Trauma can produce hydrocephalus, brain tumors can produce hydrocephalus, and congenital hydrocephalus in children, so where exactly does hydrocephalus come from? The secretion and absorption of normal cerebrospinal fluid is often in a dynamic balance. In pathological conditions, excessive intracranial cerebrospinal fluid accumulates in the ventricular system, or sometimes in the subarachnoid space, mostly with increased intracranial pressure, called hydrocephalus. Hydrocephalus occurs when the cerebrospinal fluid circulation system becomes obstructed at any site, with hydrocephalus caused by brain tumors being the most common. The areas that tend to cause hydrocephalus are: Interventricular foramen: Cerebrospinal fluid from the ventricles enters the third ventricle through this foramen. When a tumor occurs in this area, this foramen becomes obstructed and enlargement of one of the lateral ventricles occurs. The common tumor is glioma. Third ventricle: It is a necessary pathway for cerebrospinal fluid circulation in both lateral ventricles. When obstruction occurs, symmetrical enlargement of both ventricles will occur. Common tumors include glioma and craniopharyngioma. Pineal region: Cerebrospinal fluid from the third ventricle flows into the fourth ventricle through the aqueduct of the midbrain, and the pineal region is located just behind the aqueduct. Usually both lateral ventricles and the third ventricle are enlarged at the same time. Common tumors include glioma and germ cell tumors. Posterior cranial fossa: Includes the fourth ventricle, cerebellopontine angle, occipital foramen, and slope. It can cause enlarged effusion in the ventricles above the fourth ventricle. Sensory tumors include glioma, auditory neuroma, chordoma, meningioma, etc.