Anatomy of the Ventricular System

The Pathway for Cerebrospinal Fluid in the Brain

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The ventricular system consists of four ventricles in the brain. Ventricles are a communicating network of chambers filled with cerebrospinal fluid (CSF).

The ventricular system is the pathway for the CSF and is critical to the central nervous system’s overall functioning. Developmental anomalies that impact the ventricular system include hydrocephalus and neural tube defects.

Ventricular system of the brain

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Anatomy

The pair of lateral ventricles are the largest of the four ventricles in the brain. They are located in the largest part of the brain, the cerebrum. The third ventricle is in the diencephalon, located in the center of the brain. The fourth ventricle is located in the hindbrain.

Each lateral ventricle, one on each side of the brain, sits in a “C” shape. Each side connects to the third ventricle by the interventricular foramina. The fourth ventricle is diamond shaped and sits below the third ventricle. The cerebral aqueduct connects the third ventricle to the fourth.

Anatomical Variations

A number of developmental anomalies can impact the ventricular system. 

Congenital hydrocephalus occurs when the brain fails to develop correctly in utero. The condition is marked by a disproportionally large head size due to the buildup of excess CSF in the ventricles. Pressure from the extra fluid can damage the brain and impair brain function.

Hydrocephalus can also occur in children and adults due to trauma, infection, stroke, and tumors. Risks for congenital hydrocephalus include maternal infections in the mother like toxoplasmosis or syphilis, other congenital neural tube malformations, or a genetic defect.

The most prominent symptom is an enlarged head, but other symptoms may also be present. The fontanelle (soft spot) on a newborn’s head may bulge, the baby may be irritable, sleep too much, vomit, or feed poorly.

Neural tube defects are congenital malformations of the brain and spinal cord. They occur very early in pregnancy. The most common neural tube defects are spina bifida and anencephaly.

Spina bifida occurs when the neural tube does not close all of the way in utero, resulting in damage to the spinal cord and nerves. Spina bifida can lead to intellectual and physical disabilities.

It is unknown what causes spina bifida. To reduce the risk of spina bifida, pregnant people are advised to supplement with 400 micrograms (mcg) of folic acid.

Anencephaly occurs when the fetal brain, skull, and scalp do not fully develop. Newborns with this condition usually only live for a few hours to several days. Often pregnancies with anencephaly end with miscarriage or stillbirth. 

A combination of things may cause anencephaly. Known prenatal risk factors include lack of folic acid during pregnancy, diabetes, high body temperature from the use of saunas and hot tubs, certain medications including opioids, and obesity.

Dandy-Walker syndrome occurs when the cerebellum does not properly form and the ventricles fail to open. A marker of Dandy-Walker syndrome is the presence of a posterior fossa cyst.

The condition may result in brain and central nervous system abnormalities. Hydrocephalus occurs in a majority of cases. The prominent symptom is an enlarged head and intracranial pressure.

Function

The ventricular system produces, transports, and excretes CSF, which coats the central nervous system. Each ventricle contains choroid plexus, which makes the circulating CSF.

The CSF moves from the lateral ventricles to the third ventricle and finally to the fourth ventricle, where it exits and bathes the brain and spinal cord. The CSF is then absorbed back into the bloodstream.

The ventricular system helps the central nervous system function properly. The fluid it produces protects the brain and provides the correct mix of chemicals that keep the brain in balance.

Associated Conditions

Hydrocephalus is the buildup of CSF in the ventricles. It can be congenital, but it can also occur in children and adults. When it occurs in children and adults, it is often a result of trauma, infection, stroke, or tumors

Symptoms in children include headaches, vision changes, head enlargement, sleepiness, nausea and vomiting, trouble with balance and coordination, loss of appetite, irritability, and cognitive delay or decline. 

Symptoms in adults include headaches, sleepiness, problems with balance and coordination, frequent urination and incontinence, vision changes, and difficulty with memory and concentration. People over 60 may additionally experience a decline in thinking and reasoning skills and may have trouble walking.

Tests

Conditions that affect the ventricular system require diagnosis by a doctor, usually a neurologist. Some ventricular system conditions are treatable.

Hydrocephalus

Congenital hydrocephalus may be diagnosed by fetal ultrasound. Most of the time, the condition is suspected during a physical exam following birth. In infants, children, and adults, a diagnosis may be confirmed with computed tomography (CT scan), magnetic resonance imaging (MRI), or an ultrasound. Genetic tests are sometimes ordered.

Treatment of hydrocephalus is focused on reducing fluid in the brain. A shunt may be inserted to drain fluid. A surgery called endoscopic third ventriculostomy (ETV) involves placing a small hole in the deep part of the brain so that the CSF can flow unimpeded.

Emergency treatment may be necessary and could include medication, a lumbar puncture (also called a spinal tap), and a procedure to drain fluid from the brain until a shunt can be put in.  

Spina Bifida

Spina bifida can be diagnosed during pregnancy with a blood test to measure alpha-fetoprotein (AFP), an ultrasound, or amniocentesis. After birth, diagnosis is made through a physical exam, X-ray, MRI, or CT scan.

Treatment for spina bifida depends on how the condition has impacted the body. Options include surgery on the fetus to close the spine, treatment for hydrocephalus, surgery to repair a tethered spinal cord, and the use of braces, crutches, walkers, and wheelchairs.

Anencephaly

Anencephaly can be diagnosed prenatally with a blood test called a quad marker screen, an ultrasound, a fetal MRI, and an amniocentesis. The condition is untreatable and fatal.

Dandy-Walker

Dandy-Walker is diagnosed with ultrasound, MRI, and CT scans. Treatment involves a shunt to drain a cyst and/or ventricles. 

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3 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. C.S. Mott Children’s Hospital, Michigan Medicine. Congenital hydrocephalus. Updated May 27, 2020.

  2. Centers for Disease Control and Prevention. What is spina bifida? Updated September 3, 2020.

  3. Cleveland Clinic. Anencephaly. Updated August 18, 2020.