CSF shunts

Question 1

Primary treatment for hydrocephalus

Answer 1

Mechanical shunting

Question 2

Most common pediatric neurosurgical procedure performed in the US

Answer 2

Placement of a CSF shunt
- it is also the neurosurgical procedure with the highest incidence of postoperative complications

Question 3

Three components of a CSF shunt system

Answer 3

1. Proximal tubing passed into he ventricle via a burr hole
2. Valve chamber that establishes the pressure gradient
3. Distal tubing that connects the valve chamber to a drainage point

Question 4

The valve chamber allows access to the shunt system for

Answer 4

Patency testing
Pressure measurement
CSF sampling
Medication injection (chemotherapy, antibiotics)
Contrast administration

in some cases a separate reservoir is used for these

Question 5

Most common drainage site

Answer 5

Peritoneal cavity

others:
- right atrium
- gallblader
- pleural cavity
- ureter

Question 6

Most common complications encountered with CSF shunts

Answer 6

Shunt malfunction

Others include shunt infections

Question 7

Shunt malfunctions can be due to

Answer 7

1. Obstruction (m/c)
2. Mechanical failure
3. Overdrainage
4. Loculation of ventricles
5. Abdominal complications

Question 8

Most common location of obstruction

Answer 8

Proximal tubing (usually occur within the first years after shunt insertion)

followed by the distal tubing, and then the valve chamber

Question 9

Most commonly encountered obstructions in shunts in place for >2 years

Answer 9

Distal obstruction

Question 10

Causes of distal obstruction

Answer 10

Kinking or disconnection of the tube
Pseudocyst formation
Infection

Question 11

Mechanical failure of shunts can be secondary to

Answer 11

Fracture
Disconnection
Migration
Misplacement

Question 12

Remarks on fracture of CSF shunts

Answer 12

Typically, fractures appear in the distal tubing many years after shunt placement;

this is due to both degradation of tubing and stress from the growth of the patient

It is not unusual for a fracture to be found incidentally because the shunt tract often serves as a condiuit between the fractured segments

Question 13

Most common location of fracture of a CSF shunt

Answer 13

Along the clavicle or lower ribs

Question 14

Presentation of overdrainage

Answer 14

1. Cyclical symptoms of increased ICP
2. Slit ventricle syndrome

Question 15

What is this

Answer 15

Trapped fourth ventricle syndrome, presumably from closure of the sylvian aqueduct

Question 16

Most commonly encountered serious abdominal complication is

Answer 16

Malfunction due to pseudocyst formation
- pseudocysts are localized abdominal fluid collections that form around the perotoneal catheter; infection is the major cause

Question 17

This may have the highest correlation with shunt malfunction

Answer 17

Decrease in level of consciousness

often the presenting complaint is vague. no single symptoms or sign is accurate in predicting shunt malfunction

Question 18

Remarks on engorgement of the third ventricle

Answer 18

Paralysis of upward gaze (or sundowning) is caused by impingement on the brainstem by the third ventricle as it engorges

Question 19

Remarks on slit ventricle syndrome

Answer 19

Symptoms of slit ventricle syndrome are exacerbated or precipitated when the patient stands or exercises due to excessive CSF drainage

and are relieved when the patient lies down or is in the Trendelenburg postiion

Question 20

Evaluate shunt function b

Answer 20

manual testing and radiologic studies

Question 21

Compression of the valve chamber

Answer 21

Proximal flow obstruction: slow refill (i.e., >3 seconds)

Distal flow obstruction: diffulty compressing

Compression is inaccurate for identifying shunt obstruction because up to 40% of obstructed shunts show normal refill during manual palpation

Question 22

Component of a shunt series

Answer 22

Skull x-ray, AP and lateral
Chest, AP
Abdomen, ap

Question 23

Plain radiograph can identify

Answer 23

Kinking
Migration
Disconnection

Question 24

CT is required to evaluate

Answer 24

Ventricular size

Question 25

Remarks on CT scan results in patients with suspected shunt malfunction

Answer 25

**Compare with previous CT scans because many patients with shunts have an abnormal baseline ventricular size.** **Unremarkable findings on CT and/or radiographic shunt series cannot be relied on to exclude shunt obstruction**ª **Thus, obtain neurosurgical consultation whenever shunt malfunction is suspected** ## Footnote ª*Between 9% and 15% of pediatric patients will have profound alterations in brain compliance leaving ventricular size unchanged even in profound shunt failure with high intracranial pressures.*

Question 26

Remarks on doing shunt taps

Answer 26

Unless a CNS emergency exists, the shunt tap should be performed by a **neurosurgeon** to avoid damage to the valve apparatus.

Question 27

Emergency physicians should be prepared to perform a shunt tap if

Answer 27

a neurosurgeon is unavailable or if a shunt tap is needed to control life-threatening increased intracranial pressure

Question 28

Results of a shunt tap

Answer 28

Proximal obstruction: - no fluid returns or flow ceases - low pressures Distal obstruction - opening pressure ≥20 cm H2O

Question 29

The normal basal intracranial pressure

Answer 29

12 ± 2 cm H2O

Question 30

Treatment of shunt malfunction

Answer 30

1. Surgical intervention is generally required for shunt obstruction 2. Osmotic diuresis (mannitol) 3. Remove CSF via the reservoir if the malfunction is distal and surgical intervention is not immediately available

Question 31

Reminders on CSF removal

Answer 31

1. To prevent choroid plexus bleeding, remove CSF slowly 2. Discontinue the process when intracranial pressure reaches 10 to 20 cm H2O

Question 32

Half of all shunt **infections** present withtin

Answer 32

within the first 2 weeks of placement *70% present within 2 months*

Question 33

Prognosis for CSN shunt infections

Answer 33

The mortality is low if shunt infection is diagnosed and treated in a timely fashion. However, if **ventriculitis** develops, mortality is high, underscoring the need for **prompt diagnosis and aggressive management.**

Question 34

Most common bacteria in CNS shunt infections

Answer 34

**Staphylococcus epidermidis**, which accounts for nearly _half_ of all shunt infections *followed by S aureus and Propionibacterium acnes*

Question 35

CNS shunt infection agent that is associated with the highest mortality

Answer 35

Gram-negative infections

Question 36

a chronic complication of vascular shunts involving chronic bacteremia

Answer 36

Shunt nephritis *Chronic bacteremia from coagulase-negative Staphylococcus leading to an immune response* Patients present with a nephritic syndrome

Question 37

Required to exclude a CSF shunt infection

Answer 37

**Shunt tap** ***A traditional lumbar puncture often misses CSF shunt infection*** *and has no meaningful role in the evaluation when shunt infection is suspected

Question 38

Required to exclude mechanical shunt malfunction

Answer 38

CT and plain radiographs ***mechanical shunt malfunction often coexist with shunt infection***

Question 39

Blood cultures are only helpful when?

Answer 39

in patients with ventriculoatrial shunts *in most other cases, hematogenous dissemination of infection is rare, thus rendering blood cultures of limited value.*

Question 40

Management of CSF shunt infections

Answer 40

1. Emergent neurosurgical consultation and admission 2. Ceftriaxone + vancomycin 3. Early removal of the colonized device

Question 41

Can be given for treatment of recurrent gram-positive infections

Answer 41

**Rifampin** *(given along with vancomycin)* because it easily penetrates the CSF