Hydrocephalus is a disorder that occurs in the head due to various causes. The term hydrocephalus is actually derived from a Greek word which means accumulation of fluid within the head. One could add to the definition, ‘with a secondary increase in the CSF spaces’1, so that in practical clinical terms, one can observe an increase in the ventricular or subarachnoid space in a CT scan. However, the definition makes no reference to the level of intracranial pressure (ICP). But generally, hydrocephalus has to be associated the increased intracranial pressure1. This has to be very much correct because when there is an increased CSF volume, it should definitely lead to an increased pressure in the cranium.

CSF
Cerebrospinal fluid is a fluid that circulates in the cavities of the brain. It is produced by the choroid plexus in the lateral ventricles, from where it flows through the foramen of Munro into the third ventricle and then into the fourth ventricle via the aqueduct of Sylvius. It leaves the ventricular system via small openings in the roof of the fourth ventricle, called the foramina of Magendie and Luschka. From here the fluid flows in the subarachnoid space before being reabsorbed into the blood supply via arachnoid villae.
In normal subjects, CSF is produced at a rate of 0.3-0.5 ml/min. But even when the production rate is normal, the accumulation of CSF can occur due to some obstruction, leading to the hydrocephalus condition.
The CSF formation rate can be influenced by: increased secretion that occurs with a choroid plexus papilloma, Frusemide and Acetazolamide and hypothermia2.
The cerebrospinal fluid production occurs by two main mechanisms:
→ That dependent on choroidal capillary blood flow from which itself is a two step process with, first, an ultra filtrate of plasma produced hydrostatically through the lax choroidal capillary endothelium and second, an active process involving secretion of sodium into and out of the apical choroidal villi. The raised osmotic pressure causes water to follow passively.
→ The second mechanism is a direct neurogenic stimulation of choroidal villi, which is independent of choroidal blood flow. Stimulation of adrenergic fibres may reduce CSF flow by approximately one-third.

CLASSIFICATION OF HYDROCEPHALUS
Hydrocephalus can be generally classified into a communicating and a non-communicating type.
In communicating hydrocephalus, the ventricular pathways are clear and a failure of reabsorption (following, for example, in the case of bleeding into the subarachnoid space) results in increased cerebrospinal fluid volume.
In non-communicating type or obstructive hydrocephalus, the blockage occurs at one of the ventricular levels, with expansion of the ventricular system above the block.
Hydrocephalus can also be classified further into:
→ Panventricular hydrocephalus :- dilation of the lateral third and fourth ventricles (in aqueduct stenosis the fourth ventricle is smaller than the normal size). An isolated fourth ventricle (‘double compartment hydrocephalus’ or ‘trapped fourth ventricle’) occurs when there is outlet obstruction from that ventricle and stricture of the aqueduct.

→ Unilateral hydrocephalus:- abnormal dilation of the body, frontal and/or posterior horn of the lateral ventricle on one side. This may be due to compression of the ventricular system on the opposite side, obstruction to one foramen of Munro, slit ventricle syndrome or a hemi parenchymal atrophy.

→ Slit ventricle:- a reduction in the size of the ventricular system seen on a CT scan, usually in response to excessive CSF drainage. The slit ventricle syndrome is distinguished from radiological slit ventricles by the presence of symptoms and clinical signs caused due to this overdrainage.

AETIOLOGY
Hydrocephalus may be due to congenital causes such as the Arnold-Chiari malformation in Spina bifida cystica, stenosis or forking of the aqueduct of Sylvius, atresia of the Foramina of Magendie and Luschka, failure of development of the basal subarachnoid cisterns, and congenital toxoplasmosis. Rarely, the disease is inherited as a recessive sex-linked condition when due to atresia of the aqueduct. There is also an autosomal recessive form due to atresia of the foramina of Luschka and Magendie, when the fourth ventricle distends into a huge cyst (Dandy-Walker syndrome). Acquired causes of hydrocephalus include the reaction of the meninges to pyogenic or tuberculous meningitis, intracranial tumours, intracranial haemmorhage at birth, metastatic tumours and brain abscess.
The general aetiology of hydrocephalus is summarized in the Table 1 below.

