Shunts Gone Bad!
Transcript of Shunts Gone Bad!
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CSF Shunts gone bad!Brad Sobolewski, MD
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Ventricular system
4th
CISTERNSSubarachnoid space
3rd
LATERALLATERAL
STATS Total volume 50ml
Production 20ml/hr
Turnover 3-4x/day
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Hydrocephalus
Imbalance of absorption and production of CSF
Estimated incidence of 1/500-1000 children
125,000+ shunts
OBSTRUCTIVE: Ventricular system is blocked
Not possible to have complete obstruction
COMMUNICATING: Subarachnoid system blocked
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Etiology
Congenital
infection: Rubella, CMV, Toxo, Syphilis
Acquired: Infection, trauma, tumors, head bleeds
Neural tube defects: associated with Chiari or aqueductalstenosis. Linked to teratogens and deficiency of folate.
Isolated: aqueductal stenosis (inflammation d/t intrauterineinfection)
X-Linked hydrocephalus: stenosis of aqueduct of Sylvius
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Etiology CNS malformations
Often accompanies NTD
Brainstem and Cerebellum are
displaced caudally
Chiari II
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Large posterior fossa cyst continuous
with 4th ventricle
Abnormal cerebellar developmentHydrocephalus in 70-90%
Dandy-Walker
Etiology CNS malformations
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Obstructive Hydrocephalus
Ventricular system is
blocked
CSF accumulatesproximally
4th
CISTERNSSubarachnoid space
3rd
LATERALLATERAL
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Communicating Hydrocephalus
Subarachnoid system blocked
Results in impaired absorption
Entire system is dilated
Causes
IVH/SAH
Meningitis
Scarring after inflammatory process
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Pseudotumor cerebri
Isnt it due to overproduction of CSF?
Pathogenesis unknown
Cerebral venous outflow abnormalities
Increased CSF outflow resistance at arachnoid or lymphatic
level
Obesity related changes to intracranial venous pressure
Altered Na and H2O retention mechanisms
Abnormal Vitamin A metabolism
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Excessive CSF Production
Rare
Only really happens in cases of a functional
choroid plexus papilloma
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Symptoms of hydrocephalus
Headache
Vomiting: increased ICP in the posterior fossa
Behavioral changes
Drowsiness: midbrain/brainstem dysfunction Visual changes: Optic Nerve compression
Incoordination
Loss of developmental milestones
Head circumference increases rapidly
Sunsetting eyes: fixed downward gaze
Pro-Tip: These symptoms obviously vary based on the age of the patient
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Shunt Devices
Proximal portion is placed in a ventricle (usually R)
Could also be in an intracranial cyst or lumbar
subarachnoid space
Distal portion
Internalized: peritoneum, pleura, atrium
Externalized EVD: Acute hydrocephalus for pressure monitoring, infected shunt
Ommaya reservoir: Generally for administration of drugs
(antibiotics or chemo)
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Shunt Complications
Mechanical Obstruction (Malfunction/Failure)
proximal tip is obstructed with cells, choroid plexus, or debris
Kinking of the tubing
Migration of the distal end Infection
Acquired Chiari I due to over draining
Slit ventricle syndrome
Intraventricular hemorrhage (subdural)
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Shunt infections
Risk of 5-15% overall
Sx are generally few, fever is variable
Paucity of meningeal Sx as there is no
communication between shunt and meninges
VP shunt infections can manifest as peritonitis
VA shunt infections as bacteremia/endocarditis
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Shunt infections
Increased risk
Highest in initial month after placement
Risk extends up to 6 months post op
Patients requiring serial revisions
Intracranial hemorrhage
Cranial fracture with CSF leak
Craniotomy
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Shunt infections
What are the most common infectious agents
Proximal end: skin flora
50% coag negative staph, 33% S. aureus
Distal end: peritonitis/intestinal perforation or
hematogenous seeding
Streptococci, gram negative (P. aeruginosa),
anaerobes, mycobacteria, fungi
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Shunt infections
Treatment
No RCTs or prospective data
Remove the device + IV antibiotics (vanc + gram
negative)
Decreasing risk
Periop Vanc Antibiotic impregnated catheters
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Shunt malfunctions
Mechanical failure
Majority of 1st failures due to obstruction
Shunt over drains
Ventricles shrink
Tip gets clogged against choroid plexus
15% due to fractured tubing
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Shunt malfunctions
Median survival of a shunt (before need for revision)
child under 2 years of age is 2 years
over two years of age is 8 - 10 years
Also associated with decreased survival
Shunts inserted prior to first birthday
Inserted when pt. weighed
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Symptoms associated with shunt malfunctions
PEC, 2008
647 visits to the ED
