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# Hydrocephalus

Hydrocephalus is a build-up of cerebrospinal fluid in the brain's cavities, which widen and can raise pressure inside the skull.

Updated 2026-10-29

## Structures involved

Tap one to see what it is and open it in 3D.

- [Lateral ventricles](https://durgical.com/en/anatomy/lateral-ventricle/)
- [Third ventricle](https://durgical.com/en/anatomy/third-ventricle/)
- [Cerebral aqueduct](https://durgical.com/en/anatomy/aqueduct-of-midbrain/)
- [Fourth ventricle](https://durgical.com/en/anatomy/fourth-ventricle/)
- [Choroid plexus](https://durgical.com/en/anatomy/choroid-plexus/)
- [Superior sagittal sinus](https://durgical.com/en/anatomy/superior-sagittal-sinus/)
- [Cerebellar tonsils](https://durgical.com/en/anatomy/tonsil-of-cerebellum/)
- [Corpus callosum](https://durgical.com/en/anatomy/corpus-callosum/)

## Microorganisms that cause it

- [Taenia solium](https://durgical.com/en/microbiology/taenia-solium/)

## In histology

- [Gray and white matter, cerebellar cortex, meninges](https://durgical.com/en/histology/gray-and-white-matter-cerebellar-cortex-meninges/)
- [Blood–brain barrier, choroid plexus and cerebrospinal fluid](https://durgical.com/en/histology/blood-brain-barrier-choroid-plexus-and-cerebrospinal-fluid/)

## In embryology

- [Neurulation and closure of the neural tube](https://durgical.com/en/embryology/neurulation-and-closure-of-the-neural-tube/)
- [Skull: neurocranium, viscerocranium, sutures and fontanelles](https://durgical.com/en/embryology/skull-neurocranium-viscerocranium-sutures-and-fontanelles/)
- [Craniosynostosis](https://durgical.com/en/embryology/craniosynostosis/)
- [Achondroplasia (FGFR3)](https://durgical.com/en/embryology/achondroplasia/)
- [Brain vesicles: from three to five and what each becomes](https://durgical.com/en/embryology/brain-vesicles-from-three-to-five-and-what-each-becomes/)
- [Ventricles and cerebrospinal fluid](https://durgical.com/en/embryology/ventricles-and-cerebrospinal-fluid/)
- [Neural tube defects: anencephaly, spina bifida and encephalocele](https://durgical.com/en/embryology/neural-tube-defects-anencephaly-spina-bifida-and-encephalocele/)
- [Chiari malformations](https://durgical.com/en/embryology/chiari-malformations/)
- [Congenital hydrocephalus: aqueductal stenosis](https://durgical.com/en/embryology/congenital-hydrocephalus-aqueductal-stenosis/)
- [Dandy–Walker malformation](https://durgical.com/en/embryology/dandy-walker-malformation/)

## In the clinical exam

- [Intracranial hypertension syndrome](https://durgical.com/en/clinical-exam/intracranial-hypertension-syndrome/)

## In physiology

- [Cerebral blood flow, brain metabolism and intracranial pressure](https://durgical.com/en/physiology/cerebral-blood-flow-brain-metabolism-and-intracranial-pressure/)
- [CSF and the blood–brain barrier](https://durgical.com/en/physiology/csf-and-the-blood-brain-barrier/)

## What it is

Abnormal build-up of cerebrospinal fluid in the ventricles of the brain, which enlarge and may raise intracranial pressure. It can be congenital or acquired, and obstructive or communicating.

## Who gets it

Occurs from infancy to old age: congenital forms and those linked to prematurity and neural tube defects in children, and normal pressure hydrocephalus in older adults. In Colombia, neurocysticercosis and infections are important acquired causes.

## Causes

- Obstruction of flow: aqueductal stenosis, tumours (especially of the posterior fossa), cysts such as ventricular neurocysticercosis
- Impaired absorption: after subarachnoid haemorrhage or meningitis
- Congenital malformations: Chiari II with myelomeningocele, Dandy-Walker malformation
- Intraventricular haemorrhage in premature infants
- Rarely overproduction ([choroid plexus](https://durgical.com/en/anatomy/choroid-plexus/) papilloma)

## Risk factors

- Prematurity
- Neural tube defects
- Meningitis and neurocysticercosis
- Subarachnoid or intraventricular haemorrhage
- Brain tumours and head injury
- Older age (normal pressure hydrocephalus)

## Pathophysiology

CSF made by the choroid plexus flows from the [lateral ventricles](https://durgical.com/en/anatomy/lateral-ventricle/) through the [third ventricle](https://durgical.com/en/anatomy/third-ventricle/), aqueduct and [fourth ventricle](https://durgical.com/en/anatomy/fourth-ventricle/) to the subarachnoid space, then drains to the venous sinuses. Blocked flow within the ventricles causes obstructive hydrocephalus; impaired absorption causes communicating hydrocephalus. In infants with open sutures the head enlarges; in older patients pressure rises quickly.

