnoid cyst? How is it formed and how is it treated? Intracranial arachnoid cysts, as the name implies, are cystic occupying lesions containing cerebrospinal fluid formed by the intracranial arachnoid membrane. Congenital intracranial arachnoid cysts are cystic cavities formed during the embryonic period due to increased accumulation of cerebrospinal fluid, which is a developmental abnormality, while acquired intracranial arachnoid cysts are usually formed due to birth or postnatal trauma, intracranial hemorrhage, infection producing mucous secretions or craniotomy injury causing arachnoid adhesions, which in turn block the subarachnoid space and brain pool. Cerebrospinal fluid accumulation. Intracranial arachnoid cysts are divided into intra-arachnoid cysts and subarachnoid cysts according to their pathological characteristics. Intra-arachnoid cysts, also known as true arachnoid cysts, are basically surrounded by the arachnoid membrane. A subarachnoid cyst, also known as a soft membrane cyst, has an arachnoid membrane at the top of the cyst wall and soft meninges at the bottom. Intracranial arachnoid cysts account for approximately 1%-3% of intracranial occupying lesions, occurring in approximately 70% of children, with a male to female ratio of approximately 4:1, with more cysts on the left side of the temporal region than on the right. According to the chance of occurrence, the lateral fissure and anterior temporal region are the most common, followed by the greater occipital pool, cerebral convexity, tetrahymenal pool, and pontocerebellar horn. Approximately 60% to 80% of arachnoid cysts present with clinical manifestations, most notably headache and vomiting due to increased intracranial pressure, and the first clinical presentation is a seizure. Children may present with cranial enlargement, localized skull augmentation, mental retardation, and ataxia. The clinical presentation of cysts can vary from location to location, for example, cysts in the posterior cranial fossa may present with early signs of hydrocephalus, while cysts in the temporal lobe may present with seizures. Children with arachnoid cysts can develop intracranial hemorrhage after trauma. Adjunctive examinations for intracranial arachnoid cysts are based on CT scan and MRI of the brain. CT of the brain may show cysts with the same density of cystic fluid as cerebrospinal fluid. MRI shows low signal in T1-weighted images and high signal in T2-weighted images, and the cyst fluid is the same signal as the cerebrospinal fluid. In addition, cerebral pool imaging is often used clinically to distinguish whether the cyst is connected to the cerebrospinal fluid circulation. Intracranial arachnoid cysts do not require urgent surgery if they are asymptomatic. Surgery is advocated when there is an increase in intracranial pressure. In children, temporal lobe cysts are promptly removed surgically if they present with epilepsy and developmental disorders. In addition, modern medicine shows that neuropsychological tests with mild neuropsychiatric symptoms, memory loss, cognitive decline, and obvious limited neurological deficits should be actively and decisively taken to surgery, which has a good prognosis.