|Classification and external resources|
Hydrocephalus seen on a CT scan of the brain.
|ICD-9||331.3, 331.4, 741.0, 742.3|
Hydrocephalus (pronounced /ˌhaɪdrɵˈsɛfələs/), also known as Water on the Brain, is a medical condition. People with hydrocephalus have 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, and mental disability. Hydrocephalus can also cause death.
Hydrocephalus was first described by the ancient Greek physician Hippocrates, but 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.
Hydrocephalus affects both pediatric and adult patients. According to the NIH website, there are an estimated 700,000 children and adults living with hydrocephalus.
Pediatric hydrocephalus affects one in every 500 live births, making it one of the most common developmental disabilities, more common than Down syndrome or deafness. It is the leading cause of brain surgery for children in the United States. There are over 180 different causes of the condition, one of the most common acquired etiologies being brain hemorrhage associated with premature birth. Pediatric hydrocephalus may also be a heritable condition and runs in certain families mostly affecting boys.
One of the most performed treatments for hydrocephalus, the cerebral shunt, has not changed much since it was developed in 1960. The shunt must be implanted through neurosurgery into the patient's brain, a procedure which itself may cause brain damage. An estimated 50% of all shunts fail within two years, requiring further surgery to replace the shunts. In the past 25 years, death rates associated with hydrocephalus have decreased from 54% to 5% and the occurrence of intellectual disability has decreased from 62% to 30%.
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 fluid, 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 convulsions and mental retardation. These signs occur sooner in adults, whose skulls no longer are 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. Hydrocephalus occurs in about one out of every 500 live births and was routinely fatal until surgical techniques for shunting the excess fluid out of the central nervous system and into the blood or abdomen were developed. Hydrocephalus is detectable during prenatal ultrasound examinations.
Usually, hydrocephalus does not cause any intellectual disability if recognized and properly treated. A massive degree of hydrocephalus rarely exists in typically functioning people, though such a rarity may occur if onset is gradual rather than sudden.
The elevated intracranial pressure may cause compression of the brain, leading to brain damage and other complications. Conditions among affected individuals vary widely. Children who have had hydrocephalus may have very small ventricles, and presented as the "normal case".
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 compresses the nervous tissue and dilates the ventricles. 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 internal pressures. 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. If CSF accumulates in the subarachnoid space, the condition is called external hydrocephalus. In this condition, pressure is applied to the brain externally, compressing neural tissues and causing brain damage. Thus resulting in further damage of the brain tissue and leading to necrotization.
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 arachnoid 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, Chiari malformation, and congenital absence of arachnoidal granulations (Pacchioni's granulations). 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.
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. For details on other manifestations of increased intracranial pressure:
The triad (Hakim 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).
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. 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. 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 common 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 below the level of being officialy mentaly 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."
This article is from the 1911 Encyclopaedia Britannica. Medical science has made many leaps forward since it has been written. This is not a site for medical advice, when you need information on a medical condition, consult a professional instead.
HYDROCEPHALUS (Gr. iiSwp, water, and Ke4laX', head), a term applied to disease of the brain which is attended with excessive effusion of fluid into its cavities. It exists in two forms - acute and chronic hydrocephalus. Acute hydrocephalus is another name for tuberculous meningitis (see Meningitis).
Chronic hydrocephalus, or "water on the brain," consists in an effusion of fluid into the lateral ventricles of the brain. It is not preceded by tuberculous deposit or acute inflammation, but depends upon congenital malformation or upon chronic inflammatory changes affecting the membranes. When the disease is congenital, its presence in the foetus is apt to be a source of difficulty in parturition. It is however more commonly developed in the first six months of life; but it occasionally arises in older children, or even in adults. The chief symptom is the gradual increase in size of the upper part of the head out of all proportion to the face or the rest of the body. Occurring at an age when as yet the bones of the skull have not become welded together, the enlargement may go on to an enormous extent, the spaces between the bones becoming more and more expanded. In a well-marked case the deformity is very striking; the upper part of the forehead projects abnormally, and the orbital plates of the frontal bone being inclined forwards give a downward tilt to the eyes, which have also peculiar rolling movements. The face is small, and this, with the enlarged head, gives a remarkable aged expression to the child. The body is ill-nourished, the bones are thin, the hair is scanty and fine and the teeth carious or absent.
The average circumference of the adult head is 22 in., and in the normal child it is of course much less. In chronic hydrocephalus the head of an infant three months old has measured 29 in.; and in the case of the man Cardinal, who died in Guy's Hospital, the head measured 33 in. In such cases the head cannot be supported by the neck, and the patient has to keep mostly in the recumbent posture. The expansibility of the skull prevents destructive pressure on the brain, yet this organ is materially affected by the presence of the fluid. The cerebral ventricles are distended, and the convolutions are flattened. Occasionally the fluid escapes into the cavity of the cranium, which it fills, pressing down the brain to the base of the skull. As a consequence, the functions of the brain are interfered with, and the mental condition is impaired. The child is dull, listless and irritable, and sometimes imbecile. The special senses become affected as the disease advances; sight is often lost, as is also hearing. Hydrocephalic children generally sink in a few years; nevertheless there have been instances of persons with this disease living to old age. There are, of course, grades of the affection, and children may present many of the symptoms of it in a slight degree, and yet recover, the head ceasing to expand, and becoming in due course firmly ossified.
Various methods of treatment have been employed, but the results are unsatisfactory. Compression of the head by bandages, and the administration of mercury with the view of promoting absorption of the fluid, are now little resorted to. Tapping the fluid from time to time through one of the spaces between the bones, drawing off a little, and thereafter employing gentle pressure, has been tried, but rarely with benefit. Attempts have also been made to establish a permanent drainage between the interior of the lateral ventricle and the sub-dural space, and between the lumbar region of the spine and the abdomen, but without satisfactory results. On the whole, the plan of treatment which aims at maintaining the patient's nutrition by appropriate food and tonics is the most rational and successful. (E. 0. *)
Species: H. carens - H. mandiki - H. minor
type-species: Hydrocephalus Carens Barande,1846