Hydrocephalus is a medical condition in which there is an unusual buildup of cerebrospinal fluid (CSF) in brain cavities known as ventricles. According to the National Institute of Nervous Disorders and Stroke (NINDS), the exact number of hydrocephalus is hard to determine because it strikes both children and adults. Hydrocephalus can be a congenital condition. However, it can also be acquired in cases of head trauma before, during, or birth.
What is Hydrocephalus?
The condition’s name comes from the Greek words “hydro” (water) and “cephalus” (head). Its literal translation is “water on the brain,” but the liquid that accumulates in the ventricles is not water but CSF. CSF is necessary for the brain to function. CSF protects the brain by serving as a cushion for the cerebral cortex. It also protects the brain from infections and minor impacts to the skull. Additionally, CSF helps regulate the involuntary function of the circulatory system in the brain.
CSF fits inside the subarachnoid space and within the ventricular system in and around the brain and the spinal cord. A healthy brain usually produces 500 mL of CSF daily. The central nervous system constantly reabsorbs CSF, so the average amount of the liquid within the brain and spinal cord at any given time is approximately 100-160 mL.
Hydrocephalus’ various forms occur when there is a problem with the flow or reabsorption of CSF. According to NINDS, there are two main types of hydrocephalus: congenital, which is present at birth, and acquired. External factors, including other diseases or head trauma, usually cause acquired hydrocephalus.
Both of the main forms of hydrocephalus come in two categories: communicating and non-communicating. In communicating hydrocephalus, the ventricles of the brain are still open and CSF can still flow inside them. However, the CSF can’t flow out of the ventricles because the exits are somehow blocked.
In non-communicating hydrocephalus, the flow of CSF along the narrow passages that connect the ventricles is completely blocked. A common cause of non-communicative hydrocephalus is the narrowing of the passage called the aqueduct of Sylvius. This small pathway connects the third and fourth ventricles.
These forms of the condition mainly affect children. Per NINDs, the prevalence of hydrocephalus is around 1-2 per 1,000 babies born in the U.S.
Causes of Hydrocephalus
In most cases, it is hard to identify what causes hydrocephalus. Genetic abnormalities or developmental disorders linked to conditions such as spina bifida sometimes cause the congenital forms of hydrocephalus. Other possible causes are meningitis, tumors, intraventricular bleeding, or subarachnoid hemorrhages. Traumatic head injuries before or during delivery can also cause blockages in the cranial ventricles and prevent the normal flow of CSF in a baby’s central nervous system.
Symptoms of Hydrocephalus
The severity of hydrocephalus symptoms depends on many variables, including a person’s age, how advanced the condition is, and personal differences in tolerance for the disease. Some babies, for instance, don’t experience any negative effects from hydrocephalus because the size of their skulls increases. In these cases, CSF continues to flow normally among the ventricles because the elasticity of the still-growing skull prevents narrowing of the cranial passages.
In cases where the aqueduct of Sylvius and other passages are blocked, the symptoms are more severe. The most obvious signs of hydrocephalus in babies are an abnormally large head or an unusually fast increase of the head’s circumference. Hydrocephalus may also cause headaches, irritability, vomiting, seizures, and sleepiness. In severe cases, hydrocephalus may also cause comas.
Shunt surgery is the most common form of hydrocephalus treatment. Doctors generally insert catheters called shunts into the cerebral ventricles. The shunts allow CSF to flow normally in the central nervous system and prevent further accumulation of the liquid in the ventricles. The excess fluid flows into other spaces in the body and then reabsorbed.
This form of treatment usually works well, but it can cause complications if problems occur with the shunts. The two main problems associated with surgically-implanted shunts are:
- Shunt failures
- Shunt infections
According to the Hydrocephalus Association, 50% of all shunts fail within two years. They usually fail due to the natural changes in the skull as a child gets older. Shunts are made to last a long time and are resilient, but the components can wear out over time. In some cases, they can get loose or break in several pieces. Shunts can also be clogged or get disconnected. Shunt failure results in renewed pooling of CSF and the return of symptoms such as headaches, nausea, and vomiting.
Per the Mayo Clinic, additional symptoms of shunt failure include:
- Vision problems
Shunt systems need both constant monitoring and regular medical follow-ups. This helps to keep the negative effects of shunt failure under control and allows physicians to schedule shunt replacement operations to prevent further complications.
Per the Hydrocephalus Clinical Research Network (HCRN), an estimated 8-10% of shunt procedures result in infections. Bacteria already present in a child’s body often cause shunt infections. Symptoms may include redness or tenderness along the shunt tract, sore neck or shoulder muscles, and a low-grade fever.
Another surgical treatment for hydrocephalus is a procedure called third ventriculostomy. Using a tiny fiber optic camera called a neuroendoscope, doctors inspect the ventricular surface. When the neuroendoscope is in place, they use a tiny tool to drill a small opening on the third ventricle’s floor. This hole removes the blockage in the ventricle and allows the CSF to flow normally again.
According to Boston Children’s Hospital, the long-term outlook for a child with hydrocephalus depends on early detection, timely treatment of the condition, and preventing infection during surgery. Shunts and third ventriculostomies relieve the pressure inside the skull and prevent more neurological damage. Nevertheless, some children may still experience adverse effects such as persistent headache even though the intracranial pressure is gone.
Because medical researchers don’t have a clear understanding about hydrocephalus, there is no easy way to predict general outcomes. Medical researchers know that there is a connection between specific causes of hydrocephalus and their outcomes. Beyond that, predicting a specific child’s prognosis depends on such variables as early detection of the condition, if any other disorders are present, and how well the child responds to the treatment.
Because hydrocephalus often causes neurological damage, it can have a negative effect on a child’s intellectual and physical development. If left untreated, progressive hydrocephalus can be fatal.
However, parents and loved ones should know that a hydrocephalus diagnosis is not necessarily a death sentence for a baby. Effective treatments for hydrocephalus exist. Proper monitoring by parents and caregivers can minimize its effects. As a result, many children with hydrocephalus grow up to lead normal lives with relatively few difficulties.