The aim of this presentation is to illustrate the potential of magnetic resonance imaging (MRI) in diagnosis, differential diagnosis, treatment planning and evaluation of therapy effectiveness of pyogenic brain abscesses, through the use of morphological (or conventional) and functional (or advanced) sequences.

2. Summary
 Etiology, Pathogenesis, Clinical
Features of Pyogenic Cerebritis and
Brain Abscesses.
 Imaging (MRI, DWI, PWI, MRS, SWI)
 Differential Diagnosis, Treatment
Planning, Follow-up

3. Cerebritis and Brain Abscess in
Children
 1-2 % of brain occupying lesions in
western countries – 8% in developing
countries
 15-30 % of the cases involve young
patients (< 15 yo)
 Pyogenic brain abscesses: 1/3 of all
cerebral abscesses.
Muccio et al. J Neuroradiol 2014 Jul:41(3):153-167

4. Bacteria entering the CNS…
How?
 Hematogenous Spread (distant infection,
sepsis)
 Extension from Contiguous Infections
(otomastoiditis, sinusitis, meningitis)
 Direct Traumatic Implantation (craniofacial
trauma, neurosurgery)
 Association with Cardiopulmonary
Malformation (congenital heart disease,
hereditary Hemorragic telangiectasia)
Tortori-Donati P, Rossi A, Bianchieri R. Pediatric neuroradiology: Brain,
Head, Neck and Spine. Springer 2005. pp 498-511

5. Who?
 Aerobic: Staphylococcus, Streptococcus,
Pneumococcus.
 Anaerobic: Clostridium species, Actinomyces.
Neonatal Age
 Commonly brain abscesses complicate
meningitis
 Gram -
Fitz CR. Inflammatory diseases of the brain in childhood.
AJNR Am J Neuroradiol 1992; 13:551–567.

6.  Supratentorial Region in
subcortical white matter
(+++)  hematogeneous
spread
 Basal Ganglia (rare)
Where?

7.  Temporal Lobe and Cerebellum (middle
ear otitis)
 Multiple Lesions (immunocompromised)
Neonatal Age
 Multiple Lesions
 Periventricular location
Where?

8. Clinical Features
 Non-specific
 Fever (??)  common condition in hospitalized
children, only 55% body temp > 38.5°
 Focal Neurological Signs (40-60%)  location
 Seizure, Vomiting, Lethargy
 Sign of increase ICP (newborns)  Head Circ.
Erdogan E et al. Pyogenic brain abscess. Neurosurg Focus
2008;24(6):E2

9. Clinical Features
 COMPLICATIONS:
- Intraventricular Rupture
- Dissemination
- Acute Hydrocephalus

10. Clinical Features
 COMPLICATIONS: Sinus Thrombosis
Cerebellar Abscess in 8-year-old boy with Otomastoiditis (*)
complicated by thrombosis of the sigmoid sinus and jugular vein
(arrows)
Tortori-Donati P, Rossi A, Bianchieri R. Pediatric neuroradiology: Brain,
Head, Neck and Spine. Springer 2005. pp 498-511

11. Anatomical Theatre , University of
Padua - Italy (1594)
Andrea Vesalius, De Humani Corporis
Fabrica (1542)
…what we see in imaging has an
anatomical/pathological correlation…
…remember the lesson of the masters…

12. From focal cerebritis to mature
abscess…
Tortori-Donati P, Rossi A, Bianchieri R. Pediatric neuroradiology: Brain,
Head, Neck and Spine. Springer 2005. pp 498-511

13. Early Cerebritis
 Days 1-3 following inoculation
 Injury of brain microvasculature due to
bacteria
 Spread of the bacteria across wall of
injured vessel to GM/WM
 Local inflammation, vascular congestion,
necrosis, microhemorrhages,
perivascualr edema

14. Early Cerebritis
Osborn – Brain 2014

15. Early Cerebritis
Tortori-Donati P, Rossi A, Bianchieri R. Pediatric neuroradiology: Brain,
Head, Neck and Spine. Springer 2005. pp 498-511

16.  Days 4-9
 Necrotic center confined by an irregular layer
of inflammatory granulation tissue
 In absence of treatment  host response
formation of abscess capsule
Late Cerebritis

17. Late Cerebritis
 Initial necrosis
 Peripheral rim
(not completely
formed)
 More mass
effect

18. Late Cerebritis
Tortori-Donati P, Rossi A, Bianchieri R.
Pediatric neuroradiology: Brain, Head,
Neck and Spine. Springer 2005. pp 498-
511
 Central
necrosis (*)
 Not complete
encapsulation
 Peripheral C.E.

