Head size and growth are assessed best by a childā€™s clinician over time. This page provides general information about hydrocephalus; it cannot diagnose a child or replace an in-person medical assessment.

What hydrocephalus means

Hydrocephalus is a build-up of cerebrospinal fluid (CSF) in spaces within the brain. In babies, whose skull bones have not yet fused, this may contribute to a head that increases in size more quickly than expected. A larger head alone does not establish the cause, so a clinician should interpret it alongside the childā€™s examination and growth record. NHS: symptoms of hydrocephalus MedlinePlus: hydrocephalus

Changes to discuss promptly with a childā€™s doctor

The following are among the changes recognised in infants with hydrocephalus. They can also occur for other reasons, so they need clinical assessment rather than self-diagnosis:

  • an unusually rapid increase in head size;
  • a tense or bulging soft spot (fontanelle);
  • eyes that appear to look downward;
  • repeated vomiting, poor feeding, unusual sleepiness, or marked irritability.

These symptoms are drawn from the NHS and MedlinePlus Medical Encyclopedia. If a child is severely unwell, very difficult to wake, has a seizure, or has trouble breathing, seek emergency medical help immediately.

What a head circumference chart canā€”and cannotā€”tell you

A head circumference chart tracks a childā€™s head growth over time. It is not a separate test for hydrocephalus. Clinicians plot repeat measurements on a standardised growth chart, account for prematurity where appropriate, and consider development, symptoms and examination findings. A single home measurement or photograph cannot establish a diagnosis.

A large head can sometimes run in families. A changing growth pattern needs a different assessment from a consistently large head in a child developing normally. NICE recommends paediatric assessment when measurements cross two or more centile lines, with immediate referral when signs of raised pressure are also present. Parents should ask their clinician to interpret the chart rather than use a centile number to rule a problem in or out. NICE NG127: head shape or size abnormalities, recommendations 1.22.2ā€“1.22.4

How clinicians investigate a concern

Assessment may include a medical history, clinical examination and imaging when appropriate. In young babies, ultrasound is one of the tests that may be used; other imaging can be considered according to the clinical situation. The choice and urgency of testing should be decided by the treating clinician. MedlinePlus Medical Encyclopedia

Possible causes

Hydrocephalus can be present at birth or develop later. Causes described by MedlinePlus include a blockage affecting the flow of CSF, infection such as meningitis, bleeding in or around the brain, injury, and some tumours. The cause cannot be determined from symptoms alone. MedlinePlus Medical Encyclopedia

If hydrocephalus is diagnosed: treatment and follow-up questions

The neurosurgical team explains whether treatment is needed and how urgently. A shunt diverts fluid to another part of the body, usually the abdomen. Endoscopic third ventriculostomy (ETV) creates another route for fluid flow and may be suitable for some obstructive cases; it is not suitable for everyone. Shunts can become blocked or infected, and an ETV opening can later become blocked. Treatment therefore does not remove the need for follow-up or assessment of returning symptoms. NHS: hydrocephalus treatment

Useful questions for the treating team include:

  • What do the growth record, examination and scans show?
  • What options are appropriate for this child, and why?
  • Which warning signs need urgent help, and whom should we contact?
  • When is the next review, and how will growth and development be followed?

Preparing for the assessment

Bring the childā€™s health record, dated head measurements, any previous scan reports and a current medicine list. Note when changes in feeding, vomiting, alertness or development began. These notes can help the consultation, but do not delay urgent care to collect them.

Further reliable information

Dr. Simranjeet Singh is a Consultant Neurosurgeon and Neurointervention Specialist at Max Smart Super Speciality Hospital, Saket, New Delhi. His qualifications include MBBS (MAMC), M.Ch. Neurosurgery (AIIMS Delhi), and a Fellowship in Neurovascular Intervention at G. B. Pant Hospital, Delhi. Delhi Medical Council registration: DMC/R/13915. This article is general educational information.

Content updated: 18 October 2026.