Specific Types & Syndromes
Hydranencephaly
Hydranencephaly is a rare, severe condition in which most of the brain's hemispheres are absent and replaced by fluid, distinct from hydrocephalus.
In short: Hydranencephaly
- Most of the cerebral hemispheres are absent, replaced by fluid.
- It is distinct from hydrocephalus, though they can appear similar.
- It is a severe condition with a serious outlook.
- It is identified on brain imaging.
What it is
Hydranencephaly is a rare, severe condition in which most of the cerebral hemispheres (the largest part of the brain) are absent and replaced by cerebrospinal fluid, while some deeper structures may remain. Despite the fluid-filled appearance, it is fundamentally different from hydrocephalus.
Understanding Hydranencephaly
In hydranencephaly, the cerebral hemispheres have largely failed to develop or have been destroyed (for example, by a vascular event during development), leaving fluid in their place. This is distinct from hydrocephalus, where the brain is present but the ventricles are enlarged by fluid under pressure. The two can look similar on initial imaging, so careful evaluation distinguishes them, which matters because they differ greatly in nature and outlook. Hydranencephaly is a severe condition with a serious prognosis, and care is focused on comfort and supporting the child and family. The care team approaches these difficult situations with honesty and compassion.
Why it matters
Understanding hydranencephaly helps families see that it is distinct from hydrocephalus — the brain is largely absent rather than compressed — and that distinguishing the two is important because they differ greatly in nature, treatment, and outlook.
Common questions
Is hydranencephaly the same as hydrocephalus?
No — it is a distinct, severe condition where most of the hemispheres are absent.
Why can they look similar?
Both can appear fluid-filled on initial imaging.
How is it identified?
On brain imaging, with careful evaluation to distinguish it from hydrocephalus.
Bottom line
Hydranencephaly is a rare, severe condition where most of the cerebral hemispheres are absent and replaced by fluid, distinct from hydrocephalus.
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