Transcript Document

CSF Shunts:
A Primer
Tamara Simon, M.D.
July 2004
• CSF flow:
Purpose
– 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
• Allows for relief of hydrocephalus
• Allows for prevention of increased ICP
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Tumors
Congenital anomalies
Posttraumatic hemorrhage
Intraventricular hemorrhage
Postinfectious obstruction
Other causes
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
• 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)
• 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
• Rickham reservoir with
antisiphon device (left)
• Single chamber reservoir
(middle)
• Rickham reservoir with
double chamber
reservoir/valve system
(right)
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)
• 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
• 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
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
• 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
• 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 highcompliance 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
• 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 Malfunction
• Varied signs and symptoms
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Swelling or erythema around shunt tract
Bulging or full fontanel
Increased head circumference
Headache
Irritability
Increased seizures
Vomiting
Papilledema
- Lethargy
- Ataxia
- Neck pain
- Back pain
- Blurred vision
- Sun setting eyes
- Behavioral changes
- Not acting right
• Most predictive?
– Vomiting, lack of fever, parental suspicion
Complication: Infection
• Second most common complication, seen in 230% of shunt procedures
• Increased risk in children under 1 year of age, a
short duration from shunt procedure
• Most common organisms:
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Coagulase-negative Staph species
Staph epidermidis
Staph aureus
Gram negative rods (6-20%)
Pathogens that cause meningitis (more remote)
Complication: Infection
• Vague signs and symptoms
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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
• 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 normalsized ventricles
Complication: Proximal Catheter
Obstruction
• Medical signs of increased ICP
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Hyperventilation
Diuretics (acetazolamide, mannitol)
Elevate head of bed
Ventricular puncture through burr hole or open
fontanel
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
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Intussusception
Intractable hiccup
Omental cyst torsion
Volvulus around catheter
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
• 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
• 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.