Ventriculoperitoneal shunt complications

Background

• Highest incidence of postoperative complications of any neurosurgical procedure
• May drain into peritoneal cavity or less commonly the R atrium, pleural cavity, ureter, GB

Clinical Features

• Develop over several days
• Adults
  • Cephalgia, N/V, lethargy, ataxia, altered mental status
  • Paralysis of upward gaze, dilated pupilsCN palsies
• Infants
  • Vomiting, irritability, bulging fontanelle

Obstruction

Background

• Most common type of shunt malfunction
  • Usually occurs at proximal tubing, followed by distal tubing followed by valve chamber
• Proximal obstructions usually occurs within first years of insertion
• Distal obstruction usually occurs only with shunts in place for >2yr

Causes

• Proximal obstruction
  • Tissue debris
  • Choroid plexus
  • Clot
  • Infection
  • Catheter-tip migration
  • Localized immune response to the tubing
• Distal obstruction
  • Kinking or disconnection of the tube
  • Pseudocyst formation
  • Infection

Mechanical Failure

• Causes
  • Fracture of tubing
    • Occurs many years after shunt placement in distal tubing
    • May present w/ mild symptoms of incr ICP and local symptoms of pain, erythema, edema
  • Disconnection
    • Occurs shortly after insertion
  • Migration
  • Misplacement
    • Usually manifests postoperatively

Overdrainage (Slit Ventricle Syndrome)

• Overdrainage -> tissue occluding the orifices of the proximal shunt apparatus
  • As pressure increases the occluding tissue diesengages allowing drainage to resume
  • Leads to cyclic incr ICP complaints that worsen when pt stands

Loculation of Ventricles

• Separate, noncommunicating CSF accumulations may develop within a ventricle
  • Shunt device unable to drain entire ventricular system -> incr ICP

Abdominal Complications

• Pseudocyst may form around the peritoneal catheter
  • Can lead to occlusion and/or abdominal pain (depending on size)

Work-Up

• Physical Exam
  • Neither Sn nor Sp
  • Locate valve chamber
    • Gently compress chamber and observe for refill
    • Difficulty compressing chamber indicates distal flow obstruction
    • Slow refill (>3s) indicates proximal obstruction
• Imaging
  • Shunt series
    • AP and lateral skull, AP chest and abdomen
    • Identifies kinking, migration, or disconnection
  • CT
    • Needed to evaluate ventricular size
    • Very helpful to compare to previous study (many pts w/ shunts have abnormal baseline)

Management

• Assume shunt malfunction in pts w/ suggestive features regardless of findings on imaging
• Shunt Tap
  • Should only be performed by emergency physician in an emergency
  • Alleviates incr ICP and helps make definitive diagnosis
  • Procedure
    • Prepare tap site in sterile manner
    • 23ga needle or butterfly attached to a manometer is inserted into the reservoir
      • If no fluid returns or flow ceases, a proximal obstruction is likely
    • Measure opening pressure (nl = 12 +/- 2)
      • Measure while reservoir outflow is occluded
      • Opening pressure >20 indicates distal obstruction; low pressure indicates proximal
    • Fluid removal (for incr ICP)
      • Remove slowly to avoid choroid plexus bleeding
      • Remove until pressure is 10-20

Infection

Background

• Occurrence
  • 50% within first 2 weeks of placement
  • 70% within 2 months of placement
  • 80% within 6 months of placement
  • 10% present >1 year after surgery

Types

• External Infection
  • Involve the subcutaneous tract around the shunt
• Internal Infection
  • Involves the shunt and CSF contained within the shunt

Bacteriology

• 50% of cases caused by S. epidermidis
• Also caused by S. aureus, Gram-negatives, anaerobes

Clinical Features

• Internal Infection
  • Mental status changes, HA, N/V, irritability
  • Neck stiffness (33% of pts)
  • Fever is often absent
  • Abdominal pain (VP shunt)
• External Infection
  • Swelling, erythema, tenderness along site of shunt tubing

Management

• Emergent neurosurgical consultation and admission
• Shunt tap
  • LP often misses CSF shunt infections and has no role when shunt infection is suspected
• Imaging
  • Useful to exclude mechanical shunt malfunction (often coexists w/ infection)
• Abx
  • Cefepime/Ceftazidime or carbapenem + vancomycin

See Also

CSF Studies

Source

Tintinalli