19. From focal cerebritis to mature
abscess…
Tortori-Donati P, Rossi A, Bianchieri R. Pediatric neuroradiology: Brain,
Head, Neck and Spine. Springer 2005. pp 498-511

20. From focal cerebritis to mature abscess…
Barkovich AJ, Raybaud C. Pediatric
Neuroimaging. LWW 2012
 Neonate
 Diffuse areas of
restriction
 Hemorrhagic
necrosis on T2*
 Patchy cortical-
subcortical c.e.
 Mild mass effect

21. From focal cerebritis to mature abscess… (5 DAYS
LATER…)
Barkovich AJ, Raybaud C. Pediatric
Neuroimaging. LWW 2012
 DWI : large confluent frontal WM restriction
 Enhancing capsule
 +++ Mass effect (subfalcine herniation)

22.  Days 10 and later
 5 layers:
- Necrotic centre
- Granulation tissue
- Lymphocytes and plasma cells
- Dense fibrous tissue
- Surrounding edema/gliosis
Abscess
capsule

23. Abscess
Necrosis
Capsule
Transition zone
(edema/gliosis)
Normal Brain

24. Stage III (early capsule) VS Stage IV(mature capsule)
 Bilocular lesion
 Difference in capsule!
 *edema Tortori-Donati P, Rossi A, Bianchieri R.
Pediatric neuroradiology: Brain, Head,
Neck and Spine. Springer 2005. pp 498-
511

25. Abscess: Imaging
 Central necrosis : T2 Hyper, T1 Hypo
(sometimes variable T2 signal intensity!!!)
 External capsule: T2 Hypo, T1 Hyper
(possible non typical signal: Iso/Hypo T1-
Hyper T2)*
 Surrounding Edema: T2 Hyper, T1 Hypo
 Rim enhancement
*collagen fibers-macrophages releasing free radicals with
paramagnetic effect.

26. • * Core
•  capsule
•  edema

27. External capsule: non typical signal

28. Core: variable signal Satellite Abscesses

29. Neonates and Small Infants
 Gram Negative (Serratia,
Pseudomonas, Proteus),
S.Aureus
 Complication of Meningitis
 Multiple, PV white matter:
rupture in lateral ventricles
 Larger
 Incomplete: without well
definite capsule -> rapid
enlargement
Muccio et al. J Neuroradiol 2014
Jul:41(3):153-167

30. Citrobacter Diversus, 5 weeks Old Infant.
Multiple infected cavities with rim
enhancement, daughter cysts and fluid
with different signal intensity (blood and
pus).
Blaser S, Jay V et al. MRI of the Neonatal Brain.
Chapter 10 (Rutherford M.)

31.  Critical support in the diagnosis of
cerebral abscesses
 Central necrotic area: proteins, bacterial
and cellular debris 
 Hyper DWI – Low ADC (0.28 – 0.73 x 10-13 mm2/s)
 Wide range of ADC: type of bacteria, immune response
Diffusion Weighted Imaging

35. Lee EJ et al. Unusual findings in cerebral Abscess: report of two cases.
Br J Radiol 2006;79:e156-61

36. Hernandez M I et al. Stroke Patterns in Neonatal Group B Streptococcal
Meningitis. Pediatr Neurol. 2011; 44(4):282-8

38.  Central Necrotic area: lipids+lactate
(0.8/1.2 – 1.3 ppm). No NAA and Cho
 Alanine (1.5 ppm) and other amino acids
(0.9 ppm): proteolisis enzymes released by
neurtrophils
 Acetate (1.9 ppm), succinate (2.4 ppm):
bacterial glicolisis and fermentation
MR-spectroscopy

