shunts gone bad!

8/22/2019 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

Brad Sobolewski, 2013


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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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Intubate if:

Respiratory failure

Loss of airway protective reflexes

Refractory hypoxia GCS


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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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Experimental therapies

Hypothermia

Indomethacin

Stuff that doesnt help

Steroids (unless swelling from a tumor or abscess)



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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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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

Brad Sobolewski 2013

shunts gone bad!

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