MAGNETIC RESONANCE FEATURES OF PYOGENIC BRAIN ABSCESSES AND DIFFERENTIAL

DIAGNOSIS

Summary Etiology, Pathogenesis, Clinical

Features of Pyogenic Cerebritis and Brain Abscesses.

Imaging (MRI, DWI, PWI, MRS, SWI)

Differential Diagnosis, Treatment Planning, Follow-up

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

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

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.

Supratentorial Region in subcortical white matter (+++) hematogeneous spread

Basal Ganglia (rare)

Where?

Temporal Lobe and Cerebellum (middle ear otitis)

Multiple Lesions (immunocompromised)

Neonatal Age

Multiple Lesions Periventricular location

Where?

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

Clinical Features COMPLICATIONS: - Intraventricular Rupture

- Dissemination

- Acute Hydrocephalus

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

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…

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

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

Early Cerebritis

Osborn – Brain 2014

Early Cerebritis

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

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

Late Cerebritis Initial necrosis

Peripheral rim (not completely formed)

More mass effect

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.

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

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

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)

Days 10 and later 5 layers:

- Necrotic centre

- Granulation tissue- Lymphocytes and plasma cells- Dense fibrous tissue - Surrounding edema/gliosis

Abscesscapsule

Abscess

Necrosis

Capsule

Transition zone (edema/gliosis)

Normal Brain

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

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.

• * Core • capsule• edema

External capsule: non typical signal

Core: variable signal Satellite Abscesses

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

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.)

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

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

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

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

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

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

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

Differential Diagnosis Necrotic Brain Tumors

Fungal Abscesses

Tubercular Abscesses

Toxoplasmosis

Neurocysticercosis

Necrotic Brain TumorsHGG 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)

DWI restriction described in metastases from lung, breast, colorectal, testicular and bladder cancers

DWI increased signal: intratumoral hemorrhage

Necrotic Brain TumorsHGG 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

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

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

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

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

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

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

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