Frederick A. Zeiler, MD

Patrick J. McDonald, MD, MHSc, FRCSC

DESCRIPTION

Hydrocephalus is an active distension of the ventricular system of the brain related to the inadequate passage of CSF from its point of production within the ventricular system to its point of absorption into the systemic circulation (1).

EPIDEMIOLOGY

Incidence

Congenital hydrocephalus affects approximately 3–4 per 1,000 live births and is commonly associated with any congenital brain malformation. The overall combined incidence of congenital and acquired hydrocephalus in both children and adults is not known.

Prevalence

Difficult to determine due to most studies only quoting pediatric cases. Mathematical models predict the prevalence of adult and children shunt dependent in the US to be 290,000 patients in 2010 (2) though the real number is unknown.

RISK FACTORS

• Risk factors for hydrocephalus include prematurity (from intraventricular hemorrhage), several first-degree male relatives with congenital hydrocephalus, meningitis, intracranial hemorrhage (especially subarachnoid and intraventricular hemorrhage), congenital brain malformations (spinal dysraphism, Chiari malformations), posterior fossa, and third ventricle tumors.
• Pregnancy is not contraindicated in women with treated hydrocephalus. Development of hydrocephalus during pregnancy is rare.

Genetics

Although most cases are acquired, up to 40% of cases of hydrocephalus have a possible genetic cause, with up to 43 mutants/loci being identified (3). A number of genetic disorders are associated with hydrocephalus, such as X-linked hydrocephalus, cytogenetic abnormalities including trisomies 9, 3, and 18, and Mendelian conditions such as Hurler's syndrome, Walker–Warburg syndrome, and the craniosynostosis syndromes (Crouzon's and Apert’s).

GENERAL PREVENTION

No real general preventative measures.

PATHOPHYSIOLOGY

Results from an excess of CSF in the brain due to an increase in production of CSF or, more commonly, an obstruction of normal CSF flow or decreased absorption of CSF. The result of this overabundance of CSF is an increase in intracranial pressure (ICP) with corresponding enlargement of the ventricular system of the brain.

ETIOLOGY

Hydrocephalus can be congenital or acquired and communicating or obstructive (noncommunicating). Acquired hydrocephalus can occur after intracranial hemorrhage, especially intraventricular hemorrhage associated with prematurity, infection, or severe head trauma, or in association with brain tumors. In addition, normal pressure hydrocephalus (NPH) can occur in adults.

COMMONLY ASSOCIATED CONDITIONS

Myelomeningocele (80–90% require shunts), Chiari malformations, certain genetic disorders (see “Genetics”), brain tumors, intracranial hemorrhage, severe head trauma, CNS infections.

[Outline]

• Information
• Description
• Epidemiology
  • Incidence
  • Prevalence
• Risk Factors
  • Genetics
• General Prevention
• Pathophysiology
• Etiology
• Commonly Associated Conditions

HISTORY

Headache, nausea, and vomiting, diplopia, vision changes, decreased level of consciousness, confusion or difficulty concentrating in older patients. In children, irritability is commonly seen in hydrocephalus. In NPH, there is a classic triad of dementia, gait abnormalities, and urinary incontinence.

PHYSICAL EXAM

Papilledema, abducens and upward gaze palsies, and gait changes. In young children, enlarging head circumference, a bulging and tense fontanelle, splayed sutures, bradycardia, and sunsetting eyes.

DIAGNOSTIC TESTS AND INTERPRETATION

Lab

Initial Lab Tests

No laboratory tests diagnose hydrocephalus.

Follow-Up & Special Considerations

With suspected CSF infection, CSF should be sampled prior to placement of a CSF shunt.

Imaging

Initial Approach

CT, MRI, or ultrasound (in infants) scans shows enlargement of the ventricular system and may show the underlying cause of the hydrocephalus.

Follow-Up & Special Considerations

• MRI scan is indicated in cases of suspected aqueductal stenosis and to rule out associated Chiari malformations.
• In cases of suspected NPH, a number of ancillary tests to predict responsiveness of NPH to shunting are available. These include a nuclear medicine CSF flow study (using^99mTc-DPTA) and lumbar puncture (LP). A patient whose symptoms improve after withdrawal of CSF by LP may be more likely to respond to permanent CSF shunting.

Diagnostic Procedures/Other

• Diffusion weighted and diffusion tensor MRI sequences can offer understanding of CSF flow through subarachnoid spaces and the degree of changes in white matter tracts, respectively (3).
• Antenatal U/S and MRI may be utilized (4).

