What is hydrocephalus?

Hydrocephalus: Definition, Diagnosis, and Management

Hydrocephalus is a condition characterized by abnormal accumulation of cerebrospinal fluid (CSF) in the brain's ventricles, which may cause increased intracranial pressure (ICP) and lead to significant morbidity and mortality if left untreated. 1

Clinical Presentation

Hydrocephalus presents with a constellation of symptoms that vary depending on age of onset, acuity, and underlying cause:

• Common symptoms include:

  • Headache
  • Alteration in sensorium/consciousness
  • Gait abnormality
  • Urinary incontinence
  • Nausea and vomiting
  • Cognitive changes 2

• In infants:

  • Increased head circumference
  • Bulging fontanelles
  • Developmental delays

Etiology

Hydrocephalus can be classified based on cause:

1. Congenital hydrocephalus:

   • Neural tube defects
   • Aqueductal stenosis
   • Genetic syndromes 1

2. Acquired hydrocephalus:

   • Post-infectious: Following meningitis or ventriculitis
   • Post-hemorrhagic: After intraventricular hemorrhage (IVH) or subarachnoid hemorrhage
   • Secondary to tumors: Obstruction of CSF pathways
   • Post-traumatic: Following traumatic brain injury
   • Normal pressure hydrocephalus (NPH): Typically in older adults 2

Pathophysiology

Hydrocephalus develops through several mechanisms:

1. Obstruction of CSF flow (non-communicating hydrocephalus)
2. Impaired CSF absorption (communicating hydrocephalus)
3. Excessive CSF production (rare)

The obstruction can occur at various points in the ventricular system, leading to ventricular enlargement and potentially increased ICP 2, 3.

Diagnosis

Diagnosis relies on clinical assessment and neuroimaging:

• Neuroimaging:

  • MRI: Preferred for detailed assessment of ventricular size, etiology, and associated abnormalities
  • CT scan: Often used in emergency settings
  • Ultrasound: Used in infants with open fontanelles 2

• Key imaging findings:

  • Ventriculomegaly (enlarged ventricles)
  • Transependymal edema in acute cases
  • Potential identification of obstruction site 2

• Additional diagnostic tools:

  • Lumbar puncture: To measure opening pressure (with caution in suspected obstructive hydrocephalus)
  • ICP monitoring: In selected cases 2

Management

Acute Management of Increased ICP

For patients with acute hydrocephalus and elevated ICP:

1. External ventricular drainage (EVD):

   • Indicated for patients with decreased level of consciousness and hydrocephalus
   • Allows for CSF drainage and ICP monitoring
   • Reduces mortality in patients with hydrocephalus 2

2. ICP monitoring:

   • Consider in patients with GCS ≤8 or clinical evidence of transtentorial herniation
   • Target cerebral perfusion pressure (CPP) of 50-70 mmHg 2

3. Medical management:

   • Head positioning: Elevate head of bed 30° to facilitate venous drainage
   • Hyperosmolar therapy: May be used for transient ICP reduction, though efficacy of prophylactic use is not well established
   • Avoid corticosteroids: Not recommended for ICP management in hydrocephalus 2

Definitive Treatment

1. Surgical CSF diversion:

   • Ventriculoperitoneal (VP) shunt: Most common permanent treatment
   • Endoscopic third ventriculostomy (ETV): Alternative to shunting in selected cases
   • Lumboperitoneal shunt: Used in specific scenarios 2, 3

2. Pharmacological approaches:

   • Limited role in definitive management
   • Acetazolamide (with or without furosemide) may be used in specific circumstances as temporary measures
   • Fibrinolytic therapy may be considered for intraventricular hemorrhage with hydrocephalus 4

Complications and Monitoring

Common complications include:

1. Shunt malfunction: Obstruction, infection, or mechanical failure
2. Shunt infection: Requires prompt identification and treatment
3. Over-drainage: Can lead to subdural collections
4. Under-drainage: Persistent or recurrent hydrocephalus 5, 3

Special Considerations

1. Hydrocephalus in pregnancy:

   • Treatment should be considered before pregnancy when possible
   • Management during pregnancy requires careful risk-benefit analysis 2

2. Pediatric hydrocephalus:

   • Higher lifetime risk of complications
   • May require multiple shunt revisions throughout life
   • Careful monitoring of developmental outcomes 2

3. Post-hemorrhagic hydrocephalus:

   • Common after intraventricular hemorrhage
   • May require temporary EVD followed by permanent shunting 2

Hydrocephalus remains a significant clinical challenge requiring prompt diagnosis and appropriate intervention to minimize morbidity and mortality. Ongoing research into improved shunt technologies and potential pharmacological treatments offers hope for better outcomes in the future.