What Is Hydrocephalus?
A plain-language guide for parents — causes, shunts, warning signs, and living with this diagnosis
The morning my son’s pediatrician first used the word “hydrocephalus,” I did what every terrified parent does: I went home and searched it online. What I found was a wall of clinical language — ventricles, cerebrospinal fluid, intraventricular — interspersed with worst-case scenarios that made my hands shake. What I needed, and couldn’t find, was someone to sit down with me and explain it plainly. That’s what this article is.
Hydrocephalus is not rare. It affects approximately one in every 500 children born in the United States, and millions of people around the world live full, meaningful lives with this condition. But it is serious, and it is lifelong — which means the moment you receive this diagnosis, you are beginning a different kind of parenthood. One that involves neurosurgeons, shunt revision schedules, and learning to read your child in ways most parents never have to.
This guide covers what hydrocephalus actually is, what causes it, how it’s treated, and — most importantly — what you can expect once you leave the hospital and begin the real work of living with it.
What Is Hydrocephalus?
The brain is bathed, at all times, in a clear fluid called cerebrospinal fluid, or CSF. This fluid does important work: it cushions the brain against impact, carries away waste products, and maintains the chemical environment the brain needs to function. Your body produces roughly half a litre of it every day, and it circulates continuously through a system of chambers inside the brain — called ventricles — before being absorbed back into the bloodstream.
Hydrocephalus occurs when this system breaks down. Either too much CSF is produced, not enough is absorbed, or — most commonly — the flow becomes blocked somewhere along its path. The fluid accumulates. The ventricles expand. And the pressure inside the skull begins to rise.
The word itself comes from the Greek: hydro (water) and kephalos (head). It is sometimes called “water on the brain,” though that phrase is misleading — the fluid isn’t on the brain but inside it, within the ventricles that run through the brain’s core.
What Causes It?
Hydrocephalus has many causes, and the cause matters — it shapes the type of treatment, the likelihood of complications, and the long-term prognosis. Broadly, cases fall into two categories.
Congenital Hydrocephalus
Present at or before birth, congenital hydrocephalus develops during fetal development. The most common cause is aqueductal stenosis — a narrowing or blockage of the cerebral aqueduct, a narrow channel connecting two of the brain’s main ventricles. Other causes include:
- Neural tube defects, particularly myelomeningocele (a form of spina bifida), which is associated with hydrocephalus in over 80% of cases
- Dandy-Walker malformation, a developmental abnormality of the cerebellum
- Arachnoid cysts, fluid-filled sacs that can obstruct CSF flow
- Genetic conditions, though the genetic component in most cases is not straightforward
Acquired Hydrocephalus
This develops after birth — sometimes in infancy, sometimes in adulthood — usually as a secondary effect of another event:
- Intraventricular hemorrhage (IVH): Bleeding into the ventricles, common in premature infants born before 32 weeks. Blood clots can block CSF drainage pathways.
- Meningitis: Inflammation from infection can scar the tissues responsible for CSF absorption.
- Brain tumors: A mass in or near a ventricle can obstruct flow.
- Head trauma: Injury can disrupt CSF dynamics.
- Normal pressure hydrocephalus (NPH): A form that predominantly affects older adults, characterized by the classic triad of gait disturbance, urinary incontinence, and cognitive changes.
How Is It Diagnosed?
In infants, hydrocephalus is often first suspected when head circumference measurements track unusually high on the growth chart, or when a bulging fontanelle (the soft spot on a baby’s skull) is noticed. A tense, full fontanelle under normal conditions — not just during crying — is a significant sign.
Other symptoms that raise concern include:
- Eyes that appear to gaze persistently downward (“sunsetting eyes”) — this reflects pressure on the nerves controlling eye movement
- Unusual irritability or a high-pitched cry
- Vomiting, especially projectile
- Scalp veins that appear prominently distended
- Lethargy or difficulty feeding
In older children, when the skull has hardened and can no longer expand, symptoms shift toward those of increased intracranial pressure: headaches (classically worse in the morning), nausea, blurred or double vision, and in severe cases, loss of consciousness.
Diagnosis is confirmed through imaging. An MRI provides the most detailed picture of the ventricles and any underlying structural causes. A CT scan is often used in emergency situations for speed. Prenatal ultrasound can detect ventriculomegaly — enlarged ventricles — in utero, and fetal MRI may follow to characterize the finding.
Treatment: The Shunt
There is no medication that treats hydrocephalus. The excess fluid must be physically diverted or drained, and this is done surgically.
The most common treatment remains the ventriculoperitoneal (VP) shunt — a thin, flexible tube implanted by a neurosurgeon. The catheter runs from one of the brain’s ventricles, tunnels under the skin of the neck and chest, and drains CSF into the peritoneal cavity (the abdomen), where it is safely absorbed by the body. A small programmable valve, usually positioned behind the ear under the scalp, controls the flow rate.
