Hydrocephalus often doesn't occur in isolation. Several conditions — particularly ones affecting the development of the brain and spine — are closely associated with it. If you or your child has been diagnosed with one of these, understanding the connection can help make sense of the bigger picture.
Spina bifida (myelomeningocele) Spina bifida is a birth defect in which the spine and spinal cord don't form completely, leaving an opening. The most significant form, myelomeningocele, is very frequently accompanied by hydrocephalus. The link is usually through the Chiari II malformation (see below), which disrupts CSF flow at the base of the brain. A large proportion of children with myelomeningocele develop hydrocephalus requiring treatment. Because of this strong association, babies with spina bifida are monitored closely for hydrocephalus, and many receive a shunt or ETV.
Chiari malformation A Chiari malformation involves brain tissue (part of the cerebellum) extending lower than normal, toward or into the space where the spinal cord begins. There are different types:
- Chiari II is closely tied to spina bifida and to hydrocephalus in infants, because it disrupts normal CSF flow.
- Chiari I is more often seen in older children and adults and can sometimes be associated with CSF flow problems, including hydrocephalus in some cases, though many people with Chiari I never develop hydrocephalus.
When hydrocephalus and a Chiari malformation occur together, treating the hydrocephalus is often an important early step, and the two conditions are managed in a coordinated way.
Dandy-Walker malformation This is a congenital malformation involving the fourth ventricle and the cerebellum at the back of the brain. It typically includes enlargement of the fourth ventricle and underdevelopment of part of the cerebellum. Hydrocephalus is common in Dandy-Walker malformation because the malformation can interfere with normal CSF flow and absorption. Treatment may involve a shunt (sometimes specifically draining the affected fluid space) or other approaches tailored to the anatomy.
Other associations Hydrocephalus can also accompany conditions such as certain genetic syndromes, arachnoid cysts (fluid-filled sacs that can sometimes obstruct CSF flow), and other developmental differences of the brain.
Why the connections matter Understanding these associations helps in several ways:
- It explains why hydrocephalus developed in the context of another diagnosis.
- It guides coordinated, multidisciplinary care, since these conditions often involve neurosurgery, neurology, developmental specialists, and others working together.
- It helps families know what to monitor — for example, watching for signs of hydrocephalus in a child with spina bifida or Dandy-Walker malformation.
If your child has one of these related conditions, your care team will explain how it connects to hydrocephalus in your specific case and how the conditions will be managed together. The encouraging reality is that, even when hydrocephalus is part of a larger picture, it remains a treatable component, and coordinated specialized care helps children do as well as possible.