Pathological Findings

Destruction of the ependymal lining of the ventricle, compression of peri-ventricular blood vessels, stretching of axons, and eventual loss of neuronal connections (5).

DIFFERENTIAL DIAGNOSIS

Brain atrophy (resulting in ex vacuo hydrocephalus) secondary to brain ischemia and neurodegenerative disorders, benign intracranial hypertension, hydranencephaly, developmental anomalies (agenesis of the corpus callosum, septo-optic dysplasia).

[Outline]

• History
• Physical Exam
• Diagnostic Tests and Interpretation
  • Lab
    • Initial Lab Tests
    • Follow-Up & Special Considerations
  • Imaging
    • Initial Approach
    • Follow-Up & Special Considerations
  • Diagnostic Procedures/Other
  • Pathological Findings
• Differential Diagnosis

MEDICATION

First Line

Medication is not the first-line treatment in hydrocephalus. Mannitol can be considered in the acute management of elevated ICP. Acetazolamide may temporarily decrease CSF production but is not a long-term therapy

Second Line

None indicated.

ADDITIONAL TREATMENT

General Measures

Once the diagnosis is established and the need for treatment confirmed, one should proceed to the specifically indicated surgical option. In cases of acute hydrocephalus where ICP is elevated to a life-threatening level, the usual emergency measures used to lower ICP can be done (elevate the head of the bed, administer 1 g/kg mannitol IV). These measures cannot be a substitute for prompt neurosurgical management of the underlying problem. In cases of neonatal intraventricular hemorrhage, serial LP or ventricular taps can be done until the child has grown large enough that a permanent shunt can be placed.

Issues for Referral

Patients typically follow-up post operatively in 4–6 weeks, after which annual follow-up with a neurosurgeon is typical.

Additional Therapies

None

COMPLEMENTARY AND ALTERNATIVE THERAPIES

• Symptomatic treatment
  • The mainstay of symptomatic treatment is surgical therapy.
• Adjunctive treatment
  • Supportive care, especially in children, involves monitoring of heart and respiratory rates. Bradycardia and periods of apnea can be ominous signs of increased ICP.

SURGERY/OTHER PROCEDURES

Surgical treatment is the mainstay of therapy for hydrocephalus. Several surgical options are available, the goal of which is to bypass the regular CSF pathways (6)[A],(7)[A],(8)[A].

• CSF shunt
  • As a permanent solution to hydrocephalus, closed ventricular draining systems have been in use for >50 years. All CSF shunting systems consist of a proximal ventricular catheter; a 1-way valve and reservoir; and a distal catheter terminating in another body compartment. The most common sites for termination of the distal catheter are (in order) the peritoneum, the pleural space, and the venous system (usually the right atrium or superior vena cava).
• Endoscopic third ventriculostomy (6)[A]
  • In selected cases of hydrocephalus, specifically aqueductal stenosis, where the fourth ventricle is normal in size and the lateral and third ventricles enlarged, endoscopic third ventriculostomy (ETV) is a treatment option. In this procedure, a fiberoptic endoscope is passed into the lateral ventricle and then into the third ventricle through the foramen of Munro. A hole is made in the floor of the third ventricle, bypassing the obstruction at the aqueduct. A successful ETV will obviate the need for a permanent CSF shunt. ETV is less successful in cases of hydrocephalus without aqueductal stenosis.
• External ventricular drainage
  • In cases where placement of a permanent shunt is not feasible (e.g., infection or acute hemorrhage) or where drainage of CSF is required temporarily until CSF flow pathways are reestablished (e.g., posterior fossa tumor), placement of an external ventricular drain (EVD) can be a temporizing measure until a permanent shunt can be placed or the indication for CSF diversion is no longer present. The drain is passed into the lateral ventricle and tunneled out through the scalp, draining into an external system. Prolonged use of an EVD is associated with a high CSF infection rate.

IN-PATIENT CONSIDERATIONS

Initial Stabilization

Revolves around acute ICP management and prompt CSF diversion.

Admission Criteria

All patients with symptomatic hydrocephalus should be admitted for management of the condition.

IV Fluids

No specific recommendations in the literature; wavoiding hypotonic solutions recommended as these could aggravate ICP issues.

Nursing

Close monitoring of neuro-vital signs is recommended in the acute phase.

