NOTE! This site uses cookies and similar technologies.

If you not change browser settings, you agree to it. Learn more

I understand

In order to make our website more comfortable and intuitive, we use cookies: they are small files of information needed to understand how users navigate in our website and make your browsing experience more enjoyable and more efficient in the future. Cookies do not store any personal information, and will not be stored any identifiable data. If you want to disable the use of cookies you have to customize the settings of your internet browser by removing all existing cookies and disabling their storage. To proceed without modifying the application of the cookies just continue the surfing.

Please visit for more information about cookies and how they affect your browsing experience.

Types of cookies used:

Technical cookie 
These cookies are essential for the website navigation; without some of these, technical issues could not work.

Performance cookie
These cookies collect informations about how visitors use the website: for example, which pages are most popular, and which pages have reported warnings or error messages. These cookies do not collect any personal information about the visitor, and they are used only to improve the website operation. By using our website, you agree that these cookies may be installed on your device.

Functionality Cookie
Cookies allow the website to remember the choices made by the user (for example, to remember the language choice) and provide custom functionality. These cookies can also be used to remember changes to the text size and other features of web pages that you can customize. They can also be used to provide services such as watching a video or sharing on social networks. The information gathered from these types of cookies can be anonymous and can't track your browsing activity on other websites. By using our website, you agree that these cookies may be installed on your device.

Google Analytics
This website uses Google Analytics, a web analytics service provided by Google Inc.
The information generated by the cookie about your use of the website (including your anonymous IP address) will be transmitted and stored in Google's servers in the United States. Google will use this information with the purpose of evaluating your use of the website, compiling reports on website activity for the operators and providing other services relating to website activity and internet usage. Google may also transfer this information to third parties, unless required by law, or where such third parties process the information on Google's behalf. Google will not associate your IP address with any other data held by Google. By using this website, you allow Google to process the data about you in the manner and purposes set out above.

This website uses plugins from the social network, which is operated by Facebook Inc., 1601 S. California Ave, Palo Alto, CA 94304, USA (subsequently called "Facebook"). When opening a website that contains such a plugin, your browser will establish a direct connection to the Facebook servers. Facebook will transfer the content of the plugin directly to your browser, the latter of which will embed it in the website. This website hence does not have any influence on the amount of data that Facebook collects through this plugin and informs you according to its best knowledge. Through embedding the plugins Facebook receives the information that you have opened the respective website. If you are logged in to Facebook, Facebook can link this information to your Facebook account. If you interact with the plugins, for example by clicking the Like-button or commenting, your browser will submit this information directly to Facebook, which will save it. If you are not a member of Facebook, Facebook nonetheless might identify and save your IP address. Purpose and scope of the data collection as well as its distribution and usage of the data by Facebook as well as respective rights and preferences regarding privacy can be found in Facebook's privacy policy If you are a member of Facebook and do not want Facebook to collect data through this website and connect it to your Facebook profile, you have to log out from Facebook prior to visiting this site.


Hydrocephalus is a pathological condition characterized by an abnormal accumulation of cerebrospinal fluid (CSF) within brain ventricles.


  • Estimated prevalence - 1-1,5%;
  • Congenital hydrocephalus incidence - 0,9-1,8/1000 births (the most common surgery condition treated during pediatric age);
  • Acquired hydrocephalus incidence is difficult to estimate due to different kinds of manifestation, either as prevalent clinical condition or complication of many CNS affections.


Cerebrospinal fluid physiology

  • CSF surrounds the brain and spinal cord and circulates within the subarachnoid space. It is a colorless fluid with specific gravity of 1.007 and a pH of 7,33-7,35. It has many function such as shock absorber and immunological defense for the CNS;
  • Intracranial CSF is produced by the choroid plexuses located in both lateral ventricles and in fourth one; a small amount may also be produced by the ependymal lining of the ventricles and by interstitial space;
  • Spinal CSF produced in the dura of the nerve root sleeves;
  • Production rate is independent of the intracranial pressure (ICP);
  • CNS is produced at a rate of about 450ml/24hrs which correspond with 3 times every day turn over (if we consider the average total CSF volume is 150 ml);
  • CSF is absorbed by arachnoid villi (Pacchioni’s granulations) located into the dural venous sinus. A small amount may also be absorbed by lymphatics and the choroid plexuses;
  • Absorption rate is pressure dependent (it increases with ICP raising).



