Hydrocephalus

{{short description|Abnormal increase in cerebrospinal fluid in the ventricles of the brain}}
{{distinguish|Hypocephalus|Hydranencephaly}}
{{about|the medical condition|the creature in American folklore|Melon heads|the trilobite|Hydrocephalus (trilobite)}}

{{Infobox medical condition (new)
| image           = Hydrocephalus (cropped).jpg
| caption         = Hydrocephalus as seen on a [[CT scan]] of the brain. The black areas in the middle of the brain (the [[lateral ventricles]]) are [[Ventriculomegaly|abnormally large]] and filled with fluid.
| field           = [[neurosurgery]]
| synonyms        = Water on the brain<ref name=NIH2016/>
| pronounce       = {{IPAc-en|ˌ|h|aɪ|d|r|əʊ|ˈ|s|ɛ|f|ə|l|ə|s}}<ref>{{cite web |title=Hydrocephalus |url=https://www.collinsdictionary.com/dictionary/english/hydrocephalus |website=Collins |access-date=1 April 2020}}</ref>
| symptoms        = '''Babies''': rapid head growth, [[vomiting]], sleepiness, [[seizures]]<ref name=NIH2016/><br>'''Older people''': [[Headache]]s, [[double vision]], poor balance, [[urinary incontinence]], personality changes, [[mental impairment]]<ref name=NIH2016/>
| complications   =
| onset           =
| duration        =
| causes          = [[Neural tube defects]], [[meningitis]], [[brain tumors]], [[traumatic brain injury]], brain bleed during birth, [[intraventricular hemorrhage]]<ref name=NIH2016/>
| risks           =
| diagnosis       = Based on symptoms and [[medical imaging]]<ref name=NIH2016/>
| differential    =
| prevention      =
| treatment       = Surgery<ref name=NIH2016/>
| medication      =
| prognosis       = Variable, often normal life<ref name=NIH2016/>
| frequency       = Varies throughout the world, from 1 per 256 live births to 1 per 9,000, depending on access to prenatal health care, prenatal tests, and abortion<ref name=NIH2016/><ref name=Stev2003/>
| deaths          =
}}
<!-- Definition and symptoms -->
'''Hydrocephalus''' is a condition in which an accumulation of [[cerebrospinal fluid]] (CSF) occurs within the [[brain]].<ref name=NIH2016>{{cite web |url=http://www.ninds.nih.gov/disorders/hydrocephalus/detail_hydrocephalus.htm |title=Hydrocephalus Fact Sheet |date=April 5, 2016 |website=NINDS |archive-url=https://web.archive.org/web/20160727231854/http://www.ninds.nih.gov/disorders/hydrocephalus/detail_hydrocephalus.htm |archive-date=27 July 2016 |url-status=live |access-date=5 September 2016}}</ref> This typically causes increased [[intracranial pressure|pressure inside the skull]].<!-- <ref name=NIH2016/> --> Older people may have [[headache]]s, [[double vision]], poor balance, [[urinary incontinence]], personality changes, or [[mental impairment]].<!-- <ref name=NIH2016/> --> In babies, it may be seen as a rapid increase in head size.<!-- <ref name=NIH2016/> --> Other symptoms may include [[vomiting]], sleepiness, [[seizures]], and [[Parinaud's syndrome|downward pointing of the eyes]].<ref name=NIH2016/>

<!-- Cause and diagnosis -->
Hydrocephalus can occur due to [[birth defect]]s or be acquired later in life.<ref name=NIH2016/> Associated birth defects include [[neural tube defects]] and those that result in [[aqueductal stenosis]].<ref name=NIH2016/><ref>{{cite journal | vauthors = Kahle KT, Kulkarni AV, Limbrick DD, Warf BC | title = Hydrocephalus in children | journal = Lancet | volume = 387 | issue = 10020 | pages = 788–799 | date = February 2016 | pmid = 26256071 | doi = 10.1016/s0140-6736(15)60694-8 | s2cid = 27947722 }}</ref> Other causes include [[meningitis]], [[brain tumors]], [[traumatic brain injury]], [[intraventricular hemorrhage]], and [[subarachnoid hemorrhage]].<!-- <ref name=NIH2016/> --> The four types of hydrocephalus are communicating, noncommunicating, ''ex vacuo'', and [[normal pressure hydrocephalus|normal pressure]].<!-- <ref name=NIH2016/> --> Diagnosis is typically made by physical examination and [[medical imaging]].<ref name=NIH2016/>

<!-- Treatment and prognosis -->
Hydrocephalus is typically treated by the surgical placement of a [[shunt system]].<ref name=NIH2016/> A procedure called a [[third ventriculostomy]] is an option in some people.<ref name=NIH2016/> Complications from shunts may include overdrainage, underdrainage, mechanical failure, [[infection]], or obstruction.<ref name=NIH2016/> This may require replacement.<ref name=NIH2016/> Outcomes are variable, but many people with shunts live normal lives.<ref name=NIH2016/><!-- Quote = Affected individuals and their families should be aware that hydrocephalus poses risks to both cognitive and physical development. However, many children diagnosed with the disorder... go on to lead normal lives with few limitations. --> Without treatment, permanent disability or death may occur.<ref name=NIH2016/>

<!-- Epidemiology, history, and culture -->
About one to two per 1,000 newborns have hydrocephalus.<ref name=NIH2016/><ref name=Stev2003>{{cite book|author1-link=David K. Stevenson | vauthors = Stevenson DK, Benitz WE |title=Fetal and Neonatal Brain Injury: Mechanisms, Management and the Risks of Practice |date=2003 |publisher=[[Cambridge University Press]] |location=Cambridge |isbn=9780521806916 |page=117 |url=https://books.google.com/books?id=RuekFAj_tIAC&pg=PA117 |url-status=live |archive-url=https://web.archive.org/web/20161221212406/https://books.google.com/books?id=RuekFAj_tIAC&pg=PA117|archive-date=2016-12-21}}</ref> Rates in the [[developing world]] may be higher.<ref name=Ab2012/> Normal pressure hydrocephalus is estimated to affect about 5 per 100,000 people, with rates increasing with age.<ref>{{cite book | vauthors = Ferri FF |title=Ferri's Clinical Advisor 2017: 5 Books in 1|date=2016 |publisher=Elsevier Health Sciences |isbn=9780323448383 |page=621 |url=https://books.google.com/books?id=rRhCDAAAQBAJ&pg=PA621 |url-status=live |archive-url=https://web.archive.org/web/20161221201502/https://books.google.com/books?id=rRhCDAAAQBAJ&pg=PA621 |archive-date=2016-12-21}}</ref> Description of hydrocephalus by [[Hippocrates]] dates back more than 2,000 years.<ref name=Ab2012>{{cite book | vauthors = Ellenbogen RG, Abdulrauf SI, Sekhar LN |title=Principles of Neurological Surgery |url=https://books.google.com/books?id=vMtRtuz5mnwC&pg=PA105 |year=2012 |publisher=Elsevier Health Sciences |isbn=978-1-4377-0701-4 |pages=105}}</ref> The word ''hydrocephalus'' is from the Greek {{lang-grc|text=ὕδωρ|label=none|translit=hydōr}}, meaning 'water' and {{lang-grc|text=κεφαλή|label=none|translit=kephalē}}, meaning 'head'.<ref name=Dor2000>{{cite book |title=Dorland's electronic medical dictionary. |date=2000 |publisher=W.B. Saunders Co |isbn=9780721694931 |edition=29th}}</ref>

