What Is Hydrocephalus (Water On The Brain)? What Causes Hydrocephalus?

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Main Category: Neurology / Neuroscience
Also Included In: Pediatrics / Children's Health
Article Date: 10 Mar 2010 - 0:00 PST

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Hydrocephalus, also called Water on the Brain is a condition in which there is an abnormal build up of CSF (cerebrospinal fluid) in the cavities (ventricles) of the brain. The buildup is often caused by an obstruction which prevents proper fluid drainage. The fluid buildup can raise intracranial pressure inside the skull which compresses surrounding brain tissue, possibly causing progressive enlargement of the head, convulsions, and brain damage. Hydrocephalus can be fatal if left untreated.

The damage to the brain can cause headaches, vomiting, blurred vision, cognitive problems, and walking difficulties.

The term water on the brain is incorrect, because the brain is surrounded by CSF (cerebrospinal fluid), and not water. CSF has three vital functions:

• It protects the nervous system (brain and spinal cord) from damage
• It removes waste from the brain
• It nourishes the brain with essential hormones

The brain produces about 1 pint of CSF each day. The old CSF is absorbed into blood vessels. If the process of replenishment and release of old CSF is disturbed, CSF levels can accumulate, causing hydrocephalus.

There are three types of hydrocephalus:

• Congenital hydrocephalus - this is present at birth. According to the National Health Service (UK), approximately 1 in every 1,000 babies are born with congenital hydrocephalus, while The Mayo Clinic, USA, says 1 in every 500 US babies are born with it. It may be caused by an infection in the mother during pregnancy, such as rubella or mumps, or a birth defect, such as spina bifida. It is one of the most common developmental disabilities, more common than Down syndrome or deafness.
• Acquired hydrocephalus - this develops after birth, usually after a stroke, brain tumor or as a result of a serious head injury.
• Normal pressure hydrocephalus - only affects people aged 50 years or more. It may develop after stroke or injury. In most cases doctors do not know why it occurred. 2 in every 100,000 people are affected by normal pressure hydrocephalus in England each year.

According to the National Institutes of Health (NIH), USA, approximately 700,000 American children and adults live with hydrocephalus. Hydrocephalus is also the leading cause of brain surgery for children in the USA. The NIH adds that over the past 25 years death rates linked to hydrocephalus have dropped from 54% to 5%, while the occurrence of intellectual disability has dropped from 62% to 30%.

The NIH says there are more than 180 different possible causes of hydrocephalus; a common cause being brain hemorrhage linked to premature birth.

A prenatal ultrasound examination can sometimes detect hydrocephalus in the developing baby.

According to Medilexicon's medical dictionary:

Hydrocephalus is " A condition marked by an excessive accumulation of cerebrospinal fluid resulting in dilation of the cerebral ventricles and raised intracranial pressure; may also result in enlargement of the cranium and atrophy of the brain."

The outlook for a patient with hydrocephalus depends mainly on how quickly the condition is diagnosed and treated, and whether there are any underlying disorders.

Treatment for hydrocephalus often involves using a shunt - a thin tube that is implanted in the brain to drain away excess cerebrospinal fluid (CSF).

What are the signs and symptoms of hydrocephalus?

A symptom is something the patient senses and describes, while a sign is something other people, such as the doctor notice. For example, drowsiness may be a symptom, while dilated pupils may be a sign.

Signs and symptoms of congenital hydrocephalus (present at birth):

• Breathing difficulties.
• Muscles in the baby's arms and legs may be stiff and prone to contractions.
• Some of the developmental stages may be delayed, such as sitting up or cradling.
• Tense fontanelle - an outward curving of an infant's soft spot (fontanelle). The soft part of the top of the baby's head bulges outwards.
• The baby may be irritable and/or drowsy
• The baby may be unwilling to bend or move his/her neck or head.
• The baby may feed poorly.
• The baby's head seems larger than it should be.
• The baby's scalp is thin and shiny. There may be visible veins on the scalp.
• The pupils of the baby's eyes may be right close to the bottom of the eyelid; sometimes known as the setting sun.
• There may be a high-pitched cry.
• There may be seizures.
• There may be vomiting.

