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CSF Shunts: A Primer

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CSF Shunts: A Primer. Tamara Simon, M.D. July 2004. Purpose. CSF flow: produced in choroid plexus of ventricles Flows through lateral ventricles, through foramen of Monro, to third ventricle Flows through aqueduct of Sylvius to fourth ventricle

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CSF Shunts:A Primer

Tamara Simon, M.D.

July 2004

purpose
Purpose
  • CSF flow:
    • produced in choroid plexus of ventricles
    • Flows through lateral ventricles, through foramen of Monro, to third ventricle
    • Flows through aqueduct of Sylvius to fourth ventricle
    • Flows through foramina of Lushka and Magendie to subarachnoid space
    • Reabsorbed by arachnoid villi and arachnoid granulations into the venous sinuses
  • Hydrocephalus develops when there is an increase in CSF production, decrease in CSF absorption, or (most commonly) obstruction to flow
procedure
Procedure
  • Allows for relief of hydrocephalus
  • Allows for prevention of increased ICP
    • Tumors
    • Congenital anomalies
    • Posttraumatic hemorrhage
    • Intraventricular hemorrhage
    • Postinfectious obstruction
    • Other causes
types of shunts
Types of Shunts
  • Named for position of proximal and distal catheters
  • Most commonly, ventriculoperitoneal shunts are placed
  • Proximal catheters are in lateral, third, or fourth ventricles or in intracranial cyst
  • Distal catheters can be in peritoneal space, right atrium, pleural space, gallbladder, ureter, urinary bladder, bone marrow, mastoid, thoracic duct, fallopian tube, and other locations
anatomy of a csf shunt
Anatomy of a CSF shunt
  • Proximal catheter
    • Placed in ventricle
    • Exits skull through burr hole
  • One way valve system
    • Allows one-way drainage of CSF at predetermined pressure differential
    • May be integrated into distal catheter or separate
    • On exterior of skull
anatomy of a csf shunt cont
Anatomy of a CSF shunt (cont)
  • Distal catheter
    • Tunneled under skin to final destination
  • Other components:
    • On-off valves
      • Used for intermittent shunting
      • Can be used to assess shunt function
    • Antisiphon devices
      • Prevents overdrainage of CSF
    • Reservoirs (single or double chamber)
      • Allows withdrawal of CSF or drug infusion
      • On exterior of skull proximal to one way valve
sample csf shunts
Sample CSF Shunts
  • Rickham reservoir with antisiphon device (left)
  • Single chamber reservoir (middle)
  • Rickham reservoir with double chamber reservoir/valve system (right)
temporary shunts
Temporary Shunts
  • In patients who have rapidly progressive ventriculomegaly or progressive or symptomatic ventriculomegaly, patients
    • can be quite small
    • have persistently proteinaceous and cellular CSF
    • be at high risk for shunt obstruction and infection
  • Some preterm infants will not evolve to permanent, shunt-dependent hydrocephalus by term, so a temporary technique is at times expeditious
    • Several studies cite 25% of patients with posthemorrhagic hydrocephalus ultimately recover
temporary shunts continued
Temporary Shunts (continued)
  • Surgeons believe that wound dehiscence and skin breakdown over shunt hardware are less frequent in larger infants as well
  • Clinical endpoint:
      • infant reaches term and
      • weight of 2 kg.
temporary shunt evd
Temporary Shunt: EVD
  • External ventricular drainage
  • Drain placed into CSF space and drained directly externally.
  • Pros: Attain temporary drainage
  • Cons:
    • drain interferes with nursing care
    • drain is easily dislodged
    • drain obstruction is frequent because of low CSF flow volumes
    • formidable risk of infection with prolonged drainage
temporary shunt subgaleal ventricular reservoir shunt
Temporary Shunt: Subgaleal Ventricular Reservoir/ Shunt

Reservoir and outlet of the shunt sit in the subgaleal space

CSF drains into a subgaleal pocket

Plug is removed if the surgeon intends to use the device as a shunt

Plug can be left in place, and the device can be used as a simple ventricular reservoir