==Signs and symptoms==
[[File:Hydrocephalus CDC.png|thumb|400px|Illustration showing different effects of hydrocephalus on the brain and cranium]]
[[File:Gould Pyle 94.jpg|thumb|Adult showing cranial deformity from pediatric hydrocephalus]]
The clinical presentation of hydrocephalus varies with [[chronicity]]. Acute dilatation of the [[ventricular system]] is more likely to manifest with the nonspecific signs and symptoms of increased intracranial pressure (ICP). By contrast, chronic dilatation (especially in the elderly population) may have a more insidious onset presenting, for instance, with [[Hakim's triad]] (Adams' triad).<ref>{{Cite web |title=Normal_Pressure_Hydrocephalus_Hakim-Adams_Syndrome_Clinical_Symptoms_Diagnosis_and_Treatment |url=https://www.researchgate.net/publication/339884128 |website=[[ResearchGate]]}}</ref><ref>{{Cite web |title=Normal pressure hydrocephalus |url=https://www.researchgate.net/publication/11822140 |website=ResearchGate}}</ref>

Symptoms of increased ICP may include [[headache]]s, [[vomiting]], [[nausea]], [[papilledema]], [[somnolence|sleepiness]], or [[coma]]. With increased levels of CSF, there have been cases of hearing loss due to CSF creating pressure on the auditory pathways or disrupting the communication of inner ear fluid.<ref name=":1">{{cite journal | vauthors = Satzer D, Guillaume DJ | title = Hearing loss in hydrocephalus: a review, with focus on mechanisms | journal = Neurosurgical Review | volume = 39 | issue = 1 | pages = 13–24; discussion 25 | date = January 2016 | pmid = 26280639 | doi = 10.1007/s10143-015-0650-2 | s2cid = 24439157 }}</ref> Elevated ICP of different etiologies have been linked to sensorineural hearing loss (SNHL). Transient SNHL has been reported after the loss of CSF with shunt surgeries.<ref>{{cite journal | vauthors = Dixon JF, Jones RO | title = Hydrocephalus-associated hearing loss and resolution after ventriculostomy | journal = Otolaryngology–Head and Neck Surgery | volume = 146 | issue = 6 | pages = 1037–1039 | date = June 2012 | pmid = 22166958 | doi = 10.1177/0194599811431234 | s2cid = 38240969 }}</ref> Hearing loss is a rare but well-known sequela of procedures resulting in CSF loss.<ref name=":1" /> Elevated ICP may result in [[brain herniation|uncal or tonsillar herniation]], with resulting life-threatening [[brain stem]] compression.<ref name=":4">{{cite journal | vauthors = Riveros Gilardi B, Muñoz López JI, Hernández Villegas AC, Garay Mora JA, Rico Rodríguez OC, Chávez Appendini R, De la Mora Malváez M, Higuera Calleja JA | display-authors = 6 | title = Types of Cerebral Herniation and Their Imaging Features | journal = Radiographics | volume = 39 | issue = 6 | pages = 1598–1610 | date = October 2019 | pmid = 31589570 | doi = 10.1148/rg.2019190018 | s2cid = 203924869 }}</ref>

Hakim's triad of [[gait]] instability, [[urinary incontinence]], and [[dementia]] is a relatively typical manifestation of the distinct entity normal-pressure hydrocephalus. [[Focal neurological deficit]]s may also occur, such as [[abducens nerve]] palsy and vertical [[gaze palsy]] ([[Parinaud syndrome]] due to compression of the [[quadrigeminal plate]], where the neural centers coordinating the [[Conjugate eye movement|conjugated vertical eye movement]] are located). The symptoms depend on the cause of the blockage, the person's age, and how much [[brain tissue]] has been damaged by the swelling.<ref name=":4" />

In infants with hydrocephalus, CSF builds up in the central nervous system (CNS), causing the [[fontanelle]] (soft spot) to bulge and the head to be larger than expected. Early symptoms may also include:<ref name=":4" />
* Eyes that appear to gaze downward
* Irritability
* Seizures
* Separated sutures
* Sleepiness
* Vomiting

Symptoms that may occur in older children can include:<ref name=":4" />
* 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 milestone]]s
* [[Failure to thrive]]
* Slow or restricted movement
* Vomiting<ref>{{cite web |vauthors=Kaneshiro NK, Zieve D, Black B, ((A.D.A.M. Editorial team)) |title=Hydrocephalus |url=https://www.nlm.nih.gov/medlineplus/ency/article/001571.htm |work=MedlinePlus}}</ref>

Because hydrocephalus can injure the brain, thought and behavior may be adversely affected. [[Learning disability|Learning disabilities]], including [[Amnesia|short-term memory loss]], are common among those with hydrocephalus, who tend to score better on verbal IQ than on performance IQ, which is thought to reflect the distribution of nerve damage to the brain.<ref name="NIH2016" /> Hydrocephalus that is present from birth can cause long-term complications with speech and language. Children can have issues such as nonverbal learning disorder, difficulty understanding complex and abstract concepts, difficulty retrieving stored information, and spatial/perceptual disorders. Children with hydrocephalus are often known in having the difficulty in understanding the concepts within conversation and tend to use words they know or have heard.<ref>{{cite journal | vauthors = Barnes MA, Dennis M | title = Discourse after early-onset hydrocephalus: core deficits in children of average intelligence | journal = Brain and Language | volume = 61 | issue = 3 | pages = 309–334 | date = February 1998 | pmid = 9570868 | doi = 10.1006/brln.1998.1843 | s2cid = 13336454 }}</ref><ref>{{Citation| vauthors = Oi S |title=Hydrocephalus Associated with Spina Bifida: Specific Pathophysiology and Therapeutic Problems|date=1999|work=Spina Bifida|pages=177–184|publisher=Springer Japan|isbn=978-4-431-70260-3}}</ref> However, the severity of hydrocephalus can differ considerably between individuals, and some are of average or above-average intelligence. Someone with hydrocephalus may have coordination and visual problems, or clumsiness. They may reach puberty earlier than the average child (this is called [[precocious puberty]]). About one in four develops [[epilepsy]].<ref>{{Cite web |title=Hydrocephalus |url=https://academic.oup.com/edrv/article/24/5/668/2424459 |access-date=2022-05-16 }}</ref>

