Hydrocephalus also known as “water in the brain” is derived from Greek words “hydro” means water and “cephalus” meaning head, as the name suggest it is abnormal accumulation of cerebrospinal fluid in the ventricles, or in cavities of the brain. This may cause increased intra-cranial pressure inside the skull and progressive enlargement of the head, convulsion, tunnel vision and mental disability. Excess of CSF occurs in all conditions in which there is a diffuse atrophy of the brain, as in cerebral arteriosclerosis, general paresis, and the presenile dementias. The hydrocephalus is then compulsory. Hydrocephalus produces symptoms when the CSF is under increased pressure.. Two varieties of this are recognized. In one, the raised pressure of the fluid is due to an obstruction at some point in its course between its formation by the choroid plexuses and its exit from the fourth ventricle by the median and lateral apertures of the fourth ventricle. This type of hydrocephalus is called obstructive. When there is no obstruction within or to the outflow from the ventricular system and the cerebrospinal fluid freely reaches the spinal subarachnoid space and is found to be under increased pressure there, the condition is known as communicating hydrocephalus.
Hydrocephalus can be caused by impaired cerebrospinal fluid (CSF) flow, reabsorption, or excessive CSF production.
- The most common cause of hydrocephalus is CSF flow obstruction, hindering the free passage of cerebrospinal fluid through the ventricular system and subarachnoid space (e.g., stenosis of the cerebral aqueduct or obstruction of the interventricular foramina -foramina of Monro secondary to tumors, hemorrhages, infections or congenital malformations).
- Hydrocephalus can also be caused by overproduction of cerebrospinal fluid (relative obstruction) (e.g., papilloma of choroid plexus).
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.
- Normal pressure hydrocephalus (NPH) is a particular form of communicating hydrocephalus, characterized by enlarged cerebral ventricles, with only intermittently elevated cerebrospinal fluid pressure. The diagnosis of NPH can be established only with the help of continuous intraventricular pressure recordings (over 24 hours or even longer), since more often than not instant measurements yield normal pressure values. Dynamic compliance studies may be also helpful. Altered compliance (elasticity) of the ventricular walls, as well as increased viscosity of the cerebrospinal fluid, may play a role in the pathogenesis of normal pressure hydrocephalus.
- Hydrocephalus ex vacuo also refers to an enlargement of cerebral ventricles and subarachnoid spaces, and is usually due to brain atrophy (as it occurs in dementias), post-traumatic brain injuries and even in some psychiatric disorders, such as schizophrenia. As opposed to hydrocephalus, this is a compensatory enlargement of the CSF-spaces in response to brain parenchyma loss – it is not the result of increased CSF pressure.
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).
- Foramen of Monro obstruction may lead to dilation of one or, if large enough (e.g., in Colloid cyst), both lateral ventricles.
- The aqueduct of Sylvius, normally narrow to begin with, may be obstructed by a number of genetically or acquired lesions (e.g., atresia, ependymitis, hemorrhage, tumor) and lead to dilation of both lateral ventricles as well as the third ventricle.
- Fourth ventricle obstruction will lead to dilatation of the aqueduct as well as the lateral and third ventricles (e.g., Chiari malformation).
- The foramina of Luschka and foramen of Magendie may be obstructed due to congenital failure of opening (e.g., Dandy-Walker malformation).
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.
This condition is acquired as a consequence of CNS infections, meningitis, brain tumors, head trauma, intracranial hemorrhage(subarachnoid or intraparenchymal) and is usually extremely painful. It may be due to tumour in the third or fourth ventricle or in the midbrain where the cerebral aqueduct may be narrowed also by ependymitis. Thrombosis of the superior sagittal sinus may impair the absorption of the fluid. When this secondary to otitis it is known as otitic hydrocephalus.
Signs and Symptoms
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. Elevatedintracranial 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 syndromedue 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:
- Eyes that appear to gaze downward (Sundowning)
- Separated sutures
Symptoms that may occur in older children can include:
- Brief, shrill, high-pitched cry
- Changes in personality, memory, or the ability to reason or think
- Changes in facial appearance and eye spacing
- Crossed eyes or uncontrolled eye movements
- Difficulty feeding
- Excessive sleepiness
- Irritability, poor temper control
- Loss of bladder control (urinary incontinence)
- Loss of coordination and trouble walking
- Muscle spasticity (spasm)
- Slow growth (child 0–5 years)
- Slow or restricted movement
Pressure of the cerebrospinal fluid is increased in communicating hydrocephalus and in benign intracranial hypertension may reach as high as 00mm of water. Examination of the spinal fluid is dangerous in obstructive hydrocephalus as it may cause coning( displacement of parts of the brain between its compartments). Radiographs of the skull may show enlargement of the calvarium and thinning and exaggeration of the convolutional markings and sometimes separation of the sutures. Owing to the large head, severe congenital infantile hydrocephalus is usually easy to diagnose. Later in life hydrocephalus usually presents with the symptoms of increased intracranial pressure with little or no localized evidence as to cause. The investigation calls initially for X-rays of the skull and CT scan, which will show enormous dilatation of the ventricular system except in benign intracranial hypertension, in which the ventricles are normal in size.
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. This is the treatment.
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.
Shunt in Developing countries
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.