Medical Video Review

Shunt Malfunctions Brad Sobolewski, MD

February 28, 2012

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Background information

• School aged M w/ MRCP spastic quadriplegia d/t grade III IVH as neonate

• VP shunt shortly after birth

• Epilepsy: no seizures in 3 years, on Trileptal

• On Baclofen for spasticity

• Uses wheelchair, stands with support

• Picture board to communicate

• 20 minute seizure last night, first in 3 years

– Diastat x2 at home

– No fevers or recent infectious Sx

– No changes to meds or missed doses

• Uncertain of whether or not he was still seizing

– Got Ativan IV x1 then fosphenytoin

– 20ml/kg NS bolus

– Head CT

“This isn’t normal for him” -The Dad

The head CT

Then Now

“We need to get him intubated” -The Neurosurgeon

• Neurosurgery eval at bedside

• Elected to intubate

– Lido, etomidate and sux

• Bedside shunt tap

Diagnosis:

Shunt malfunction

Ventricular system

4th

CISTERNS Subarachnoid space

3rd

LATERAL LATERAL

STATS • Total volume 50ml • Production 20ml/hr • Turnover 3-4x/day

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

Etiology

• Congenital

– infection: Rubella, CMV, Toxo, Syphilis

• Acquired: Infection, trauma, tumors, head bleeds

• Neural tube defects: associated with Chiari or aqueductal stenosis. Linked to teratogens and deficiency of folate.

• Isolated: aqueductal stenosis (inflammation d/t intrauterine infection)

• X-Linked hydrocephalus: stenosis of aqueduct of Sylvius

Etiology – CNS malformations

Often accompanies NTD Brainstem and Cerebellum are displaced caudally

Chiari II

Large posterior fossa cyst continuous with 4th ventricle Abnormal cerebellar development Hydrocephalus in 70-90%

Dandy-Walker

Etiology – CNS malformations

Obstructive Hydrocephalus

• Ventricular system is blocked

• CSF accumulates proximally

4th

CISTERNS Subarachnoid space

3rd

LATERAL LATERAL

Communicating Hydrocephalus

• Subarachnoid system blocked

– Results in impaired absorption

– Entire system is dilated

• Causes

– IVH/SAH

– Meningitis

– Scarring after inflammatory process

Pseudotumor cerebri

• Isn’t 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

Excessive CSF Production

• Rare

• Only really happens in cases of a functional choroid plexus papilloma

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

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)

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)

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

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

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

Shunt infections

• Treatment

– No RCTs or prospective data

– Remove the device + IV antibiotics (vanc + gram negative)

• Decreasing risk

– Periop Vanc

– Antibiotic impregnated catheters

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

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 <3,000g

Pro-Tip: Children with NTD have longer shunt survival than children with hydrocephalus from other etiologies

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

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

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

Imaging test characteristics

• Zorc, PEC, 2002

– 60/233 reviewed retrospectively had a shunt malfunction

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

3rd ventricle – Highest success in cases of IVH and trauma – Midline shift decr success – Caveat: Not studied in shunted patients

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

Shunt tap

• Procedure

– 23 or 25G butterfly needle

– Aspiration can suck choroid plexus into the tube = bad

• Utility

– Opening pressure >25cm H2O associated with distal obstruction in 90%

– Poor flow associated with proximal shunt in >90%

Shunt tap

• When should a shunt tap be performed?

– Miller – J. Neurosurg Peds, 2008

– Retro review of 155 patients

– Low utility overall, doesn’t often contribute to Dx

– Risks

• Infection

• Changes in flow dynamics post shunt tap can cause a partially working shunt to malfunction

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Miller, J. Neurosurg Pediatrics 2008

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

ICP Management In 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 (don’t 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

ICP Management In 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 <8

– Acute herniation needing hyperventilation

ICP Management In 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

ICP Management In shunt malfunctions NONE of these are as important as a trip to the OR

• Experimental therapies

– Hypothermia

– Indomethacin

• Stuff that doesn’t help

– Steroids (unless swelling from a tumor or abscess)

ICP Management In 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 trauma patients

– May have beneficial effects on cerebrovascular regulation

– Effective to a serum osmo of 360

ICP Management In 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

Patient follow-up

• Proximal catheter malfunction noted in OR

• Extubated POD #1

• Had some desats on floor – not related to seizures

• Follow up with Neurosurgery and Rehab

• Stable ventricles in September on CT

• No loss of milestones or cognitive decline