Table 1 Aetiology of hydrocephalus
Causes of prenatally determined hydrocephalus

Congenital (chromosomal) malformations
Maternal diabetes resulting in holoprosencephaly
Neural tube defects
Occipital meningocele and encephalocele
The Cleland-Chiari II malformation
Dandy-Walker syndrome
Hydraencephaly
Multicystic encephalomalacia
Schizencephaly
Achondroplasia
Arachnoid cysts
Quadrigeminal plate cysts, retrocerebellar cysts, cysts of the cerebellopontaine angle and supracellar cysts
Congenital craniosynostosis (e.g. Apert’s Syndrome)
Agenesis of the corpus callosum and cysts of the cavum septum pellucidum and cavum vergae
Encephalocraniocutaneous lipomatosis
Isolated stenosis of the Aqueduct of Sylvius
Sex-linked stenosis of the Aqueduct of Sylvius
Hydrocephalus associated with giant hairy nervus (melanosis of the leptomeninges)
Aneurysm of the great vein of Galen
Hurler’s disease
Basilar impression
Osteogenesis imperfecta (rarely)
Paget’s disease
Colpocephaly
Lissencephaly
Say-Gerald syndrome

Causes of acquired hydrocephalus

Posthemorrhagic causes
Neonatal intraventricular hemorrhage
Subarachnoid hemorrhage
Subdural hemorrhage
Postmeningetic causes
Toxoplasmosis
Mumps (aqueductitis, ependymitis)
Pyogenic organisms (pneumococcus, haemophilus, etc.)
Cytomegalovirus
Other viral meningitides
Rubella
Tuberculous meningitis and tuberculoma
Space occupying causes
Tumor
Clot
Cyst
Abscess
Postasphyxial
Injury

Other causes
Stenosis of the aqueduct of Sylvius
1. Due to raised intracranial pressure with secondary kinking of the aqueduct
2. Due to aqueductitis and ependymitis associated with mumps, toxoplasma, tuberculomas, pyogenic meningitis, rarely CMV, rubella and tumors.

Dystrophia myotonia
Otitic hydrocephalus
Choroid plexus papilloma
Intrathecal contrast agents
Fungal infection (Cryptococcus and blastomyces)
Cysticercosis
Sarcoidosis
Spinal tumor
Dural venous thrombosis
Isolated Chiari type I deformity

Alcohol can also have a serious damaging effect on the developing nervous system. It is one of the commonest causes of learning difficulty and neuro behavioural disturbance in young children across the world. The reduced brain mass and neuro behavioural disturbances associated with fetal alcohol syndrome may be reflected in the recent observation in rats that ethanol can trigger widespread apoptotic neurodegeneration.
Alcohol has harmful effects throughout the developing pregnancy, unlike some known teratogens. There is a significant risk of fetal alcohol syndrome associated with higher dose exposure (estimated blood alcohol concentration of 150 mg per deciliter or more, at least weekly for several weeks in the first trimester).
Congenital infections can occur due to teratogens like cytomegalovirus, herpes simplex, parovirus, rubella, syphilis, toxoplasmosis and varicella. The risk of congenital infections and the outcome of such infection is crucially dependent on the stage of pregnancy.
The differential diagnosis of microcephaly is important for the recognisation of congenital infections. Intracranial calcification identified on a cranial ultrasound or CT scan during the investigation of developmental delay or seizures should arouse suspicion of congenital infection, especially cytomegalovirus or toxoplasmosis (calcification is not picked up well by MRI). Detailed ophthalmological assessments may reveal clues such as chorioretinis or cataract that may help in the retrospective diagnosis of congenital infection.