Idrocephalus develops because of an imbalance between CNS reabsorption and production:

  • Subnormal CSF reabsorption - It is the dominant mechanism in most cases and could be functionally divided in two main types;

Obstructive hydrocephalus (non-communicating)

There is a block proximal to arachnoid granulations to CSF discharge leading to mono/bi/tri-ventricular idrocephalus based on blocking level

Communicating hydrocephalus (non-obstructive)

It defects in CSF reabsorption by arachnoid granulations

  • CSF overproduction - It is a rare condition (e.g. choroid plexus papilloma) which could be more tolerated unless a concomitant reabsorption deficit.



Congenital hydrocephalus

  • Chiari Type 2 malformation with (29%) or without (38%) myelomeningocele (MM)
  • Chiari Type 1 malformation
  • Primary aqueductal stenosis
  • Secondary aqueductal gliosis due to germinal matrix hemorrhage or intrauterine infection
  • Dandy Walker malformation
  • X-linked inherited disorder

Acquired hydrocephalus post-infectious (the most common cause of communicating HCP)

  • Meningitis
  • Cysticercosis

Acquired hydrocephalus post-hemorrhagic (second most common cause of communicating HCP)

  • Post-SAH (subarachnoid hemorrhage)
  • Post-IVH (intraventricular hemorrhage)
  • Secondary to mass either neoplastic or non neoplastic (e.g. vascular malformation)
  • Post-op: 20% of pediatric patients develop permanent HCP
  • Neurosarcoidosis

Special forms of HP

  • Normal pressure hydrocephalus (also known as Hakim-Adams Syndrome)

Features of Hakim-Adams Syndrome

It is a particular condition described both in adult and child; it is characterized by stable ventriculomegaly at neuroimaging without clinical manifestation of increased ICP. Anyway it is associated with chronic suffering of cerebral tissue due to only apparent normal ICP which can occasionally rise up.
It’s characterized by a suggestive (but not pathognomonic) clinical triad:

  • Gait disturbance which usually precedes other symptoms
  • Dementia with primarily memory impairment
  • Urinary incontinence
  • Arrested hydrocephalus 

Features of Arrested hydrocephalus

It is a sort of compensated HCP which needs no treatment because of the absence of clinical manifestation of increased ICP. However patients should be advised to seek medical attention to cues of possible “involution” of the situation (decompensation).

  • Entrapped fourth ventricle (also known as Isolated fourth ventricle)

Features of Isolated fourth ventricle

It is a condition in which 4th ventricle doesn’t communicate neither with 3rd ventricle nor with basal cisterns. It is usually seen with chronic shunting of the lateral ventricles, especially in those with repeated shunt infections.

Symptoms and Signs

In older children (with rigid cranial vault) and adults

  • Symptoms are those of increased ICP, such as:
  • Papilledema
  • Upward gaze palsy
  • 6th nerve palsy
  • Gait changes

In young children (without rigid cranial vault)

  • Abnormalities in head circumference

Evaluation of the occipital-frontal circumference (OFC)

That’s why the occipital-frontal circumference (OFC) should be followed in every growing child and especially in those with suspected or documented HCP. The OFC of a normal infant should equal the distance from crown to rump.

  • Cranium enlargement
  • Fontanelle full and bulging
  • Splaying of cranial sutures (be seen on plain skull x-ray)
  • Enlargement and engorgement of scalp veins
  • Macewen’s sign: cracked pot sound on percussing over dilated ventricles
  • Setting sun sign due to upward gaze palsy
  • 6th nerve palsy (the most sensitive to pressure nerve due to its long intracranial course)
  • Irritability
  • Hyperactive reflexes
  • Irregular respiration with apneic spells

Symptoms of increased ICP

In addition, headache, vomiting, visus, respiratory and consciousness disorder could be sudden or progressive depending on the acute or chronic development of HCP, respectively



Blindness is a rare complication most likely resulting from:

  • Occipital lobe infarctions due to posterior cerebral arteries occlusion caused by downward trans tentorial herniation or in alternative by upward cerebellar herniation (cortical or post-geniculate blindness);
  • Chromic papilledema causing injury to optic nerve at the optic disc (pre-geniculate blindness);
  • Dilatation of the 3rd ventricle causing compression of optic chiasm (pre-geniculate blindness).



TC and MRI represent the gold standard to demonstrate HCP.