Shunts work. For most children with hydrocephalus, a shunt is what makes a normal life possible. But shunts also fail — and this is the central, ongoing challenge of life with hydrocephalus.
Studies suggest that roughly 40% of shunts fail within the first year, and the majority require at least one revision over a lifetime. Failure can be mechanical (a kink, a disconnection, a blocked catheter) or functional (the valve becomes incompetent). The symptoms of shunt failure — headache, vomiting, vision changes, altered consciousness — are the same as the symptoms of untreated hydrocephalus. A malfunctioning shunt is a medical emergency.
Learning to recognize your child’s shunt failure pattern is one of the most important skills you will develop as a caregiver. Over time, most parents become finely attuned to subtle changes — a shift in behavior, a certain quality of tiredness, something that is hard to articulate but unmistakable once you know it. Trust that knowledge.
The Alternative: Endoscopic Third Ventriculostomy (ETV)
For children with obstructive hydrocephalus — where a blockage prevents CSF from flowing through the ventricles — a procedure called ETV may offer a shunt-free alternative. The surgeon uses a small endoscope to create a new opening in the floor of the third ventricle, allowing CSF to bypass the obstruction and drain naturally.
ETV is not appropriate for all types of hydrocephalus, and success rates depend heavily on the patient’s age, the underlying cause, and the specific anatomy. In well-selected cases, however, ETV can provide lasting relief without a permanent implant — eliminating the ongoing risk of shunt failure and revision.
Your neurosurgeon will assess whether your child is a candidate. If the topic hasn’t been raised, it is worth asking about directly.
Living With Hydrocephalus: What to Expect
The diagnosis is only the beginning. The lived reality of hydrocephalus is not primarily one of surgery — though surgery will happen — but of vigilance and adaptation. Here is what experience teaches:
Develop Your Emergency Criteria
Work with your neurosurgeon to establish a clear, written list of symptoms that warrant an immediate emergency room visit versus those that warrant a call to the office. Post it. Review it at every clinic visit. This list will change as your child grows, and it will save you critical minutes when minutes matter.
Know Your Child’s Baseline
Most shunt failure is recognized because something is different, not because it matches a textbook description. Your intimate knowledge of your child’s normal — their energy level, their mood, their sleep, their gait — is a diagnostic instrument that no neuroimaging can replace.
Keep Records
Document every surgery, every shunt revision, every hospitalization, and every significant symptom episode. Include dates, the operating surgeon, the shunt hardware model and settings, and the outcome. Families with hydrocephalus often move, change hospitals, and encounter emergency physicians who know nothing about their child’s history. Your records are the continuity of care.
Understand the Shunt Hardware
Ask your neurosurgeon what brand and model of shunt valve your child has, and write it down. Some programmable valves can be inadvertently reset by strong magnetic fields — including the magnets in MRI machines and some everyday objects like iPad cases. Knowing the hardware lets you ask the right questions and avoid risks.
Prepare for School
Many children with hydrocephalus experience subtle learning differences — not in intelligence, but in processing speed, working memory, and attention. These are neurological effects, not effort or attitude. An individualized education program (IEP) or 504 accommodation plan can provide accommodations that make a significant difference. Request a neuropsychological evaluation if your child’s school performance doesn’t match their intellectual capability.
The Emotional Geography of This Diagnosis
There is a particular grief that comes with a chronic childhood diagnosis — not the grief of death, but something quieter and more persistent. It is the grief of the future you imagined, now being renegotiated. It exists alongside love and alongside hope, and it does not resolve on a schedule.
What I’ve learned, two and a half years into my son’s hydrocephalus journey, is that the grief and the love become inseparable. You hold both. The hypervigilance becomes second nature. The research becomes purposeful. And somewhere along the way, you realize that you have become fluent in a language — of neurology, of hospital systems, of your child’s subtleties — that you never wanted to learn, but that you are deeply grateful to have.
You are not alone in this. There are millions of families navigating the same territory. Find them.
Key Resources
- Hydrocephalus Association (hydroassoc.org) — the leading U.S. patient advocacy organization, with a hospital directory and caregiver support programs
- HEADS UP Program — a database tracking outcomes for children with hydrocephalus across North American centers
- Your neurosurgery center’s nurse coordinator — often your most important ongoing point of contact; don’t hesitate to call them
Medical Disclaimer: This article is for general informational purposes and does not constitute medical advice. Hydrocephalus management should always be guided by a qualified neurosurgical team. If you suspect shunt failure or increased intracranial pressure, seek emergency medical care immediately.