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Diagnoses and systems from the American hydrocephalus Association

Posted Sep 01 2010 11:45am
If you think that you or someone you care about may have hydrocephalus, we recommend you learn about the symptoms and diagnostic tests for this condition. We also encourage you to trust your instincts. If you notice changes or have an intuitive feeling that something is not right with the person you are concerned about, act on that feeling and seek medical attention.

Only a medical doctor can make a diagnosis of hydrocephalus. The information here is intended to help you understand and navigate through the process of seeking medical advice. In children, it is often a pediatrician who first suspects hydrocephalus. A pediatric neurosurgeon will typically make the final diagnosis. In adults, hydrocephalus is often diagnosed by a neurologist working with a neurosurgeon.

If you have already received a diagnosis, the information below will help you make sense of the classifications and causes of hydrocephalus.

Symptoms and Diagnostic TestsSymptoms of untreated hydrocephalus are variable. During pregnancy, routine ultrasound can detect enlarged ventricles (spaces) within the baby’s brain. In children the symptoms tend to be related to high pressure and may include nausea, vomiting, headache and vision problems. In young and middle aged adults symptoms run the gamut of those seen in children and in older adults and most often include dizziness and vision problems. In older adults with NPH the symptoms are more likely to be loss of function in three main areas: walking, thinking and bladder control.

Infants and Children Young & Middle Aged Adults Older Adults (NPH)
Abnormal Head Enlargement Difficulty Walking Difficulty Walking
Tense, Bulging Fontanel Cognitive Challenges Cognitive Challenges
Prominent Scalp Veins Urinary Urgency or Incontinence Urinary Urgency or Incontinence
Skull bones may feel seperated Chronic Headaches
Vomiting, Sleepiness, Irritability
Headache, Nausea, Vomiting, Vision
Downward Deviation of Eyes

The most common initial diagnostic test to determine hydrocephalus at any age is an image of the brain (CT Scan or MRI) to identify the enlarged ventricles (spaces) within the brain that are typical of hydrocephalus. More tests are often performed in adults. The following links take you to detailed information about the signs, symptoms and diagnostic tests for hydrocephalus in various age groups.

■Infants, Children and Teenagers
■Adults Diagnosed in Young and Middle Age
■Older Adults with Normal Pressure Hydrocephalus (NPH)

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Classifications & CausesDoctors often identify hydrocephalus in one of three ways. Congenital hydrocephalus results from a complex interaction of genetic and environmental factors and is present at birth. Though it might not be recognized and diagnosed immediately, congenital hydrocephalus is now often diagnosed before birth through routine ultrasound. Hydrocephalus diagnosed in adulthood may have existed since birth and can still be considered congenital and may be referred to as compensated hydrocephalus. Acquired hydrocephalus develops after birth as a result of neurological conditions such as head trauma, brain tumor, cyst, intraventricular hemorrhage or infection of the central nervous system. If the cause of hydrocephalus is unknown, it is referred to as idiopathic which is most commonly true of normal pressure hydrocephalus (NPH).

Another set of terms you may hear from a doctor to describe hydrocephalus are “communicating” and “non-communicating”. If the cerebrospinal fluid (CSF) flows freely throughout the brain’s ventricular system and the subarachnoid space, it is referred to as communicating hydrocephalus. If there is a physical blockage such as a tumor somewhere in that system, it is called non-communicating hydrocephalus.

CausesThe most common causes of congenital and acquired hydrocephalus are listed below.

Congenital■Aqueductal stenosis
■Neural tube defect
■Arachnoid cysts
■Dandy-Walker syndrome
■Chiari malformation
Acquired■Intraventricular hemorrhage
■Head injury
■Brain tumor

Aqueductal Stenosis
The most common cause of congenital hydrocephalus is an obstruction called aqueductal stenosis. When the long, narrow passageway between the third and fourth ventricles (the aqueduct of Sylvius) is narrowed or blocked, perhaps because of infection, hemorrhage, or a tumor. Fluid accumulates “upstream” from the obstruction, producing hydrocephalus.

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Neural Tube Defect
Another common cause is a neural tube defect (NTD). An open NTD, where the spinal cord is exposed at birth and is often leaking CSF, is called a myelomeningocele. This condition is often referred to as spina bifida. This kind of NTD usually leads to the Chiari II malformation, which causes part of the cerebellum and the fourth ventricle to push downward through the opening at the base of the skull into the spinal cord area, blocking CSF’s flow out of the fourth ventricle and producing hydrocephalus. Please see the websites of the Spina Bifida Association and the International Association for Spina Bifida and Hydrocephalus for more information on neural tube defects.

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Arachnoid Cysts
Congenital hydrocephalus can also be caused by arachnoid cysts, which may occur anywhere in the brain. In children, they’re often located at the back of the brain (posterior fossa) and in the area of the third ventricle. These cysts are filled with CSF and lined with the arachnoid membrane (one of the three meningeal coverings). Some arachnoid cysts are self-contained, while others are connected with the ventricles or the subarachnoid space. The fluid trapped by the cysts may block the CSF pathways, producing hydrocephalus.

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Dandy-Walker Syndrome
In Dandy-Walker syndrome, another cause of congenital hydrocephalus, the fourth ventricle becomes enlarged because its outlets are partly or completely closed, and part of the cerebellum fails to develop. Dandy-Walker syndrome may also be associated with abnormal development in other parts of the brain and sometimes leads to aqueductal stenosis. In some instances, two shunts are placed in the child’s ventricles — one in the lateral ventricle and another in the fourth ventricle to manage the hydrocephalus. Please see the Dandy-Walker Alliance website for further information.

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Chiari Malformation
There are two types of Chiari malformation. Both types occur in the bottom of the brain stem where the brain and spinal cord join. The lowest portion of the brain is displaced and is lower than normal pushing down into the spinal column. Chiari II is explained under Neural Tube Defects. To learn more about Chiari I, please visit

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Intraventricular Hemorrhage
An intraventricular hemorrhage, which most frequently affects premature newborns, may cause an acquired form of hydrocephalus. When small blood vessels alongside the ventricular lining rupture, blood may block or scar the ventricles or plug the arachnoid villi, which allow CSF to be absorbed. When the CSF can’t be absorbed, hydrocephalus results.

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Meningitis is an inflammation of the membranes of the brain and spinal cord. Caused by a bacterial or (less frequently) viral infection, meningitis can scar the delicate membranes (meninges) that line the CSF pathway. An acquired form of hydrocephalus may develop if this scarring obstructs the flow of CSF as it passes through the narrow ventricles or over the surfaces of the brain in the subarachnoid space.

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Head Injury
A head injury can damage the brain’s tissues, nerves, or blood vessels. Blood from ruptured vessels may enter the CSF pathway, causing inflammation. Sites of CSF absorption might then be blocked by scarred membranes (meninges) or by blood cells. The CSF flow is restricted, and hydrocephalus develops.

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Brain Tumors
In children, brain tumors most commonly occur in the back of the brain (posterior fossa). As a tumor grows, it may fill or compress the fourth ventricle, blocking the flow of CSF and causing hydrocephalus. A tumor somewhere else in the brain might also block or compress the ventricular system. For more information, please see the National Brain Tumor Foundation website.
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