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

1. Proximal obstruction
   1. Tissue debris
   2. Choroid plexus
   3. Clot
   4. Infection
   5. Catheter-tip migration
   6. Localized immune response to the tubing
2. Distal obstruction
   1. Kinking or disconnection of the tube
   2. Pseudocyst formation
   3. Infection

Mechanical Failure

Causes

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

Overdrainage (Slit Ventricle Syndrome)

Background

• 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

Background

• 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

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

Management

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

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

Management

1. Emergent neurosurgical consultation and admission
2. Shunt tap
   1. LP often misses CSF shunt infections and has no role when shunt infection is suspected
3. Imaging
   1. Useful to exclude mechanical shunt malfunction (often coexists w/ infection)
4. Abx
   1. CTX + vancomycin

Source

Tintinalli