Hydrocephalus

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] Associate Editor-In-Chief: Cafer Zorkun M.D., PhD.,Kalsang Dolma, M.B.B.S.[2]

Hydrocephalus is a term derived from the Greek words “hydro” meaning water, and “cephalus” meaning head, and this condition is sometimes known as “water on the brain”. People with this condition have 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 mostly results due to CSF flow obstruction, hindering the free passage of cerebrospinal fluid through the ventricular system and it can also be caused by overproduction of cerebrospinal fluid (relative obstruction).

Hydrocephalus affects one in every 500 live births, making it one of the most common birth defects, more common than Down syndrome or deafness. There are an estimated 700,000 children and adults living with hydrocephalus, and it is the leading cause of brain surgery for children in the United States.

Premature babies are often at higher risk.

Hydrocephalus is caused by impaired cerebrospinal fluid (CSF) flow, impaired CSF reabsorption, or excessive CSF production. Brain hemorrhage associated with premature birth is a common cause.

Hydrocephalic children are at increased risk of various developmental disabilities such as learning disabilities, visual problems and problems with coordination.

Symtoms of hydrocephalus are mainly due to increased intracranial pressure and depend on age, severity and cause.

Physical examination shows progressive enlargement of head in infants. Depending upon the rate of development duration of hydrocephalus, signs of increased intracranial pressure may be seen.

CT and MRI are used to evaluate ventricular size. MRI affords better imaging of the posterior fossa so can be used to evaluate posterior fossa lesion.

• Acetazolamide and furosemide may provide temporary relief but long term results are disappointing.
• Surgery is the preferred treatment of hydrocephalus. Various shunt surgeries are done to bypass the cerebrospinal fluid flow obstruction and drain the excess fluid into other body cavities.

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Syed Ahsan Hussain, M.D.[2]

• The historical prespective of hydrocephalus is given below:^[1]
  • Hydrocephalus cases were diagnosed by Hippocrates, Galen and Arabian physicians. They believed that the disease was caused by an extracerebral accumulation of water.
  • Evacuation of superficial intracranial fluid in hydrocephalic children was first described in detail in the 10th century by Abulkassim Al Zahrawi.
  • In 1744, LeCat published findings on a ventricular puncture.
  • In 1881, a few years after the landmark study of Key and Retzius, Wernicke inaugurated sterile ventricular puncture and external cerebrospinal fluid (CSF) drainage.
  • These were followed in 1891 by serial lumbar punctures (Quincke) and, in 1893, by the first permanent ventriculo-subarachnoid-subgaleal shunt (Mikulicz).
  • Ventriculostomy without implants (Anton 1908), with implants, and plexus coagulation initially had a very high operative mortality and were seldom successful in the long term, but gradually improved over the next decades.
  • In 1949, Nulsen and Spitz implanted a shunt successfully into the caval vein with a ball valve.
  • Between 1955 and 1960, four independent groups invented distal slit, proximal slit, and diaphragm valves almost simultaneously.
  • Around 1960, the combined invention of artificial valves and silicone led to a worldwide therapeutic breakthrough.

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] Associate Editor(s)-in-Chief: Syed Ahsan Hussain, M.D.[2]

Hydrocephalus is classified based upon the underlying cause such as impaired cerebrospinal fluid (CSF) flow, impaired CSF reabsorption, or excessive CSF production.

• Based on its underlying mechanisms, hydrocephalus can be classified into:^[1][2]
  • Communicating (non-obstructive).
  • Non-communicating (obstructive).

• Both communicating and non-communicating forms can be either:
  • Congenital.
  • Acquired.

• The mechanism of hydrocephalus is given below:^[1][3]
  • It is caused by impaired cerebrospinal fluid resorption in the absence of any CSF-flow obstruction.
  • It has been theorized that this is due to functional impairment of the arachnoid granulations.
  • Arachnoid granulations 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.
  • Congenital absence of arachnoidal granulations (Pacchioni’s granulations).

Sub-types of communicating hydrocephalus:

(a) Normal pressure hydrocephalus (NPH):

• 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).

• It refers to an enlargement of cerebral ventricle
• Hydrocephalus ex vacuo occurs as a result of compensatory enlargement of the CSF-spaces in response to brain parenchyma loss.

• Non-communicating hydrocephalus, or obstructive hydrocephalus, is caused by a CSF-flow obstruction (either due to external compression or intraventricular mass lesions) which leads to:^[1][4]
  • 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 dilatation 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.
  • The foramina of Luschka and foramen of Magendie may be obstructed due to congenital failure of opening (e.g., Dandy-Walker malformation).
  • The subarachnoid space surrounding the brainstem may also be obstructed due to inflammatory or hemorrhagic fibrosing meningitis, leading to widespread dilatation, including the fourth ventricle.

• 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][5]
  • Intraventricular matrix hemorrhages in premature infants
  • Infections
  • Type II Arnold-Chiari malformation
  • Aqueduct atresia and stenosis
  • Dandy-Walker malformation.
  • About 80-90% of fetuses or newborn infants with spina bifida which are often associated with meningocele or myelomeningocele, develops hydrocephalus.

