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Hydrocephalus is a condition characterized by an abnormal accumulation of cerebrospinal fluid (CSF) within cavities called ventricles inside the brain.


CSF is produced in the ventricles, circulates through the ventricular system and is absorbed into the bloodstream. Hydrocephalus occurs when there is an imbalance between the amount of CSF that is produced and the rate at which it is absorbed. As the CSF builds up, it causes the ventricles to enlarge and the pressure inside the head to increase, resulting in hydrocephalus.


Hydrocephalus can occur at any age, though the most well-known forms of hydrocephalus are those that occur at the extremes of life — in infants or the elderly. Hydrocephalus has a variety of causes.


Prenatal Hydrocephalus

In this condition, hydrocephalus is diagnosed in utero (before birth). Hydrocephalus can be detected in a fetus as early as the latter part of the first trimester of pregnancy. Prenatal hydrocephalus is generally not treated until after birth, when a shunt may be inserted into the baby's brain to divert CSF fluid.


Hydrocephalus in Infants and Children

This form of hydrocephalus is frequently diagnosed at birth or shortly thereafter, but sometimes it is not diagnosed until the child is a little older. In many children the problem is there at birth ­­­— this kind of hydrocephalus is referred to as congenital. Most cases of congenital hydrocephalus are thought to be caused by a complex interaction of genetic and environmental factors. Hydrocephalus that develops later in life in some children, and even in adults, but is caused by a condition that existed at birth, is still considered a form of congenital hydrocephalus. When hydrocephalus develops after birth and is caused by a factor such as head injury, meningitis or a brain tumor, it is termed acquired hydrocephalus.


Hydrocephalus Diagnosed in Young and Middle-Aged Adults (SHYMA)

This form of hydrocephalus is different from hydrocephalus diagnosed in infancy and early childhood, or adult-onset normal pressure hydrocephalus (NPH) found in older adults (typically age 60 and older). Doctors are just beginning to identify and describe this distinct form of hydrocephalus.


Adult-Onset Normal Pressure Hydrocephalus

This form of hydrocephalus is marked by an accumulation of CSF that causes the ventricles in the brain to become enlarged, sometimes with little or no increase in intracranial pressure. It is most commonly seen in older adults (age 50 and older)