Signs and symptoms of acquired hydrocephalus (develops after birth):

• Bowel incontinence (rare)
• Confusion and/or disorientation
• Drowsiness
• Headaches
• Irritability, which may be progressive
• Lack of appetite
• Lethargy
• Nausea
• Personality changes
• Problems with eyesight, such as blurred or double vision
• Seizures (fits)
• Urinary incontinence
• Vomiting
• Walking difficulties (more common in adults)

Signs and symptoms of normal pressure hydrocephalus (affects people aged 50+) - signs and symptoms may take many months or years to develop.

• Changes in gait - the patient may feel as if they are frozen on the spot when taking their first step to start walking. The individual may appear to shuffle rather than walk.
• Normal thinking process slows down - the patient may respond to questions more slowly than normal, there may be delayed reactions to situations. The individual's ability to process information slows down.
• Urinary incontinence - this usually comes after changes in gait.

What are the risk factors for hydrocephalus?

A risk factor is something which increases the likelihood of developing a condition or disease. For example, obesity significantly raises the risk of developing diabetes type 2. Therefore, obesity is a risk factor for diabetes type 2. The following are possible risk factors for hydrocephalus:

• Being born prematurely - infants born prematurely have a higher risk of intraventricular hemorrhage (bleeding within the ventricles of the brain), which may result in hydrocephalus.
• Problems during pregnancy - an infection in the uterus during pregnancy may increase the risk of hydrocephalus in the developing baby.
• Problems with fetal development, such as incomplete closure of the spinal column. Some congenital defects may not be detectable at birth - but the baby may be at increased risk of developing hydrocephalus when he/she is older (still during childhood).
• Lesion and tumors of the spinal cord or brain.
• Infections of the nervous system.
• Bleeding in the brain.
• Having a severe head injury
.

What are the causes of hydrocephalus?

Hydrocephalus occurs when too much fluid builds up in the brain; specifically, excess CSF (cerebrospinal fluid) accumulates in the cavities (ventricles) of the brain.

How does CSF (cerebrospinal fluid) circulate through the brain?

The brain is like gelatin and floats in CSF. CSF flows through the brain through chambers; these chambers are known as ventricles, and they lie deep inside the brain. The fluid-filled ventricles protect the brain; like a cushion. Most of the CSF is made in the choroid plexus, a part of the brain.

Surplus CSF is removed from the brain through the dural venous sinuses; a series of channels. The dural venous sinuses run down the arachnoid villi, a layer of tissue which is like a one-way valve. The arachnoid villi allow excess CSF to leave the brain and filter into the bloodstream, while at the same time preventing blood from getting into the brain and causing damage.

It is important that the production, flow and absorption of CSF occur in such a way that normal pressure is maintained inside the skull - it is a delicate balance.

Hydrocephalus may occur if:

• Too much CSF is produced in the choroid plexus.
• One of the ventricles in the brain is blocked or narrowed, stopping or restricting the flow of CSF, which means it cannot leave the brain.
• CSF cannot filter into the bloodstream because there is something wrong with the arachnoid villi.

Causes of congenital hydrocephalus (present at birth):

The baby is born with a blockage in the cerebral aqueduct, a long passage in the midbrain that connects two large ventricles. This is the most common cause.

The choroid plexus produces too much CSF.

Health conditions in the developing baby can cause problems in how the brain develops. According to the National Health Service (NHS), UK, 70% of children with severe spina bifida develop hydrocephalus.

Infections during pregnancy - if the pregnant mother develops some infections, there is a risk that the normal development of the baby's brain may be affected. Examples include:

• CMV (Cytomegalovirus) - a virus which infects over 50% of American adults by the time they are 40 years old. Also known as the virus that is most commonly transmitted to a child before birth. This virus is responsible for glandular fever.
• German measles (rubella) - an infectious disease caused by the rubella virus. The virus passes from person-to-person via droplets in the air expelled when infected people cough or sneeze - the virus may also be present in the urine, feces and on the skin. The hallmark symptoms of rubella are an elevated body temperature and a pink rash.
• Mumps - an acute (short-term) viral infection in which the salivary glands, particularly the parotid glands (the largest of the three major salivary glands) swell.
• Syphilis - an STD (sexually transmitted disease) caused by a bacterium Treponema pallidum.
• Toxoplasmosis - in infection caused by a single-celled parasite - Toxoplasma gondii.

