Ventriculoperitoneal Shunt

Aka: Ventriculoperitoneal Shunt, Ventriculo-Peritoneal Shunt, Cerebrospinal Fluid Shunt, CSF Shunt, VP Shunt, Ventriculoperitoneal Shunt Malfunction, Shunt Series XRay, Ventriculostomy

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II. Indications: VP Shunt for Hydrocephalus (CSF accumulation)

  1. Intraventricular Hemorrhage of prematurity
  2. Spina bifida
  3. Lisencephaly
  4. Holoprosencephaly
  5. Meningitis complication

III. Technique: Shunt position

  1. VP Shunt proximal catheter tip
    1. Ventricles
  2. Reservoir and One-Way Valve
    1. Located at edge of skull
    2. Distal tube and proximal tube connect to the one-way valve (which does not allow back flow into brain)
    3. One way valve should be compressible (unless obstructed)
  3. VP Shunt course
    1. Subcutaneously via the right parietal scalp and down neck
  4. VP Shunt distal tip
    1. Peritoneum (most common)
    2. Alternative sites (if limited by prior peritonitis history)
      1. Pleural space
      2. Right atrium
      3. Lumbar region

IV. Complications: Shunt

  1. Mechanical shunt malfunction (presumed cause until proven otherwise)
    1. Shunt obstruction (see management below)
    2. Detached shunt tubing or otherwise broken shunt
    3. Shunts Fracture most commonly in the distal tubing (esp. near clavicle or lower ribs)
    4. Cannula dislodged with inadequate drainage
    5. Shunt failure occurs in 40% within 1 year and in 50% by 2 years after implantation
  2. Infection
    1. Complicates 3-10% of shunt procedures
      1. Accounts for up to 60% of shunt-related mortality
      2. Very old and very young are at highest infection risk
    2. Causes
      1. Typically within 8 weeks of shunt placement, manipulation or revision (accounts for 70% of shunt infections)
      2. Ascending infection may occur (e.g. peritonitis from Appendicitis)
    3. Findings of suspected shunt infection
      1. Meningismus
      2. Fever without a source
      3. Persistent Abdominal Pain
    4. Consult with neurosurgery
      1. Neurosurgery typically performs shunt tap as described below
      2. In some cases, neurosurgery will remove the shunt and temporize with external ventricular drain
    5. Start Antibiotics as soon as shunt tap completed
      1. In some cases they will recommend starting Antibiotics prior to shunt tap
      2. Vancomycin is typically used
      3. Staphylococcus Epidermidis (or other skin flora) causes 75% of shunt infections
        1. Also cover for abdominal flora (due to distal tubing in Abdomen)
  3. Intraabdominal complications (especially if distal tip migration)
    1. Ascites
    2. Peritonitis
    3. Ruptured Viscus
  4. Excessive removal of fluid (less common now with programmable shunts)
    1. Postural Headache
    2. Subdural Hematoma (result from tearing of bridging veins)

V. Complications: Shunt obstruction

  1. Initial symptoms
    1. Positional Headache
      1. Worse when upright and improved while supine
    2. Lethargy or Somnolence
    3. Vomiting
    4. Children with subacute presentation may have behavioral changes, feeding problems, irritability, Headaches
  2. Later symptoms suggestive of imminent Herniation
    1. Cranial Nerve palsy
    2. Unilateral pupilary dilation (Blown Pupil)
    3. Upward Gaze Paralysis (eye sunsetting)
    4. Cushing's Triad (Hypertension, Bradycardia, Irregular breathing)
    5. Altered Mental Status
    6. Bulging Fontanelle or Bradycardia (infants)
  3. Findings
    1. Shunt one-way valve (at lateral skull) is not compressible
    2. Acute Hydrocephalus
  4. Unrelated findings
    1. Seizure Disorders are common among children with Hydrocephalus
      1. Shunt obstruction presents with Seizures uncommonly (<3% of cases)
      2. Isolated Seizure without other findings does not require additional evaluation
    2. Head Trauma
      1. VP Shunts do not appear to significantly increase complications from minor Head Trauma

VI. Imaging" Preferred Studies

  1. Head Circumference (exam)
    1. Compare measurement to prior Head Circumference measurements (significant increase ay suggest obstruction)
  2. Head Ultrasound
    1. Consider in infants with open Fontanelles
  3. CT Head (or MRI Brain)
    1. Normal CT Head with unchanged ventricles in 11% of shunt obstruction cases
    2. Abnormal CT with enlarged ventricles indicates neurosurgical revision of shunt
    3. Low dose CT Head or MRI should be considered in non-critically ill children
      1. See CT-associated Radiation Exposure
    4. Findings
      1. Ventricular size (Hydrocephalus, ventriculomegaly)
      2. Obstructive lesions (e.g. CNS Mass, Subarachnoid Hemorrhage)
      3. CNS Structural abnormalities
      4. Findings of Increased Intracranial Pressure
        1. Midline shift
        2. Brainstem Herniation
        3. Cerebral Ventricle or basilar cistern effacement (compressed, flattened, or obliterated)
        4. Loss of differentiation between grey and white matter
    5. Precautions: Shunt malfunction suspected despite negative Head CT
      1. Consult with neurosurgery
      2. Consider shunt tap
  4. Ultra-low dose whole body CT
    1. Fully evaluates VP Shunt complications with 100% Test Sensitivity and Specificity
    2. Actionable for surgical planning and intervention
    3. Less than half the Radiation Exposure (0.67 mSv) than conventional shunt series (1.57 mSv)
    4. Afat (2022) AJNR Am J Neuroradiol 43(11): 1597-602 [PubMed]

