Hydrocephalus
Pediatrics > Hydrocephalus

Key points
Hydrocephalus may be broadly defined as a neurologic disorder that results from a disruption in the balance between the formation, flow, or absorption of cerebrospinal fluid (CSF) in the brain
If blockage of CSF flow happens rapidly, for example, following a sudden hemorrhage, the brain has little time to compensate and the intracranial pressure (ICP) may rise rapidly and to a sufficient degree to cause rapid deterioration into coma. Immediate consultation with a neurosurgeon is indicated
Symptoms include headache, nausea, and vomiting, followed in a period of a few hours by confusion, agitation, and then somnolence
If a patient presents with papilledema, blurred vision, and episodes of 'graying out' it may be indicative of serious optic nerve compromise secondary to a rise in ICP and should be treated as an emergency. Immediate consultation with a neurosurgeon is indicated
Never perform a lumbar puncture in a patient suspected of having hydrocephalus without first performing imaging studies of the brain. The risk of cerebral herniation associated with lumbar puncture is correlated with the degree of ICP
Surgical treatment is the therapy of choice for hydrocephalus. It is most commonly treated by the surgical placement of a shunt system within the brain, which diverts the flow of CSF from within the central nervous system (CNS) to a site outside the CNS where it can be absorbed by the circulatory system
Prognosis depends on the specific cause of the hydrocephalus. It is further complicated by the presence of associated disorders, the speed at which the hydrocephalus was diagnosed, and the effectiveness of the shunt surgery
Background
Description

Hydrocephalus may be broadly defined as a neurologic disorder that is caused by a disruption in the balance between the formation, flow, or absorption of CSF in the brain, resulting in an increase in the volume that the CSF occupies in the CNS
Congenital hydrocephalus is present at birth and is associated with a genetic predisposition or the malformation of critical structures within the brain during development; for example, stenosis of the aqueduct of Sylvius accounts for 10% of all cases of hydrocephalus in newborns
Acquired hydrocephalus may occur at any time after birth and is usually associated with traumatic injury, disease, tumor obstruction, intracranial hemorrhage, and infection
Hydrocephalus may be an acute, subacute, or chronic condition and several different forms of the disease exist, including communicating, noncommunicating, and normal pressure hydrocephalus
Surgical treatment is the therapy of choice for hydrocephalus. Commonly treated by surgical placement of a shunt system within the brain, which diverts the flow of CSF from within the CNS to a site outside the CNS where it can be absorbed by the circulatory system
Excess CSF accumulation in the brain results in an increase in the volume occupied by the fluid in the CSF and often a concomitant increase in ICP
If acute hydrocephalus is not treated emergently, the patient's ICP will reach the point at which cerebral perfusion is compromised and the patient will deteriorate from coma to death
Communicating hydrocephalus occurs when there is full communication between the ventricles and subarachnoid space. It is most often associated with defective absorption of CSF, occasionally venous drainage insufficiency, and rarely overproduction of CSF
Noncommunicating hydrocephalus occurs when the CSF flow is obstructed, resulting in a lack of communication between the ventricles and the subarachnoid space
Normal pressure hydrocephalus is a form of communicating hydrocephalus that rarely occurs in patients younger than 60 years. Associated with a triad of distinct symptoms: progressive gait ataxia, incontinence, and dementia
Benign external hydrocephalus is a self-limiting absorption deficiency seen in infancy and early childhood. It is associated with raised ICP and enlarged subarachnoid spaces. Ventricles are generally not significantly enlarged. Condition usually resolves within 1 year
Arrested hydrocephalus is a rare phenomenon associated with stable ventriculomegaly. The neurologic status is stable, probably because of triggering of compensatory mechanisms. Diagnosis may be difficult because children can present with very subtle neurologic deterioration (eg, decline in performance at school). Patients may decompensate, particularly following head trauma
Hydrocephalus 'ex-vacuo' occurs when there is loss or shrinkage of brain tissue due to damage caused by stroke or injury. Although there is a larger volume of CSF than usual, the CSF pressure in the brain is normal because of the extra space resulting from the loss of brain tissue
Compensatory hydrocephalus can occur as a result of spontaneous intracranial hypotension
Prognosis is linked to the specific cause of the hydrocephalus and is further complicated by presence of associated disorders, speed at which the hydrocephalus was diagnosed, and effectiveness of shunt surgery in the management of the disease
Epidemiology

