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Case Report

Fungal brain abscess e Typical MRI features

Anoop Singh Arora a,*, Subhash Gupta b, Abhishek Agarwal c,Sumaid Kaul d

a Senior Consultant, Department of Radiology, Indraprastha Apollo Hospital, New Delhi 110076, Indiab Senior Consultant, Department of Gastroenterology & Liver Transplant, Indraprastha Apollo Hospital,

New Delhi 110076, Indiac Resident, Department of Radiology, Indraprastha Apollo Hospital, New Delhi 110076, Indiad Senior Consultant, Department of Pathology, Indraprastha Apollo Hospital, New Delhi 110076, India

a r t i c l e i n f o

Article history:

Received 25 April 2014

Accepted 2 August 2014

Available online xxx

Keywords:

Fungal brain abscess

Magnetic resonance imaging

Diffusion weighted imaging

Ring enhancing lesion

* Corresponding author.E-mail address: asarora54@yahoo.com (A

Please cite this article in press as: Arora Adx.doi.org/10.1016/j.apme.2014.08.002

http://dx.doi.org/10.1016/j.apme.2014.08.0020976-0016/Copyright © 2014, Indraprastha M

a b s t r a c t

Objective: To evaluate the diagnostic value of magnetic resonance imaging (MRI) in brain

abscess induced by fungal infection of the central nervous system.

Methods: We analyzed an immune-compromised patient with various neurological symp-

toms. Imaging studies included T2, T1, post-contrast T1 and diffusion weighted imaging

(DWI). The patient had typical imaging features of fungal brain abscess which was later

confirmed by histo-pathology.

Results: The fungal abscess showed irregular walls with intracavitary projections. The ab-

scess showed peripheral ring enhancement with non enhancement of the intra-cavitatory

projections. The periphery of the abscess showed susceptibility artifact, thus indicating

towards its fungal composition. In the fungal abscesses, the wall and projections showed

low ADC; however, the cavity itself showed high ADC.

Conclusion: MRI-DWI and contrast enhanced MRI changes can improve the early diagnosis

of brain abscess & distinguish the fungal brain abscess from pyogenic & tubercular

abscesses.

Copyright © 2014, Indraprastha Medical Corporation Ltd. All rights reserved.

1. Introduction

Brain abscess is defined as purulence and inflammation in one

or more localized regions within the brain parenchyma.1 It is

one of several forms of severe intracranial infection. Cerebral

abscess is a well-described condition in immunocompro-

mised patients. Abscesses may be secondary to bacterial,

fungal, or parasitic organisms. These lesions often produce

.S. Arora).

S, et al., Fungal brain a

edical Corporation Ltd. A

complex clinical and radiologic findings and require prompt

recognition and treatment to avoid a fatal neurologic

outcome. It begins with an area of unencapsulated inflam-

mation, known as cerebritis, and develops into a collection of

necrotic pus surrounded by a vascular capsule.2,3 In the past

decade the population prevalence of chronic immune sup-

pression and immunocompromise has grown, and with it

there has been a rise in opportunistic and fungal brain ab-

scess. It accounts for less than 1% of intracranial lesions in the

bscess e Typical MRI features, Apollo Medicine (2014), http://

ll rights reserved.

a p o l l o m e d i c i n e x x x ( 2 0 1 4 ) 1e42

developed world, as opposed to roughly 8% in developing

countries.4,5

2. Case report

A 34-year-old Asian man was referred to our hospital for liver

transplant due to decompensated Hepatitis B & Hepatitis C

related chronic liver disease, which was incidentally diag-

nosed 8 months ago. Thereafter he was started on anti-viral

medications for his hepatitis B virus infection, but his condi-

tion deteriorated & was thus referred for liver transplant.

During his pre-transplant evaluation patient had normal

neurological parameters. On second post-operative day (post

right lobe graft transplantation) the patient was started on

immunosuppressive drug regime (tacrolimus/cyclosporine).

On seventh post-operative day, the patient developed a single

episode of seizure followed be a 10min of post-ictal confusion.

A non-contrast CT was done to evaluate any intracranial

bleed. However, the CT revealed a hypodense space occupying

lesion in the left occipital lobe with peri-lesional edema &

mass effect (Fig. 1).

