Neurosurgery: Infectious Disease

Question 1

What are the three main mechanisms for inoculation with bacteria for cerebral abscess formation?

Answer 1

Contiguous spread (most common): sinusitis, otitis media, dental abscess
Hematogenous spread: pulmonary AVF, bacterial endocarditis, lung infections, congenital cyanotic heart disease, GI infections, immunodeficiency
Penetrating injury: trauma, neurosurgery, CSF leak

Question 2

What are the most common pathogens causing cerebral abscesses?

Answer 2

Streptococcus (most common)
Strep. milleri and Strep. anginosis (sinusitis)
Bacteroides
Proteus
Staph. aureus (trauma)
Staph. epidermidis (iatrogenic)
Actinomyces (dental)
Fungal (immunocompromised)

Question 3

What are the stages and timelines for the development of cerebral abscesses? (Hint: 4 stages)

Answer 3

Early cerebritis (2-5 days)
Late cerebritis (5d - 2 weeks)
Early capsule (2-3 weeks)
Late capsule (>3 weeks)

Question 4

Which stage of cerebral abscesses is most resistant to aspiration?

Answer 4

Late capsule stage

Question 5

Which stage of cerebral abscesses classically restricts diffusion on DWI/ADC MRI?

Answer 5

Late capsule stage

Question 6

When is ring-type enhancement seen on CT imaging of cerebral abscesses and how does it appear during the different stages?

Answer 6

All stages

Thick ring in the cerebritis stages
Thin ring in the capsular stages

Question 7

How are cerebral abscesses managed if the pathogen is known and the patient is doing well overall?

Answer 7

IV antibiotics for at least 6 weeks

Question 8

If a cerebral abscess exhibits mass effect, is near the ventricle, there is an unknown pathogen, or the patient’s condition is deteriorating then how should it be managed?

Answer 8

CT or stereotactic-guided aspiration

Craniotomy and excision if late capsular stage (since the abscess will be very resistant to aspiration)

Question 9

What are the two major routes of spread of subdural empyema or epidural abscess?

Answer 9

Contiguous spread (e.g. meningitis)
Penetrating trauma

Question 10

What are the common organisms implicated in subdural empyema?

Answer 10

Streptococci
H. influenza
S. aureus
S. epidermidis
Anaerobes

Question 11

What other pathology is commonly associated with subdural empyema?

Answer 11

Cerebral abscess in 25% of cases

Question 12

How do subdural empyemas often present?

Answer 12

Febrile (more often than cerebral abscesses)
Meningismus
Cortical venous infarcts
Secondary cerebritis/abscess

Question 13

What is the treatment for a subdural empyema or epidural abscess?

Answer 13

Antibiotics and multiple burr holes for drainage (or craniotomy for debridement if chronic

Question 14

What are common pathogens involved in shunt infections?

Answer 14

S. epidermidis
S. aureus
Gram-negatives

Question 15

How do VPS infections present?

Answer 15

Systemic infection, abdominal pain, tenderness along tubing, obstruction

Question 16

What is the general treatment scheme for shunt infections?

Answer 16

Remove shunt and externally drain CSF
IV antibiotics (often vancomycin)
Await for at least 3 days of sterile CSF before replacing shunt

Question 17

What is the most common pathogen involved in osteoemyelitis/infected bone flap?

Answer 17

S. aureus

S. epidermidis is second most common

Question 18

How is osteomyelitis/infected bone flap treated?

Answer 18

Removal of bone flap/debridement
6-24 weeks of IV antibiotics
Cranioplasty after at least 6 months