==Cause==

===Congenital===
[[File:Hydrocephalus with sunset eyes.jpg|thumb|A one-year-old girl with hydrocephalus showing "sunset eyes", before shunt surgery]]
[[File:Kleeblattschadel Syndrome 3.jpg|thumb|Hydrocephalus in a child with kleeblattschadel]]
Congenital hydrocephalus is present in the infant prior to birth, meaning the fetus developed hydrocephalus ''[[Uterus|in utero]]'' during [[fetal development]]. The most common cause of congenital hydrocephalus is aqueductal stenosis, which occurs when the narrow passage between the third and fourth ventricles in the brain is blocked or too narrow to allow sufficient cerebral spinal fluid to drain. Fluid accumulates in the upper ventricles, causing hydrocephalus.<ref>{{cite web |title=The Hydrocephalus Association |url=http://www.hydroassoc.org |archive-url=https://web.archive.org/web/20060820210617/http://www.hydroassoc.org/ |archive-date=2006-08-20}}</ref>

Other causes of congenital hydrocephalus include [[neural tube|neural-tube]] defects, [[arachnoid cyst]]s, [[Dandy–Walker syndrome]], and [[Arnold–Chiari malformation]].
The [[cranial bone]]s fuse by the end of the third year of life. For head enlargement to occur, hydrocephalus must occur before then. The causes are usually genetic, but can also be acquired and usually occur within the first few months of life, which include intraventricular matrix hemorrhages in [[premature infants]], infections, type II Arnold-Chiari malformation, aqueduct atresia and stenosis, and Dandy-Walker malformation.<ref>{{Citation | vauthors = Nagra G, Del Bigio MR |title=Pathology of Pediatric Hydrocephalus |date=2018 |url=https://doi.org/10.1007/978-3-319-31889-9_43-1 |work=Pediatric Hydrocephalus |pages=1–25 | veditors = Cinalli G, Ozek MM, Sainte-Rose C |place=Cham |publisher=Springer International Publishing |language=en |doi=10.1007/978-3-319-31889-9_43-1 |isbn=978-3-319-31889-9 |s2cid=81899785 |access-date=2022-05-17 }}</ref><ref>{{Cite web |title=Congenital Hydrocephalus - an overview {{!}} ScienceDirect Topics |url=https://www.sciencedirect.com/topics/nursing-and-health-professions/congenital-hydrocephalus |access-date=2022-05-17 |website=www.sciencedirect.com}}</ref> Hydrocephalus can also occur with [[craniosynostosis]], being a constant feature of [[Kleeblattschaedel|kleeblattschadel]] and frequently seen in syndomic cases (mostly in [[Crouzon syndrome]]).<ref>{{Cite journal |last1=Cinalli |first1=G. |last2=Sainte-Rose |first2=C. |last3=Kollar |first3=E. M. |last4=Zerah |first4=M. |last5=Brunelle |first5=F. |last6=Chumas |first6=P. |last7=Arnaud |first7=E. |last8=Marchac |first8=D. |last9=Pierre-Kahn |first9=A. |last10=Renier |first10=D. |date=February 1998 |title=Hydrocephalus and craniosynostosis |url=https://pubmed.ncbi.nlm.nih.gov/9452225/ |journal=Journal of Neurosurgery |volume=88 |issue=2 |pages=209–214 |doi=10.3171/jns.1998.88.2.0209 |issn=0022-3085 |pmid=9452225}}</ref> Hydrocephalus has also been seen in cases of [[congenital syphilis]].<ref>{{cite journal | vauthors = Arnold SR, Ford-Jones EL | title = Congenital syphilis: A guide to diagnosis and management | journal = Paediatrics & Child Health | volume = 5 | issue = 8 | pages = 463–469 | date = November 2000 | pmid = 20177559 | pmc = 2819963 | doi = 10.1093/pch/5.8.463 }}</ref>

In newborns and toddlers with hydrocephalus, the head circumference is enlarged rapidly and soon surpasses the 97th percentile. Since the skull bones have not yet firmly joined, bulging, firm [[anterior fontanelle|anterior]] and [[posterior fontanelle]]s may be present even when the person is in an upright position.{{citation needed|date=May 2022}}

The infant exhibits fretfulness, poor feeding, and frequent vomiting. As the hydrocephalus progresses, [[torpor]] sets in, and infants show lack of interest in their surroundings. Later on, their upper eyelids become retracted and their eyes are turned downwards ("sunset eyes") (due to hydrocephalic pressure on the [[mesencephalic tegmentum]] and [[paralysis]] of upward gaze). Movements become weak and the arms may become [[Tremor|tremulous]]. Papilledema is absent, but vision may be reduced. The head becomes so enlarged that they eventually may be bedridden.<ref>{{Cite web  |title=What You Should Know About Macrocephaly |url=https://www.webmd.com/brain/what-you-should-know-about-macrocephaly |access-date=2022-05-17 |website=[[WebMD]] |language=en}}</ref>

About 80–90% of fetuses or newborn infants with [[spina bifida]]—often associated with [[meningocele]] or [[myelomeningocele]]—develop hydrocephalus.<ref>{{cite web |url=http://www.spinabifidamoms.com/english/about.html |title=Spina Bifida |publisher=Spinabifidamoms.com |access-date=2014-01-29 |url-status=dead |archive-url=https://web.archive.org/web/20131101014750/http://www.spinabifidamoms.com/english/about.html |archive-date=2013-11-01}}</ref>

===Acquired===
This condition is acquired as a consequence of CNS [[infections]], [[meningitis]], [[brain tumors]], [[traumatic brain injury|head trauma]], [[toxoplasmosis]], or [[stroke|intracranial hemorrhage]] (subarachnoid or intraparenchymal), and is usually painful.<ref>{{Cite web|url=https://www.ucsfbenioffchildrens.org/conditions/acquired_hydrocephalus/|title=Acquired Hydrocephalus {{!}} Conditions & Treatments {{!}} UCSF Benioff Children's Hospital|website=www.ucsfbenioffchildrens.org|access-date=2020-04-09}}</ref>

==Type==
The cause of hydrocephalus is not known with certainty and is probably multifactorial. It may be caused by impaired CSF flow, reabsorption, or excessive CSF production.<ref>{{Cite journal | vauthors = Nelson Jr SL, Espay AJ, Hord ED | veditors = Talavera F |date=2022-02-02 |title=Hydrocephalus: Practice Essentials, Background, Pathophysiology |url=https://emedicine.medscape.com/article/1135286-overview | journal = Medscape }}</ref>
* Obstruction to CSF flow hinders its free passage through the ventricular system and [[subarachnoid space]] (e.g., [[stenosis]] of the [[cerebral aqueduct]] or obstruction of the [[interventricular foramina (neural anatomy)|interventricular foramina]] secondary to [[tumor]]s, [[hemorrhage]]s, [[infection]]s or [[congenital]] malformations) and can cause increases in ICP.<ref>{{Cite journal | vauthors = Nelson SL, Murro AM, Espay AJ, Hord ED |date=2022-03-11 | veditors = Talavera F |title=Ventricles of the Brain: Overview, Gross Anatomy, Microscopic Anatomy |url=https://emedicine.medscape.com/article/1923254-overview | journal = Medscape }}</ref>
* Hydrocephalus can also be caused by overproduction of CSF (relative obstruction) (e.g., [[choroid plexus papilloma]], villous [[hypertrophy]]).<ref name="AdunkaBuchman2010">{{cite book | vauthors = Adunka O, Buchman C |title=Otology, Neurotology, and Lateral Skull Base Surgery: An Illustrated Handbook |url=https://books.google.com/books?id=2kv-Z-L5UUAC&pg=PT353 |access-date=12 August 2013 |date=11 October 2010 |publisher=Thieme |isbn=978-3-13-149621-8 |pages=353– |url-status=live |archive-url=https://web.archive.org/web/20140705102607/http://books.google.com/books?id=2kv-Z-L5UUAC&pg=PT353 |archive-date=5 July 2014}}</ref><ref name="pmid20367337">{{cite journal | vauthors = Nimjee SM, Powers CJ, McLendon RE, Grant GA, Fuchs HE | title = Single-stage bilateral choroid plexectomy for choroid plexus papilloma in a patient presenting with high cerebrospinal fluid output | journal = Journal of Neurosurgery. Pediatrics | volume = 5 | issue = 4 | pages = 342–345 | date = April 2010 | pmid = 20367337 | doi = 10.3171/2009.10.peds08454 }}</ref>
* Bilateral [[ureter]]ic obstruction is a rare, but reported, cause of hydrocephalus.

