In Vivo 1H MRS Observation of Brain Succinate in a Subject With Cerebritis and Gram Positive Sepsis

Proton brain MRS studies was conducted on a 2-year old diagnosed with cerebral palsy, developmental delay, cerebritis and gram positive sepsis. 2D CSI H MRS study on a T2 hyperintense region in the left posterior frontal and parietal regions indicated significantly elevated levels of lactate, slightly elevated choline and decreased NAA. In addition, a large singlet peak was observed at 2.40 ppm in the spectra from the lesion. This appears to be that of the succinate, judging from its chemical shift and line shape. This metabolite was previously reported in in vitro and in vivo studies of brain abscess (1,2). In these studies, normal metabolites such as NAA, creatine and choline were absent, and acetate, succinate, amino acid and/or alanine were observed. In our subject, in addition to the strong succinate resonance, significant levels of the normal metabolites were detected and no acetate, alanine or amino acid was seen. In addition, our MRI data shows no evidence of frank intracranial abscess but a more diffuse cerebritis. Materials and methods MRS/MRI studies were conducted on a Siemens Magnetom Vision 1.5T MR scanner with a circularly polarized head coil. Clinical T1 and T2 weighted, diffusion, and 3D TOF MRA of the circle of Willis images were conducted. Three-plane HASTE images were obtained to guide the positioning of the region of interest. 2D H CSI spectroscopy through the level of centrum semiovale (Fig.1) was conducted in the axial plane in a 7 (A/P) x7 (L/R) x 1.5 (S/I) cm region, with point-resolved spectroscopy (PRESS) (3) localization technique. Spectral parameters were: TR = 1600 msec, TE = 135 msec, 16 x 16 phase encoding, two scan averages with a total acquisition time of 13.46 minutes. Prior to Fourier transform and phase correction the raw spectral data was multiplied with an exponential function corresponding to a 4 Hz line broadening. No baseline correction was performed. Figure 1. Figure 2. Figure 3. Figure 4. Figure 5. Figure 6. Discussion In addition to succinate, several other metabolites such as pyruvate (4), glutamine and glutamate all are know to have resonance signal(s) in the vicinity and thus can contribute to this signal observed at 2.40 ppm in the MR spectrum. Although contribution from glutamine and glutamate (Glx) can not be ruled out completely, contamination from Glx should be small under the current study condition (TE=135 msec). In addition, this resonance line appeared to be a sharp single peak which is not compatible with the normal pattern of Glx which have a broad pattern of multiplet peaks due to extensive spin couplings. Pyruvate (2.38 ppm) is highly unlikely, as there is no evidence of enzymatic defects (5). The MR appears to be that of cerebritis, without frank intracranial abscess. Inflammatory demyelination can mimic cerebritis on MR, but the clinical setting strongly favorsan infectious etiology. MRS data also favors cerebritis, with spectral patterns different from that previously reported in brain abscess. References1. Remy C, Grand S, Lai S, et al. H MRS of human brain abscesses in vivo and in vitro., Magnetic Resonance in Medicine. 34(4):508-14, 19952. Akutsu H, Matsumura A, et al. Chronlogical change of brain abscess inH magnetic resonance spectroscopy, Neuroradiology, 2002; 44:574578.3. Bottomley PA, Spatial localization in NMR spectroscopy in vivo. Ann NY Acad Sci 1987;508:333-3484. Wang D., Simon E., et al., In vivo 'H MRS observation of brain pyruvate in a neonate with pyruvate dehydrogenase deficiency, ISMRM 2546,2002 5. Brown GK, Otero J. Pyruvate dehydrogenase deficiency. J Med Genetics, 1994; Nov 21(11): 875-9ResultsMR exam revealed the largest lesion in the leftposterior frontal and parietal lobes with lesserinvolvement of the right frontal lobe (Fig.1).Cortical necrosis in the left parietal lobe wasalso observed. Fig. 2 shows the 2D CSIspectral map from the left centrum semiovaleregion. Localized spectra shown in Fig.3 and 4indicate significantly elevated levels of lacticacid, succinate and slightly decreased NAA andelevated choline in the lesion. Contralateralcingulate gyrus region shows decreased NAAand slightly elevated choline and lactate but nosuccinate (Fig. 5, 6). The line shape andchemical shift seems to indicate that resonanceat 2.4 ppm is from that of succinate. The peakarea ratios of the succinate to creatine, NAA tocreatine and lactate to creatine are 0.95, 1.21and 0.93, respectively for spectra extractedfrom the center of the lesion. Proc. Intl. Soc. Mag. Reson. Med. 11 (2003)2108