SIGNS AND SYMPTOMS
The clinical features depend on whether the disease process is acute or chronic and whether the process produces complete or partial obstruction. The acute presentation is usually accompanied by severe headache, nausea and vomiting. There are usually no localizing symptoms or signs, but there is papilloedema and there may be a sixth nerve lesion.
The symptoms and signs of progressive hydrocephalus in infants are listed in Table 2 below.

Table 2 Most common clinical features of progressive infantile hydrocephalus (50% of cases are asymptomatic)

Symptoms
Headache or irritability
Vomiting
Anorexia
Drowsiness or lethargy

Signs
Inappropriately increasing OFC (approx. 75%)
Tense anterior fontanel
Splayed sutures
Scalp vein distension
Sunsetting (loss of upward gaze)
Neck retraction or rigidity
Pupillary changes
Neurogenic stridor
Decerebration

Usually the symptoms of progressive hydrocephalus in infants are vague. They may show irritability and vomiting. But about half the cases, no symptoms can be felt.
But some common clinical signs are inappropriately increasing head circumference, followed by a tense nonpulsatile fontanel, then clinical and radiological separation of the sutures, scalp vein distension with taut skin over the scalp. A very common sign of hydrocephalus is due to compensation for raised ventricular pressure called ‘sunsetting’. This is the inability to look upwards. It may initially be intermittent but becomes continuous later. This is caused due to the pressure on the superior quadrigeminal plate against the free edge of the tentorium causing paralysis of the fourth nerve.
Neurogenic stridor is a result of deranged lower brainstem function caused by bilateral corticobulbar disruption and is a feature of pseudobulbar paresis. Abnormalities of sucking and feeding may also occur in hydrocephalic infants with seriously raised intracranial pressure.
The symptoms of chronic hydrocephalus can be see in poor performance at school, intermittent headaches over many months, behavioral and personality changes, failure to thrive and dizziness.
Arrested long standing hydrocephalus show distinct signs and symptoms, such as ataxic and spastic cerebral palsy, precious puberty, mental retardation and specific learning problems. Older infants who present with enlarged head circumference but is otherwise asymptomatic is likely to have hydrocephalus if there is additional development retardation.
Since unusual features of raised ventricular pressure include neurogenic pulmonary edema, profuse sweating, ptosis, neurogenic stridor, pseudobulbar paresis and skin rashes.

DIAGNOSIS AND ASSESSMENTS
Prenatal diagnosis and termination of affected pregnancies is only one of a range of reproductive options open to parents at increased risk of having children with neuro developmental abnormalities such as hydrocephalus (congenital). For the majority of developmental disorders of the nervous systems preimplantation genetic diagnosis is not yet feasible. For a condition with a strong environmental component, it is imperative that measures are taken to minimize the risk of exposure in future pregnancies. For neural tube defects, preconceptual supplementation with high-dose folic acid has been shown to reduce the risk of recurrence in future pregnancies. When a specific diagnosis has been made and a chromosomal anomaly, genetic mutation, or biochemical defect has been identified, it is normally possible to offer prenatal diagnosis by chorionic villus sampling at 11 weeks of gestation in a future pregnancy. If this is not the case, detailed ultrasound scanning may be helpful in some instances; for example, neural tube defects where anencephaly can be easily visualized by 13 or 14 weeks of gestation, and spina bifida by 18 to 20 weeks.