Hydrocephalus can be classified into communicating and noncommunicating (obstructive). Both forms can be either congenital or acquired.<ref>{{Cite web |title=Different Types of Hydrocephalus |url=https://ana-neurosurgery.com/hydrocephalus/different-types/ |access-date=2022-05-17 |website=Advanced Neurosurgery Associates |language=en-US}}</ref>

===Communicating===
Communicating hydrocephalus, also known as nonobstructive hydrocephalus, is caused by impaired CSF reabsorption in the absence of any obstruction of CSF flow between the ventricles and subarachnoid space. This may be due to functional impairment of the [[arachnoid villi|arachnoidal granulations]] (also called arachnoid granulations or [[Pacchioni's granulations]]), which are located along the [[superior sagittal sinus]], and is the site of CSF reabsorption back into the venous system. Various neurologic conditions may result in communicating hydrocephalus, including subarachnoid/intraventricular hemorrhage, meningitis, and congenital absence of arachnoid villi. Scarring and fibrosis of the subarachnoid space following infectious, inflammatory, or hemorrhagic events can also prevent reabsorption of CSF, causing diffuse ventricular dilatation.<ref>{{Cite book| vauthors = Kaye A, Fox C, Diaz J |title=Essentials of Pediatric Anesthesiology |publisher=Cambridge University Press |year=2014 |pages=106 }}</ref>
[[File:Hydrocephalus_cranial_deformity_2.jpg|75px|thumbnail|right|An adult  with congenital hydrocephalus in the [[Philippines]]]]
===Noncommunicating===
Noncommunicating hydrocephalus, or obstructive hydrocephalus, is caused by an obstruction to the flow of CSF.<ref>{{Cite web |date=2020-02-21 |title=Communicating and Non-communicating Hydrocephalus {{!}} Helpful |url=https://www.hydroassoc.org/communicating-non-communicating-hydrocephalus/ |access-date=2022-05-17 |website=www.hydroassoc.org |language=en-US}}</ref>
* [[Interventricular foramina (neural anatomy)|Foramen of Monro]] obstruction may lead to dilation of one, or if large enough (e.g., in [[colloid cyst]]), both lateral ventricles.
* The [[Cerebral aqueduct|aqueduct of Sylvius]], normally narrow, may be obstructed by a number of genetic or acquired lesions (e.g., atresia, [[ependymitis]], hemorrhage, or tumor) and lead to dilation of both lateral ventricles, as well as the [[third ventricle]].
* [[Fourth ventricle]] obstruction leads to dilatation of the aqueduct, as well as the lateral and third ventricles (e.g., [[Chiari malformation]]).
* The [[foramina of Luschka]] and [[Median aperture|foramen of Magendie]] may be obstructed due to congenital malformation (e.g., [[Dandy–Walker malformation]]).

===Other===
[[File:BrainAtrophy(exvacuo).png|thumb|Hydrocephalus ''ex vacuo'' from vascular dementia as seen on MRI]]
* [[Normal pressure hydrocephalus]] (NPH) is a particular form of chronic communicating hydrocephalus, characterized by enlarged cerebral ventricles, with only intermittently elevated cerebrospinal fluid pressure. Characteristic triad of symptoms are; dementia, apraxic gait and urinary incontinence. The diagnosis of NPH can be established only with the help of continuous intraventricular pressure recordings (over 24 hours or even longer), since more often than not instant measurements yield normal pressure values. Dynamic compliance studies may be also helpful. Altered compliance ([[wikt:elastic#Adjective|elasticity]]) of the ventricular walls, as well as increased [[viscosity]] of the cerebrospinal fluid, may play a role in the pathogenesis.<ref>{{cite journal | vauthors = Martin BA, Loth F | title = The influence of coughing on cerebrospinal fluid pressure in an in vitro syringomyelia model with spinal subarachnoid space stenosis | journal = Cerebrospinal Fluid Research | volume = 6 | issue = 1 | pages = 17 | date = December 2009 | pmid = 20043856 | pmc = 2806373 | doi = 10.1186/1743-8454-6-17 | doi-access = free }}</ref>
* ''Hydrocephalus ex vacuo'' also refers to an enlargement of cerebral ventricles and subarachnoid spaces, and is usually due to brain [[atrophy]] (as it occurs in [[dementia]]s), post-[[traumatic brain injury|traumatic brain injuries]], and even in some psychiatric disorders, such as [[schizophrenia]].<ref name=":0">{{Cite book|title=Complications in neuroanesthesia| vauthors = Hemanshu P |isbn=9780128040751|oclc=939553425|date = 2016-02-29| publisher = Elsevier Science }}</ref> As opposed to hydrocephalus, this is a compensatory enlargement of the CSF-spaces in response to brain [[parenchyma]] loss; it is not the result of increased CSF pressure.<ref name=":0" />

==Mechanism==
[[File:Intracerebral hemorrhage.jpg|thumb|upright=1.2|Spontaneous [[intracerebral hemorrhage|intracerebral]] and [[intraventricular hemorrhage]] with hydrocephalus shown on CT scan<ref name="Yadav07">{{cite journal | vauthors = Yadav YR, Mukerji G, Shenoy R, Basoor A, Jain G, Nelson A | title = Endoscopic management of hypertensive intraventricular haemorrhage with obstructive hydrocephalus | journal = BMC Neurology | volume = 7 | pages = 1 | date = January 2007 | pmid = 17204141 | pmc = 1780056 | doi = 10.1186/1471-2377-7-1 | doi-access = free }}</ref>]]
[[File:3DPX-003132 Cast of Lateral ventricles in Hydrocephaly NevitDilmen.stl|thumb|3D cast of lateral ventricles in hydrocephalus]]
Hydrocephalus is usually due to blockage of CSF outflow in the ventricles or in the subarachnoid space over the brain. 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.<ref>{{cite web |url=http://www.ninds.nih.gov/disorders/hydrocephalus/detail_hydrocephalus.htm |title=Hydrocephalus Fact Sheet |archive-url=https://web.archive.org/web/20160727231854/http://www.ninds.nih.gov/disorders/hydrocephalus/detail_hydrocephalus.htm |archive-date=2016-07-27 |work=National Institute of Neurological Disorders and Stroke |date=August 2005}}</ref>