Incidence

Hydrocephalus is one of the most common birth defects
In the U.S., the incidence of congenital hydrocephalus is believed to be approximately 200 cases per 100,000 live births
In addition, approximately 6,000 children annually develop acquired hydrocephalus during the first 2 years of life
Overall incidence of acquired hydrocephalus is not known
Demographics

Age:

There are two peaks associated with the relationship between incidence and age of onset of hydrocephalus
First peak occurs in infancy and is associated with a number of congenital malformations
Second peak occurs in adulthood and is mostly associated with normal pressure hydrocephalus
Approximately 60% of the total cases of hydrocephalus are congenital or acquired in childhood. Hydrocephalus is a common and significant pediatric problem
Gender:

In general, there is no difference in incidence between males and females
One exception is Bickers-Adams syndrome, which is an X-linked recessive hydrocephalus that is manifested only in males and affects approximately 1/30,000 males at birth
Normal pressure hydrocephalus is slightly more common in males
Genetics:

There are a number of rare genetic causes of hydrocephalus, the most important of which is the Bickers-Adams syndrome
Causes and risk factors

Common causes

Congenital causes in infants and children:

Aqueductal abnormalities: noncommunicating hydrocephalus develops most commonly in infants and children because of an abnormality of the aqueduct or a lesion in the fourth ventricle. Aqueductal stenosis results from an abnormally narrow or completely occluded aqueduct of Sylvius
Chiari malformation (types I and II): Arnold-Chiari malformation type II is characterized by progressive hydrocephalus and myelomeningocele
Congenital infections (eg, cytomegalovirus, toxoplasmosis, rubella)
Dandy-Walker syndrome: enlarged fourth ventricle due to obstruction in pathway
Spina bifida and neural tube defects (NTDs)
Hemorrhage or internal bleeding in the brain
Neurofibromatosis
Arteriovenous malformation (eg, vein of Galen)
Acquired causes in infants and children:

Brain tumors (benign or malignant)
Cysts, abscesses, or hematoma may cause hydrocephalus
Intraventricular hemorrhage most frequently affects premature newborn infants. May be related to premature birth, head injury, or rupture of vascular abnormality
Subarachnoid hemorrhage: Communicating hydrocephalus most commonly follows a subarachnoid hemorrhage, which may block the arachnoid villi leading to obstruction of CSF flow. It is usually a result of intraventricular hemorrhage in a premature infant
Infection, particularly bacterial meningitis and cerebral abscess
Increased venous sinus pressure may be related to some craniostenosis, achondroplasia, or venous thrombosis
Leukemic infiltrates of CNS may seed the subarachnoid space and cause communicating hydrocephalus
Acquired causes in adults:

Benign or malignant tumors may cause blockage of CSF flow. Ependymoma, subependymal giant cell astrocytoma, choroid plexus papilloma, craniopharyngioma, pituitary adenoma, hypothalamic or optic nerve glioma, hamartoma, and metastatic tumors are most commonly associated with hydrocephalus
Subarachnoid hemorrhage accounts for one-third of the cases of hydrocephalus in adults. The arachnoid villi are blocked by the hemorrhage, but communication is preserved between the ventricles and the subarachnoid space creating a form of hydrocephalus that is both obstructive and communicating
Head injury: Hydrocephalus is commonly caused by a subarachnoid hemorrhage that is produced by injury to the head
Idiopathic hydrocephalus: Approximately one-third of cases of hydrocephalus are idiopathic
Previous posterior fossa surgery: Normal pathways of CSF may become blocked as a result of the surgery
Congenital aqueductal stenosis: Individuals may be asymptomatic for hydrocephalus until adulthood
Infections: for example, bacterial meningitis, cerebral abscess
Medication: Infliximab infusion can cause communicating hydrocephalus
Causes of normal pressure hydrocephalus:

Subarachnoid hemorrhage
Head injury
Infection, particularly meningitis
Tumor
Prior posterior fossa surgery: Normal pathways of CSF may become blocked as a result of the surgery
Idiopathic: The mechanisms underlying normal pressure hydrocephalus are not yet completely understood
Rare causes

Bickers-Adams syndrome: an X-linked recessive hydrocephalus that manifests as congenital hydrocephalus in males
Excess CSF production by a choroid plexus papilloma is a very rare but real cause of hydrocephalus
Risk factors

Recent head trauma
Premature infants who are born before 34 weeks' gestation or who weigh less than 4 lb (1.8 kg) at birth have a high risk of intraventricular hemorrhage, which can lead to hydrocephalus
Associated disorders

Meningitis: due to adhesive thickening of the arachnoid villi
Encephalitis
Spina bifida, meningocele, or encephalocele: Hydrocephalus with Chiari II defect develops in 80% of patients with myelomeningocele
Microgyria or macrogyria
Porencephaly
Subarachnoid hemorrhage blocks arachnoid villi
Dandy-Walker syndrome consists of cystic expansion of the 4th ventricle; 90% of patients also have hydrocephalus
Head trauma
Syringomyelia or hydromyelia
Arnold-Chiari malformation: Hydrocephalus is more commonly associated with type II
Arachnoid cysts
Intracranial tumor can lead to obstructive hydrocephalus
Screening
Summary approach

Routine, second-trimester, screening morphology ultrasonography may identify hydrocephalus
Maternal serum α-fetoprotein screening is offered to all pregnant women. Elevated levels suggest a NTD, often associated with hydrocephalus
All children with myelomeningocele should be screened for hydrocephalus with transfontanelle ultrasonography, as signs and symptoms may develop later
Screening modalities

Second-trimester morphology ultrasound scan

All pregnant women should have a detailed fetal morphology ultrasound scan at 16 to 20 weeks of gestation
Scan may reveal ventriculomegaly and abnormal CSF distribution
Primary prevention
Summary approach

Periconception advice and measures to prevent risk of NTDs (and associated hydrocephalus) are essential for all patients planning a pregnancy. Inadequate intake of folic acid before and during early pregnancy is the main factor responsible for NTDs. The spina bifida defect occurs by the fourth week of pregnancy, before many women realize that they are pregnant. Consequently it is recommended that all women of childbearing age take a folic acid supplement. It is estimated that up to 70% of cases of spina bifida can be prevented by periconceptional maternal folic acid supplementation.

Preventive measures

Prenatal care:

Hemorrhaging, traumatic brain injury, and infection are seen in some premature births; premature births may, therefore, be a risk factor for hydrocephalus. Pregnant women can reduce the risk of hydrocephalus in their unborn child by taking appropriate precautions to reduce the likelihood of a premature birth, for example, by establishing appropriate prenatal care
Women should ensure adequate intake of folic acid prior to and in weeks following conception to reduce the risk of NTDs
Foods that are naturally high in folic acid include spinach (130 µg/half cup), navy beans (125 µg/cup), wheat germ (80 µg/cup), avocados (55 µg/cup), and oranges (45 µg/cup)
Fortification of pasta, rice, cornmeal, and flour with 0.15 mg folic acid per 100 g was mandated in the U.S. in 1998, but this is not sufficient to meet levels required to prevent NTDs; folic acid supplementation is still recommended
Infection:

Seeking prompt treatment for infections such as meningitis and other diseases that are associated with hydrocephalus
Physical activity:

Measures should be taken to reduce the risk of post-traumatic hydrocephalus. Infants and children can be protected from head injury by careful handling and by ensuring that a helmet is worn during activities such as cycling, skateboarding, and rollerblading