Hydrocephalus, especially normal pressure hydrocephalus, has become a major health risk killer. Normal pressure hydrocephalus refers to hydrocephalus in which the intracranial pressure is not high on lumbar puncture manometry, but the ventricles are progressively enlarged. It is mainly manifested by three main signs: mental retardation, physical activity disorder and urinary and fecal disorder. The manifestations of mental retardation are: people are getting dumber and dumber, even showing childish behavior, slow reaction, dull gaze, unable to take care of themselves, disorientation, and easily lost. Physical activity disorders are: unstable walking, easy to fall over and fall down. Urinary and fecal disorders are manifested as uncontrollable urination and defecation, even in public, and personality disorders. If these three main signs appear, normal pressure hydrocephalus should be highly suspected and should be promptly seen in the hospital. Cranial CT and MRI suggest ventricular enlargement and subventricular fingering edema, at which point hydrocephalus can be basically confirmed. The diagnosis of normal pressure hydrocephalus is established when the cerebrospinal fluid pressure is normal by lumbar puncture. Normal pressure hydrocephalus is mainly distinguished from various types of dementia, especially cerebrovascular dementia. However, sometimes it is still difficult to differentiate. This is when a method is needed to further help confirm the diagnosis. Normal pressure hydrocephalus has a relatively quiescent period and theoretically does not heal completely on its own, often eventually failing and dying if not treated aggressively. This requires surgical treatment with a cerebrospinal fluid shunt. However, there are still some patients who do not resolve hydrocephalus after surgery. This requires us to confirm the presence of hydrocephalus before surgery and to predict the outcome after hydrocephalus shunting. The cerebrospinal fluid perfusion test is a method that was created to address this paradox. A normal adult produces about 500 ml of cerebrospinal fluid per day, and this 500 ml is completely absorbed within the central nervous system. If 1% of the cerebrospinal fluid is not absorbed each day, that is, 5 mL is not absorbed, that is 150 mL for a month, and 150 mL is enough to cause severe neurological deficits or even death. The cerebrospinal fluid perfusion test is to measure the absorption capacity of the cerebrospinal fluid. The specific method is to inject artificial cerebrospinal fluid into the subarachnoid space at a certain rate after lumbar puncture. A normal person will absorb it well and will not experience more than a certain magnitude of intracranial hypertension within a certain period of time, while a patient with cerebrospinal fluid absorption disorder will quickly experience intracranial hypertension, and the magnitude of the increase is much greater than that of a normal person. The effect of surgical shunting is judged according to the changes in the patient’s clinical performance before and after the release of fluid. If the patient’s condition improves after the release of fluid, then the patient’s condition is more likely to improve after shunt surgery. This technique is simple and easy to perform, does not require expensive equipment, is minimally invasive, and has been used in clinical practice.