HOW TO APPROACH HYDROCEPHALUS?
Hydrocephalus is a condition which can be easily be observed in a patient. Except during early stages or during infancy (when there is a genetic defect), the abnormalities occurring due to hydrocephalus is very prominent. An abnormally large head, a frontal bulking, crushing pain in the head, a heavy feeling in the head are all probable symptoms of hydrocephalus.
When a patient is quite suspicious of his condition, to confirm his situation, he should visit a doctor. The meeting should be arranged as early as possible. The patient can also obtain lot information about hydrocephalus from the internet3. A lot people suffering from this problem discuss their condition in various forums dedicated to hydrocephalus. There are also contributions from expert doctors giving their advice. Even patients, who have been treated successfully from hydrocephalus, give advice and hope to others in the forum.
Not all forms of hydrocephalus are completely treatable. They can be relieved a little, but not always completely. In such cases, the person may turn out to be hopeless and depressed. But when one goes through the forum thoroughly, he may come across a person who might have had a similar problem or one who is sharing the same problem. They may share advice, tips and most importantly some hope between each other.
Counseling is always very helpful in such situations. The patient may feel depressed and embarrassed of his abnormality in his head. Thus they may be morally deteriorated. Hence, they should regularly undergo counseling till things turn out to be fine for them.

CLINICAL ASSESSMENT
X-ray examination of the skull may show a ‘copper-beaten’ appearance, shallow orbits and splayed sutures. Computed axial tomography, ultrasound or magnetic resonance image scans will all define ventricular size. Although repeated ultrasound examinations may show progressive hydrocephalus, it is advisable to have a definite CT or MRI investigation prior to any surgical intervention. The CT scan requires sedation or anesthesia in case of infants and young children. CT scans provide information about the size and symmetry of the ventricles and whether there is any underlying pathology. A single CT scan, like a single ultrasound or MRI scan, may not reveal whether there is a progressive or an arrested hydrocephalus. When there is significantly elevated intraventricular pressure from progressive hydrocephalus, periventricular lucenics, rounding of ventricles, absence of a cortical subarachnoid space and a spherical appearance of the third ventricle are seen on CT scan.
A study4 was done in Department of Radiology and Center for Imaging Science, Sungkyunkwan University School of Medicine, Seoul, Republic of Korea, to characterize the computed tomography (CT) and magnetic resonance (MR) imaging findings and clinical features of intraventricular (IV) meningiomas. 12 patients (Five men and seven women, whose mean age was 36 years and the age range was 14-68 years) with pathologically proven IV meningiomas were considered for this study. 8 of them had CT scans. Whereas all 12 of them had MRI scans taken. Particular attention was put on the size and shape of the mass; internal architecture such as necrosis or calcification within the tumor; peritumoral edema; associated hydrocephalus and clinical features such as symptoms, treatment, and prognosis. The result obtained was as such: There were five of benign, three of atypical, and four of malignant subtype. All lesions were located in the lateral ventricle ranging in maximum diameters from 4.0 to 7.3 cm (mean, 5.4 cm). All tumors had lobulated shape. Five (71%, 5/7) of the atypical and malignant IV meningiomas, but just two (40%, 2/5) benign IV meningiomas, had irregular lobulation. The tumors were isointense (n=7) or hypointense (n=5) to gray matter on T1-weighted images, whereas isointense (n=9) or hyperintense (n=3) on T2-weighted images. On gadolinium-enhanced T1-weighted images, homogeneous enhancement was seen in five lesions, and heterogeneous enhancement was seen in seven lesions, Most patients (n=10) had associated localized hydrocephalus due to ventricular entrapment. Intratumoral necrosis was seen in two cases (17%, 2/12), all of these were malignant subtype. In two cases of atypical and malignant subtypes, recurrences were found during the follow-up period after surgical resection. CONCLUSION: More than half (n=7, 58%) of the IV meningiomas were of atypical (n=3) or malignant (n=4) subtype. IV meningiomas tend to have a lobulated shape, especially irregular lobulation, and intratumoral necrosis was frequently seen in the atypical or malignant subtypes.
The most commonly used index of ventricular dilation is the V/P ratio, that is, the ventricular diameter at the mid-portion of the lateral ventricles divided by the biparietal diameter from inner table to outer table. Hydrocephalus is defined as a ration higher than 0.26.
The ultrasound for assessment of fetal hydrocephalus is indexed slightly differently. The commonly used parameters are biparietal diameter and the ratio of the lateral ventricular width divided by the width of the head. The latter is approximately 0.61 at 14 weeks, 0.29 at 27 weeks and 0.29 at term. Absolute measurements of ventricular width are done using the atrium as reference point. Ultrasound estimate of ventricomegaly in utero may be exaggerated by a factor of about 10% due to the distortion of sound signals passing through two thirds (amniotic and CSF). If hydrocephalus is suspected, ultrasound is done weekly with elective cesarean section at 36 weeks. Intracranial Doppler blood flow velocities should be measured in addition to the BPD.

