What Are Brain Ventricles?

Ventricles of the brain are cavities within the brain that produce and store cerebrospinal fluid (CSF). This liquid surrounds your brain and spinal cord, cushioning them and protecting them from trauma. It is also responsible for removing waste and delivering nutrients to your brain.

The four brain ventricles are essential to maintaining your central nervous system (CNS), which your brain and spinal cord comprise. The CNS is where information is processed in the body so that functions from temperature regulation to thought, movement, and much more can be controlled.

This article takes a closer look at the anatomy and functions of the brain ventricles. It also contains information about health conditions related to your ventricular system and how those conditions are diagnosed.

Brain Ventricle Anatomy

Your brain's ventricular system is comprised of four ventricles as well as small structures that connect each ventricle called foramina. In this way, your brain ventricles are continuous with one another.

The first and second ventricles are lateral ventricles. These C-shaped structures are located on each side of your cerebral cortex, the wrinkly outer layer of your brain. Usually, the lateral ventricles are symmetrical. But between 5% and 12% of the population are anatomically different, with one side larger than the other. When this happens, it's usually the left side that's larger.

The third ventricle is a narrow, funnel-shaped structure situated between your right and left thalamus, just above your brain stem.

The fourth ventricle is a diamond-shaped structure that runs alongside your brain stem. It has four openings through which cerebrospinal fluid drains into an area surrounding your brain (subarachnoid space) and the central canal of your spinal cord.

CSF takes the following route through the four ventricles of the brain:

1. The walls of the lateral ventricles and the roofs of the third and fourth ventricles are lined with a layer of specialized tissue known as the choroid plexus. It's within the choroid plexus that CSF is produced.
2. CSF passes from the lateral ventricles, through two holes called the interventricular foramina, and into the third ventricle.
3. From there, CSF passes through a connecting structure called the cerebral aqueduct and into the fourth ventricle.
4. CSF exits the fourth ventricle and drains into the subarachnoid space. CSF also passes through a structure called the obex before draining into the central canal of the spinal cord.

The average adult has about 150 milliliters (mL) of CSF circulating through their ventricles and subarachnoid space at any given time.

Brain Ventricle Function

Aside from cerebrospinal fluid, your brain ventricles are hollow. Their sole function is to produce and secrete cerebrospinal fluid to protect and maintain your central nervous system.

CSF is constantly bathing the brain and spinal column, clearing out toxins and waste products released by nerve cells. One such waste product—the amyloid A-b peptide—increases the risk of Alzheimer's disease if too much accumulates in the brain.

In addition, cerebrospinal fluid serves a number of other important functions:

• Shock absorption: When you fall, get into a car accident, or otherwise knock your head, the CFS encasing your brain absorbs the shock so that your brain does not smack against your skull.
• Nutrition: CSF supplies your central nervous system with essential nutrients, such as glucose, proteins, lipids, and electrolytes.
• Intracranial pressure: A steady flow of CSF keeps the pressure around your brain stable. Too much CSF, possibly due to a traumatic brain injury or brain tumor, raises intracranial pressure.
• Waste removal: CSF washes through your subarachnoid space, cleaning up toxins and waste products, which are then carried to your lymphatic ducts for filtration.
• Temperature: CSF circulation keeps the temperature of your brain and spine stable.
• Immune function: CSF contains numerous immune cells that monitor your central nervous system for foreign agents that could damage your vital organs.
  

Associated Conditions

Infection, head trauma, and bleeding in the brain can cause inflammation in the ventricles and subarachnoid space. That inflammation blocks the flow of cerebrospinal fluid, causing the brain ventricles to swell in size and placing pressure on the brain.

The following ventricle-related conditions are life-threatening. If you are experiencing any of the symptoms described below, call 911 or have someone take you to the nearest ER immediately.

Hydrocephalus

Hydrocephalus is a life-threatening medical condition in which cerebrospinal fluid gets blocked and builds up in the ventricles or subarachnoid space. As a result, the pressure within the skull increases and the ventricles enlarge.

Hydrocephalus can be present at birth due to a genetic or developmental abnormality. It can also develop due to a brain or spinal cord tumor, a stroke or head trauma that causes bleeding in the brain, or an infection like bacterial meningitis.

