The authors represent a cooperative group of 15 institutions that examined the feasibility of using metabolic fea tures observed in vivo with 'H-magnetic resonance (MR) spectroscopy to characterize brain tumors of the glial type.The institutions provided blinded, centralized MR spectroscopy data processing along with independent central review of MR spectroscopy voxel placement, composition and contamination by brain, histopathological typing using current World Health Organization criteria, and clinical data, Proton 'H-MR spectroscopy was performed using a spin-echo technique to obtain spectra from 8-cc voxels in the tumor and when feasible in the contralateral brain. Eighty-six cases were assessable, 41 of which had contralateral brain spectra. Glial tumors had significantly elevated intensities of choline signals, decreased intensities of creatine signals, and decreased intensities of N-acetyl asp art ate compared to brain. Choline signal intensities were highest in astrocytomas and anaplastic astrocytomas, and creatine signal intensi ties were lowest in glioblastomas. However, whether expressed relative to brain or as intratumoral ratios, these meta bolic characteristics exhibited large variations within each subtype of glial tumor. The resulting overlaps precluded diagnostic accuracy in the distinction of low-and high-grade tumors. Although the extent of contamination of the ]H-MR spectroscopy voxel by brain had a marked effect on metabolite concentrations and ratios, selection of cases with minimal contamination did not reduce these overlaps. Thus, each type and grade of tumor is a metabolically hetero geneous group. Lactate occurred infrequently and in all grades. Mobile lipids, on the other hand, occurred in 41% of high-grade tumors with higher mean amounts found in glioblastomas. This result, coupled with the recent demonstra tion that intratumoral mobile lipids correlate with microscopic tumor cell necrosis, leads to the hypothesis that mobile lipids observed in vivo in E H-MR spectroscopy may correlate independently with prognosis of individual patients. W. G. Negendank, et ciL rylcholine), one primarily from creatines (creatine and phosphocreatine), and one primarily from acetyl aspar tate (NAA), In disease, signals from lactate and mobile lipids may also be observed.Studies of extracts of surgical specimens of human as trocytic tum ors using ]H -N M R spectroscopy indicated an increase in the ratio o f cholines to creatines, and a decrease in the ratio of N A A to creatines, with increas ing histopathological grades of m alignancy.16,45'61 Studies in patients using !H-N M R spectroscopy, referred to as MR spectroscopy, indicated sim ilar correlations betw een m etabolic features in vivo and the histopathological grades of astrocytic tum ors. 4'11'14'21,32,43'57'58'61 Other MR spectroscopy studies indicated that lactate is more likely to be present in high-than in low-grade tumors4, 14,15'20'21 and that the am ount of lactate may correlate with the extent of hyperm etabolic glucose consumption sho...

A 37-year-old macrocephalic woman was investigated for increasing gait disturbance due to longstanding spasticity and ataxia. MRI showed widespread bilateral increase in signal from cerebral white matter on T2-weighted images. Numerous subcortical cysts were visible in anterior-temporal and parietal regions. These clinical and neuroradiological features are those of megalencephalic leukoencephalopathy with subcortical cysts (MLC), a recently delineated white-matter disease with onset in childhood. Quantitative localised proton MR spectroscopy of white matter revealed marked reduction of N-acetylaspartate, creatine, and choline with normal values for myo-inositol, consistent with axonal loss and astrocytic proliferation. Diffusion tensor imaging showed an increased apparent diffusion coefficient and reduced anisotropy in affected white matter pointing to reduced cell density with an increased extracellular space. These findings are in line with histological changes alterations known to occur in MLC.

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Medullomyoblastoma is a rare variant of medulloblastoma containing myoblastic elements. A 9-year-old boy developed a cerebellar syndrome and signs of increased intracranial pressure, the cause of which was a tumor of the cerebellar vermis measuring 7 x 4.5 x 4.5 cm. Morphologically the tumor largely consisted of a medulloblastoma component but displayed glial, myoblastic and ganglionic differentiation on light microscopic, immunohistochemical and ultrastructural examination. The non-enhancing rim of the tumor on magnetic resonance imaging showed extensive ganglionic differentiation. The tumor did not express bcl-2, c-myc, or c-erb-B2 oncoproteins and was negative for the p53 gene product. On molecular genetic studies, the tumor did not show allelic loss on chromosome loci, frequently altered in medulloblastomas, such as 17p, 1q and 9q.

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