Discharge Criteria

Patients can be discharged within 1–3 days of surgery provided their symptoms of increased ICP have resolved and the surgeon is satisfied that the shunt is functioning properly. Many neurosurgeons obtain a CT or MRI scan of the brain before discharge to ensure that the ventricular catheter is in proper position and the ventricles reduced in size.

[Outline]

• Medication
  • First Line
  • Second Line
• Additional Treatment
  • General Measures
  • Issues for Referral
  • Additional Therapies
• Complementary And Alternative Therapies
• Surgery/Other Procedures
• In-Patient Considerations
  • Initial Stabilization
  • Admission Criteria
  • IV Fluids
  • Nursing
  • Discharge Criteria

FOLLOW-UP RECOMMENDATIONS

Many neurosurgeons monitor on an annual basis with intermittent CT or MRI imaging. Imaging is indicated urgently if a shunt malfunction is suspected.

Patient Monitoring

CSF shunt devices are associated with a high failure rate (40% at 1 year) and infection rate (5–10%). As such, patients with shunt devices in situ require immediate attention should they develop symptoms of shunt failure. Symptoms of shunt failure or obstruction are similar to those of untreated hydrocephalus and include headache, nausea and vomiting, and a decreased level of consciousness. Evaluation of the patient with a suspected shunt malfunction includes a CT or MRI scan of the brain and a “shunt series” (a series of plain radiographs tracing the path of the shunt from the skull to the abdomen). In cases where shunt function is equivocal, a radionuclide shunt study can be undertaken to determine if the shunt is patent. Shunt infection can manifest as a shunt obstruction or as fever with no other identifiable source. Shunt infection can be diagnosed by sampling CSF from the shunt reservoir. When shunt malfunction or infection is suspected, immediate referral to a neurosurgeon is indicated. It is not uncommon for a shunted patient to develop subdural fluid collections, which can indicate CSF overdrainage.

DIET

No specific recommendations.

PATIENT EDUCATION

• Patients and families of those with treated hydrocephalus, either by a CSF-shunting device or ETV, should be educated as to the signs and symptoms of shunt failure and to seek prompt medical attention should they develop. Patients with CSF shunts can pursue all regular activities.
• Hydrocephalus Association of America
• Spina Bifida and Hydrocephalus Association of Canada

PROGNOSIS

CSF-shunting devices are associated with a high failure rate. Prior to the development of an adequate surgical treatment of hydrocephalus, the outcome was universally poor. With the use of shunts, mortality for infants with non-tumor–related hydrocephalus has dropped from 64% (9) to 3–10%. Seventy percent are socially independent and <10% are unemployable.

COMPLICATIONS

Shunt failure, shunt infections, slit ventricle syndrome, and intracranial hypotension from excessive CSF drainage and acute neurological impairment from ETV can occur.

[Outline]

• Follow-Up Recommendations
  • Patient Monitoring
• Diet
• Patient Education
• Prognosis
• Complications

ICD9

• 331.3 Communicating hydrocephalus
• 331.4 Obstructive hydrocephalus
• 742.3 Congenital hydrocephalus

• Acute hydrocephalus is an emergency and can be fatal if not diagnosed and treated promptly.
• Proper patient education is necessary to identify signs and symptoms of worsening hydrocephalus.
• CT or MRI is the first-line imaging study.
• Close long-term neurosurgical follow-up is needed in all patients.

1. Rekate HL. A contemporary definition and classification of hydrocephalus. Semin Pediatr Neurol 2009;16:9–15.
2. Stein SC, Wensheng G. The prevalence of shunt treated hydrocephalus: a mathematical model. Surg Neurol 2009;72:131–137.
3. Zhang L, Williams MA, Rigamonti D. Genetics of human hydrocephalus. J Neurol 2006;253:1255–1266.
4. Rich P, Jones R, Britton J, et al. MRI of the foetal brain. Clin Radiol 2007;62:303–313.
5. Del Bigio M. Neuropathology and structural changes in hydrocephalus. Dev Disabil Res Rev 2010;16:16–20.
6. Drake J. The surgical management of pediatric hydrocephalus. Neurosurgery 2008;62(Suppl 2):633–642.
7. Bergsneider M, Miller C, Vespa PM, et al. Surgical management of adult hydrocephalus. Neurosurgery 2008;62(Suppl 2):643–660.
8. Hamilton MG. Treatment of hydrocephalus in adults. Semin Pediatr Neurol 2009;16:34–41.
9. Laurence K, Coates S. The natural history of hydrocephalus: detailed analysis of 187 unoperated cases. Arch Dis Child 1962;37:345–362.