A contrast enhanced MRI was soon followed as MRI is the

best modality to evaluate the nature of such lesions. MRI

revealed a relatively well defined space occupying cavitatory

lesion in the left occipital region. The lesions appeared

hypointense on T1W sequences (Fig. 2a), hyperintense on

T2W sequences (Fig. 2b), showed signal suppression of the T2

hyperintense centre on FLAIR images; suggesting its necrotic

nature (Fig. 2c). Peripheral blooming was appreciated on GRE

sequences; suggesting fungal etiology of the lesion (Fig. 2d).

Multiple internal projections were seen from the periphery of

Fig. 1 e Non-contrast axial CT scan of brain at the level of

occipital horn showing ovoid, cystic lesion withmarginally

hyperdense walls & peri-lesional white matter edema in

the left occipital region.

Please cite this article in press as: Arora AS, et al., Fungal brain adx.doi.org/10.1016/j.apme.2014.08.002

the lesion displaying hyperintense signal on T1 & FLAIR im-

ages & hypointense on T2 images.

On diffusion weighted imaging, the periphery & the intra-

cavitatory papillary projections of the lesion displayed

restricted diffusion (increasingly hyperintense on increasing b

values with reversal on ADC images) with mean ADC value of

0.453 � 10�3 mm2/s. While the centre of the lesion showed

facilitated diffusion (decreasingly hyperintense on increasing

b value with reversal on ADC images) withmean ADC value of

2.792 � 10�3 mm2/s (Fig. 3).

On post-contrast sequences, the cavitatory lesion showed

peripheral ring enhancement with non-enhancing papillary

projections (Fig. 4). MR Spectroscopy (MRS) could not be done

due to markedly unstable condition of the patient. MRS has

been shown to complement other findings of MRI & help in a

better diagnosis of the abscess etiology. However in retrospect

it was felt that MR Spectroscopy would not have contributed

extra to the diagnostic evaluation, thereby saving the patient

physical & economic discomfort.

Marked peri-lesional white matter edema was seen with

mass effect and compression on the occipital horn of left

lateral ventricle.

Being diagnosed as a case of fungal abscess on imaging, the

patientwas taken for drainage of the abscess. The abscesswas

drained & the specimen sent for histo-pathology. On silver

stain branching fungal hyphae could bewell visualized (Fig. 5).

After abscess drainage the condition of the patient

improved significantly. The patient was later managed on

systemic anti-fungal&within next seventeen days the patient

was discharged with normal neurological functions.

3. Discussion

3.1. Conventional MR imaging features

In the cerebritis stage, pyogenic abscesses are seen as T1

hypointense and T2 hyperintense areas with minimal or non-

homogenous enhancement.6 Tuberculous cerebritis is seen as

an ill-defined, hypoattenuated area with gyral enhancement.7

Fungal cerebritis lesions are non-enhancing and are usually

located in the basal ganglia and deep white matter.8 Periph-

eral rim enhancement has been reported in mature pyogenic

and fungal abscesses.6,8 On the basis of conventional MR

findings, it is not possible to characterize the cause of brain

abscess in both cerebritis and abscess stages of formation. In

most of the pyogenic& tubercular abscess, the outermargin of

the wall will either be smooth or lobulated in contrast to the

fungal lesions, which will have crenated wall in more than

half of the abscesses.9 Almost all the fungal abscesses shows

intra-cavitatory projections directed centrally from the wall

without any contrast enhancement in these projections.9

These projections are not seen in the other types and

seemed to be a distinguishing feature of a fungal cause on

conventional MR imaging.9

3.2. Diffusion-weighted imaging

Pyogenic brain abscesses usually shows low ADC value

(0.28e0.70 � 10�3 mm2/s) due to the presence of intact

bscess e Typical MRI features, Apollo Medicine (2014), http://

Fig. 2 e a, b, c, d shows T1W, T2W, FLAIR & GRE axial scans of brain respectively. Relatively well defined cavitatory lesion

with internal projections & surrounding white matter edema could be appreciated on all scans. The internal projections &

periphery shows peripheral blooming on GRE scan. The center of the lesion shows signal intensity that of fluid.

