Introduction to Hydrocephalus

Hydrocephalus is a condition characterized by an abnormal accumulation of cerebrospinal fluid (CSF) within the ventricles or subarachnoid space of the brain. This accumulation leads to increased intracranial pressure, which can result in a variety of neurological symptoms and, if left untreated, can cause brain damage.

The condition can occur at any age but is most common in infants and older adults. It can be congenital (present at birth) or acquired later in life. Hydrocephalus is not a single disease but a pathophysiological condition with multiple causes, presenting challenges in diagnosis and management.

Etiology of Hydrocephalus

Hydrocephalus can result from various causes, which can be broadly categorized as follows:

• Congenital causes:
  • Neural tube defects (e.g., spina bifida, encephalocele)
  • Aqueductal stenosis
  • Dandy-Walker malformation
  • Chiari malformation
  • Genetic disorders (e.g., L1CAM mutations)
• Acquired causes:
  • Intracranial hemorrhage (especially intraventricular hemorrhage in premature infants)
  • Central nervous system infections (e.g., meningitis, cysticercosis)
  • Brain tumors
  • Head trauma
  • Subarachnoid hemorrhage
• Idiopathic Normal Pressure Hydrocephalus (iNPH): A specific form commonly seen in older adults, with unknown etiology.

Pathophysiology of Hydrocephalus

The pathophysiology of hydrocephalus involves an imbalance between CSF production and absorption. This can occur due to:

1. Obstruction of CSF flow: This can occur at various points in the ventricular system or subarachnoid space, leading to obstructive (non-communicating) hydrocephalus.
2. Impaired CSF absorption: Usually at the level of the arachnoid granulations, leading to communicating hydrocephalus.
3. Overproduction of CSF: Rare, but can occur in choroid plexus papillomas.

Based on the underlying mechanism, hydrocephalus is classified into:

• Obstructive (non-communicating) hydrocephalus: Due to a blockage within the ventricular system.
• Communicating hydrocephalus: Due to impaired CSF absorption or rarely, overproduction.
• Normal Pressure Hydrocephalus (NPH): A form of communicating hydrocephalus with normal CSF pressure but enlarged ventricles.

The increased intracranial pressure can lead to various pathological changes, including ventricular enlargement, compression of brain tissue, and potential ischemic damage.

Clinical Presentation of Hydrocephalus

The clinical presentation of hydrocephalus varies depending on the age of onset and the rate of CSF accumulation:

• In infants:
  • Rapid head growth (increased head circumference)
  • Bulging fontanelle
  • Prominent scalp veins
  • Sunset eye sign (downward gaze with visible sclera above the iris)
  • Irritability, poor feeding
  • Vomiting
  • Developmental delays
• In older children and adults:
  • Headache
  • Nausea and vomiting
  • Vision problems (e.g., papilledema, optic atrophy)
  • Cognitive impairment
  • Gait disturbances
  • Urinary incontinence
  • Lethargy or coma in severe cases
• In Normal Pressure Hydrocephalus:
  • Gait disturbance (magnetic gait)
  • Urinary incontinence
  • Cognitive decline (subcortical dementia)

The onset can be acute, subacute, or chronic, influencing the severity and progression of symptoms.

Diagnosis of Hydrocephalus

Diagnosis of hydrocephalus involves a combination of clinical evaluation and imaging studies:

1. Clinical assessment:
   • Detailed history and physical examination
   • Neurological examination
   • Head circumference measurement in infants
2. Imaging studies:
   • Ultrasonography: Used in infants with open fontanelles
   • CT scan: Shows ventricular enlargement and potential causes
   • MRI: Provides detailed images of brain structure, CSF flow, and potential etiologies
   • Cisternography: Can be used to assess CSF flow dynamics
3. CSF studies:
   • Lumbar puncture: To measure CSF pressure and analyze CSF composition
   • Continuous ICP monitoring: In some cases to assess pressure dynamics
4. Neuropsychological testing: Particularly useful in NPH to assess cognitive function

For suspected NPH, additional tests may include:

• Gait assessment
• Large-volume lumbar puncture (tap test)
• Extended lumbar drainage

Treatment of Hydrocephalus

The primary goal of treatment is to reduce intracranial pressure by diverting CSF flow. Treatment options include:

1. Shunt systems:
   • Ventriculoperitoneal (VP) shunt: Most common
   • Ventriculoatrial (VA) shunt
   • Ventriculopleural shunt
   • Lumboperitoneal shunt: For communicating hydrocephalus
2. Endoscopic Third Ventriculostomy (ETV):
   • Creates a bypass for CSF flow
   • Particularly useful in obstructive hydrocephalus
3. Choroid plexus cauterization: To reduce CSF production in select cases
4. Medical management:
   • Acetazolamide or furosemide: May be used temporarily to reduce CSF production
   • Treatment of underlying causes (e.g., tumors, infections)

Treatment choice depends on the type of hydrocephalus, age of the patient, and underlying cause. Regular follow-up is crucial to monitor shunt function and overall neurological status.

Complications and Prognosis of Hydrocephalus

Complications:

• Shunt-related complications:
  • Infection
  • Obstruction
  • Over-drainage or under-drainage
  • Shunt failure requiring revision
• Cognitive impairment
• Epilepsy
• Visual impairment
• Endocrine dysfunction

Prognosis:

Prognosis varies widely depending on:

• Underlying cause
• Age of onset
• Duration and severity before treatment
• Response to treatment

With appropriate treatment, many patients can lead normal or near-normal lives. However, some may experience long-term neurological deficits. Regular follow-up is essential for early detection and management of complications.

In NPH, approximately 60-80% of properly selected patients show improvement after shunt surgery, particularly in gait and urinary symptoms. Cognitive improvement may be less predictable.