How to Perform Shunt Tap

Ventriculoperitoneal (VP), ventriculoatrial (VA) and ventriculopleural shunts are commonly encountered neurosurgical devices used for chronic CSF diversion. A shunt tap is often required to evaluate for shunt problems.

• Indications:
  • Obtain CSF for analysis
  • Evaluate shunt function
  • Measure intraventricular pressure
  • Temporizing measure to remove CSF in a distally occluded shunt
  • Injection of antibiotic or chemotherapeutic agents
  • Injection of contrast agents
• Contraindications:
  • Scalp infection around shunt site
  • Severe coagulopathy or platelets <25K
  • Collapsed or slit ventricles
• Anesthesia:
  None usually needed
• Equipment:
  • Sterile prep solution
  • Sterile gloves and towels
  • 25-gauge or 23-gauge butterfly needles
  • 10-ml syringe
  • Manometer with stopcock
• Positioning:
  Supine
• Technique:
  • Palpate scalp for shunt bulb, which is usually in the right frontal or right occipital regions within 2 cm of the scalp incision used to insert the shunt. Do not tamper with other shunt components because this may affect shunt function.
    
  • Shave and prep the area for 5 minutes.
  • Introduce the butterfly needle into bulb at a slight oblique angle and observe for spontaneous flow of CSF into tubing.
    
  • Attach stopcock with manometer to end of tubing, ensuring that the zero level on the manometer is level with the bulb. Alternately, if no manometer is available, the distance that CSF travels up the butterfly tubing when held vertically may be measured.
  • If no spontaneous CSF flow is observed, take 5-ml syringe and gently attempt to aspirate CSF. If CSF is aspirated easily, then the ventricular pressure is at or near zero. If CSF is difficult to aspirate or no CSF is obtained, then the proximal end of the shunt is occluded or the ventricles are collapsed, and aborting the procedure is necessary.
  • • Send CSF for laboratory analysis.
    • Inject chemotherapeutic or antimicrobial agent if desired.
    • Withdraw needle and hold gentle pressure over bulb.
  • Complications and Management:
    • Ventriculitis
      • Every time the shunt is manipulated, there is a chance of introducing infection into the system.
      • In patients with systemic infection with no obvious central nervous system source whose shunt was placed more than 2 months prior to the date of the intended tap, a lumbar puncture should be performed rather than a shunt tap to reduce the chance of seeding the shunt.
    • Occlusion
      • In patients with collapsed or slit-like ventricles, attempting to aspirate CSF can cause occlusion of the proximal shunt. A head CT should always be obtained prior to shunt tap to minimize the risk of this complication.