The acquired condition is the result of^[5][1]:

• Infections.
• Meningitis.
• Brain tumors.
• Head trauma.
• Intracranial hemorrhage (subarachnoid or intraparenchymal) and is usually extremely painful for the patient.

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Syed Ahsan Hussain, M.D.[2]

Hydrocephalus mostly results due to CSF flow obstruction, hindering the free passage of cerebrospinal fluid through the ventricular system and it can also be caused by overproduction of cerebrospinal fluid (relative obstruction).

• The pathophysiology of hydrocephalus is given below:.^{[1][2][3][4][5]}
• Intracranial pressure is normally ≤15 mmHg in adults, and pathologic intracranial hypertension (ICH) is present at pressures ≥20 mmHg.
• ICP is normally lower in children than adults.
• In adults, the intracranial compartment is protected by the skull which can hold internal volume of 1400 to 1700 mL.
• Mass lesions, abscesses, and hematomas also causes the intracranial compartment pressure.
• ICP is a function of the volume and compliance of each component of the intracranial compartment.
• The volume of brain parenchyma is relatively constant in adults which constitutes 80% of total volume.
• The volumes of CSF and blood in the intracranial space vary to a greater degree.
• Abnormal increases in the volume due to mass lession or cerebral edema which lead to ICP elevation.
• The volume of brain parenchyma is constant, with the exception of any abnormality like mass lesions or cerebral edema.
• The volumes of CSF and blood in the intracranial space vary to a greater degree.
• CSF is produced by the choroid plexus and elsewhere in the central nervous system (CNS) at a rate of approximately 20 mL/h (500 mL/day).
• CSF is resorbed by arachnoid granulations into the venous system.
• CSF abnormal flow generally result from impaired outflow due to ventricular obstruction or venous congestion.
• The Venous sinus thrombosis can be pathologically increase which can be seen in the setting of choroid plexus papilloma.
• The other causes of increased ICP are given below:
  • Intracranial mass lesions (eg, tumor, hematoma).
  • Cerebral edema.
  • Acute hypoxic ischemic encephalopathy.
  • Large cerebral infarction.
  • Severe traumatic brain injury.
  • Choroid plexus papilloma (increased ICP).
  • Arachnoid granulation adhesions after bacterial meningitis (decreased ICP).
  • Venous sinus thrombosis.
  • Idiopathic intracranial hypertension (pseudotumor cerebri).

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] Associate Editor(s)-in-Chief: Syed Ahsan Hussain, M.D.[2]

Hydrocephalus is caused by impaired cerebrospinal fluid (CSF) flow, impaired CSF reabsorption, or excessive CSF production. Brain hemorrhage associated with premature birth is a common cause.

• The common causes are given below:^[1][2][3]
  • Brain hemorrhage associated with premature birth
  • Meningitis
  • Aquaductal stenosis
  • Chiari malformation
  • Choroid plexus papilloma
  • Meningioma
  • Dandy-Walker syndrome
  • Achondroplasia
  • Arteriovenous malformation

• The causes of hydrocephalus according to system is given below:^[2][4][1]

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Syed Ahsan Hussain, M.D.[2]

• The incidence, prevelance and case-fatality rates of hydrocephalus are given below:^[1][2][3]
  • The incidence of hydrocephalus is approximately 68 per 100,000 individuals in U.S and Canada.
  • The prevalence of hydrocephalus is estimated to be 0.82/1000 cases annually.
  • The incidence of hydrocephalus is approximately 68 per 100,000 individuals with a case-fatality rate of 5% in U.S and Canada.
  • The case-fatality rate of hydrocephalus is approximately 5%.

• Age:
  • Hydrocephalus commonly affects pre-term individuals.
• Race:
  • Hydrocephalus usually affects individuals of the Latin American and African race. The individuals in U.S and Canada are less likely to develop hydrocephalus.
• Sex:
  • Hydrocephalus affects men and women equally.
  • The majority of hydrocephalus cases are reported in Africa and Latin America.
  • Hydrocephalus is a rare disease that tends to affect Latin American and African.

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Syed Ahsan Hussain, M.D.[2]

• The common risk factors of hydrocephalus include:^[1][2][3]
  • Lack of pre-natal care.
  • Multiparous gestation.
  • Maternal diabetes.
  • Maternal chronic hypertension.
  • Maternal hypertension during gestation.
  • Alcohol use during pregnancy.

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1];Associate Editor(s)-in-Chief: Syed Ahsan Hussain, M.D.[2]

Hydrocephalic children are at increased risk of various developmental disabilities such as learning disabilities, visual problems and problems with coordination. Prognosis is poor if left untreated.

• The natural history and complications, prognosis are given below:^[1][2]
• This depends on the cause of the dialated ventricles
• Cerebral shunt: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%.

• Because hydrocephalus injures the brain, thought and behavior may be adversely affected. Learning disabilities 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 differs considerably between individuals and some are of average or above average intelligence. Someone with hydrocephalus may have motivation and visual problems, problems with coordination, and may be clumsy. They may hit puberty earlier than the average child (see precocious puberty). About one in four develops epilepsy.

• Elevated intracranial pressure may result in uncal and/or cerebellar tonsill herniation, with resulting life threatening brain stem compression.

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