Hydrocephalus diagnosis and shunt procedures

Hydrocephalus diagnosis and shunt procedures

Hydrocephalus diagnosis and shunt procedures

On this page

🧠 Pathophysiology - Brain Fluid Fiasco

  • Non-communicating (Obstructive): Blockage within the ventricular system prevents CSF from reaching the subarachnoid space.
    • Causes: Aqueductal stenosis, tumors, intraventricular hemorrhage.
  • Communicating: Impaired CSF reabsorption by arachnoid granulations; ventricles are in communication with the subarachnoid space.
    • Causes: Post-meningitis scarring, subarachnoid hemorrhage (SAH) debris.

⭐ Acute hydrocephalus after SAH is often obstructive (blood clots), while chronic is communicating (impaired absorption).

Hydrocephalus: Communicating vs. Non-communicating Causes

🧠 Head Full of Trouble

  • Presentation varies dramatically by age, primarily due to skull suture fusion status. ↑ ICP drives symptoms.
FeatureInfants (Open Sutures)Children & Adults (Fused Sutures)
Head/ICPMacrocephaly, bulging fontanellesHeadache (worse AM), papilledema
Eyes"Sunsetting" eyes (tonic downward gaze)6th nerve palsy (lateral gaze deficit)
FunctionIrritability, poor feeding, developmental delayGait instability, cognitive decline, lethargy
-   📌 **Hakim's Triad: "Wet, Wobbly, Wacky"**
-   Urinary incontinence, magnetic gait, dementia.

⭐ In NPH, gait disturbance is typically the first symptom to appear and the most likely to improve with CSF shunting.

Infant with hydrocephalus: clinical signs

🧠 Diagnosis - Spotting the Swell

  • Imaging (CT/MRI): First-line test shows ventriculomegaly.
    • For Normal Pressure Hydrocephalus (NPH), calculate the Evan's Index.
    • Evan's Index > 0.3 is diagnostic for NPH.
      • $Evan's\ Index = \frac{Maximal\ Frontal\ Horn\ Width}{Maximal\ Internal\ Skull\ Diameter}$
  • NPH Confirmation:
    • 💡 High-Volume Lumbar Puncture (LP Tap Test): Remove 30-50 mL CSF.
    • Transient improvement in gait/cognition predicts positive shunt response.

⭐ In NPH, ventriculomegaly is disproportionately large compared to sulcal effacement, distinguishing it from hydrocephalus ex vacuo (brain atrophy).

Axial and Coronal MRI: Ventriculomegaly in NPH

🧠 Management - Draining the Brain

  • Ventriculoperitoneal (VP) Shunt: The primary surgical treatment for most hydrocephalus types.
    • A catheter drains excess CSF from a lateral ventricle through a one-way valve.
    • The distal catheter is tunneled subcutaneously to the peritoneal cavity for CSF absorption.

Ventriculoperitoneal (VP) Shunt Placement in a Child

  • Endoscopic Third Ventriculostomy (ETV):
    • Alternative for obstructive hydrocephalus (e.g., aqueductal stenosis).
    • Creates a bypass by fenestrating the floor of the third ventricle, allowing CSF to flow directly into the interpeduncular cistern.

⭐ Shunt malfunction (obstruction, infection) is the most common complication. Infection risk is highest 1-3 months post-op, typically with Staphylococcus epidermidis.

⚠️ Complications - When Shunts Go South

  • Infection: Most common within 6 months post-op.
    • Causative organisms: Staphylococcus epidermidis (biofilm), S. aureus.
    • Presents with fever, ↑ICP signs, shunt site erythema.
  • Malfunction/Obstruction: Most common cause of shunt failure.
    • Proximal (ventricular catheter) or distal (peritoneal) blockage.
    • Presents with recurrent hydrocephalus symptoms.
  • Overdrainage: Excessive CSF removal.
    • Leads to slit ventricle syndrome (postural headaches).
    • Risk of subdural hematomas from torn bridging veins.

⭐ Shunt infection within the first few months is almost always due to skin flora (S. epidermidis) introduced during surgery.

⚡ Biggest Takeaways

  • Normal Pressure Hydrocephalus (NPH) presents with the classic triad: "wet, wobbly, and wacky" (incontinence, ataxia, dementia).
  • CT/MRI is the initial diagnostic test, showing ventriculomegaly. NPH diagnosis is supported by improvement after a high-volume LP.
  • Ventriculoperitoneal (VP) shunt is the definitive treatment for most forms of hydrocephalus.
  • Key shunt complications include infection (S. epidermidis), obstruction, and overdrainage (subdural hematoma).
  • In infants, suspect hydrocephalus with a rapidly increasing head circumference, bulging fontanelle, and sunset eyes.

Practice Questions: Hydrocephalus diagnosis and shunt procedures

Test your understanding with these related questions

A 25-year-old man with no significant past medical history is brought in by ambulance after a witnessed seizure at home. On physical exam, temperature is 102.3 deg F (39.1 deg C), blood pressure is 90/62 mmHg, pulse is 118/min, and respirations are 25/min. He is unable to touch his chin to his chest and spontaneously flexes his hips with passive neck flexion. Appropriate empiric treatment is begun. CT head is unremarkable, and a lumbar puncture sample is obtained. Gram stain of the cerebrospinal fluid (CSF) reveals gram-positive diplococci. Which of the following would you expect to see on CSF studies?

1 of 5

Flashcards: Hydrocephalus diagnosis and shunt procedures

1/6

Herniated contents may be at risk for _____, which is characterized by ischemia and necrosis

TAP TO REVEAL ANSWER

Herniated contents may be at risk for _____, which is characterized by ischemia and necrosis

strangulation

browseSpaceflip

Enjoying this lesson?

Get full access to all lessons, practice questions, and more.

Start Your Free Trial