“Waterhead” is a colloquial term for hydrocephalus, a condition where excess cerebrospinal fluid builds up inside the brain. This fluid normally cushions and nourishes the brain, flowing through a series of chambers called ventricles before being absorbed back into the bloodstream. When something blocks that flow or prevents absorption, the fluid accumulates, the ventricles swell, and pressure builds inside the skull. In infants, this can cause the head to visibly enlarge, which is where the term “waterhead” comes from.
Hydrocephalus affects roughly 1 in 1,000 infants, though it can also develop later in life after injury, infection, or as part of aging. It is one of the most common congenital abnormalities of the nervous system.
Why Fluid Builds Up
Your brain produces cerebrospinal fluid continuously, about a pint a day. Normally, old fluid gets absorbed at the same rate new fluid is made. Hydrocephalus happens when that balance breaks down, and it can break down in a few different ways.
In one type, called obstructive (or noncommunicating) hydrocephalus, something physically blocks the fluid’s path through the ventricles. This could be a cyst, a tumor, or a structural abnormality the person was born with. The fluid has nowhere to go, so it backs up. In the other type, communicating hydrocephalus, the fluid flows freely through the ventricles but isn’t absorbed properly once it reaches the brain’s surface. The end result is the same: fluid accumulates and pressure rises.
What Causes It
When hydrocephalus is present at birth, it’s often linked to problems that developed during pregnancy. Neural tube defects like spina bifida are a common cause. Some babies are born with abnormally narrow passages between their brain’s ventricles, or with structural malformations that block fluid flow from the start.
Hydrocephalus can also develop after birth at any age. In premature infants, bleeding inside the brain (intraventricular hemorrhage) is a frequent trigger. In older children and adults, the causes include meningitis, traumatic brain injury, brain tumors, and strokes. In many older adults, hydrocephalus develops gradually with no identifiable cause, a form known as normal pressure hydrocephalus.
Symptoms in Babies
In infants, the skull bones haven’t yet fused together, so rising fluid pressure causes the head to grow abnormally fast. This is often the first and most obvious sign. Parents or doctors may notice a bulging soft spot (fontanelle) on the top of the head, or that the baby’s head circumference is increasing faster than expected on growth charts.
Other signs in babies include eyes that seem fixed downward (sometimes called “sunsetting eyes”), unusual sleepiness or irritability, poor feeding, vomiting, and seizures. Because the skull can expand to accommodate the extra fluid, some infants don’t show pain or distress right away, which makes regular head measurements at well-child visits important for early detection.
Symptoms in Children and Adults
Once the skull bones have fused, usually by age two, the head can no longer expand to relieve pressure. This means symptoms tend to come on more acutely and can be more serious. Headaches, nausea, vomiting, blurred or double vision, balance problems, and difficulty concentrating are common.
In older adults with normal pressure hydrocephalus, the classic pattern involves three problems that develop gradually: difficulty walking (often described as a shuffling gait or feeling like the feet are stuck to the floor), bladder control issues, and memory loss or declining thinking skills. Because these symptoms overlap with dementia and Parkinson’s disease, normal pressure hydrocephalus in the elderly is frequently misdiagnosed or overlooked entirely.
How It’s Diagnosed
Doctors confirm hydrocephalus using brain imaging, typically an MRI or CT scan. These scans show whether the ventricles are enlarged relative to the rest of the brain. A key measurement is the Evans index, which compares the width of the front ventricles to the widest part of the skull. A ratio above 0.3 indicates ventricular enlargement.
Imaging alone isn’t always enough, especially in older adults where the brain may have shrunk from aging. Doctors look for additional clues on the scan: thinning of brain tissue between the ventricles, changes in fluid flow patterns, and a specific pattern where some brain spaces widen while others narrow. For normal pressure hydrocephalus, a spinal tap that temporarily drains fluid can help predict whether treatment will improve symptoms. If walking or thinking improves after the fluid is removed, that’s a strong sign the person will benefit from surgery.
Treatment Options
Hydrocephalus almost always requires surgery. There is no medication that can reliably reduce cerebrospinal fluid buildup over the long term.
The most common procedure is a shunt, a thin tube placed inside the brain’s ventricles that drains excess fluid to another part of the body, usually the abdominal cavity, where it gets absorbed naturally. The tube runs under the skin from the head down through the neck and chest to the abdomen. A small valve in the system regulates how much fluid drains. Shunts work well, but they’re permanent devices that can malfunction, become infected, or need replacement over time.
The other main option is a procedure where a surgeon creates a small opening in the floor of one of the brain’s ventricles, giving the trapped fluid a new pathway to flow and be absorbed. This approach works best for obstructive hydrocephalus and avoids the need for a permanent implant. It’s less invasive than a shunt and doesn’t carry the same long-term risk of device failure, but it isn’t suitable for every type of hydrocephalus.
Living With a Shunt
For many people with hydrocephalus, a shunt becomes a lifelong companion. The devices work reliably for years in many cases, but complications are common enough that anyone with a shunt needs to know the warning signs of trouble. About 22% of shunts require surgical revision over the first several years, and the majority of complications happen within the first year after placement. The overall complication rate in that first year is roughly 21 per 100 patients.
Infection is the most serious early risk, occurring in about 6% of cases. Signs of shunt malfunction or infection include new or worsening headaches, nausea, confusion, seizures, fever, or redness along the path of the tubing under the skin. If the valve drains too much fluid, it can cause a different set of problems, pulling the brain away from the skull and potentially causing bleeding. Any sudden change in symptoms in someone with a shunt warrants prompt imaging of the brain.
Children who receive shunts as infants typically need one or more revisions as they grow, since the tubing can become too short or shift position. Adults with shunts generally need fewer revisions, but the device still requires monitoring for the rest of their lives.
Outlook and Quality of Life
The prognosis for hydrocephalus depends heavily on the underlying cause, how early it’s caught, and how much brain tissue was affected before treatment. Many children treated early go on to live full, active lives with normal or near-normal intelligence, though some experience learning difficulties, problems with coordination, or vision issues that require ongoing support.
For older adults with normal pressure hydrocephalus, shunt surgery can dramatically improve walking, bladder control, and, to a lesser extent, cognitive function. The earlier the condition is identified and treated, the better the response tends to be. When memory loss has been present for a long time before treatment, it’s less likely to fully reverse.