Hydrocephalus is not one single disease. Doctors classify it according to how cerebrospinal fluid circulation is disrupted and when the condition develops. Understanding these differences helps explain why some infants need shunts, while others may qualify for procedures that restore or redirect fluid flow.
How cerebrospinal fluid normally circulates
The brain produces cerebrospinal fluid within its ventricular system.
The fluid moves through connected chambers and narrow passages.
It eventually circulates around the brain and spinal cord.
The body then absorbs the fluid through specialized pathways.
When a passage becomes blocked or absorption becomes impaired, fluid can accumulate.
The ventricles may enlarge and affect surrounding tissue.
Doctors use imaging to identify the pattern of enlargement and its likely cause.
Obstructive hydrocephalus
Obstructive hydrocephalus is also called noncommunicating hydrocephalus.
It occurs when CSF cannot pass normally through part of the ventricular system.
One possible cause is aqueductal stenosis.
The cerebral aqueduct is a narrow channel connecting two regions of the ventricular system.
When this passage is narrowed or blocked, fluid may collect upstream.
A cyst, structural abnormality, or other obstruction may produce a similar problem.
Treatment depends on the location and cause of the blockage.
Communicating hydrocephalus
Communicating hydrocephalus occurs when fluid can move out of the ventricles but is not absorbed properly.
The problem is often associated with impaired absorption after inflammation or bleeding.
Meningitis can damage pathways involved in CSF circulation.
Blood products following a hemorrhage may also interfere with normal absorption.
A shunt is commonly used when ongoing fluid diversion is necessary.
However, treatment decisions depend on the child's condition.
Congenital hydrocephalus
Congenital hydrocephalus is associated with conditions that develop before birth.
Some babies have structural differences that obstruct CSF circulation.
Others have hydrocephalus associated with neural tube defects.
Spina bifida and certain hindbrain abnormalities can affect the movement of cerebrospinal fluid.
A congenital diagnosis does not automatically mean that an obstetric injury occurred.
The underlying developmental condition must be evaluated independently.
Post-hemorrhagic hydrocephalus
Post-hemorrhagic hydrocephalus develops after bleeding within or around the brain.
It is particularly important in premature infants with intraventricular hemorrhage.
Blood can obstruct fluid pathways or interfere with absorption.
The ventricles may enlarge gradually after the initial bleed.
Doctors often use repeated cranial ultrasounds to monitor progression.
Some babies need temporary fluid drainage before a permanent treatment is considered.
Why classification affects treatment
A procedure that works for one form of hydrocephalus may not be suitable for another.
For example, endoscopic third ventriculostomy may be considered for selected obstructive conditions.
It is generally less successful in some very young infants, particularly when impaired CSF absorption is the main problem.
A ventriculoperitoneal shunt can treat several forms of hydrocephalus by diverting fluid away from the brain.
The choice depends on anatomy, age, cause, and other medical factors.
Fast facts about hydrocephalus types
The terms congenital and acquired describe when or why hydrocephalus developed.
The terms communicating and obstructive describe the fluid-flow problem.
A baby can have more than one relevant classification, such as congenital obstructive hydrocephalus.
Common questions around hydrocephalus types
Is congenital hydrocephalus always inherited?
No. Many congenital cases are not caused by a known inherited condition.
Can a brain bleed cause obstructive hydrocephalus?
Yes. Blood or resulting tissue changes may obstruct fluid pathways.
Is communicating hydrocephalus treated differently?
It can be. The underlying fluid-circulation problem influences the treatment choice.