39.  Type A: Lac, aa, ala, acetate, succinate
and lipids obligate anaerobes
 Type B: Lac, aa  obligate aerobes
 Type C: lac alone  streptococcus and
treated abscesses

40. Type A: Lac, aa, ala, acetate, succinate and lipids obligate
anaerobes

41.  Few studies
 Low perfusion in capsule (compared to
WM)
 Useful for differential diagnosis
 Late stage: fibroblasts  low CBV
Perfusion Weighted Imaging
Harris M et al. Differentiation of infective from neoplastic brain lesions by dynamic contrast-
enhanced MR. Neuroradiology 2008;50:590-603
Erdogan C et al. Brain abscess and cistic brain tumor: discriminationwith dynamic susceptibility
contrast-perfusion-weighted MRI. J Comput Assist Tomogr 2005;29:663-7

43. Differential Diagnosis
 Necrotic Brain Tumors
 Fungal Abscesses
 Tubercular Abscesses
 Toxoplasmosis
 Neurocysticercosis

44. Necrotic Brain Tumors
HGG and Meta
 Rim: T2 hypo but often NOT COMPLETE
 Rim: non-homogeneous c.e. (meta can have complete rim
c.e. similar to pyogenic abscesses!)
 Nodular c.e. in the cavity
 Increase rCBV
 H-MRS: no aa, acetate, succinate
 DWI: hypo (often)
 SWI “double rim” sign : present in abscess but no in
necrotic gliomas (Toh et al AJNR 2012)

45.  DWI restriction described in
metastases from lung, breast, colorectal,
testicular and bladder cancers
 DWI increased signal: intratumoral
hemorrhage
Necrotic Brain Tumors
HGG and Meta
Park SH et al. Diffusion Weighted MRI in cystic or neurotic intracranial lesions. Neuroradiology
2000;42:716-21
Duygulu G et al. Intracranial metastases showing restricted diffusion: correlation with
histopathological findings. Eur J Radiol 2010;74:117-20

48. Toh et al. Differentiation of pyogenic brain abscesses from necrotic
glioblastoma with use of susceptibility-weigthed imaging. AJNR
2012;33(8):1534-8
Fibrocollagenous
capsule
Granulation
tissue

49.  Rare
 Rim c.e. and DWI/ADC similar to
pyogenic abscesses
 More often hemorrhagic strokes (but
also Strepto in neonates!!!)
 Look for primary aspergillosis (lungs,
paranasal sinuses)
Fungal Abscesses

51.  Rim: T2 hypo and c.e. (similar to PA)
 Core variable in T2 and DWI (caseous
or liquefactive necrosis)
 High peripheral rCBV !!
 Association with meningitis
Tuberculoma

52.  Type 1: Caseous Necrosis, T2 HYPO,
high ADC
 Type 2: slightly hypertnese in T2 ,
intermediate ADC
 Type 3: Liquefactive necrosis, strongy
HYPER T2, low ADC (similar PA)
Tuberculoma: core
Gupta RK et al. Eu J Radiol 2005, 85(3): 384-92

54.  Immunocompromised patients, multiple lesions
 “Eccentric Target Sing” : eccentric area of c.e.
 “Concentric Target Sign” :T2 concentric
alternating zones of hypo- and hyperintensity
 DWI / ADC : hypo / high (useful in dd with PA)
 CBV similar to PA
Cerebral Toxoplasmosis
Mahadevan A et al. Neuropatological correlate of the “concentric target sign” in MRI of HIV
associated cerebral toxoplasmosis. J Magn Reson Imaging 2013;38(2):488-95

57. Neurocysticercosis
 Core Hypo T1, Hper T2
 Capsule: hypo T2 with c.e.
 SCOLEX: eccentric hypo T2 nodule with c.e.
 Interventricular spread (54%)
 DWI / ADC: hypo / high (dd with PA)
 Low rCBV (similar to PA)
Sinha S, Sharma B. Intraventricular neurocysticercosis: a review of current status and
management issues. Br J Neurosurg 2012;26(3):305-9

59. THANK YOU