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Hydrocephalus is a condition in which cerebrospinal fluid (CSF) builds up within and/or around the brain, which can cause pressure to increase in the skull. Symptoms may vary according to age.<!--

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Hydrocephalus can occur due to birth defects (primary) or can develop later in life (secondary). The word hydrocephalus is from the Greek , meaning 'water' and , meaning 'head'.

Signs and symptoms

thumb|400px|Illustration showing different effects of hydrocephalus on the brain and cranium

thumb|Adult showing cranial deformity from pediatric hydrocephalus

Infants

Hydrocephalus is difficult to detect clinically before birth, although enlarged ventricles can be spotted on ultrasonography as early as 18–20 weeks gestation. Since infants' skulls are not fully fused together at the cranial sutures yet, they have soft spots on their skulls known as open fontanelles. This anatomic characteristic means that infants' skulls can visibly grow in size when cerebrospinal fluid accumulates. Therefore, infants with hydrocephalus may present with an enlarged skull (or rapid growth in skull size), bulging fontanelles, or separated cranial sutures. Parents or physicians may also note that the infant is more irritable or tired than normal. Other symptoms include seizures, inability to look upwards ("sunset eyes" or "setting sun" sign), and pauses in breathing. Imaging can be done to confirm the suspected diagnosis of hydrocephalus. In infants, the open fontanelles allow for use of head ultrasonography. This allows pediatricians to minimize radiation exposure and come up with a diagnosis quickly.

  • Brief, shrill, high-pitched cry
  • Changes in personality, memory, or the ability to reason or think
  • Changes in facial appearance and eye spacing (craniofacial disproportion)
  • Crossed eyes or uncontrolled eye movements
  • Difficulty feeding
  • Excessive sleepiness
  • Headaches
  • Irritability, poor temper control
  • Loss of bladder control (urinary incontinence)
  • Loss of coordination and trouble walking
  • Muscle spasticity (spasm)
  • Slow growth (child 0–5 years)
  • Delayed milestones
  • Failure to thrive
  • Slow or restricted movement
  • Vomiting

Since increased ICP can damage the brain, thought and behavior may be negatively affected. Learning disabilities, including short-term memory loss, are common among those with hydrocephalus. Affected children tend to score better on verbal IQ than on performance IQ, a pattern which is thought to reflect the distribution of nerve damage to the brain. However, the severity of hydrocephalus can differ considerably between individuals, and some are of average or above-average intelligence. Aside from learning disabilities, a child with hydrocephalus may also have coordination and visual problems. They may reach puberty earlier than the average child (this is called precocious puberty). About one in four develops epilepsy.

Adults

In adults, acute hydrocephalus can have many of the same signs and symptoms (headaches, vomiting, nausea, papilledema, sleepiness, or coma) of increased ICP that are seen in children. Increased volumes of CSF can also result in hearing loss, including sensorineural hearing loss (SNHL). Hearing loss is a rare but well-known sequela of procedures resulting in CSF loss. Elevated ICP can also cause a portion of the brain to move out of place (uncal or tonsillar herniation), which can result in brain stem compression and possible death. This is most commonly seen in patients with neurodegenerative disorders such as Alzheimer's disease (due to hippocampal atrophy specifically). Therefore, the presenting symptoms of this condition will likely be those of Alzheimer's: memory loss, loss of language skills or comprehension (aphasia), inability to perform purposeful movements (apraxia), and inability to conduct activities of daily living independently. Hydrocephalus ex vacuo can also occur due to traumatic brain injuries or due to strokes.

Causes

Hydrocephalus can be caused by a combination of factors and is not fully understood. Any medical condition that interrupts the flow of cerebrospinal fluid (CSF) can cause this build-up of excess fluid. This occurs due to blocked pathways of cerebrospinal fluid (CSF), issues with CSF reabsorption, or increased CSF production.

Hydrocephalus can be classified as primary or secondary (acquired) based on the cause.

Primary

Primary hydrocephalus involves congenital, developmental, and genetic factors that lead to excess CSF build-up.

Developmental disorders including neural-tube defects, arachnoid cysts, Dandy–Walker malformations, and Arnold–Chiari malformations can cause primary hydrocephalus. Dandy-walker malformations and Arnold-Chiari malformations lead to structural abnormalities in the brain, which disrupts the flow of CSF and causes hydrocephalus.

Neural tube defects are commonly caused by a deficiency of folic acid during pregnancy. Spina bifida is a neural tube defect that involves defects in the development of the spine, and it can cause hydrocephalus. Myelomeningocele is the most severe type of spina bifida, involving an open spinal column and the exact mechanism of hydrocephalus involved in this condition is unclear.

Secondary (Acquired)

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

Intraventricular hemorrhage, or bleeding within the ventricles of the brain, leads to hydrocephalus in 51–89% of patients. This is because the blood in the ventricles blocks the regular flow of CSF, leading to build-up of excess CSF]]Normal pressure hydrocephalus (NPH) most often occurs in elderly patients with symptoms including gait disturbance, urinary incontinence, and cognitive issues. It is commonly divided into two categories, idiopathic NPH (with unknown cause) and secondary NPH (due to trauma, hemorrhage, etc.).

