Core Terms & Classification
Hydrocephalus ex vacuo
Hydrocephalus ex vacuo is enlargement of the ventricles due to loss of brain tissue, rather than a buildup of fluid under pressure.
In short: Hydrocephalus ex vacuo
- The ventricles enlarge because surrounding brain tissue has been lost.
- It is not true hydrocephalus and is not caused by raised pressure.
- It does not require shunting for pressure.
- It is identified by imaging and clinical context.
What it is
Hydrocephalus ex vacuo is ventricular enlargement that occurs because brain tissue around the ventricles has been lost (atrophy), allowing the ventricles to expand into the available space. Despite the name, it is not true hydrocephalus.
Understanding Hydrocephalus ex vacuo
When brain tissue is lost — for example, due to a stroke, injury, certain degenerative conditions, or normal aging — the ventricles can appear larger simply because there is more room. This is fundamentally different from true hydrocephalus, where fluid accumulates under pressure. Because there is no excess pressure to relieve, hydrocephalus ex vacuo does not call for a shunt to treat pressure. Doctors distinguish it from true hydrocephalus using imaging and the clinical picture, including whether pressure-related symptoms are present.
Why it matters
Understanding hydrocephalus ex vacuo helps families see that not all enlarged ventricles mean true hydrocephalus, and that this form — caused by tissue loss, not pressure — is managed differently. The distinction guides whether treatment for pressure is needed.
Common questions
Is hydrocephalus ex vacuo true hydrocephalus?
No — it results from brain tissue loss, not fluid under pressure.
Does it need a shunt?
Not for pressure, since there is no excess pressure to relieve.
What causes it?
Loss of brain tissue from stroke, injury, degeneration, or aging.
Bottom line
Hydrocephalus ex vacuo is ventricular enlargement from brain tissue loss, not true hydrocephalus, and is not treated with a shunt for pressure.
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