ABOUT HYDROCEPHALUS

WHAT IS HYDROCEPHALUS?

The term hydrocephalus is derived from the Greek words «hydro» meaning water and “cephalos” meaning head. As its name suggests, is a condition in which the primary characteristic is excessive accumulation of fluid in the brain. Although hydrocephalus was once known as “water on the brain”, the “water” is actually cerebrospinal fluid. This is a clear fluid surrounding the brain and spinal cord. The excessive accumulation of cerebrospinal fluid resulting in dilation of the spaces in the brain called ventricles. This dilation causes potentially harmful pressure on brain tissue.

Normal brain ventricles	Hydrocephalus (dilation of the cerebral ventricles by accumulation of cerebrospinal fluid)

The ventricular system consists of four ventricles connected by narrow pathways. Normally, the cerebrospinal fluid flows through the ventricles, exits into cisterns (closed spaces that serve as reservoirs) at the base of the brain and spinal cord, and then is absorbed into the bloodstream.

Circulation of intraventricular cerebrospinal fluid	Schematic of the circulation of cerebrospinal fluid by intraventricular and subarachnoid space to be absorbed into the arachnoid granulations
Drain point cerebrospinal fluid to venous blood passes through the arachnoid granulations	Arachnoid granulations through which passes the cerebrospinal fluid into the venous blood

The balance between production and absorption of cerebrospinal fluid is critical. Ideally, the liquid passes almost completely into the bloodstream as it passes the blood through the veins of the upper brain. However, there are circumstances which, when present, prevent or disrupt the production of cerebrospinal fluid or that inhibit its normal flow. When this balance is disturbed hydrocephalus happens.

WHAT ARE THE DIFFERENT TYPES OF HYDROCEPHALUS?

Hydrocephalus can be congenital or acquired. Congenital hydrocephalus is present at birth and can be caused by environmental influences during foetal development or genetic predisposition. Acquired hydrocephalus develops after birth. This type of hydrocephalus can affect people of all ages and can be caused by injury or disease.

Congenital Hydrocephalus in myelomeningocele	Occipital encephalocele with congenital hydrocephalus
Alobar holoprosencephaly with congenital hydrocephalus	Anencephaly

Hydrocephalus can also be communicating or not communicating. Communicating hydrocephalus occurs when the flow of cerebrospinal fluid is blocked after leaving the ventricles. This form is called communicating because the cerebrospinal fluid can still flow between the ventricles, which remain open. Non-communicating hydrocephalus, also called obstructive, occurs when the flow of cerebrospinal fluid is blocked along one or more of the narrow pathways connecting the ventricles. One of the most common causes of hydrocephalus is “aqueductal stenosis”. In this case, hydrocephalus results from a narrowing of the aqueduct of Sylvius, a small passage between the third and fourth ventricle in the midbrain.

Points of obstruction to the flow of cerebrospinal fluid, causing hydrocephalus	Colloid cyst as a cause of obstructive hydrocephalus

There are two forms of hydrocephalus which do not fit neatly into the categories described above and mainly affect adults: hydrocephalus ex vacuo and normal pressure hydrocephalus.

Hydrocephalus ex-vacuo occurs when there is damage to the brain caused by stroke or traumatic injury. In these cases, there may be a real contraction (atrophy) of brain tissue. Normal pressure hydrocephaluscommonly occurs in the elderly and is characterized by many of the same symptoms associated with other conditions that occur more often in the elderly, such as memory loss, dementia, gait disturbance, urinary incontinence and overall reduction in activities of daily living.

WHAT IS THE ORIGIN OF HYDROCEPHALUS?

It may result from genetic inheritance (aqueduct stenosis) or developmental disorders, such as those associated with neural tube defects, including spina bifida and encephalocele. Other possible causes include complications of prematurity such as intraventricular haemorrhage, diseases such as meningitis, tumors, head trauma or subarachnoid hemorrhage that blocks the exit of the ventricles to the cisterns and the flow of fluid in them.

WHAT ARE THE SYMPTOMS?

They vary with age, the progression of the disease and individual differences in the tolerance of cerebrospinal fluid. The child’s skull can expand to accommodate increased cerebrospinal fluid because the sutures (fibrous joints that connect the bones of the skull) have not been closed yet.

