Hydrocephalus

Definition & Types - Brainy Waterworks

• Definition: Excess CSF → ventricular dilation ± ↑ICP.
• Types:
  • Communicating (Non-obstructive): Impaired CSF reabsorption (arachnoid villi) or rare CSF overproduction (choroid plexus papilloma).
    • Causes: Post-meningitis, SAH.
  • Non-communicating (Obstructive): CSF flow blocked within ventricles/outlets.
    • Causes: Aqueductal stenosis, tumors, Chiari malformations.
  • Normal Pressure Hydrocephalus (NPH): Communicating type. Triad: Gait disturbance, Dementia, Urinary incontinence (📌 Wet, Wobbly, Wacky).
  • Hydrocephalus ex-vacuo: Ventricular dilation from brain atrophy; normal ICP. Not true hydrocephalus.

⭐ Aqueductal stenosis is the most common cause of congenital hydrocephalus.

Pathophysiology - CSF Traffic Jam

Hydrocephalus: Imbalance in CSF production, flow, or absorption.

• Mechanisms causing CSF build-up:
  • Obstruction (Non-communicating): Blockage within ventricular pathways.
    • 📌 Aqueductal stenosis: Most common site.
    • Others: Tumors, IVH, congenital malformations.
  • Impaired Absorption (Communicating): Dysfunction at arachnoid granulations.
    • Post-infectious (meningitis), post-hemorrhagic (SAH).
  • Overproduction (Rare): e.g., Choroid plexus papilloma.
• Consequences: Ventricular dilation → ↑ICP, neurological deficits.

⭐ Aqueductal stenosis: most common cause of congenital hydrocephalus; key site for non-communicating type.

Clinical Features - Spotting the Swell

• Infants (Open Fontanelles/Sutures):
  • Head: Rapidly ↑ head circumference (HC), crossing centiles.
  • Fontanelle: Bulging, tense anterior.
  • Sutures: Split, widened.
  • Scalp veins: Dilated, prominent.
  • Macewen sign ("cracked pot" sound). 📌 "Mac's Pot"
  • Eyes: "Setting sun" sign (downward gaze).
  • General: Irritability, poor feeding, vomiting.
  • 
• Older Children (Fused Sutures):
  • ↑ ICP signs:
    • Headache (AM, improves with vomiting).
    • Nausea, vomiting (AM, projectile).
    • Papilledema.
    • CN VI palsy (diplopia).
  • Other: Gait ataxia, spasticity, cognitive decline.
  • Late: Cushing's triad (hypertension, bradycardia, irregular respirations).

⭐ "Setting sun" sign: Paresis of upward gaze in infants, due to pressure on tectal plate (Parinaud's syndrome).

Diagnosis - Brain Scan Clues

• Imaging:
  • USG (infants): Initial.
  • CT: Acute.
  • MRI: Gold standard (etiology).
• Ventriculomegaly Signs:
  • Evans' Index > 0.3.
  • Temporal horn dilatation (early).
  • "Mickey Mouse" sign (frontal horns, coronal). 📌
• Other Clues:
  • Periventricular lucency/hyperintensity (CSF seepage).
  • Effaced sulci.
  • Corpus callosum: Stretched, upward bowed.
• Type (MRI):
  • Non-communicating: Obstruction (e.g., aqueductal stenosis → triventricular hydrocephalus).
  • Communicating: Diffuse dilatation, patent pathways.

⭐ Triventricular hydrocephalus (dilated lateral/3rd ventricles, normal 4th) on MRI strongly suggests aqueductal stenosis.

Management & Complications - Drain & Outlook

• Surgical (Mainstay):
  • VP Shunt: Most common; programmable/fixed pressure valves.
  • ETV (Endoscopic Third Ventriculostomy): For non-communicating hydrocephalus; ETV Success Score (ETVSS) guides.
• Medical (Adjunctive/Temporary): Acetazolamide, Furosemide (↓CSF production).
• Shunt Complications:
  • Infection (5-15%): S. epidermidis/aureus.
  • Malfunction/Obstruction: Signs of ↑ICP.
  • Overdrainage: Subdural collections, slit ventricle syndrome.
• Outlook: Variable; depends on cause, timely management. Lifelong follow-up.

  ⭐ Shunt infection, often by Staphylococcus epidermidis, is the most frequent serious complication, necessitating shunt removal, EVD, and antibiotics.

High-Yield Points - ⚡ Biggest Takeaways

• Hydrocephalus is an abnormal CSF accumulation causing ventricular dilatation and ↑ICP.
• Key types: Communicating (impaired absorption) and Non-communicating/Obstructive (CSF flow blockage).
• Infants present with rapid head growth, bulging fontanelle, and sunset sign.
• Older children show headache, vomiting, papilledema, and gait ataxia.
• Common causes include aqueductal stenosis, meningitis, IVH, and posterior fossa tumors.
• Diagnosis via ultrasound in infants; CT/MRI are definitive imaging.
• Mainstay of treatment is ventriculoperitoneal (VP) shunt; ETV for obstructive types.