Hydrocephalus

Hydrocephalus is a build-up of cerebrospinal fluid (CSF), the clear fluid that surrounds the brain and spinal cord, inside the fluid-filled spaces of the brain called the ventricles. It happens when the fluid's flow is blocked or it isn't absorbed properly. The ventricles enlarge, and the pressure in the head may rise1.

Types

Hydrocephalus means different things at different ages12:

• Congenital hydrocephalus is present at birth, for example with spina bifida or a narrowing of the channel between ventricles.
• Acquired hydrocephalus develops after bleeding in the brain, meningitis, a head injury or a tumor that blocks fluid flow, at any age.
• Normal pressure hydrocephalus (NPH) affects older adults, usually without a clear cause. It causes difficulty walking, problems with thinking and memory, and loss of bladder control.

Large ventricles caused by loss of brain tissue, for example in dementia, are a different situation and aren't treated by draining fluid3.

Symptoms

Symptoms depend on age4:

• Babies: a rapidly growing head, a bulging soft spot (fontanelle), vomiting, sleepiness, irritability and eyes that look downward.
• Older children and adults: headache, nausea and vomiting, blurred or double vision, drowsiness and problems with balance.
• Normal pressure hydrocephalus: a slow, shuffling, wide-based walk, forgetfulness and slowed thinking, and urgency or incontinence of urine, developing over months.

Treatment

There are two main treatments5:

• A shunt is a thin tube that drains fluid from a ventricle to another part of the body, usually the abdomen, through a valve that controls the flow. Shunts with antibiotic-impregnated tubing reduce infection: in the BASICS trial of 1,605 patients, 2% needed a revision for infection with antibiotic shunts against 6% with standard ones6.
• Endoscopic third ventriculostomy (ETV) makes a small opening in the floor of the third ventricle so fluid can bypass a blockage, without leaving a device in the body. It suits selected causes of hydrocephalus and can close months or years later.

See shunts and endoscopic third ventriculostomy.

Shunt and ETV failure: an emergency

Shunts can block, disconnect or become infected, and an ETV opening can close. Headache, vomiting, drowsiness, a fit, or symptoms returning in someone with a shunt or ETV need urgent medical assessment, and severe or rapidly worsening symptoms need emergency care7. See shunt and ETV problems.

Normal pressure hydrocephalus

NPH is diagnosed from the combination of symptoms, brain imaging, and a test in which CSF is drained to see whether walking improves8. In a 2025 trial, 99 people who had improved with a drainage test received a shunt set either to drain or not to drain, without knowing which. After three months, walking speed and balance improved with an open shunt, but memory and thinking and bladder control did not improve significantly more than with the closed setting9. See hydrocephalus in adults and normal pressure hydrocephalus.

Living with hydrocephalus

Most people with treated hydrocephalus live full lives, although some have lasting effects on learning, memory or movement, and anyone with a shunt needs to know the warning signs of failure for life2. See living with hydrocephalus.

About the editor

Dr. Kamran Aghayev

Neurosurgeon, Associate Professor of Neurosurgery · Istanbul

Dr. Kamran Aghayev is a neurosurgeon in Istanbul and an associate professor of neurosurgery, with more than 20 years in practice. He trained in neurosurgery at Hacettepe University in Ankara, completed spinal oncology and neuro-oncology fellowships at the H. Lee Moffitt Cancer Center in Tampa, Florida, and taught there as a clinical instructor before returning to Turkey. He chaired the neurosurgery department at Biruni University in Istanbul from 2017 to 2020. His published work includes a surgical technique for jugular vein decompression in atlanto-styloid compression and the PURED operation for thoracic outlet syndrome, and he is a named inventor on 13 U.S. patents for spinal devices.

How this site is editedkamranaghayev.com

References

1. NHS. Hydrocephalus: Overview. Source ↩
2. US National Library of Medicine. MedlinePlus Medical Encyclopedia: Hydrocephalus. Source ↩
3. AANS Neurosurgical Members. Adult-onset Hydrocephalus. 15 July 2024. Source ↩
4. NHS. Hydrocephalus: Symptoms. Source ↩
5. NHS. Hydrocephalus: Treatment. Source ↩
6. Mallucci CL et al. Antibiotic or silver versus standard ventriculoperitoneal shunts (BASICS). Lancet. 2019;394:1530–1539. doi:10.1016/S0140-6736(19)31603-4. Source ↩
7. NHS. Hydrocephalus: Complications. Source ↩
8. Nakajima M et al. Guidelines for Management of Idiopathic Normal Pressure Hydrocephalus (Third Edition). Neurol Med Chir. 2021;61:63–97. doi:10.2176/nmc.st.2020-0292. Source ↩
9. Luciano MG et al. A Randomized Trial of Shunting for Idiopathic Normal-Pressure Hydrocephalus. N Engl J Med. 2025;393:2198–2209. doi:10.1056/NEJMoa2503109. Source ↩

Related pages

• Symptoms and diagnosisAge, history, examination and imaging all matter; symptoms and ventricular size alone cannot establish a diagnosis.
• Hydrocephalus in babies and childrenCauses, neonatal care, development and family questions need a pediatric perspective.
• Hydrocephalus in adultsAcquired and longstanding disease deserve separate assessment; adult hydrocephalus is broader than iNPH.
• Possible shunt and ETV problemsPossible treatment failure needs professional assessment, including when symptoms are unfamiliar or appear long after treatment.