In childhood, the most obvious indication of hydrocephalus is typically the rapid increase in the circumference of the head or head size extra large. Other symptoms may include vomiting, sleepiness, irritability, squinting down (also called “sunset”) and seizures.

Increased skull size in untreated hydrocephalus in infancy	Eyes in the setting sun in hydrocephalus

Older children and adults may experience different symptoms because their skulls cannot expand to accommodate the increase in cerebrospinal fluid. They symptoms may include headache followed by vomiting, nausea, papilloedema (swelling of the optic disc, which is part of the optic nerve), blurred vision, diplopia (double vision), downward deviation of the eyes, problems with balance, poor coordination, gait disorder, urinary incontinence, growth delay, drowsiness, irritability, or other changes in personality or knowledge, including memory loss.

HOW IS HYDROCEPHALUS DIAGNOSED?

 
By means of clinical neurological examination and practice of neuroimaging techniques such as ultrasonography, computed tomography (CT), magnetic resonance (MR) or circulation monitoring techniques of cerebrospinal fluid.

CTscan image of hydrocephalus	MR imaging of hydrocephalus
Measuring the cerebrospinal fluid pressure through a lumbar puncture	Measuring the cerebrospinal fluid pressure through an external ventricular drainage

Pressure measuring cerebrospinal fluid by lumbar puncture pressure measurement cerebrospinal fluid by external ventricular drainage.

WHAT IS THE USUAL TREATMENT?

Often, hydrocephalus is treated by the implantation of a ventriculo-peritoneal shunt. This system diverts the flow of cerebrospinal fluid from one place within the central nervous system to another area of ​​the body where it can be absorbed as part of the circulatory process.

A shunt system consists of proximal catheter, valve and distal catheter. A catheter placed in the central nervous system, most of the time in the ventricle inside the brain, but also can be placed within a cyst or a place close to the spinal cord. The distal end of the catheter is usually placed within the peritoneal cavity (abdominal), but also can be placed elsewhere within the body, such as in a heart chamber or a cavity in the lung where the cerebrospinal fluid can be drained and be absorbed. A valve located along the catheter maintains the flow in one direction and regulates the amount of cerebrospinal fluid drained.

Components of a cerebrospinal fluid shunt for the treatment of hydrocephalus

V-P shunt	Ventriculo-atrial shunt	Lumbo-peritoneal shunt

	A limited number of patients can be treated with a different procedure called ventriculostomy of the third ventricle floor. In this procedure, with a neuroendoscope, we make a small hole at the floor of the third ventricle, allowing cerebrospinal fluid to bypass the obstruction and flow toward the site of resorption around the surface of the brain..
Outline of endoscopic ventriculostomy of the floor of the third ventricle

WHAT ARE THE POSSIBLE COMPLICATIONS OF A CSF SHUNT SYSTEM?

Shunt systems are not perfect mechanisms. Among the complications may include mechanical failure, infections, obstructions and the need to extend or replace the catheter. Generally, shunt systems require regular medical monitoring. When complications occur, the shunt system usually requires some adjustment or revision.

Shunt m alfunction with cerebrospinal fluid around the distal catheter	Obstruction of the ventricular catheter due to coroid plexus growth

Some complications can lead to other problems such as excessive or inadequate drainage. The excessive drainage occurs when the shunt allows cerebrospinal fluid to drain from the ventricles more quickly and in bigger amount than what is needed. This excessive drainage may cause the ventricles to collapse, tearing blood vessels and causing headache, haemorrhage (subdural hematoma) or collapsed ventricles (slit ventricle syndrome). The poor drainage occurs when the cerebrospinal fluid is not drained in enough quantity and the symptoms of hydrocephalus recur.

Subdural hematoma by excessive drainage in hydrocephalus	Recurrence of symptoms due to valve malfunction

Besides the common symptoms of hydrocephalus shunt infections may also cause symptoms such as fever, pain in the muscles of the neck or shoulder and redness or tenderness along the distal catheter. When there is reason to suspect that a referral system is not functioning properly, one should seek medical attention immediately.

Ulceration and infection on the valve for the treatment of hydrocephalus	Infection at the entry point of the distal catheter into the abdominal cavity

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