Brain abscesses: etiologic categorization with in vivo proton MR spectroscopy.
OBJECTIVE
To compare the metabolite patterns observed at in vivo proton magnetic resonance (MR) spectroscopy of brain abscesses in patients for whom bacteriologic information was obtained from cultures and to categorize the MR spectral patterns with respect to the underlying etiologic agents.


METHODS
MR imaging and in vivo single-voxel proton MR spectroscopic data obtained from 75 patients with brain abscesses were retrospectively analyzed. Ex vivo spectroscopic experiments with the pus from 45 of these patients also were performed, and the data were further categorized on the basis of bacteriologic information. Quantification of various metabolites and metabolite ratios and statistical analyses of lactate and lactate/amino acid (AA) ratio levels were performed by using one-way analysis of variance.


RESULTS
On the basis of in vivo proton MR spectroscopic and bacteriologic analysis findings, data were classified into three categories: Group 1 data showed resonances of lactate, AAs, and acetate, with or without succinate at proton MR spectroscopy; cultures for this group showed obligate anaerobes or a mixture of obligate and facultative anaerobes. The metabolite patterns in the group 2 and group 3 data were similar to the pattern of the group 1 data, with the exception that acetate and succinate resonances were absent. Culture was positive for either obligate aerobes or facultative anaerobes in group 2 and was sterile in group 3. At analysis of variance, in vivo data showed significant differences in lactate/AA ratios (P =.008), and ex vivo data showed significant differences in lactate levels (P =.001) among the three groups.


CONCLUSIONS
It is possible to differentiate anaerobic from aerobic or sterile brain abscesses on the basis of metabolite patterns observed at in vivo proton MR spectroscopy. This information may be useful in facilitating prompt and appropriate treatment of patients with these abscesses.
Garg
Monika
M
Dept of Radiodiagnosis, Sanjay Gandhi Post-Graduate Institute of Med Sciences, Lucknow-226014, India.
Gupta
Rakesh K
RK
Husain
Mazhar
M
Chawla
Sanjeev
S
Chawla
Jayant
J
Kumar
Rajesh
R
Rao
Sajja B
SB
Misra
Mithlesh K
MK
Prasad
Kashi N
KN
D000085:Acetates / Q000032:analysis; D000293:Adolescent; D000328:Adult; D000596:Amino Acids / Q000032:analysis*; D000704:Analysis of Variance; D001424:Bacterial Infections / Q000175:diagnosis / Q000209:etiology* / Q000382:microbiology; D001431:Bacteriological Techniques; D001922:Brain Abscess / Q000175:diagnosis / Q000209:etiology* / Q000382:microbiology; D002648:Child; D002675:Child, Preschool; D003937:Diagnosis, Differential; D005260:Female; D006801:Humans; D007090:Image Interpretation, Computer-Assisted; D007223:Infant; D019344:Lactic Acid / Q000032:analysis*; D008279:Magnetic Resonance Imaging; D009682:Magnetic Resonance Spectroscopy; D008297:Male; D008875:Middle Aged; D012680:Sensitivity and Specificity; D019802:Succinic Acid / Q000032:analysis
D000085:Acetates; D000596:Amino Acids; D019344:Lactic Acid; D019802:Succinic Acid