Hydrocephalus is a condition in which cerebrospinal fluid (CSF) builds up within the brain, which can cause pressure to increase in the skull.

Elderly adults with normal pressure hydrocephalus (NPH) may have poor balance, difficulty controlling urination, or mental impairment.

Infants: Hydrocephalus is difficult to detect clinically before delivery, although enlarged ventricles can be spotted on ultrasonography as early as 18–20 weeks gestation.

[8] This anatomic characteristic means that infants' skulls can visibly grow in size when cerebrospinal fluid accumulates.

Other symptoms include seizures, inability to look upwards ("sunset eyes" or "setting sun" sign), and pauses in breathing.

The VACTERL disorders (vertebral anomalies, anal atresia, cardiac defects, tracheoesophageal fistula, renal and radial anomalies, and limb defects) may also include hydrocephalus, and can then be called VACTERL-H.[10] Hydrocephalus can also occur as part of neurocutaneous disorders such as neurofibromatosis type I (NF I) and tuberous sclerosis.

[7] Since there is limited expansion of the skull, symptoms are more representative of the effects of increased intracranial pressure on a child's developing brain.

[10] A key feature in this age group includes headaches, due to the intracranial hypertension caused by the increased CSF in the closed space of the skull.

[10] Symptoms that may occur in older children can include:[11] Since increased intracranial pressure can damage the brain, thought and behavior may be negatively affected.

[11] Hydrocephalus ex vacuo is a condition in which there is ventriculomegaly due to loss of brain volume which then results in a subsequent increase in CSF.

[28] Secondary hydrocephalus is acquired as a consequence of CNS infections, meningitis, brain tumors, head trauma, toxoplasmosis, or intracranial hemorrhage (subarachnoid or intraparenchymal).

[32] Hydrocephalus can also be caused by overproduction of CSF (relative obstruction) (e.g., choroid plexus papilloma, villous hypertrophy).

[35] This is likely because the breakdown of brain cells leads to ventriculomegaly (enlargement of ventricles) and increased space for CSF to fill.

[36] The purpose of cerebrospinal fluid is to provide mechanical support, nutrients, and remove waste from the central nervous system.

Alternatively, the condition may result from an overproduction of the CSF, from a congenital malformation blocking normal drainage of the fluid, or from complications of head injuries or infections.

[23] When the cerebrospinal fluid builds up, it causes compression of the brain, which leads to the symptoms of convulsions, intellectual disability, and epileptic seizures.

These signs occur sooner in adults because their skulls are no longer able to expand to based on the increasing fluid volume.

Fetuses, infants, and young children with hydrocephalus have head enlargement, excluding the face, because the pressure of the fluid causes the individual skull bones—which have yet to fuse—to bulge outward at their juncture points.

Consequently, fluid builds inside the brain, causing pressure that dilates the ventricles and compresses the nervous tissue.

[45] Scarring and fibrosis of the subarachnoid space following infectious, inflammatory, or hemorrhagic events can also prevent reabsorption of CSF, causing hydrocephalus.

Altered compliance (elasticity) of the ventricular walls, as well as increased viscosity of the cerebrospinal fluid, may play a role in the pathogenesis.

[54] Rarely reported symptoms include a tense anterior fontanel, developmental delay, seizures, irritability, and vomiting.

These tests and a good medical history can help to identify external hydrocephalus from similar conditions: subdural hemorrhages or symptomatic chronic extra-axial fluid collections which are accompanied by vomiting, headaches, and seizures.

[60] Common complications requiring revision include: If shunt failure occurs, the cerebrospinal fluid begins to accumulate again.

This can cause a number of physical symptoms develop (headaches, nausea, vomiting, photophobia/light sensitivity), some extremely serious, such as seizures.

[62] Patient factors that are associated with shunt failure includes the cause of the hydrocephalus, prematurity, male sex, spina bifida, epilepsy, severity of ventricular dilation, ethnicity, and age <1 year.

For example, whether symptoms occur when the person is upright or in a prone position (lying down) with the head at roughly the same level as the feet.

[76] In the pre-historic area, there were various paintings or artifacts depicting children or adults with macrocephaly (large head) or clinical findings of hydrocephalus.

Specifically, he wrote:[78] The skull of a newborn baby is often full of liquid, either because the matron has compressed it excessively or for other, unknown reasons.

[78] In 1881, Carl Wernicke pioneered sterile ventricular puncture and external drainage of CSF for the treatment of hydrocephalus.