There are two primary types of hydrocephalus:

• Communicating hydrocephalus: CFS becomes blocked in the subarachnoid space after it exits the ventricles.
• Non-communicating hydrocephalus: CFS becomes blocked in one or more of the structures that connect the ventricles.

Any person of any age can get hydrocephalus, but it is most common in infants and adults ages 60 and older. Symptoms of hydrocephalus vary slightly among age groups. Normal pressure hydrocephalus, a communicating type in which there's no CFS pressure buildup, more often occurs in older adults.

In infants, look for these symptoms of hydrocephalus:

• The infant's head rapidly gets bigger in size
• The soft spot on the top of their head bulges
• Trouble sucking or feeding
• Sleepiness
• Irritability
• Seizures

In older adults, the symptoms include:

• Difficulty walking, balancing, or lifting their feet
• Rapid dementia or cognitive impairments
• Inability to hold their bladder

In all other age groups, the symptoms of hydrocephalus can include:

• Headache
• Vision changes
• Difficulty walking or talking
• Trouble staying awake
• Personality changes
• Memory loss

Meningitis

The subarachnoid space is lined with membranes known as the meninges. Meningitis develops when this lining, along with cerebrospinal fluid, becomes infected and inflamed.

Meningitis can be caused by bacterial, viral, parasitic, or fungal infections, but the most serious form is bacterial meningitis.

Bacterial meningitis can block the flow of CSF in the subarachnoid space and in the ventricles, ultimately resulting in hydrocephalus.

The symptoms of meningitis tend to come on very quickly and can include:

• Fever and chills
• Headache
• Stiff neck
• Sensitivity to light
• Nausea or vomiting
• Confusion
• Seizures

Ventriculitis

The choroid plexus in your ventricles contains a layer of tissue known as the ependymal lining. Ventriculitis occurs when this lining becomes inflamed due to meningitis, head trauma, or a complication of brain surgery.

Symptoms of ventriculitis mimic meningitis and can include:

• Fever and chills
• Headache
• Stiff neck
• Confusion
• Seizures

Neurodegenerative and Mental Health Disorders

Ventricular enlargement is a common finding in people diagnosed with a neurodegenerative disease, such as Alzheimer's or Huntington's disease. Enlarged ventricles also are seen in people diagnosed with bipolar disorder type I and schizophrenia.

Brain Hemorrhage

A stroke, ruptured aneurysm, or traumatic brain injury can cause bleeding in the subarachnoid space or ventricles. These injuries are known as subarachnoid hemorrhage or intraventricular hemorrhage, respectively.

Both types of brain hemorrhage can result in hydrocephalus as blood clots form and block the flow of cerebrospinal fluid in and around the ventricles of the brain.

Symptoms of brain hemorrhage come on suddenly and can include:

• A severe headache that peaks within seconds
• Stiff neck
• Blurred or double vision
• Slurred speech
• Weakness on one side of your body
• Light sensitivity
• Nausea or vomiting
• Loss of consciousness

Diagnostic Tests

Hydrocephalus, meningitis, ventriculitis, and brain hemorrhage are diagnosed using one or more of the following:

• Lumbar puncture (LP)
• Computed tomography (CT) scan
• Magnetic resonance imaging (MRI)

Lumbar puncture (LP), also called a spinal tap, can be used to measure pressure within the spinal canal. It is also used to test cerebrospinal fluid for signs of infection, inflammation, or hemorrhage.

To perform a lumbar puncture, your doctor will numb your lower spine. A needle will then be inserted in the numbed area to measure cerebrospinal fluid pressure and collect a sample for testing.

A spinal tap is often quite important for diagnosing central nervous system diseases. For instance, in a subarachnoid hemorrhage, ​a CT may be normal, but the lumbar puncture will reveal if there is blood in the cerebrospinal fluid.

Summary

Cerebrospinal fluid is produced in the lining of your brain's ventricles. After it drains from these four chambers, CFS circulates in the canals that surround your brain and spinal cord, ensuring your central nervous system is nourished and protected.

Traumatic brain injury, bacterial meningitis, and brain hemorrhage can cause inflammation in and around your ventricles. As a result, the flow of cerebrospinal fluid can get blocked and cause the ventricles to swell in size.

Medical conditions that affect the ventricles are often life-threatening. It is vital that you get treatment immediately if you notice any related symptoms. Consider joining a support group if you or a loved one has experienced one of these conditions.