Hydrocephalus

Definition

Hydrocephalus is a usually congenital condition in which an abnormal accumulation of cerebrospinal fluid in the cerebral ventricles causes enlargement of the skull and compression of an injury to brain tissue. If hydrocephalus becomes progressive, a shunt is surgically placed to reduce pressure by conducting fluid away from the brain, usually to the peritoneum. Hydrocephalus is sometimes called “water on the brain.” The word “hydrocephalus” in Greek literally means “watery head.”

Hydrocephalus

Pathophysiology

The obstruction of the cerebrospinal fluid in the subarachnoid space is believed to have been caused by a precious hemorrhage or infective conditions, such as meningitis. Because of this obstruction, the arachnoid starts to thicken and the return-flow channels are blocked as well.

It is possible that the spaces filled with cerebrospinal fluid are enlarged, with the intracranial pressure being increased. This is the normal-pressure communicating hydrocephalus. As you have seen above, the form of hydrocephalus is caused by the impaired reabsorption of the cerebrospinal fluid at the level of the arachnoid granulations. The normal-pressure hydrocephalus is mainly encountered in the older population.

The absence of the arachnoid villi can lead to the appearance of the communicating hydrocephalus. Infectious, inflammatory and hemorrhagic factors can contribute to the scarring or fibrosis that occurs at the level of the subarachnoid space, thus preventing the resorption of the cerebrospinal fluid and leading to the diffuse ventricular dilatation.

Epidemiology

• Prevalence estimates for infantile hydrocephalus vary between one and 32 per 10,000 births, depending on the definition used and the population studied.
• The most recent estimate of prevalence comes from a large, population-based investigation of idiopathic infantile hydrocephalus in Denmark over a 30 year period.
• The authors included children diagnosed before one year of age with no known extrinsic cause of their condition. C
• Chiari I and Dandy-Walker malformations were included, but neural tube defects were excluded from their study population. The authors found an estimated prevalence of 1.1 per 1,000 infants.

Types

Normal Pressure Hydrocephalus (NPH): This type of hydrocephalus is usually noticed in adults who are 60 or above. NPH occurs when the amount of cerebrospinal fluid increases in the ventricles of the brain with no or little increase in the pressure within the head.

Communicating or Non-obstructive Hydrocephalus: This type of hydrocephalus occurs when there is insufficient cerebrospinal fluid absorption.

Non-communicating or Obstructive Hydrocephalus: This type occurs when there is a blockage of cerebrospinal fluid in the ventricular system.

Congenital Hydrocephalus: This type of hydrocephalus can occur due to environmental influences at the time of fetal development or also due to genetic factors. It can develop either before or soon after birth.

Risk factors

The following factors increase the risk of hydrocephalus:

Premature birth: Infants born preterm have a higher risk of intraventricular hemorrhage, or bleeding within the ventricles of the brain, which may result in hydrocephalus.

Problems during pregnancy: An infection in the uterus during pregnancy increases the risk of hydrocephalus in the developing fetus

Problems with fetal development: Examples include the incomplete closure of the spinal column.

Other conditions that increase the risk include:

• lesion and tumors of the spinal cord or brain
• infections of the nervous system
• bleeding in the brain
• severe head injury

Causes

• Head injury
• The mechanisms behind normal pressure hydrocephalus are unknown
• Tumor
• Subarachnoid hemorrhage
• Infection such as meningitis
• Previous posterior fossa surgery

Acquired Causes in children and infants

• Malignant or benign brain tumors
• Infection such as cerebral abscess and bacterial meningitis
• Subarachnoid hemorrhage
• Leukemic infiltrates of CNS
• An increased venous sinus pressure associated with venous thrombosis, craniostenosis, and achondroplasia

Acquired Causes in adults

• Infections such as cerebral abscess
• Malignant or benign tumors may result in blockage of CSF flow
• Head injury
• Medication- Infiximab infusion may cause communicating hydrocephalus
• Subarachnoid hemorrhage
• Idiopathic hydrocephalus
• Congenital aqueductal stenosis

Symptoms

Signs and symptoms of elevated-pressure hydrocephalus include the following:

• A headache
• Nausea and vomiting, especially in the morning
• Lethargy
• Disturbances in walking (gait)
• Double vision
• Subtle difficulties in learning and memory
• Delay in achieving childhood developmental milestones

Irritability is the most common sign of hydrocephalus in infants. If this is not treated, it may lead to lethargy. Bulging of the fontanelles, or the soft spots between the skull bones may also be an early sign. When hydrocephalus occurs in infants, a fusion of the skull bones is prevented, which leads to abnormal expansion of the skull.