VII. Imaging: Shunt Series XRays

  1. Evaluates for CSF Shunt Fracture, migration, twisting or disconnection
  2. Views include anterior skull, posterior skull, lateral skull, Chest XRay, KUB Xray
  3. Alternative imaging is preferred over shunt series due to low efficacy
    1. Predicting need for intervention in suspected shunt malfunction is better with alternative imaging
      1. Shunt Series XRays do not typically affect surgical decisions (in contrast to CT Head)
      2. Consider ultra-low dose whole body CT if entire shunt course needs evaluation (see above)
    2. Young infants with open Fontanelles and Sutures
      1. Obtain Head Ultrasound instead
    3. Children
      1. Low-dose Head CT (non-contrast)
      2. Brain MRI (requires sedation in young children)
    4. Adults
      1. Head CT (non-contrast)
  4. Indications (historical)
    1. Trauma to tubing
    2. Suspected kinking or tube disruption (e.g. subcutaneous fluid collection)
      1. Shunts Fracture most commonly in the distal tubing (esp. near clavicle or lower ribs)
    3. CNS Imaging is abnormal suggesting increased Hydrocephalus or Intracranial Pressure
      1. Only obtain if mechanical shunt complications are suspected
  5. Efficacy
    1. VP Shunt series, adds little if CT Head (or MRI) is without acute changes
      1. Docter (2019) J Emerg Med PMID: 31806435 [PubMed]
    2. VP Shunt series has poor Test Sensitivity
      1. VP Shunt failure Test Sensitivity <=31%
      2. Desai (2007) Pediatr Radiol 37(5):452-6 [PubMed]

VIII. Management: Shunt Malfunction with signs Herniation

  1. See Increased Intracranial Pressure for emergent management of ICP increase
  2. Emergency - involve neurosurgery immediately!
  3. Mortality of acute shunt obstruction: 1-2%
  4. Evaluate for symptoms of obstruction (see symptoms above)
  5. Evaluate for findings of imminent Herniation (see symptoms above)
  6. Obstruction is proximal in 80% of cases (proximal tip lodges)
  7. Distal obstructions may also occur in the peritoneum
  8. Reduce Intracranial Pressure
    1. See Increased Intracranial Pressure
    2. Emergent neurosurgery Consultation
    3. Consider shunt tap if neurosurgery not available (see below)
    4. Raise head of bed to 30 degrees
    5. Mannitol
      1. Hypertonic Saline does not appear to be an effective alternative

IX. Procedure: Shunt Tap

  1. Indications (only in cases where neurosurgery is not available in an adequate time frame)
    1. Suspected shunt malfunction with ill appearing patient
    2. Signs of shunt obstruction with Herniation
  2. Preparation
    1. Patient lies supine
  3. Identify shunt reservoir
    1. Shunt reservoir sits a few centimeters inferior to entry point in skull
    2. Palpable firm hub or tube swelling along the shunt course
      1. Second hub may be palpable in some patients
      2. Either hub may be accessed
    3. Mark hub site
  4. Technique
    1. Use sterile technique
      1. Apply antiseptic solution (Betadine or Chlorhexidine) to skin overlying hub
      2. Drape the skin and wear sterile gloves
    2. Insert 25 gauge butterfly needle into hub, perpendicular to scalp
      1. Attach 3-way stopcock and 5 cc syringe
    3. Allow CSF to freely flow
      1. Attach manometer (from Lumbar Puncture kit)
        1. Distal obstruction if CSF flows and opening pressure >15-20 cm H2O
        2. Proximal obstruction if no CSF flow (not correctable in emergency department)
        3. Only drain enough fluid until opening pressure <20 cm H2O
      2. Do not apply back pressure with the syringe (risk of Subdural Hematoma)
      3. CSF under pressure of obstruction should fill the syringe with force
    4. Post-procedure
      1. Send CSF for Gram Stain and culture
      2. Anticipate marked clinical improvement after shunt tap

X. References

  1. Jhun and Roepke in Herbert (2016) EM:Rap 16(3): 17-8
  2. Herbert (2012) EM:Rap 12(9): 4
  3. Behar and Claudius in Majoewsky (2013) EM:Rap 13(9): 9
  4. Jundoria, Dave, Hoag and Lopez (2026) Crit Dec Emeg Med 40(5): 4-11

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