Compression of the brain by the accumulating fluid eventually may cause neurological symptoms such as [[convulsions]], [[intellectual disability]], and [[epileptic seizure]]s. These signs occur sooner in adults, whose skulls are no longer able to expand to accommodate the increasing fluid volume within. Fetuses, infants, and young children with hydrocephalus typically have an abnormally large head, 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]]. Another [[medical sign]], in infants, is a characteristic fixed downward gaze with whites of the eyes showing above the iris, as though the infant were trying to examine its own lower eyelids.<ref>{{cite book | vauthors = Cabot RC | date = 1919 | title = Physical diagnosis | publisher = William Wood and Company | location = New York | edition = 7th | page = 5 | via = Google Books }}</ref>

The elevated ICP may cause compression of the brain, leading to brain damage and other complications. A complication often overlooked is the possibility of hearing loss due to ICP. The mechanism of ICP on hearing loss is presumed that the transmission of CSF pressure to and from the Perilymphatic space through a patent cochlear aqueduct.<ref name=":2">{{cite journal | vauthors = Pogodzinski MS, Shallop JK, Sprung J, Weingarten TN, Wong GY, McDonald TJ | title = Hearing loss and cerebrospinal fluid pressure: case report and review of the literature | journal = Ear, Nose, & Throat Journal | volume = 87 | issue = 3 | pages = 144–147 | date = March 2008 | pmid = 18404909 | doi = 10.1177/014556130808700308 | doi-access = free }}</ref><ref>{{cite journal | vauthors = Marchbanks RJ, Reid A | title = Cochlear and cerebrospinal fluid pressure: their inter-relationship and control mechanisms | journal = British Journal of Audiology | volume = 24 | issue = 3 | pages = 179–187 | date = June 1990 | pmid = 2194603 | doi = 10.3109/03005369009076554 }}</ref> The cochlear aqueduct connects the Perilymphatic space of the inner ear with the subarachnoid space of the posterior cranial fossa.<ref name=":3">{{cite journal | vauthors = Lim HW, Shim BS, Yang CJ, Kim JH, Cho YH, Cho YS, Kong DS, Koo JW, Han JH, Chung JW | display-authors = 6 | title = Hearing loss following ventriculoperitoneal shunt in communicating hydrocephalus patients: a pilot study | journal = The Laryngoscope | volume = 124 | issue = 8 | pages = 1923–1927 | date = August 2014 | pmid = 24318317 | doi = 10.1002/lary.24553 | s2cid = 24667376 }}</ref> A loss of CSF pressure can induce Perilymphatic loss or endolymphatic hydrops resembling the clinical presentation of [[Ménière's disease]] associated hearing loss in the low frequencies.<ref name=":2" />

CSF can accumulate within the ventricles, this condition is called internal hydrocephalus and 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 [[human skull|skull]] bones are not completely [[ossified]] when the hydrocephalus occurs, the pressure may also severely enlarge the head. The [[Aqueductal stenosis|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]].<ref>{{Cite web |date=2017-12-07 |title=Hydrocephalus: Causes, symptoms, and treatments |url=https://www.medicalnewstoday.com/articles/181727 |access-date=2022-05-18 |website=www.medicalnewstoday.com |language=en}}</ref>

==Treatments==
===Procedures===
[[File:Khidmat Masy Hydrocephalus (19042957419).jpg|thumb|upright=1.2|Baby recovering from shunt surgery]]
Hydrocephalus treatment is surgical, creating a way for the excess fluid to drain away. In the short term, an [[external ventricular drain]] (EVD), also known as an extraventricular drain or ventriculostomy, provides relief. In the long term, some people will need any of various types of [[cerebral shunt]]. It involves the placement of a ventricular [[catheter]] (a tube made of [[silastic]]) into the cerebral ventricles to bypass the flow obstruction/malfunctioning arachnoidal granulations and drain the excess fluid into other body cavities, from where it can be resorbed. Most shunts drain the fluid into the [[peritoneum|peritoneal cavity]] ([[cerebral shunt|ventriculoperitoneal shunt]]), but alternative sites include the [[right atrium]] ([[cerebral shunt|ventriculoatrial shunt]]), [[pleura|pleural cavity]] ([[cerebral shunt|ventriculopleural shunt]]), and [[gall bladder|gallbladder]].
{{Further|topic=the non-invasive diagnostic medical device|ShuntCheck}}
A shunt system can also be placed in the lumbar space of the spine and have the CSF redirected to the peritoneal cavity ([[lumbar-peritoneal shunt]]).<ref name="pmid20508332">{{cite journal | vauthors = Yadav YR, Parihar V, Sinha M | title = Lumbar peritoneal shunt | journal = Neurology India | volume = 58 | issue = 2 | pages = 179–184 | year = 2010 | pmid = 20508332 | doi = 10.4103/0028-3886.63778 | doi-access = free }}</ref> An alternative treatment for obstructive hydrocephalus in selected people is the [[endoscopic third ventriculostomy]] (ETV), whereby a surgically created opening in the floor of the third ventricle allows the CSF to flow directly to the [[basal cisterns]], thereby shortcutting any obstruction, as in aqueductal stenosis. This may or may not be appropriate based on individual anatomy. For infants, ETV is sometimes combined with choroid plexus cauterization, which reduces the amount of cerebrospinal fluid produced by the brain. The technique, known as ETV/CPC, was pioneered in [[Uganda]] by neurosurgeon [[Benjamin Warf]] and is now in use in several U.S. hospitals.<ref>{{cite web |title=An American surgeon pioneers surgery for kids in Uganda that helps kids in the US |url=http://www.pri.org/stories/2015-04-27/american-surgeon-pioneers-surgery-kids-uganda-helps-kids-us |website=Public Radio International |access-date=2016-02-10 |url-status=live |archive-url=https://web.archive.org/web/20160302012700/http://www.pri.org/stories/2015-04-27/american-surgeon-pioneers-surgery-kids-uganda-helps-kids-us |archive-date=2016-03-02}}</ref><ref>{{cite journal | vauthors = Burton A | title = Infant hydrocephalus in Africa: spreading some good news | journal = The Lancet. Neurology | volume = 14 | issue = 8 | pages = 789–790 | date = August 2015 | pmid = 26091960 | doi = 10.1016/S1474-4422(15)00138-6 | s2cid = 35920581 }}</ref> Hydrocephalus can be successfully treated by placing a drainage tube (shunt) between the brain ventricles and abdominal cavity. Some risk exists of [[infection]] being introduced into the brain through these shunts, as they must be replaced as the person grows.<ref>{{cite journal | vauthors = Pople IK | title = Hydrocephalus and shunts: what the neurologist should know | journal = Journal of Neurology, Neurosurgery, and Psychiatry | volume = 73 | issue = suppl 1 | pages = i17–i22 | date = September 2002 | pmid = 12185257 | doi = 10.1136/jnnp.73.suppl_1.i17 | doi-broken-date = 31 January 2024 | pmc = 1765598 }}</ref><ref>{{Cite journal | vauthors = Engelhard III HH, Sahrakar K, Pang D | veditors = Talavera F |date=2022-03-03 |title=Neurosurgery for Hydrocephalus Treatment & Management: Approach Considerations, Medical Therapy, Surgical Therapy |url=https://emedicine.medscape.com/article/247387-treatment | journal = Medscape }}</ref>