Causes of acquired hydrocephalus (develops after birth) - usually caused by an injury or illness that results in blockage between the ventricles. The following may be causes:

• Brain hemorrhage - bleeding inside the brain.
• Brain lesions - areas of injury or disease within the brain. There are many possible causes, including injury, infection, exposure to certain chemicals, or problems with the immune system.
• Brain tumors - benign (non-cancerous) or malignant (cancerous) growths in the brain. A primary brain tumor originates in the brain, while a secondary brain tumor comes from a cancer that has spread to brain tissue from another part of the body.
• Meningitis - inflammation of the membranes of the brain or spinal cord (inflammation of the meninges).
• Stroke - a condition where a blood clot or ruptured artery or blood vessel interrupts blood flow to an area of the brain. A lack of oxygen and glucose (sugar) flowing to the brain leads to the death of brain cells and brain damage, often resulting in impairment in speech, movement, and memory.

Causes of normal pressure hydrocephalus (affects people aged at least 50 years) - in most cases doctors don't know what caused it (idiopathic normal pressure hydrocephalus). Sometimes it may develop after a stroke, infection or injury to the brain.

There are two theories:

• There is something wrong with the arachnoid villi and CSF (cerebrospinal fluid) is not reabsorbed into the bloodstream properly. Consequently the brain starts to produce less new CSF, resulting in a gradual rise in intracranial pressure over a longer period compared to other forms of hydrocephalus. The gradual rise in pressure may cause progressive brain damage.
• An underlying condition, such as heart disease, a high blood cholesterol level, or diabetes is affecting normal blood flow, which may lead to a softening of brain tissue. The softened brain tissue may result in increasing pressure.

Diagnosing hydrocephalus

Babies and young children (congenital hydrocephalus):

• A routine prenatal ultrasound scan may detect hydrocephalus during pregnancy in the developing fetus.
• After birth, the head of the baby is measured regularly. Any abnormalities in head size will probably lead to further diagnostic tests. If a baby's head is seen to be too big, or is growing more rapidly than it should, the doctor may order an ultrasound scan of the head. If the ultrasound scan shows any abnormality, further tests will be ordered, such as an MRI (magnetic resonance imaging) scan or a CT (computerized tomography) scan, which give more detailed images of the brain.

Acquired hydrocephalus (occurs after birth) - if the child or adult develops the signs and symptoms of hydrocephalus the doctor may:

• Examine the patient's medical history carefully.
• Carry out a physical and neurological examination.
• Order an imaging scan, such as a CT or MRI scan. If imaging tests reveal hydrocephalus or any other faults, the doctor will refer the patient to a brain surgeon for further evaluation and treatment.

Normal pressure hydrocephalus (occurs in patients aged 50 years and over) - diagnosing this type of hydrocephalus is more tricky because symptoms are more subtle and do not appear suddenly. Also, normal pressure hydrocephalus shares symptoms with some other common conditions, such as Alzheimer's disease.

Making a correct diagnosis is important, because treatment for normal pressure hydrocephalus does relieve symptoms, unlike Alzheimer's.

Doctors in the UK have devised the following checklist for diagnosing normal pressure hydrocephalus. The checklist looks at:

• The patient's gait (how he/she walks)
• The patient's mental ability
• Any signs of urinary incontinence
• The results of the imaging scans show moderately higher levels of cerebrospinal fluid than normal

A combination of these four characteristics will most likely lead to a diagnosis of normal pressure hydrocephalus.

What are the treatment options for hydrocephalus?

Treatment for congenital and acquired hydrocephalus - both types of hydrocephalus require urgent treatment to alleviate intracranial pressure (pressure on the brain), otherwise there is a serious risk of damage to the brainstem. Our automatic functions, such as breathing and our heartbeat are regulated by the brainstem.

• A shunt, the surgical insertion of a drainage system - this is a catheter (a thin tube with a valve) that is placed in the brain to drain away excess fluid into another part of the body, such as the abdomen or a chamber in the heart. One end is placed in one of the brain's ventricles; it is tunneled under the skin to another part of the body which is better able to absorb the fluid. Usually, this is all that is needed and no further treatment is required. Sometimes shunt repair surgery may be needed if it gets blocked or infected.
  