Ratio for the evaluation

Many features suggest HCP, such as:

  • Both temporal horns size >= 2mm in width with sylvian and interhemispheric fissures and cerebral sulci not visible;
  • Both temporal horns size >= 2mm in width with ratio FH/ID > 0.5 (FH stands for the largest width of the frontal horns, ID stands for the internal diameter from inner-table to inner-table).

Trans fontanelle US represents a very important exam to demonstrate HCP in the infant (under 2 years old) with open fontanelle; it is very useful thanks to its safety (no radiation exposure) and accuracy. Moreover, its useful during post-operative follow-up.


Differential diagnosis

HCP must be distinguished from:

  • “Hydrocephalus ex vacuo” which is characterized by an enlargement of the ventricles due to loss of cerebral tissue (cerebral atrophy) which could be as a part of normal aging but also as a result of certain CNS disease (e.g. Alzheimer disease);
  • Developmental anomalies where the ventricles or their portions appear enlarged (e.g. hydranencephaly, agenesis of corpus callosum):



It could be subdivided in non surgical and surgical one. The former approach consists of medical treatment with drugs (e.g. acetazolamide) that reduce production of CSF but their aim is only palliative. The latter consists of several surgical methods such as:

Ventriculoperitoneal shunt

It has been the most common technique used until the development of endoscopic 3rd ventricolostomy. It consists in drainaging of CSF from the ventricle to peritoneal cavity with the application of a catheter.

Endoscopic 3rd ventriculostomy

It has been the elective method since nearly twenty years. It is a sort of bypass; it consists in introducing of an endoscopic in lateral ventricle from which can be reached 3rd one passing through Monroe foramen. Once arrived at the third ventricle its wall is pierced to make it communicating with basal cisterns.




Binhammer RT. CSF anatomy with emphasis on relations to nasal cavity and labyrinthine fluids. Ear Nose Throat J. 1992; 71:292–299
Sato O, Bering EA. Extraventricular Formation of Cerebrospinal Fluid. Brain Nerv. 1967; 19:883–885

Lorenzo AV, Page LK, Wlaters GV. Relationship Between Cerebrospinal Fluid Formation, Absorption, and Pressure in Human Hydrocephalus. Brain. 1970; 93:679–692

Gri th HB, Jamjoom AB. The Treatment of Childhood Hydrocephalus by Choroid Plexus Coagulation and Artificial Cerebrospinal Fluid Perfusion. Br J Neurosurg. 1990; 4:95–100

Lemire RJ. Neural Tube Defects. JAMA. 1988; 259:558–562 

Hill A, Rozdilsky B. Congenital Hydrocephalus Secondary to Intra-Uterine Germinal Matrix/Intravenricular Hemorrhage. Dev Med Child Neurol. 1984; 26:509–527 

Schmidek HH, Auer LM, Kapp JP. The Cerebral Venous System. Neurosurgery. 1985; 17:663–678 

Parker T. Never Trust a Calm Dog: And Other Rules ofThumb. NewYork:HarperPerennial;1990 

Joynt RJ, Honch GW, Rubin AJ, Trudell RG, Frederiks JAM. In: Occipital Lobe Syndromes. Handbook of Clinical Neurology. Holland: Elsevier Science Pub- lishers; 1985:49–62 

Hoyt WF. Vascular Lesions of the Visual Cortex with Brain Herniation Through the Tentorial Incisura. ArchOphthalm.1960;64:44–57 

Rinaldi I, Botton JE, Troland CE. Cortical Visual Dis- turbances Following Ventriculography and/or Ventricular Decompression. JNeurosurg. 1962; 19:568– 576 

LeMay M, Hochberg FH. Ventricular Differences 
Between Hydrostatic Hydrocephalus and Hydrocephalus Ex Vacuo by CT. Neuroradiology. 1979; 17:191–195 

Sutton LN. Current Management of Hydrocephalus in Children. Contemp Neurosurg.1997; 19:1–7

Pang D, Zwienenberg-Lee M, Smith M, Zovickian J. Progressive cranial nerve palsy following shunt placement in an isolated fourth ventricle: case report. J Neurosurg. 2005; 102:326–331

Hakim S, Adams RD. The Special Clinical Problem of Symptomatic Hydrocephalus with Normal CSF Pres- sure. J Neurol Sci. 1965; 2:307–327
Mark S. Greenberg, Handbook of Neurosurgery, Thieme.

Guido Staffa, Elementi di Neurochirurgia, Timeo Editore.

Renzo Dionigi, Chirurgia Specialistica, Edra.




Fabio Paio, MS

Medical Student
University of Verona (Italy)