What's the diagnosis?

Diagnosis

Blocked shunt

Next step

Urgent neurosurgical review.

What's going on

In the open form of spina bifida (myelomeningocele), the base of the spinal cord didn’t close properly early in pregnancy. Almost all of these babies also have a Chiari II malformation, where the back of the brain sits low and blocks the drain for the fluid around the brain (CSF), so fluid builds up (hydrocephalus). A shunt is a thin tube with a valve that carries this fluid from the brain to the tummy. If it blocks, the pressure builds up again.

Spot it

Headache, vomiting and drowsiness. Drowsiness is the most telling of the three. Children and families often recognise their own pattern of symptoms from previous blockages, so take it seriously when they say “this is how it started last time”. If the shunt drains too much instead, the headache is usually worse when sitting up and better lying down (review).

Test

Urgent neurosurgical review. Shine advises that a child with a suspected blocked or infected shunt is seen at a neurosurgical unit within four hours. A brain scan is compared with previous scans, and X-rays along the tubing look for breaks. A normal scan can’t rule a blockage out.

Treatment

Surgery to replace the blocked part of the shunt (a shunt revision). If the shunt is infected, it’s usually removed, antibiotics are given, and a temporary drain is used until the infection clears.

Why it matters

Shunts fail often: about 30 to 40% of children’s shunts fail within a year, and around half within two years. A missed blockage can lead to brain damage or death. When a child with a shunt vomits, assume the shunt has failed until proven otherwise.

Go further

Tap a question to check your answer.

1. What is spina bifida?

   The neural tube, which becomes the brain and spinal cord, forms between about day 21 and day 28 of pregnancy. In spina bifida it doesn’t close fully at the bottom, so in the open form the cord is exposed through the back.

2. Why is the back closed so soon after birth?

   Mainly to stop infection getting in. It’s usually done within 24 to 48 hours of birth, and antibiotics are started if it has to wait longer than 48 hours. Closure protects the nerves but doesn’t reverse the damage already done.

3. Can the back be closed before birth?

   Yes, before 26 weeks of pregnancy. In the MOMS trial, 40% of babies who had surgery before birth needed a shunt, compared with 82% of those operated on after birth. The trade-off is a higher risk of premature birth and problems with the womb. The NHS has offered this surgery since 2019, through UCLH and GOSH in London and a partner centre in Belgium.

4. Safeguarding: at a later visit, her thigh is swollen and warm, with no injury anyone saw. An X-ray shows a broken femur. Is it her condition, or has she been hurt?

   Don’t assume either way. Find out. Children with spina bifida often have weaker bones and can’t feel their legs, so a fracture can happen with little force and show up as a warm, swollen leg that doesn’t hurt. But disabled children are about 3.7 times more likely to be victims of violence, and case reviews show that signs of abuse often get put down to the child’s disability. Assess her as you would any child with an unexplained fracture, and talk to the safeguarding team. A useful check: would you be worried if she weren’t disabled?

5. How can spina bifida be prevented?

   Folic acid: 400 micrograms a day from before conception until 12 weeks of pregnancy, or a higher 5 mg dose for those at higher risk. From December 2026, UK law will require non-wholemeal wheat flour to contain folic acid, which is expected to cut neural tube defects by about 20%.

Source: Shine: shunt malfunction letter for GPs · MOMS trial (NEJM 2011) · Food Standards Agency: folic acid · Jones et al, Lancet 2012 · Fractures in myelomeningocele