TREATMENT
The primary priority of treating hydrocephalus would be to reduce the intracranial pressure. This can be done by creating valves and shunt systems in order to divert the CSF from the ventricular system to another site. There are various routes through which this can be done5. For example, Spitz-Holter valve (a device with a tiny one-way valve that released controlled amounts of the cerebrospinal fluid from the brain into the atrium of the heart), Dudenz-Hakin, the Indian valve, Raimondi, etc. with latest development in technology, more sophisticated types of pressure opening devices such as the Sophy programmable and multi programmable and the Cosman ICP telesensor, have been invented to make the treatment less and complicated and more safer.
One of the earliest routes of drainage was the ventricular atrial route in which the distal tube was passed by the common facial vein into the right atrium. On occasions a ventriculo azygous route was employed. But there were obvious complications evolving from this procedure leading to serious condition. Acute infection with these shunts may is automatically accompanied by septicemia and chronic infection may result in shunt nephritis or unexplained rashes of a vasculitc nature due to complement activation from chronic septic emboli. The other chronic effects from this procedure are right heart failure from pulmonary hypertension and bacterial endocarditis, thrombosis of the superior vena cava with superior vena caval syndrome arrhythmias and possible perforation of the myocardium. The probabilities of such infections occurring are 10-30%.
There are many variations in the basic shunt system. Some shunt systems have a twin valve, one arranged proximally and another distally and some include a pump or flushing device. In the newborn a device which opens at the low pressure is advisable to drain the CSF, but as the child grows it may be necessary to avoid the development of overdrainage and cranio cerebral disproportion. A valve may be incorporated in the pump (Spitz-Holter system) or it may be a distal ‘slit valve’ at the peritoneal end. It may be a single continuous stiff tube with radiopaque gradation to avoid kinking, such as the Raimondi System.
Table 3 Complications of CSF shunting

Blockage by choroid plexus, fibrin, neuroglia, blood clot and brain segments causing raised intracranial pressure
Fractured tubing: fracture off the distal tubing may occur in the neck as a result of direct trauma or kinking of the tubing with repeated movements (fracture can also occur over the surface of the chest and exaggerated flexion/extension movements may result in a crack in the distal tube)
Infection (colonization and ventriculitis) with raised intracranial pressure
Shunt dependence
Slit Ventricle syndrome
Other decompressive effects (e.g. subdural hematoma)
the tubing Migration of proximally or distally: cases have been reported of migration of the distal tubing through the gut wall or penetration of other organs. (Cases are known where the tubing has dramatically retracted from the abdominal cavity to the intracranial space. Migration of the distal tubing may cause a volvulus. Commonly if insufficient length is implanted initially, the tubing may retract subcutaneously over the chest wall with growth. Migration of the proximal catheter extending into a different ventricle or into subcortical structures)
Intestinal obstruction (volvulus)
Peritonitis and peritoneal fibrosis
Endocarditis (VA shunts)
Chronic pulmonary hypertension (VA shunts)
Superior vena caval syndrome (VA shunts)
Arrhythmias (VA shunts)
Shunt nephritis (VA shunts): a case has been reported of shunt nephritis following a VP shunt
Hyperlordosis (TP shunts)
Acute noncomminucation (with TP shunts)
Product failure due to mechanical deficiency and faulty valve
Surgical technique (malplacement or displacement)
Ventricular collapse from excessive drainage causing the tip of the catheter to impinge through the ependyma or brain substance
Pseudocyst formation with defective drainage