===External hydrocephalus===
External hydrocephalus is a condition generally seen in infants which involves enlarged fluid spaces or subarachnoid spaces around the outside of the brain. This condition is generally [[benign]], and resolves spontaneously by two years of age<ref>{{cite book |url=https://books.google.com/books?id=0TC9Cns4Qz8C&q=Greenberg+handbook+of+neurosurgery+external+hydrocephalus&pg=PA307 |title=Handbook of Neurosurgery |isbn=9781604063264 | vauthors = Greenberg MS |date=2010-02-15 |publisher=Thieme |url-status=live |archive-url=https://web.archive.org/web/20230708022539/https://books.google.com/books?id=0TC9Cns4Qz8C&pg=PA307 |archive-date=2023-07-08}}</ref> and therefore usually does not require insertion of a shunt. Imaging studies and a good medical history can help to differentiate external hydrocephalus from [[subdural hematoma|subdural hemorrhages]] or symptomatic chronic extra-axial fluid collections which are accompanied by vomiting, headaches, and seizures.<ref>{{Cite web |title=Subdural Hematomas in the Elderly: The Great Neurological Imitator {{!}} 2000-03-01 {{!}} AHC Media: Continuing Medical Education Publishing {{!}} Relias Media - Continuing Medical Education Publishing |url=https://www.reliasmedia.com/articles/44955-subdural-hematomas-in-the-elderly-the-great-neurological-imitator |access-date=2022-05-17 |website=www.reliasmedia.com}}</ref><ref>{{Cite journal |title= External hydrocephalus: A probable cause for subdural hematoma in infancy|url=https://www.researchgate.net/publication/10800536 |journal= Pediatric Neurology|year=2003 |language=en |doi=10.1016/S0887-8994(02)00500-3|pmid=12699866 |last1=Ravid |first1=S. |last2=Maytal |first2=J. |volume=28 |issue=2 |pages=139–141 }}</ref>

===Shunt complications===
Examples of possible complications include shunt malfunction, shunt failure, and shunt infection, along with infection of the shunt tract following surgery (the most common reason for shunt failure is infection of the shunt tract). Although a shunt generally works well, it may stop working if it disconnects, becomes blocked (clogged) or infected, or it is outgrown. If this happens, the CSF begins to accumulate again and a number of physical symptoms develop (headaches, nausea, vomiting, [[photophobia]]/light sensitivity), some extremely serious, such as [[seizure]]s. The shunt failure rate is also relatively high (of the 40,000 surgeries performed annually to treat hydrocephalus, only 30% are a person's first surgery) and people not uncommonly have multiple shunt revisions within their lifetimes.<ref>{{Cite web | vauthors = Benner KW, Spellen S, Jeske A |title=Pharmacology of Shunt Infections |url=https://www.uspharmacist.com/article/pharmacology-of-shunt-infections |access-date=2022-05-18 |website=www.uspharmacist.com |language=en}}</ref>

Another complication can occur when CSF drains more rapidly than it is produced by the [[choroid plexus]], causing symptoms of listlessness, severe headaches, irritability, light sensitivity, auditory [[hyperesthesia]] (sound sensitivity), hearing loss,<ref name=":3" /> nausea, vomiting, [[dizziness]], [[Vertigo (medical)|vertigo]], [[migraines]], seizures, a change in personality, [[weakness]] in the arms or legs, [[strabismus]], and [[Diplopia|double vision]] to appear when the person is vertical. If the person lies down, the symptoms usually vanish quickly. A [[CT scan]] may or may not show any change in ventricle size, particularly if the person has a history of slit-like ventricles. Difficulty in diagnosing over-drainage can make treatment of this complication particularly frustrating for people and their families. Resistance to traditional [[analgesic]] pharmacological therapy may also be a sign of shunt overdrainage or failure.<ref>{{cite journal | vauthors = Nagahama Y, Peters D, Kumonda S, Vesole A, Joshi C, J Dlouhy B, Kawasaki H | title = Delayed diagnosis of shunt overdrainage following functional hemispherotomy and ventriculoperitoneal shunt placement in a hemimegalencephaly patient | journal = Epilepsy & Behavior Case Reports | volume = 7 | pages = 34–36 | date = 2017-01-24 | pmid = 28348960 | pmc = 5357741 | doi = 10.1016/j.ebcr.2016.12.003 }}</ref>

Following placement of a ventriculoperitoneal 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 and cause secondary endolymphatic hydrops.<ref name=":3" /> In addition to the increased hearing loss, there have also been findings of resolved hearing loss after ventriculoperitoneal shunt placement, where there is a release of CSF pressure on the auditory pathways.<ref>{{cite journal | vauthors = Sammons VJ, Jacobson E, Lawson J | title = Resolution of hydrocephalus-associated sensorineural hearing loss after insertion of ventriculoperitoneal shunt | journal = Journal of Neurosurgery. Pediatrics | volume = 4 | issue = 4 | pages = 394–396 | date = October 2009 | pmid = 19795973 | doi = 10.3171/2009.4.PEDS09103 }}</ref>

The diagnosis of CSF buildup is complex and requires specialist expertise. Diagnosis of the particular complication usually depends on when the symptoms appear, that is, whether symptoms occur when the person is upright or in a prone position, with the head at roughly the same level as the feet.<ref>{{cite journal | vauthors = Krishnan SR, Arafa HM, Kwon K, Deng Y, Su CJ, Reeder JT, Freudman J, Stankiewicz I, Chen HM, Loza R, Mims M, Mims M, Lee K, Abecassis Z, Banks A, Ostojich D, Patel M, Wang H, Börekçi K, Rosenow J, Tate M, Huang Y, Alden T, Potts MB, Ayer AB, Rogers JA | display-authors = 6 | title = Continuous, noninvasive wireless monitoring of flow of cerebrospinal fluid through shunts in patients with hydrocephalus | journal = npj Digital Medicine | volume = 3 | issue = 1 | pages = 29 | date = 2020-03-06 | pmid = 32195364 | pmc = 7060317 | doi = 10.1038/s41746-020-0239-1 }}</ref>

