54 Cerebrospinal Fluid Shunt Infections

Case 54 Cerebrospinal Fluid Shunt Infections

Jeffrey Atkinson

Clinical Presentation

A 3-month-old child with a L5-level myelomeningo cele and a ventriculoperitoneal (VP) shunt comes to the emergency department with 24 hours of progressive irritability and fever.
The child had the spinal defect closed at 2 days of life and a VP shunt inserted for progressive macrocrania and hydrocephalus at 14 days of life.
He has been on a program of home intermittent catheterizations since birth and no prophylactic antibiotics.
The exam demonstrates a child with a fever of 39.5°C, bulging fontanel, somnolent, and irritable.
The motor examination is unchanged with no plantar flexion in the feet, but otherwise normal.
The child’s incisions all look well healed.
White blood cell (WBC) count is elevated, and the urinalysis shows positive bacteria and WBCs.

Questions

What is the differential diagnosis suggested by this child’s presentation?
What investigations are appropriate and why?

Blood cultures are collected and urine cultures are sent. A computed tomography (CT) scan is done, which shows a stable ventricle size compared with the last scan done after the shunt was inserted. Shunt tap reveals 1500 WBCs and 10 red blood cells (RBCs) with no bacteria seen on a gram stain.
What is the diagnosis?
What are the usual organisms involved?
What are the treatment options for this child?
What antibiotic regimen would you choose?
What is the incidence of shunt infection after an initial procedure?
What is the time frame over which these infections usually develop?
What is the incidence of shunt infection after an initial shunt infection?
What maneuvers have shown benefit in reducing shunt infection?

Answers

What is the differential diagnosis suggested by this child’s presentation?

This child is presenting with the clinical signs of an infectious illness, and clinical signs of shunt malfunction, though the fever itself may be causing the child’s irritability independent of shunt malfunction, and a severely irritable child may present with a bulging fontanel.
The cause of the febrile illness may be viral or respiratory, but in this case, we would be worried about shunt infection or wound complication, as well as urosepsis.

What investigations are appropriate and why?

This child needs cultures of blood, urine, a complete blood count, chest x-ray as well as viral swabs of any upper respiratory tract-related secretions and a full exam to look for skin abrasions, wound complications, or other pertinent physical findings.
CT scan is indicated due to the clinical signs of increased intracranial pressure (ICP).
A tap of the shunt reservoir to obtain cerebrospinal fluid (CSF) is clearly indicated in this child given the presentation and relatively recent shunt surgery.

What is the diagnosis?

The cell count of the CSF points toward shunt infection even in the absence of an initially positive gram stain.
The culture of CSF will probably grow eventually.

What are the usual organisms involved?

Shunt infections are usually from skin colonization occurring at the time of surgery – gram-positive cocci are most common.1

In a child of this age, and especially one with uri nary catheterizations, gram-negatives and coliforms are also possible.2
What are the treatment options for this child?
- This child needs antibiotics and some type of shunt externalization procedure.
- Very few shunt infections will respond to antibiotics alone without hardware removal.
- Many centers will externalize the shunt by removing the distal catheter from the abdomen and then treat until the CSF is sterile before replacing the entire system.¹
- In the event of continued positive cultures, the entire shunt system should be converted to an external ventricular drain (EVD).²
- Some centers would externalize the EVD upfront with removal of the whole shunt system.^1,2
- The duration of antibiotic treatment before reinternalization is debatable; it averages 10 to 14 days, but three consecutive negative CSF cultures is a common standard.^2,3
What antibiotic regimen would you choose?
- Initial antibiotic regimen needs to include broad spectrum CSF penetrating coverage, and good antistaphylococcal coverage until the organism is known.^1,2
- Typical initial regimens would include a thirdgeneration cephalosporin with vancomycin plus or minus an aminoglycoside.
What is the incidence of shunt infection after an initial procedure?
- Shunt infection rates per procedure after an initial shunt placement are approximately 8 to 10% in most large studies of shunt insertions in children.¹
What is the time frame over which these infections usu ally develop?
- Most shunt infections are procedure-related and present within the first 6 months of surgery.
- Other risk factors for shunt-related infection include wound breakdown and CSF leak.¹
What is the incidence of shunt infection after an initial shunt infection?
- Shunt infections may occur up to 25% of the time when a shunt is replaced after an initial infection.¹
What maneuvers have shown benefit in reducing shunt infection?
- There are a great many studies attempting to demonstrate protocols to reduce shunt infection rates.⁴
- Efforts to reduce shunt infection rates have included perioperative antibiotics, various procedure-related technical issues such as double gloving, short duration of surgery, surgery timing, reduced mechanical manipulation of the hardware, and more recently antibiotic-impregnated shunt catheters.^4,5,6,7
- Many of these techniques including antibiotic-impregnated catheters are still the subject of some debate as to their relative efficacy.^4,6,7