What Is Hydrocephalus and How Many Types Are There?
The CSF produced every day in the brain circulates in the ventricles, passes to the brain surface and is absorbed into the blood by the arachnoid villi. When the balance between production and absorption is disrupted, the ventricles swell and press on the brain. There are three main types: in obstructive hydrocephalus there is an obstacle to CSF flow (aqueductal stenosis, tumor, bleeding); in the communicating type the flow is free but absorption is impaired; and normal-pressure hydrocephalus (NPH) is a treatable condition seen in the elderly that progresses with the triad of gait disturbance, urinary incontinence and dementia (Hakim's triad). Distinguishing which type it is (with a CSF-flow MRI when needed) is the basis of the treatment plan, because the treatment method changes entirely according to the type.
Symptoms: From Infant to Elderly
Symptoms differ by age. In infants whose fontanelle has not yet closed, a rapidly enlarging head circumference, a bulging fontanelle, vomiting, irritability and downward deviation of the eyes (the 'setting sun' sign) can be seen. In older children and adults, a severe headache that is especially marked in the mornings and accompanied by vomiting, blurred or double vision, balance disturbance and confusion come to the fore. In the elderly, the earliest sign of NPH is a 'magnetic gait' in which the feet feel stuck to the floor; urinary incontinence and a weakening of attention and memory are added to this. The importance of NPH is that it is a treatable cause of dementia; this is why a correct diagnosis is critical.
Ventriculo-Peritoneal (VP) Shunt
The VP shunt is a permanent drainage system that transfers excess CSF from the ventricles to the abdominal cavity through a valve and tubes, where it is absorbed naturally. The system consists of a ventricular catheter, a valve that regulates the flow and a peritoneal catheter. It is preferred in communicating hydrocephalus, in NPH and in many infant/child cases, or in situations where ETV is not suitable. Its advantage is that it can be applied across a wide range of patients and rapidly returns pressure to normal; in NPH, a significant proportion of patients are reported to have meaningful improvement in gait and cognitive function. Its disadvantage is lifelong dependence on the system and the cumulative increase over time of complications such as infection, blockage or disconnection; in these situations a shunt revision may be required.
Endoscopic Third Ventriculostomy (ETV)
ETV is a method that endoscopically creates a small opening (stoma) in the floor of the third ventricle, allowing the CSF to bypass the obstruction and drain into the natural subarachnoid space, thereby engaging the body's own absorption mechanism. For it to be successful, the obstruction must be below the third ventricle and the absorption mechanism must be intact; for this reason its main indication is obstructive hydrocephalus such as aqueductal stenosis. Its greatest advantage is that it leaves no foreign body in the body, so the risk of shunt infection is almost zero, and that it offers a permanent solution when successful. The procedure takes 30–60 minutes in uncomplicated cases and a 1–2 day stay is usually sufficient. Its disadvantage is that it is not suitable for every type of hydrocephalus (it is particularly not preferred in the communicating type and in NPH), the chance of success is low in small infants, and it requires surgical experience. Suitability is estimated before surgery with tools such as the ETV Success Score (ETVSS).
Which Method for Which Patient, and Programmable Valves
The decision is always made according to the type of hydrocephalus and the patient. In communicating hydrocephalus and NPH a shunt is generally used; in obstructive hydrocephalus, if suitable, ETV comes to the fore first. In infants under one year of age, since the success of ETV is low, a shunt is mostly preferred. When a shunt is chosen, the valve type is also important: fixed-pressure valves are suitable for simple and standard cases, while programmable valves, which can be adjusted from outside with a magnet without surgery, are valuable particularly in NPH and in complex patients with a history of over-drainage or requiring multiple revisions. A programmable valve is more costly but, in the right indication, markedly increases shunt success. In NPH, before the decision to shunt, a 'tap test' (CSF removal test) that helps predict the outcome can be performed. No method guarantees 100% success in every patient; our aim is to choose the right method for the right patient.