  Patients with hydrocephalus will usually need to have a shunt system in place for the rest of their lives. If the shunt is placed in a child, additional surgeries may be needed to insert longer tubing as he/she grows.
• Ventriculostomy - the surgeon makes a hole in the bottom of a ventricle so that the excess fluid flows towards the base of the brain. Normal absorption occurs at the base of the brain. This procedure is sometimes performed when the flow of fluids between ventricles is obstructed.

Treatment for normal pressure hydrocephalus - shunts may also be used. However, shunts may not be suitable for some patients. The surgeon needs to carefully assess the potential risks involved in surgery against the possible benefits.

• Lumbar puncture - some of the cerebrospinal fluid is removed from the base of the spine. If this improves the patient's gait or mental abilities, fitting a shunt will probably help him/her.
• Lumbar infusion test - a needle is inserted through the skin of the lower back into the spine. Measurements are then taken of cerebrospinal fluid pressure (CSF) as fluid is injected into the spine. The surgeon will then be able to determine the pressure of the CSF. Patients usually benefit from having a shunt fitted if their CSF pressure is over a certain limit.

What are the complications of hydrocephalus?

Hydrocephalus severity depends on several factors, including at what age it developed and how it progressed. If the condition is advanced when the baby is born, it is more likely there will be brain damage and physical disabilities. If cases are not so severe and treatment is proper and prompt, the outlook is much better.

Problems with the shunt - shunt blockage occurs in 20% of cases during the first year; after that the risk drops to 5%. Approximately 3% to 12% of shunts may have an infection; experts say the risk is linked to the patient's age and general state of health.

A patient with a malfunctioning shunt will have hydrocephalus symptoms and should be treated immediately.

Babies with congenital hydrocephalus may experience some kind of permanent brain damage, which may result in long-term complications. Examples include:

• A limited attention span
• Autism
• Learning difficulties
• Physical coordination problems
• Problems with memory
• Speech problems
• Vision problems

Prevention of hydrocephalus

Pregnancy - regular prenatal care can significantly reduce the risk of having a premature baby, which reduces the risk of the baby developing hydrocephalus.

Infectious diseases - make sure you have had all your vaccinations and attended all the screenings that are recommended for you.

Meningitis vaccine - meningitis used to be a common cause of hydrocephalus. Ask your doctor whether you should be vaccinated. Vaccination is recommended for individuals who are travelling to parts of the world where meningitis is common, people with terminal complement deficiency (an immune system disorder), patients who either had their spleen removed or have a damaged spleen, and military personnel.

Preventing head injuries

• Car seat belts:
  
  
  • Wear a seatbelt every time you drive your car or ride as a passenger.
  • Make sure children are buckled up using either a safety seat, booster seat, or a seat belt that is suitable for the child's size and age. When children outgrow their safety seats - usually when they weight about 40 pounds (18 kilos) - they should start using a booster seat.
  • Children should continue using the booster seat until the lap/shoulder belts fit properly; usually when they are about 4ft 9inches (1meter 45 centimeters) tall.
• Drinking and driving - never drive when you are under the influence of alcohol.
• Helmets or specific protective headgears should always be worn when:
  
  
  • Batting in baseball/softball or cricket (and running bases in baseball)
  • Engaged in contact sports, such as karate, boxing, or American football
  • Riding a horse
  • Riding on a motorbike, snowmobile, scooter, or all-terrain vehicle (both riders and passengers)
  • Skiing
  • Snowboarding
  • Using a skateboard
  • When roller-skating or in-line skating
• Living areas for seniors (UK: elderly people):
  
  
  • Grab bars should be installed next to the bathtub, shower and/or toilet
  • Seniors should keep physically active to make sure lower body strength and balance is adequate (thus lowering the risk of falls)
  • Make sure lighting in the house is bright enough
  • On bathtub and shower floors use nonslip mats
  • Remove throw rugs and other objects which may be cause tripping
  • Stairways should ideally have handrails on both sides
• Living areas for children:
  
  
  • Install window guards
  • Place safety gates at the bottom and top of stairs if the children are young
• Children's play areas - the ground surface of a child's playground should be made of hardwood mulch, sand or some specific shock-absorbing material.
• Firearms - Firearms should be stored, unloaded, in a locked safe or cabinet. Bullets should not be stored in the same location.

Written by Christian Nordqvist
Copyright: Medical News Today
Not to be reproduced without permission of Medical News Today

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