Fig. 3 e Diffusion weighted axial images of brain showing cavitatory lesion in left occipital region which shows restricted

diffusion at its periphery & facilitated diffusion at its center.

a p o l l o m e d i c i n e x x x ( 2 0 1 4 ) 1e4 3

Please cite this article in press as: Arora AS, et al., Fungal brain abscess e Typical MRI features, Apollo Medicine (2014), http://dx.doi.org/10.1016/j.apme.2014.08.002

Fig. 4 e Post-contrast T1 weighted MR images of brain in

axial plane. Images show ring enhancing lesion in left

occipital region with non-enhancing papillary projections.

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inflammatory cells and bacteria that collectively impede the

microscopic motion of water molecules.10 For the exact same

reason, tubercular abscesses also have low ADC values.10,11

Low ADC in fungal cerebritis and fungal abscess has also

been described & thus it is difficult to differentiate between

the fungal and non-fungal causes of brain abscess.8,12 How-

ever, the analysis of DWI images and ADC values shows that

in most cases restricted diffusion is present in the projections

andwall of the fungal abscess. The wall& internal projections

of the fungal abscesses is reported to be composed of fungal

Fig. 5 e Periodic acideSchiff (PAS) stained specimen, which

shows branching fungal hyphae.

Please cite this article in press as: Arora AS, et al., Fungal brain adx.doi.org/10.1016/j.apme.2014.08.002

hyphae, fibrocollagenous tissue, inflammatory cells&necrotic

materials.9

The rest of the core of the abscess shows no restricted

diffusion, whereas the pyogenic and tubercular group shows

restricted diffusion in the core of the cavity.9,11,12

4. Conclusion

Fungal abscesses can be differentiated from non-fungal ab-

scesses by a combination of the conventional, diffusion

weighted imaging and proton MR Spectroscopy features. A

ring enhancing T2 heterointense lesion with irregular walls

and irregular projections into the cavity with low ADC and no

contrast enhancement of these projections carries a high

probability of being a fungal abscess.

Conflicts of interest

All authors have none to declare.

r e f e r e n c e s

1. Lazzeri E, Signore A, Erba PA, et al. Radionuclide Imaging ofInfection and Inflammation: A Pictorial Case-Based Atlas.2013:166.

2. Grigoriadis E, Gold WL. Pyogenic brain abscess caused byStreptococcus pneumoniae: case report and review. Clin InfectDis. Nov 1997;25(5):1108e1112.

3. Lu CH, Chang WN, Lin YC, et al. Bacterial brain abscess:microbiological features, epidemiological trends andtherapeutic outcomes. QJM. Aug 2002;95(8):501e509.

4. Prasad KN, Mishra AM, Gupta D, et al. Analysis of microbialetiology and mortality in patients with brain abscess. J Infect.Oct 2006;53(4):221e227.

5. Bhatia R, Tandon PN, Banerji AK. Brain abscessean analysisof 55 cases. Int Surg. Aug 1973;58(8):565e568.

6. Whiteman MLH, Bowen BC, Post MJD, et al. Intracranialinfection. In: Atlas SW, ed. Magnetic Resonance Imaging of theBrain and Spine. 3rd ed. Philadelphia: Lippincott Williams andWilkins; 2002:1099e1177.

7. Jinkins JR, Gupta R, Chang KH, et al. MR imaging of centralnervous system tuberculosis. Radiol Clin North Am.1995;33:771e786.

8. Gaviani P, Schwartz RB, Hedley-Whyte ET, et al. Diffusion-weighted imagingof fungal cerebral infection. AJNR Am JNeuroradiol. 2005;26:1115e1121.

9. Luthra G, Parihar A, Nath K, et al. Comparative evaluation offungal, tubercular, and pyogenic brain abscesses withconventional and diffusion MR imaging and proton MRspectroscopy. AJNR Am J Neuroradiol. 2007Aug;28(7):1332e1338.

10. Mishra AM, Gupta RK, Saksena S, et al. Biological correlatesof diffusivity in brain abscess. Magn Reson Med.2005;54:878e885.

11. Gupta RK, Prakash M, Mishra AM, et al. Role of diffusionweighted imaging in differentiation of intracranialtuberculoma and tuberculous abscess from cysticercusgranulomasda report of more than 100 lesions. Eur J Radiol.2005;55:384e392.

12. Tung GA, Rogg JM. Diffusion-weighted imaging of cerebritis.AJNR Am J Neuroradiol. 2003;24:1110e1113.

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