Standardized protocols for inserting cerebral shunts have been shown to reduce shunt infections.<ref>{{cite journal | vauthors = Yang MM, Hader W, Bullivant K, Brindle M, Riva-Cambrin J | title = Calgary Shunt Protocol, an adaptation of the Hydrocephalus Clinical Research Network shunt protocol, reduces shunt infections in children | journal = Journal of Neurosurgery. Pediatrics | volume = 23 | issue = 5 | pages = 559–567 | date = February 2019 | pmid = 30797206 | doi = 10.3171/2018.10.PEDS18420 | s2cid = 73507028 }}</ref><ref>{{cite journal | vauthors = Kestle JR, Riva-Cambrin J, Wellons JC, Kulkarni AV, Whitehead WE, Walker ML, Oakes WJ, Drake JM, Luerssen TG, Simon TD, Holubkov R | display-authors = 6 | title = A standardized protocol to reduce cerebrospinal fluid shunt infection: the Hydrocephalus Clinical Research Network Quality Improvement Initiative | journal = Journal of Neurosurgery. Pediatrics | volume = 8 | issue = 1 | pages = 22–29 | date = July 2011 | pmid = 21721884 | pmc = 3153415 | doi = 10.3171/2011.4.PEDS10551 }}</ref> There is tentative evidence that preventative antibiotics may decrease the risk of shunt infections.<ref>{{cite journal | vauthors = Arts SH, Boogaarts HD, van Lindert EJ | title = Route of antibiotic prophylaxis for prevention of cerebrospinal fluid-shunt infection | journal = The Cochrane Database of Systematic Reviews | volume = 6 | pages = CD012902 | date = June 2019 | issue = 6 | pmid = 31163089 | pmc = 6548496 | doi = 10.1002/14651858.CD012902.pub2 }}</ref>

==Epidemiology==
The hydrocephalus disease burden are concentrated in the developing world while North America has the least number of cases. A systematic review in 2019 estimated that there are 180,000 childhood hydrocephalus cases from the African continent per year, followed by 90,000 cases from Southeast Asia and the Western Pacific. Latin America also has a high prevalence of hydrocephalus. However, data on hydrocephalus disease burden in adults are lacking.<ref name="pmid29701543">{{cite journal |vauthors=Dewan MC, Rattani A, Mekary R, Glancz LJ, Yunusa I, Baticulon RE, Fieggen G, Wellons JC, Park KB, Warf BC |title=Global hydrocephalus epidemiology and incidence: systematic review and meta-analysis |journal=Journal of Neurosurgery |volume= 130|issue= 4|pages=1065–1079 |date=April 2018 |pmid=29701543 |doi=10.3171/2017.10.JNS17439 |s2cid=13859207 |url=|doi-access=free }}</ref>

==History==
[[File:Vimont Traite de Phrenologie 022.jpg|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. However, due to lack of writing, it was unknown how the people thought of the disorder at that time and the ways to treat the disease.<ref name="Cinalli 2019">{{Cite book |last=Cinalli |first=G |chapter-url=http://link.springer.com/10.1007/978-3-319-27250-4 |chapter=Pediatric Hydrocephalus |date=2019 |publisher=Springer International Publishing |isbn=978-3-319-27248-1 |editor-last=Cinalli |editor-first=Giuseppe |location=Cham |language=en |doi=10.1007/978-3-319-27250-4 |s2cid=128359318 |editor-last2=Özek |editor-first2=M. Memet |editor-last3=Sainte-Rose |editor-first3=Christian}}</ref>

References to hydrocephalic skulls can be found in [[Ancient Egyptian medicine|ancient Egyptian]] medical literature from 2,500 BC to 500 AD.<ref name=Aschoff/> Hydrocephalus was described more clearly by the ancient Greek physician Hippocrates in the fourth century BC, while a more accurate description was later given by the [[Medicine in ancient Rome|Roman]] physician [[Galen]] in the second century AD.<ref name=Aschoff/>

The first clinical description of an operative procedure for hydrocephalus appears in the ''[[Al-Tasrif]]'' (1,000 AD) by the [[Medicine in medieval Islam|Arab]] surgeon [[Abu al-Qasim al-Zahrawi|Abulcasis]], who clearly described the evacuation of superficial intracranial fluid in hydrocephalic children.<ref name="Aschoff">{{cite journal | vauthors = Aschoff A, Kremer P, Hashemi B, Kunze S | title = The scientific history of hydrocephalus and its treatment | journal = Neurosurgical Review | volume = 22 | issue = 2–3 | pages = 67–93; discussion 94–5 | date = October 1999 | pmid = 10547004 | doi = 10.1007/s101430050035 | s2cid = 10077885 }}</ref> He described it in his chapter on [[Neurosurgery|neurosurgical]] disease, describing infantile hydrocephalus as being caused by mechanical compression. He wrote:<ref name="Aschoff" />

{{blockquote|The skull of a newborn baby is often full of liquid, either because the matron has compressed it excessively or for other, unknown reasons. The volume of the skull then increases daily, so that the bones of the skull fail to close. In this case, we must open the middle of the skull in three places, make the liquid flow out, then close the wound and tighten the skull with a bandage.}}

[[File:Hydrocephalus-baby.jpg|thumb|200px|Historical specimen of an infant with severe hydrocephalus, probably untreated|alt=Preserved corpse of a newborn with an enlarged head|left]]
In 1881, a few years after the landmark study of [[Gustaf Retzius|Retzius]] and Key, [[Carl Wernicke]] pioneered sterile ventricular puncture and external drainage of CSF for the treatment of hydrocephalus.<ref name="Aschoff" /> It remained an intractable condition until the 20th century, when [[cerebral shunt]] and other neurosurgical treatment modalities were developed.{{citation needed|date=May 2020}}

It is a lesser-known medical condition; relatively little research is conducted to improve treatment, and still no cure has been found. In developing countries, the condition often goes untreated at birth. Before birth, the condition is difficult to diagnose, and access to medical treatment is limited. However, when head swelling is prominent, children are taken at great expense for treatment. By then, brain tissue is undeveloped and neurosurgery is rare and difficult. Children more commonly live with undeveloped brain tissue and consequential intellectual disabilities and restrictions.<ref>{{Cite web|url=https://www.geni.com/projects/Hydrocephalus/49669|title=Hydrocephalus genealogy project|website=geni_family_tree|language=en-US|access-date=2020-04-09}}</ref>

==Society and culture==
=== Name ===
The word ''hydrocephalus'' is from the Greek {{Lang-grc|text=ὕδωρ|label=none|translit=hydōr}} meaning 'water' and {{Lang-grc|text=κεφαλή|label=none|translit=kephalē}} meaning 'head'.<ref name=Dor2000/> Other names for hydrocephalus include "water on the brain", a historical name, and "water baby syndrome".<ref name="NIH2016" /><ref>{{Cite book|url=https://books.google.com/books?id=H9KsNAWbcMcC&q=hydrocephalus+%22water+baby%22&pg=PA53|title=Death, Modernity, and the Body: Sweden 1870-1940| vauthors = Åhrén E |publisher=[[University of Rochester Press]]|year=2009|isbn=9781580463126|location=[[Rochester, New York]]|pages=53|language=en}}</ref>

===Awareness campaign===
[[File:Hydrocephalus ribbon two tone blue.jpg|thumb|150px|Hydrocephalus [[awareness ribbon]]]]

September was designated National Hydrocephalus Awareness Month in July 2009 by the [[U.S. Congress]] in {{USBill|111|hres|373}}. 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. Many hydrocephalus organizations, such as the [[One Small Voice Foundation]], promote awareness and fundraising activities.{{citation needed|date=May 2020}}

