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Chordoid glioma of the third ventricle is considered to be a benign glial tumor located exclusively in the mid-anterior portion of the third ventricle near the hypothalamus and optic nerves, with the histological features of a chordoma and immuno-labeling for glial fibrillary acidic protein. Unfortunately, the clinical outcome of chordoid glioma has been poor, even in patients receiving gross total or partial removal with or without radiotherapy. Three cases of chordoid glioma of the third ventricle were treated with less invasive microsurgery for pathological diagnosis or partial removal without neuro-endocrinological complication, followed by gamma knife radiosurgery using a lower marginal dose for the optic nerves and hypothalamus. Gamma knife radiosurgery was performed after open biopsy in two patients, and after partial removal in the third patient using a lower marginal dose of 10.5 to 12 Gy. Serial magnetic resonance imaging revealed gradual decrease or at least no change in the tumor size, without significant complication at follow up 70 and 66 months later in two cases. The third patient accidentally died 13 months after gamma knife treatment. We conclude that low dose gamma knife radiosurgery after less invasive microsurgery is both safe and effective for the control of chordoid glioma of the third ventricle over a very long follow-up period.

Purpose: We evaluated the clinical usefulness of the Cho/Cr ratio of proton MR spectroscopy(1H-MRS) to differentiate residual/recurrent glioma from non-neoplastic lesions., Patients and Methods: 20 cases of glioma were involved in this study(astrocytoma grade I-II: 7, oligodendroglioma: 1, astrocytoma grade III: 2, glioblastoma: 10). Seven of the patients underwent surgical resection only, 4 underwent surgical resection and radiotherapy(40-60 Gy), and 9 underwent surgical resection and radiotherapy with concurrent chemotherapy(14-60 Gy). 1H-MRS was performed on a 1.5 Tesla clinical MR unit using a 3D-chemical shift imaging sequence(1500 msec/270 msec/1 (TR/TE/excitations), and the Cho/Cr ratio was calculated in the voxel where neoplastic lesion was most suspected on MRI. The presence of lactate + lipid peak was also evaluated. All spectra were obtained after the contrast enhanced study., Results: Cho/Cr ratios were significantly higher in cases of residual/recurrent tumors(mean +/- SD = 1.70 +/- 0.96) than in non-neoplastic lesions(mean +/- SD = 1.04 +/- 1.16) (Mann-Whitney U-test p = 0.047). If a Cho/Cr ratio of more than 1.5 was used as a marker of tumor presence, its sensitivity was 64%, specificity 83%, and accuracy 70%. One false-positive case that of radiation necrosis whose spectrum showed a high Cho/Cr ratio with markedly elevated lactate + lipid peak., Conclusion: The Cho/Cr ratio of 1H-MRS provides additional information to MRI in differentiating residual/recurrent gliomas from non-neoplastic lesions.