Hydrocephalus occurred in infants

Complications

Hydrocephalus severity depends on several factors, including when it develops and how it progresses. 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.

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

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

Diagnosis and test

Physicians have a wide variety of diagnostic tools to evaluate hydrocephalus:

Computed Tomography (CT) scan of the head uses an x-ray beam, which passes through the head allowing a computer to make a picture of the brain in slices. It is reliable, safe, painless, and quick (about 15 minutes). A CT will show if the ventricles are enlarged or if there is an obvious blockage.

Magnetic Resonance Imaging (MRI) uses radio signals and a very powerful magnet to create a picture of the brain that can reveal if the ventricles are enlarged and evaluate CSF flow.

Isotopic cisternography involves injecting a radioactive isotope into the lower back through a spinal tap. This allows the absorption of CSF to be monitored over a period of time (up to 4 days). Isotopic cisternography is considerably more involved than a CT or MRI but can aid the diagnosis of NPH.

Lumbar puncture (spinal tap) can be used to measure CSF pressure and analyze the fluid. Sometimes the procedure helps indicate whether a shunt, the common treatment for hydrocephalus, would work. If lumbar puncture improves symptoms even temporarily, then the shunt may be successful.

Intracranial pressure monitoring may be able to detect an abnormal pressure or pattern of pressure waves. Monitoring requires insertion of a catheter or small fiber optic cable through the skull into the brain. Both insertion techniques are safe and require admission to the hospital for 24 hours.

Treatment

It’s important to treat hydrocephalus right away. Untreated hydrocephalus can get worse and cause further problems in the nervous system.

Treatment can vary depending on the age of the child, the cause of the CSF build-up (whether from a blockage, overproduction of fluid, or another problem), and the child’s overall health.

Shunt Procedure

• The standard treatment for hydrocephalus is a VP shunt. In a shunt procedure, a catheter (a thin, flexible tube) is placed in the brain to drain extra fluid down to the abdominal cavity, chambers of the heart, or a space around the lungs. Then the fluid is absorbed into the bloodstream.
• A valve (a flap that opens and closes) in the shunt system regulates the flow to prevent over-draining and under-draining. Shunts can be used to treat hydrocephalus from any cause.
• While shunting has been an effective treatment for hydrocephalus, it is a burden for children and their families. Some shunts last for many years, but none last forever. When they stop working, they must be fixed with another operation. As a result, some kids will need many operations.
• Infections are a significant complication of shunt surgery. Most infections develop within the first few months after a shunt procedure. Treatment usually means a hospital stay for surgery to remove the infected shunt, IV antibiotics (given into a vein), and a second operation to replace the shunt after the infection is gone. Because of the drawbacks of shunting, other treatment can be considered in some cases.

Diagram showing a brain shunt

Endoscopic surgery

• For older kids and adults who have hydrocephalus from a blockage, a minimally invasive procedure with an endoscope can sometimes cure it. An endoscope is a surgical telescope that lets a surgeon do simple operations inside the body through very small openings.
• In these cases, a neurosurgeon uses an endoscope to make a small hole in the floor of the third ventricle, an operation called endoscopic third ventriculostomy. This creates a pathway for fluid to drain from the brain and bypass any blockages that are causing a backup. The body then absorbs the CSF into the bloodstream as it normally would.
• Endoscopic third ventriculostomy by itself was not a very successful treatment for infants with hydrocephalus until surgeons began to add a second step, choroid plexus coagulation. The choroid plexus is the tissue inside the ventricles that produces CSF, and destruction of this tissue with an electrical current makes the endoscopic treatment much more effective.

Prevention

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. Vaccination is recommended for some individuals, check with a doctor.