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|Classification and external resources|
Hydrocephalus seen on a CT scan of the brain.
|ICD-9||331.3, 331.4, 741.0, 742.3|
|Classification and external resources|
Hydrocephalus seen on a CT scan of the brain.
|ICD-9||331.3, 331.4, 741.0, 742.3|
Hydrocephalus (pron.: //), also known as "water on the brain," is a medical condition in which there is an abnormal accumulation of cerebrospinal fluid (CSF) in the ventricles, or cavities, of the brain. This may cause increased intracranial pressure inside the skull and progressive enlargement of the head, convulsion, tunnel vision, and mental disability. Hydrocephalus can also cause death. The name derives from the Greek words ὑδρο- (hydro-) "water", and κέφαλος (kephalos) "head".
The clinical presentation of hydrocephalus varies with chronicity. Acute dilatation of the ventricular system is more likely to manifest with the nonspecific signs and symptoms of increased intracranial pressure. By contrast chronic dilatation (especially in the elderly population) may have a more insidious onset presenting, for instance, with Hakim's triad (Adams triad).
Symptoms of increased intracranial pressure may include headaches, vomiting, nausea, papilledema, sleepiness or coma. Elevated intracranial pressure may result in uncal and/or cerebellar tonsill herniation, with resulting life threatening brain stem compression.
Hakim's triad of gait instability, urinary incontinence and dementia is a relatively typical manifestation of the distinct entity normal pressure hydrocephalus (NPH). Focal neurological deficits may also occur, such as abducens nerve palsy and vertical gaze palsy (Parinaud syndrome due to compression of the quadrigeminal plate, where the neural centers coordinating the conjugated vertical eye movement are located). The symptoms depend on the cause of the blockage, the person's age, and how much brain tissue has been damaged by the swelling.
In infants with hydrocephalus, CSF builds up in the central nervous system, causing the fontanelle (soft spot) to bulge and the head to be larger than expected. Early symptoms may also include:
Symptoms that may occur in older children can include:
References to hydrocephalic skulls can be found in ancient Egyptian medical literature from 2500 BC to 500 AD. Hydrocephalus was described more clearly by the ancient Greek physician Hippocrates in the 4th century BC, while a more accurate description was later given by the Roman physician Galen in the 2nd century AD. The first clinical description of an operative procedure for hydrocephalus appears in the Al-Tasrif (1000 AD) by the Arab surgeon, Abulcasis, who clearly described the evacuation of superficial intracranial fluid in hydrocephalic children. He described it in his chapter on neurosurgical disease, describing infantile hydrocephalus as being caused by mechanical compression. He states:
“The skull of a newborn baby is often full of liquid, either because the matron has compressed it excessively or for other, unknown reasons. The volume of the skull then increases daily, so that the bones of the skull fail to close. In this case, we must open the middle of the skull in three places, make the liquid flow out, then close the wound and tighten the skull with a bandage.”
In 1881, a few years after the landmark study of Retzius and Key, Carl Wernicke pioneered sterile ventricular puncture and external CSF drainage for the treatment of hydrocephalus. It remained an intractable condition until the 20th century, when shunts and other neurosurgical treatment modalities were developed. It is a lesser-known medical condition; relatively small amounts of research are conducted to improve treatments for hydrocephalus, and to this day there remains no cure for the condition. In developing countries, it is common that this condition go untreated at birth. It is difficult to diagnose during ante-natal care and access medical treatment is limited. However, when head swelling is prominent, children are taken at great expense for treatment. By then brain tissue is undeveloped and neurosurgery is rare and difficult. Children more commonly live with undeveloped brain tissue and consequential mental retardation.
Hydrocephalus is usually due to blockage of cerebrospinal fluid (CSF) outflow in the ventricles or in the subarachnoid space over the brain. In a person without hydrocephalus, CSF continuously circulates through the brain, its ventricles and the spinal cord and is continuously drained away into the circulatory system. Alternatively, the condition may result from an overproduction of the CSF, from a congenital malformation blocking normal drainage of the fluid, or from complications of head injuries or infections.
Compression of the brain by the accumulating fluid eventually may cause neurological symptoms such as convulsions, mental retardation and epileptic seizures. These signs occur sooner in adults, whose skulls are no longer able to expand to accommodate the increasing fluid volume within. Fetuses, infants, and young children with hydrocephalus typically have an abnormally large head, excluding the face, because the pressure of the fluid causes the individual skull bones — which have yet to fuse — to bulge outward at their juncture points. Another medical sign, in infants, is a characteristic fixed downward gaze with whites of the eyes showing above the iris, as though the infant were trying to examine its own lower eyelids.
The elevated intracranial pressure may cause compression of the brain, leading to brain damage and other complications. Conditions among affected individuals vary widely.