## Classification

- Obstructive (non-communicating)
- Communicating
- Normal pressure hydrocephalus (older adults)
- Congenital or acquired
- Acute or chronic

## Symptoms and signs

- Infants: rapidly growing head circumference, bulging fontanelle, separated sutures, irritability, vomiting, sunset eyes
- Older children and adults: headache worse in the morning, nausea, vomiting, drowsiness, papilloedema
- Upward gaze palsy (Parinaud syndrome) with dorsal [midbrain](https://durgical.com/en/anatomy/midbrain/) compression
- Normal pressure hydrocephalus: gait disturbance, urinary incontinence and cognitive decline
- Shunt malfunction: return of headache, vomiting and drowsiness

## Red flags

- Decreasing consciousness
- Bradycardia, hypertension and irregular breathing (Cushing response)
- Sudden vomiting and drowsiness in a child with a shunt
- Fever and abdominal pain in a shunted patient (shunt infection)

## Diagnosis

**Clinical**
Head circumference charts and fontanelle examination in infants; symptoms of raised pressure and fundoscopy in older patients; the gait-incontinence-dementia triad in normal pressure hydrocephalus.

**Tests**
CSF studies when infection is suspected. In normal pressure hydrocephalus, a high-volume lumbar tap test or lumbar drainage to see whether gait improves.

**Imaging**
Cranial ultrasound through the fontanelle in infants. CT or MRI shows enlarged ventricles and the site of obstruction; MRI is better for aqueduct and posterior fossa lesions.

## Differential diagnosis

- Brain atrophy with ex vacuo ventricular enlargement
- Benign enlargement of subarachnoid spaces in infancy
- Idiopathic intracranial hypertension
- Alzheimer disease and Parkinson disease (versus normal pressure hydrocephalus)
- Brain tumour or abscess

## Goal of treatment

Divert or restore CSF flow to relieve raised pressure and protect brain development and function, and treat the cause.

## Treatment

**Acute**
Acute obstructive hydrocephalus with deterioration: emergency external ventricular drain.

**Surgical**
Ventricular shunt, usually ventriculoperitoneal, with a valve that controls drainage.

**Surgical**
Endoscopic third ventriculostomy for selected obstructive cases, avoiding a permanent shunt.

**Surgical**
Removal of the cause when possible: tumour resection, endoscopic removal of ventricular cysticerci.

**Follow-up**
Lifelong follow-up of shunted patients for malfunction or infection; developmental follow-up in children.

## Complications

- Shunt obstruction, infection or over-drainage
- Brain herniation and death if untreated
- Visual loss from chronic papilloedema
- Developmental delay, learning difficulties and epilepsy
- Subdural collections after drainage

## Prognosis

Depends on the cause, age and speed of treatment. Many children reach good developmental outcomes, although shunt revisions are common. In normal pressure hydrocephalus, gait responds best to shunting.

## Prevention

- Folic acid before conception to reduce neural tube defects
- Prenatal care to reduce prematurity
- Prevention and treatment of neurocysticercosis and meningitis
- Vaccination against meningitis-causing bacteria

## Test yourself

Think of the answer, then tap the question to see it.

## What is the difference between obstructive and communicating hydrocephalus?

Obstructive: flow is blocked within the ventricular system; communicating: CSF reaches the subarachnoid space but is poorly absorbed.

## What is the triad of normal pressure hydrocephalus?

Gait disturbance, urinary incontinence and cognitive decline.

## Why does the head enlarge in infants with hydrocephalus?

Their cranial sutures and fontanelles are still open, so the skull expands with the raised pressure.

## Which parasitic infection is an important cause of hydrocephalus in Colombia?

Neurocysticercosis, through ventricular cysts or arachnoiditis.

## What is the most common surgical treatment for hydrocephalus?

A ventriculoperitoneal shunt; endoscopic third ventriculostomy is an option in selected obstructive cases.

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## Related conditions

- [Neurocysticercosis](https://durgical.com/en/conditions/neurocysticercosis/)
- [Bacterial meningitis](https://durgical.com/en/conditions/bacterial-meningitis/)
- [Subarachnoid haemorrhage](https://durgical.com/en/conditions/subarachnoid-haemorrhage/)
- [Spina bifida (myelomeningocele)](https://durgical.com/en/conditions/spina-bifida/)
- [Glioblastoma](https://durgical.com/en/conditions/glioblastoma/)
- [Alzheimer disease](https://durgical.com/en/conditions/alzheimer-disease/)
- [Vestibular schwannoma (acoustic neuroma)](https://durgical.com/en/conditions/vestibular-schwannoma/)

Educational information, not medical advice. For any symptom, see a health professional.

Sources: [Hydrocephalus](https://www.ncbi.nlm.nih.gov/books/NBK560875/) (StatPearls (NCBI Bookshelf), 2023).

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Representative model, for educational purposes only.

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Source: https://durgical.com/en/conditions/hydrocephalus/
License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/conditions/hydrocephalus/