Brain atrophy or breakdown in elderly patients or patients with conditions like Parkinson's or Alzheimer's can lead to acquired hydrocephalus. This is likely because the breakdown of brain cells leads to ventriculomegaly (enlargement of ventricles) and increased space for CSF to fill. The purpose of cerebrospinal fluid is to provide mechanical support, nutrients, and remove waste from the central nervous system. In a person without hydrocephalus, CSF continuously circulates through the brain, its ventricles and the spinal cord and is continuously drained away into the circulatory 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.<br />

Lateral Ventricles → Interventricular Foramen of Monro → Third Ventricle → Cerebral Aqueduct → Fourth Ventricle

The CSF then exits the fourth ventricle through the median aperture and lateral aperture. It goes into the subarachnoid space or central canal of the spinal cord. Then, it is absorbed by the vili of arachnoid granulations into the blood circulation. One theory involves the drainage of CSF into the lymphatic vessel system. The lymphatic vessel system clears proteins and fluid throughout the body, but whether they are involved in CSF drainage within the brain is controversial and not yet clear. Lymphatic vessels in the dura mater is a possible site of CSF drainage.

A rare complication of hydrocephalus is hearing loss. There are a few possible mechanisms involved in hearing loss in hydrocephalus. The cochlear aqueduct connects the perilymphatic space of the inner ear with the subarachnoid space of the posterior cranial fossa. Because of the delicate relationship between pressure and hearing, hearing loss may also be caused after a shunt is placed to treat hydrocephalus.

CSF can accumulate within the ventricles, a condition called internal hydrocephalus. It may result in increased CSF pressure. The production of CSF continues, even when the passages that normally allow it to exit the brain are blocked. Consequently, fluid builds inside the brain, causing pressure that dilates the ventricles and compresses the nervous tissue. Compression of the nervous tissue usually results in irreversible brain damage. If the skull bones are not completely ossified when the hydrocephalus occurs, the pressure may also severely enlarge the head. The cerebral aqueduct may be blocked at the time of birth or may become blocked later in life because of a tumor growing in the brainstem.

Classification

The classification of communicating vs. noncommunicating hydrocephalus are often used to describe the types of hydrocephalus. These terms describe the nonobstructive vs. obstructive mechanisms of the excess CSF build-up.

Communicating

In communicating hydrocephalus, there is no obstruction of CSF flow. Instead, there is either an increased production of CSF or difficulty reabsorbing CSF. Reabsorption occurs at the arachnoid granulations, so issues with reabsorption can occur because of arachnoid granulation impairment. There is also evidence of the lymphatic system being involved with reabsorption, so impairments of this system can also lead to excess CSF. Damage to these reabsorption sites are commonly post-hemorrhage or post-infection (such as meningitis).

Normal pressure hydrocephalus (NPH) is a form of chronic communicating hydrocephalus, with enlarged cerebral ventricles and intermittently increased cerebrospinal fluid pressure.

225x225px|thumbnail|An adult with congenital hydrocephalus in the [[Philippines]]

Noncommunicating

In noncommunicating hydrocephalus, there is obstruction to the CSF flow. Examples of common causes include hemorrhage, tumor, traumatic brain injury that disrupt the flow, leading to build-up of CSF in the brain. In the long term, some people will need any of the various types of cerebral shunts.

A shunt system can also be placed in the lumbar space of the spine. This allows the excess fluid to be redirected to the peritoneal cavity (lumbar-peritoneal shunt). Another treatment for obstructive hydrocephalus is an endoscopic third ventriculostomy (ETV). This surgery creates an opening in the floor of the third ventricle so that CSF flows directly to the basal cisterns. This treatment can shortcut any obstruction like aqueductal stenosis. This may or may not be appropriate based on individual anatomy. Some infants can be treated with ETV and choroid plexus cauterization.

External hydrocephalus

External hydrocephalus is generally seen in infants. It involves enlarged fluid spaces or subarachnoid spaces outside of the brain. The most common sign is a head circumference above the 90th percentile. In most cases, no other signs or symptoms are reported. Rarely reported symptoms include a tense anterior fontanel, developmental delay, seizures, irritability, and vomiting. Usually, this condition is benign. It resolves spontaneously by two to three years of age. Thus, it usually does not need insertion of a shunt. If surgical treatment is required, a ventriculoperitoneal shunt is usually preferred.

Shunt complications

Shunt surgery is one of the most common procedures in pediatric neurosurgery. Significant advances in shunt technology and surgical approaches have been made over the years. However, the lifetime risk for a revision surgery of a ventriculoperitoneal shunt in pediatric patients can reach up to 80%. Shunt failure rates are also high. Of the 40,000 surgeries performed annually for hydrocephalus, only 30% are a person's first surgery. Many patients require multiple revisions during their lives. Common complications requiring revision include:

  1. overdrainage of cerebrospinal fluid
  2. obstruction of the valve or catheter
  3. infection
  4. catheter disconnection/migration

Overdrainage of cerebrospinal fluid occurs when the fluid drains more rapidly than it is produced by the choroid plexus. The rate of overdrainage is estimated to be about 10% to 12% within 6.5 years after shunt placement. Signs and symptoms of overdrainage includes:

  • listlessness
  • severe headaches
  • irritability
  • light sensitivity
  • auditory hyperesthesia (sound sensitivity)
  • hearing loss A CT scan may or may not show any change in ventricle size, particularly if the person has a history of slit-like ventricles. It can be challenging to diagnose over-drainage. This can make treatment of overdrainage particularly frustrating for patients and their families. However, monitoring the intracranial pressure in combination with radiological findings has been found to be a useful tool for identifying cases of overdrainage.