78% younger than age 1 at time of insertion of shunt
38% failure rate at 3 years, 8.5% by infection
Built a decision tree model
Sign/Symptom +LR -LR
Bulging fontanel 44.6 1.84
Irritability 13.7 1.75
Nausea/Vomiting 11.1 1.58
Accelerated head growth 6.02 1.86
Headache 4.28 1.22
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Shunt series
Radiographs of the skull, neck, chest, and abdomen
Look for mechanical breaks, kinks, and disconnections in
the shunt
Utility
Pitetti, PEC, 2007 Retro review of 291 kids (461 ED visits)
78% had a shunt series
15% (71/291) Dx with malfunction 22 of these 71 had a normal head CT
6 of these 22 had an abnormal shunt series
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Neuroimaging
Head CT
Not always diagnostic, even if ventricles are
bigger
Cumulative radiation is a concern
Iskandar Pediatrics, 1998 1/3 of patients Dx
with shunt malfunction were not supported by
CT findings
Rapid sequence MRI is now being explored
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Imaging test characteristics
Zorc, PEC, 2002
60/233 reviewed retrospectively had a shunt malfunction
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Management of shunt malfunctions
Replacement or externalization If infected the EVD is preferred
Otherwise it is up to the surgeon
No comparison studies in kids
Bedside EVD Kakarla Neurosurg, 2008 retro review of 346 adults that had
bedside EVD
Analyzed success of placement, ideal ipsilateral frontal horn or
3
rd
ventricle Highest success in cases of IVH and trauma
Midline shift decr success
Caveat: Not studied in shunted patients
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Shunt tap
Indications
Diagnostic
Suspected shunt blockage, infection or meningitis
Therapeutic Severely raised ICP in the presence of a VP shunt
Contraindications
Skin infection over shunt site Coagulopathy
Lack of shunt imaging/info
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Shunt tap
Procedure
23 or 25G butterfly needle
Aspiration can suck choroid plexus into the tube =
bad
Utility
Opening pressure >25cm H2O associated withdistal obstruction in 90%
Poor flow associated with proximal shunt in >90%
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Shunt tap
When should a shunt tap be performed?
Miller J. Neurosurg Peds, 2008
Retro review of 155 patients
Low utility overall, doesnt often contribute to Dx
Risks
Infection
Changes in flow dynamics post shunt tap can cause apartially working shunt to malfunction
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M
anageme
ntofa
suspectedshunt
malfu
nction
Miller, J. Neurosurg Pediatrics 2008 Brad Sobolewski, 2013
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Treatments for elevated ICP in shunt malfunctions
Do they work?
Answer: Probably
No literature on hypertonic/osmotic therapies
General pearls are still useful prior to definitive
management
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ICP ManagementIn shunt malfunctions NONE of these are as important as a trip to the OR
Positioning
Head midline, elevated 30o
Maintain homeostasis
Treat hypoxia (sats >95%), hypercarbia , hypotension, and
hypoglycemia Temperature control
Therapeutic cooling (fever incr metabolism and CBF)
Mild sedation (dont cause hypotension)
Control severe shivering w/ paralytics
Prophylactic fosphenytoin to patients at risk for seizures
Parenchymal abnormalities, depressed skull fractures, and TBI
No definitive evidence in children
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ICP ManagementIn shunt malfunctions NONE of these are as important as a trip to the OR
Intubate if:
Respiratory failure
Loss of airway protective reflexes
Refractory hypoxia GCS
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ICP ManagementIn shunt malfunctions NONE of these are as important as a trip to the OR
In the intubated patient
Avoid high pressures (decr venous return by incr
intrathoracic pressure)
Hyperventilation: though it can lower ICP (if you get ETCO2
25-30), aggressive hyperventilation leads to cerebral
vasoconstriction and decr CBF
Reserved for patients herniating or at imminent risk
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ICP ManagementIn shunt malfunctions NONE of these are as important as a trip to the OR
Experimental therapies
Hypothermia
Indomethacin
Stuff that doesnt help
Steroids (unless swelling from a tumor or abscess)
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ICP ManagementIn shunt malfunctions NONE of these are as important as a trip to the OR
Hypertonic 3% saline 6-10ml/kg over 5-10 min
Generates an osmotic gradient between the intravascular
space and cerebral tissue
Effective plasma volume expander in multiple traumapatients
May have beneficial effects on cerebrovascular regulation
Effective to a serum osmo of 360
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ICP ManagementIn shunt malfunctions NONE of these are as important as a trip to the OR
Mannitol 20% solution 0.25-1g/kg over 10-20 min
An osmotic diuretic
Effective mainly around the lesion, where blood brain
barrier integrity is impaired It may also reduce CSF production
Hypovolemia is a real concern & pts will start diuresing in
20-30 minutes (in the scanner)
Not effective above a serum osmo of 320
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