===Exceptional case===
One case of hydrocephalus was a man whose brain shrank to a thin sheet of tissue, due to a buildup of cerebrospinal fluid in his skull. As a child, the man had a shunt, but it was removed when he was 14. In July 2007, at age 44, he went to a hospital due to mild weakness in his left leg. When doctors learned of the man's medical history, they performed a CT and MRI scan, and were astonished to see "massive enlargement" of the lateral ventricles in the skull. Dr. Lionel Feuillet of Hôpital de la Timone in [[Marseille]] said, "The images were most unusual... the brain was virtually absent."<ref>{{cite web |url=http://www.foxnews.com/story/0,2933,290610,00.html |title=Man with Almost No Brain Has Led Normal Life |archive-url=https://web.archive.org/web/20070916054402/http://www.foxnews.com/story/0,2933,290610,00.html |archive-date=2007-09-16 |publisher=Fox News |date=2007-07-25}} Also see {{cite web |url=https://www.newscientist.com/article/dn12301-man-with-tiny-brain-shocks-doctors.html |title=Man with tiny brain shocks doctors |archive-url=https://web.archive.org/web/20150712092909/http://www.newscientist.com/article/dn12301-man-with-tiny-brain-shocks-doctors.html |archive-date=2015-07-12 |work=New Scientist |date=2007-07-20}}; {{cite web |url=https://www.sciencedaily.com/releases/2007/07/070722203858.htm |title=Tiny Brain, Normal Life |archive-url=https://web.archive.org/web/20071001002639/https://www.sciencedaily.com/releases/2007/07/070722203858.htm |archive-date=2007-10-01 |work=ScienceDaily |date=2007-07-24}}</ref> Intelligence tests showed the person had an IQ of 75, considered "[[Borderline intellectual functioning]]", just above what would be officially classified as intellectually disabled.<ref>{{cite journal | vauthors = Peltopuro M, Ahonen T, Kaartinen J, Seppälä H, Närhi V | title = Borderline intellectual functioning: a systematic literature review | journal = Intellectual and Developmental Disabilities | volume = 52 | issue = 6 | pages = 419–443 | date = December 2014 | pmid = 25409130 | doi = 10.1352/1934-9556-52.6.419 }}</ref><ref>{{cite journal | vauthors = Nouwens PJ, Lucas R, Smulders NB, Embregts PJ, van Nieuwenhuizen C | title = Identifying classes of persons with mild intellectual disability or borderline intellectual functioning: a latent class analysis | journal = BMC Psychiatry | volume = 17 | issue = 1 | pages = 257 | date = July 2017 | pmid = 28716016 | pmc = 5512980 | doi = 10.1186/s12888-017-1426-8 | doi-access = free }}</ref>

The person was a married father of two children, and worked as a civil servant, leading an at least superficially normal life, despite having enlarged ventricles with a decreased volume of brain tissue. "What I find amazing to this day is how the brain can deal with something which you think should not be compatible with life", commented Dr. Max Muenke, a pediatric brain-defect specialist at the [[National Human Genome Research Institute]]. "If something happens very slowly over quite some time, maybe over decades, the different parts of the brain take up functions that would normally be done by the part that is pushed to the side."<ref>{{cite news |title=Man Lives Normal Life Despite Having Abnormal Brain |newspaper=The Globe and Mail |date=July 19, 2007 |url=https://www.theglobeandmail.com/servlet/story/RTGAM.20070719.wbrain0719/BNStory/Science/home |archive-url=https://web.archive.org/web/20070828013153/http://www.theglobeandmail.com/servlet/story/RTGAM.20070719.wbrain0719/BNStory/Science/home |archive-date=August 28, 2007 |access-date=July 15, 2012}}</ref><ref name="New Scientist Health">{{cite news |title=Man with tiny brain shocks doctors |url=https://www.newscientist.com/article/dn12301-man-with-tiny-brain-shocks-doctors.html |access-date=8 June 2013 |date=20 July 2007 |work=New Scientist and Reuters |url-status=live |archive-url=https://web.archive.org/web/20130726110907/http://www.newscientist.com/article/dn12301-man-with-tiny-brain-shocks-doctors.html |archive-date=26 July 2013}}</ref><ref name="pmid17658396">{{cite journal | vauthors = Feuillet L, Dufour H, Pelletier J | title = Brain of a white-collar worker | journal = Lancet | volume = 370 | issue = 9583 | pages = 262 | date = July 2007 | pmid = 17658396 | doi = 10.1016/S0140-6736(07)61127-1 | s2cid = 7382008 }}</ref>

=== Notable cases ===
* Ice hockey player [[Colby Cave]] had acute obstructive hydrocephalus due to a colloid cyst.<ref>{{cite web|date=April 11, 2020|title=Oilers forward Colby Cave dies after suffering brain bleed|url=https://www.cbc.ca/sports/hockey/nhl/edmonton-oilers-colby-cave-1.5529808|access-date=4 May 2021|website=CBC}}</ref>
* 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]]''.<ref>{{cite web |url=http://www.startribune.com/entertainment/books/11435616.html |title=Man of many tribes |publisher=Star Tribune |access-date=2014-01-29 |url-status=live |archive-url=https://web.archive.org/web/20130520004510/http://www.startribune.com/entertainment/books/11435616.html |archive-date=2013-05-20}}</ref>
* [[Prince William, Duke of Gloucester]] (1689–1700), probably contracted [[meningitis]] at birth, which resulted in this condition.<ref>Somerset, p. 116{{full citation needed|date=February 2018}}</ref>
* Emperor [[Ferdinand I of Austria]] (1793–1875) became emperor in 1835 despite various health issues including hydrocephalus and epilepsy.{{citation needed|date=June 2020}}
* In the [[American folklore]] of the [[U.S. state|states]] of Ohio, Michigan, and Connecticut, an urban legend exists about the [[melon heads]], the inbred descendants of families of people born with hydrocephaly.
* [[Masato Kudo]], a professional soccer player, died of hydrocephalus on October 21, 2022.
{{Clear}}

== References ==
{{reflist}}

== External links ==
{{Commons category|Hydrocephalus}}
* {{Curlie|Health/Conditions_and_Diseases/Neurological_Disorders/Hydrocephalus/}}
* [http://thejns.org/toc/pedsup/14/Suppl Guidelines for pediatric hydrocephalus]

{{Medical resources
| ICD10={{ICD10|G|91||g|90}}, {{ICD10|Q|03||q|00}}
| ICD9={{ICD9|331.3}}, {{ICD9|331.4}}, {{ICD9|741.0}}, {{ICD9|742.3}}
| OMIM=236600
| DiseasesDB=6123
| MedlinePlus=001571
| eMedicineSubj=neuro
| eMedicineTopic=161
| MeSH=D006849
}}
{{CNS diseases of the nervous system}}
{{Congenital malformations and deformations of nervous system}}
{{Authority control}}

[[Category:Congenital disorders of nervous system]]
[[Category:Disorders causing seizures]]
[[Category:Pediatrics]]
[[Category:Ventricular system]]
[[Category:Wikipedia medicine articles ready to translate]]
[[Category:Wikipedia neurology articles ready to translate]]