Shunt obstruction is the most common cause of shunt failure.

The rate of initial shunt infection ranges from 3.6 to 12.6% It is believed that these organisms are introduced to the cerebrospinal fluid at the time of surgery. Current research is dedicated to methods to prevent such infections from occurring. Using antibiotics or different shunt hardware to prevent bacterial growth is being studied. As is the efficacy of more vigilant shunt surveillance. There is tentative evidence that preventative antibiotics may decrease the risk of shunt infections.

Shunt migration is a relatively uncommon complication that requires a shunt revision.

Following placement of a VP shunt, there have been cases of a decrease in post-surgery hearing. It is presumed that the cochlea aqueduct is responsible for the decrease in hearing thresholds. The cochlea aqueduct has been considered as a probable channel where CSF pressure can be transmitted. Therefore, the reduced CSF pressure could cause a decrease in perilymphatic pressure. This may cause secondary endolymphatic hydrops.

Epidemiology

It is estimated that congenital hydrocephalus occurs in 8.5 out of 10,000 live births globally. The disease burden is more concentrated in Africa, Asia, and South America. A study in 2019 estimated that there are 180,000 childhood hydrocephalus cases from the African continent per year. It also reported 90,000 cases from Southeast Asia and the Western Pacific.

History

right|thumb|Skull of a hydrocephalic child (1800s)

In the pre-historic area, there were various paintings or artifacts depicting children or adults with macrocephaly (large head) or clinical findings of hydrocephalus. The earliest scientific description of hydrocephalus was written by the ancient Greek physician, Hippocrates. He coined the word 'hydrocephalus' from the Greek ὕδωρ, hydōr meaning 'water' and κεφαλή, kephalē meaning 'head'. In his chapter on neurosurgical disease, he stated that infantile hydrocephalus was caused by mechanical compression. Specifically, he wrote: In 1893, Jan MIkulicz-Radecki used a permanent shunt to drain CSF successfully. It was not until the 20th century that the cerebral shunt and other neurosurgical treatment modalities were developed.

Awareness

thumb|150px|Hydrocephalus [[awareness ribbon]]

There are many organizations that advocate for hydrocephalus patients and promote research about its treatments. The Hydrocephalus Association was founded as a family support group in 1983 by parents of children with hydrocephalus. It has since expanded to a non-profit patient advocacy group, and has invested over $14 million in research since 2009. The National Hydrocephalus Foundation, also started by parents of a child with hydrocephalus, is a non-profit organization established in 1979. The Pediatric Hydrocephalus Foundation was founded in 2005 for similar purposes.

September was designated National Hydrocephalus Awareness Month in July 2009 by the U.S. Congress in . The resolution campaign is due in part to the advocacy work of the Pediatric Hydrocephalus Foundation. Prior to July 2009, no awareness month for this condition had been designated.

Notable cases

  • Ice hockey player Colby Cave had acute obstructive hydrocephalus due to a colloid cyst.
  • Author Sherman Alexie, born with the condition, wrote about it in his semi-autobiographical junior fiction novel The Absolutely True Diary of a Part-Time Indian.
  • Prince William, Duke of Gloucester (1689–1700), probably contracted meningitis at birth, which resulted in this condition.
  • Emperor Ferdinand I of Austria (1793–1875) became emperor in 1835 despite various health issues including hydrocephalus and epilepsy.
  • Masato Kudo, a professional football player, died of hydrocephalus on October 21, 2022.
  • Danny Bonaduce, a TV and radio personality, revealed that he would be undergoing surgery for hydrocephalus that was impeding his ability to walk properly in 2023.
  • King Charles II of Spain, known as El Hechizado ("the Bewitched"), is thought to have suffered from many diseases, including pituitary hormone deficiency, renal tubular acidosis, Klinefelter syndrome, fragile X syndrome, and hydrocephalus.
  • King Bhumibol Adulyadej of Thailand was treated for hydrocephalus in 2015.
  • On May 22, 2025, Billy Joel announced that he was cancelling his concerts while being treated for hydrocephalus.
  • Lily Daly, a 7-year-old girl from Ireland, died at Children's Health Ireland at Temple Street Hospital in February 2019. She had had hydrocephalus and died after suffering cardiac arrest during an MRI scan.
  • Roona Begum, a girl from India who has a severe form of congenital hydrocephalus, featured in Rooting for Roona

See also

  • Microcephaly
  • Macrocephaly

References

  • Guidelines for pediatric hydrocephalus