temporary shunt subgaleal ventricular reservoir
Temporary Shunt: Subgaleal Ventricular Reservoir
  • Also called ventricular access device
  • Small, flat-bottomed reservoir attached to a ventricular catheter
    • reservoir sits on the surface of the skull under the galea of the scalp
    • percutaneous puncture of the reservoir with aspiration of CSF on a daily or every-other-day schedule serves to keep the ventricular system decompressed.
  • Clinical endpoints are arrest of ventricular dilatation, control of head growth, and elimination of symptoms and signs of elevated ICP.
temporary shunt subgaleal shunt
Temporary Shunt: Subgaleal Shunt
  • Ventricular access device with an outlet
  • Reservoir with outlet is placed in a large subgaleal pocket on the surface (hemicranium) of the skull
  • CSF decompression occurs by draining through the reservoir, out the outlet, into the subgaleal pocket
    • subgaleal space probably has some absorptive capacity
    • pocket also serves a simple mechanical function as a high-compliance receptacle for ventricular CSF
    • over weeks, scarring of scalp to periosteum obliterates the pocket, and periodic needle aspiration of the shunt reservoir can be initiated
  • Some believe that subgaleal shunts control ventricular volume more consistently
complication shunt malfunction
Complication: Shunt Malfunction
  • Most common complication, seen in 30-40% of shunt procedures and 67% of patients with shunts
  • Usually caused by simple obstruction
    • Debris, fibrosis, choroid plexus, or parenchymal occlusion of proximal catheter (first 2 years after placement in general)
    • Kinking, knotting, breaking, obstruction, migration of distal catheter (after 2 years after placement)
  • Also caused by infection, disconnection of shunt components, catheter migration, inadequate drainage, overdrainage
complication shunt malfunction1
Complication: Shunt Malfunction
  • Varied signs and symptoms
    • Swelling or erythema around shunt tract - Lethargy
    • Bulging or full fontanel - Ataxia
    • Increased head circumference - Neck pain
    • Headache - Back pain
    • Irritability - Blurred vision
    • Increased seizures - Sun setting eyes
    • Vomiting - Behavioral changes
    • Papilledema - Not acting right
  • Most predictive?
    • Vomiting, lack of fever, parental suspicion
complication infection
Complication: Infection
  • Second most common complication, seen in 2-30% of shunt procedures
  • Increased risk in children under 1 year of age, a short duration from shunt procedure
  • Most common organisms:
    • Coagulase-negative Staph species
    • Staph epidermidis
    • Staph aureus
    • Gram negative rods (6-20%)
    • Pathogens that cause meningitis (more remote)
complication infection1
Complication: Infection
  • Vague signs and symptoms
    • Swelling, erythema, cellulitis, or wound infection around shunt tract
    • Fever - Shunt malfunction
    • Nausea - Vomiting
    • Lethargy - Irritability
    • Headache -Change in sensorium
    • Feeding problems
  • When VP shunt is present, additionally:
    • Abdominal pain
    • Diarrhea
    • Peritonitis
complication slit ventricle syndrome
Complication: Slit Ventricle Syndrome
  • Found in 50-60% of patients, only symptomatic in 11-37%, require treatment in 6-7%
  • Overdrainage of CSF leads to collapse of ventricles, blocking fenestrations in proximal catheter, leading to increased ICP
  • Symptoms similar to shunt malfunction until ICP rises and ventricles re-expand
  • Some patients are position-sensitive and lying down increases ICP
  • Diagnosed when head CT shows small- to normal-sized ventricles
complication proximal catheter obstruction
Complication: Proximal Catheter Obstruction
  • Medical signs of increased ICP
    • Hyperventilation
    • Diuretics (acetazolamide, mannitol)
    • Elevate head of bed
    • Ventricular puncture through burr hole or open fontanel
complication vp shunts
Complication: VP Shunts
  • Inguinal hernia
    • Increased abdominal fluid increases intra-abdominal pressure, converting potential in clinical hernia
  • Perforation of hollow viscus
    • Bladder, stomach, small intestine, colon, gallbladder, vagina, anus, and mouth have been reported
    • Bowel perforation can present with peritonitis, meningitis, ventriculitis; with signs of shunt infection
  • Abdominal pseudocyst (0.8-10%)
    • Decreased appetite, abdominal pain, tenderness, distention, mass, and guarding; increased ICP and shunt malfunction
    • Foreign body reaction with chronic granulomatous inflammation
  • Migration of distal catheter tip
    • Through abdominal incision, through neck incision, into mediastinum, throacic cavity, umbilicus
complications other rare ones
Complications: Other Rare Ones
  • Intussusception
  • Intractable hiccup
  • Omental cyst torsion
  • Volvulus around catheter
radiographic studies
Radiographic studies
  • Shunt series
    • Plain radiographs of skull, neck, chest, abdomen
    • Used to detect disconnections, kinks, and migration of catheters
    • Proximal and distal catheters are radiopaque, reservoirs are radiolucent
  • Head CT
    • Demonstrates location of proximal catheter tip and size of ventricles
    • Comparison to prior study is critical
  • Ultrasound
    • For children with open fontanel
  • Radionucleotide clearance study
    • Radionucleotide is injected into shunt reservoir and observed as it flows proximally and distally
further diagnostic studies
Further Diagnostic Studies
  • Pumping the shunt reservoir
    • Assesses proximal and distal shunt function
    • Pitfall abound, experience is needed- consult Neurosurgery
  • Tapping the shunt
    • Assess shunt function and diagnoses shunt infection
    • Consult Neurosurgery
    • Reservoir is cleaned, 23 gauge butterfly needle +/- manometer is inserted into reservoir
    • Opening pressure, rate of flow, closing pressure, and CSF sample is obtained
    • CSF should be sent for culture, Gram stain, protein, glucose, and cell count
references
References
  • Teoh DL. Tricks of the Trade: Assessment of High-Tech Gear in Special Needs Children. Clinical Pediatric Emergency Medicine. 3(1), March 2002.
  • Baddour LM, Flynn PM, Fekete T. Infection of central nervous system shunts and other devices. Up To Date. April 30, 2004.
  • Garton HJ, Piatt JH. Hydrocephalus. Pediatric Clinics of North America, 51(2), April 2004.
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