If the foramina (pl.) of the fourth ventricle or the cerebral aqueduct are blocked, cereobrospinal fluid (CSF) can accumulate within the ventricles. This condition is called internal hydrocephalus and it results in increased CSF pressure. The production of CSF continues, even when the passages that normally allow it to exit the brain are blocked. Consequently, fluid builds inside the brain causing pressure that dilates the ventricles and compresses the nervous tissue. Compression of the nervous tissue usually results in irreversible brain damage. If the skull bones are not completely ossified when the hydrocephalus occurs, the pressure may also severely enlarge the head. The cerebral aqueduct may be blocked at the time of birth or may become blocked later in life because of a tumor growing in the brainstem.
Internal hydrocephalus can be successfully treated by placing a drainage tube (shunt) between the brain ventricles and abdominal cavity to eliminate the high intracranial pressure. There is some risk of infection being introduced into the brain through these shunts, however, and the shunts must be replaced as the person grows. A subarachnoid hemorrhage may block the return of CSF to the circulation.
This should be distinguished from external hydrocephalus. This is a condition generally seen in infants and involving enlarged fluid spaces or subarachnoid spaces around the outside of the brain. This is generally a benign condition that resolves spontaneously by 2 years of age. (Greenberg, Handbook of Neurosurgery, 5th Edition, pg 174).  Imaging studies and a good medical history can help to differentiate external hydrocephalus from subdural hemorrhages or symptomatic chronic extra-axial fluid collections which are accompanied by vomiting, headaches and seizures.
Hydrocephalus can be caused by impaired cerebrospinal fluid (CSF) flow, reabsorption, or excessive CSF production.
Based on its underlying mechanisms, hydrocephalus can be classified into communicating and non-communicating (obstructive). Both forms can be either congenital or acquired.
Communicating hydrocephalus, also known as non-obstructive hydrocephalus, is caused by impaired cerebrospinal fluid resorption in the absence of any CSF-flow obstruction between the ventricles and subarachnoid space. It has been theorized that this is due to functional impairment of the arachnoidal granulations (also called arachnoid granulations or Pacchioni's granulations), which are located along the superior sagittal sinus and is the site of cerebrospinal fluid resorption back into the venous system. Various neurologic conditions may result in communicating hydrocephalus, including subarachnoid/intraventricular hemorrhage, meningitis and congenital absence of arachnoid villi. Scarring and fibrosis of the subarachnoid space following infectious, inflammatory, or hemorrhagic events can also prevent resorption of CSF, causing diffuse ventricular dilatation.
Non-communicating hydrocephalus, or obstructive hydrocephalus, is caused by a CSF-flow obstruction ultimately preventing CSF from flowing into the subarachnoid space (either due to external compression or intraventricular mass lesions).
The cranial bones fuse by the end of the third year of life. For head enlargement to occur, hydrocephalus must occur before then. The causes are usually genetic but can also be acquired and usually occur within the first few months of life, which include 1) intraventricular matrix hemorrhages in premature infants, 2) infections, 3) type II Arnold-Chiari malformation, 4) aqueduct atresia and stenosis, and 5) Dandy-Walker malformation.
In newborns and toddlers with hydrocephalus, the head circumference is enlarged rapidly and soon surpasses the 97th percentile. Since the skull bones have not yet firmly joined together, bulging, firm anterior and posterior fontanelles may be present even when the patient is in an upright position.
The infant exhibits fretfulness, poor feeding, and frequent vomiting. As the hydrocephalus progresses, torpor sets in, and the infant shows lack of interest in his surroundings. Later on, the upper eyelids become retracted and the eyes are turned downwards (due to hydrocephalic pressure on the mesencephalic tegmentum and paralysis of upward gaze). Movements become weak and the arms may become tremulous. Papilledema is absent but there may be reduction of vision. The head becomes so enlarged that the child may eventually be bedridden.
Because hydrocephalus can injure the brain, thought and behavior may be adversely affected. Learning disabilities including short-term memory loss are common among those with hydrocephalus, who tend to score better on verbal IQ than on performance IQ, which is thought to reflect the distribution of nerve damage to the brain. However the severity of hydrocephalus can differ considerably between individuals and some are of average or above-average intelligence. Someone with hydrocephalus may have motion and visual problems, problems with coordination, or may be clumsy. They may reach puberty earlier than the average child (see precocious puberty). About one in four develops epilepsy.
Hydrocephalus treatment is surgical, generally creating various types of cerebral shunts. It involves the placement of a ventricular catheter (a tube made of silastic), into the cerebral ventricles to bypass the flow obstruction/malfunctioning arachnoidal granulations and drain the excess fluid into other body cavities, from where it can be resorbed. Most shunts drain the fluid into the peritoneal cavity (ventriculo-peritoneal shunt), but alternative sites include the right atrium (ventriculo-atrial shunt), pleural cavity (ventriculo-pleural shunt), and gallbladder. A shunt system can also be placed in the lumbar space of the spine and have the CSF redirected to the peritoneal cavity (Lumbar-peritoneal shunt). An alternative treatment for obstructive hydrocephalus in selected patients is the endoscopic third ventriculostomy (ETV), whereby a surgically created opening in the floor of the third ventricle allows the CSF to flow directly to the basal cisterns, thereby shortcutting any obstruction, as in aqueductal stenosis. This may or may not be appropriate based on individual anatomy.
Examples of possible complications include shunt malfunction, shunt failure, and shunt infection, along with infection of the shunt tract following surgery (the most common reason for shunt failure is infection of the shunt tract). Although a shunt generally works well, it may stop working if it disconnects, becomes blocked (clogged), infected, or it is outgrown. If this happens the cerebrospinal fluid will begin to accumulate again and a number of physical symptoms will develop (headaches, nausea, vomiting, photophobia/light sensitivity), some extremely serious, like seizures. The shunt failure rate is also relatively high (of the 40,000 surgeries performed annually to treat hydrocephalus, only 30% are a patient's first surgery) and it is not uncommon for patients to have multiple shunt revisions within their lifetime.
The diagnosis of cerebrospinal fluid buildup is complex and requires specialist expertise.
Another complication can occur when CSF drains more rapidly than it is produced by the choroid plexus, causing symptoms -listlessness, severe headaches, irritability, light sensitivity, auditory hyperesthesia (sound sensitivity), nausea, vomiting, dizziness, vertigo, migraines, seizures, a change in personality, weakness in the arms or legs, strabismus, and double vision - to appear when the patient is vertical. If the patient lies down, the symptoms usually vanish in a short amount of time. A CT scan may or may not show any change in ventricle size, particularly if the patient has a history of slit-like ventricles. Difficulty in diagnosing overdrainage can make treatment of this complication particularly frustrating for patients and their families.
Resistance to traditional analgesic pharmacological therapy may also be a sign of shunt overdrainage or failure. Diagnosis of the particular complication usually depends on when the symptoms appear - that is, whether symptoms occur when the patient is upright or in a prone position, with the head at roughly the same level as the feet.
Since the cost of shunt systems is beyond the reach of most people in developing countries, most people with hydrocephalus die without even getting a shunt. Worse is the rate of revision in shunt systems that adds to the cost of shunting many times. Looking at this point, a study done by Dr. Benjamin C. Warf compares different shunt systems and highlighting the role of low cost shunt systems in most of the developing countries. This study has been published in Journal of Neurosurgery: Pediatrics May 2005 issue. It is about comparing Chhabra shunt system to those of the shunt systems from developed countries. The study was done in Uganda and the shunts were donated by the International Federation for Spina Bifida and Hydrocephalus.
One interesting case involving a person with past hydrocephalus was a 44-year-old French man, whose brain had been reduced to little more than a thin sheet of actual brain tissue, due to the buildup of cerebrospinal fluid in his head. The man, who had had a shunt inserted into his head to drain away fluid (which was removed when he was 14), went to a hospital after he had been experiencing mild weakness in his left leg.
In July 2007, Fox News quoted Dr. Lionel Feuillet of Hôpital de la Timone in Marseille as saying: "The images were most unusual... the brain was virtually absent." When doctors learned of the man's medical history, they performed a computed tomography (CT) scan and magnetic resonance imaging (MRI) scan, and were astonished to see "massive enlargement" of the lateral ventricles in the skull. Intelligence tests showed the man had an IQ of 75, below the average score of 100. This would be considered "borderline intellectual functioning"- which is just next to the level of being officially considered mentally challenged.
Remarkably, the man was a married father of two children, and worked as a civil servant, leading an at least superficially normal life, despite having enlarged ventricles with a decreased volume of brain tissue. "What I find amazing to this day is how the brain can deal with something which you think should not be compatible with life," commented Dr. Max Muenke, a pediatric brain defect specialist at the National Human Genome Research Institute. "If something happens very slowly over quite some time, maybe over decades, the different parts of the brain take up functions that would normally be done by the part that is pushed to the side."
September was designated National Hydrocephalus Awareness Month in July, 2009 by the U.S. Congress in HR373. The campaign is sometimes represented by a blue ribbon or a ribbon made of unused shunt tubing (there is some dispute within the hydrocephalus community as to the exact design of awareness ribbons). Many of the hydrocephalus organizations within the United States use various ribbon designs as a part of their awareness and fundraising activities.