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Objective Magnetic resonance imaging and computed tomography provide good anatomic detail of suprasellar tumors in pediatric patients but are not able to predict histology in many cases. Proton magnetic resonance spectroscopy provides metabolic data that may add to diagnostic specificity. We preoperatively performed localized proton magnetic resonance spectroscopy on pediatric patients with suprasellar tumors and correlated the results with the histological findings. Cyst fluid obtained from patients with craniopharyngiomas was studied with high-resolution magnetic resonance spectroscopy to better understand the in vivo data. Methods Nineteen patients aged 1 to 21 years underwent spectroscopy. Surgical pathological samples were obtained from 14 patients. In each of five patients, the presence of a solid chiasmatic mass in addition to clinical evidence of neurofibromatosis Type I allowed the presumptive diagnosis of chiasmatic astrocytoma. Thus, the study population included 6 patients with craniopharyngiomas, 10 with chiasmatic/hypothalamic astrocytomas, and 3 with pituitary adenomas. The data obtained were compared with those of healthy brain from age-matched participants. Results Spectroscopy was specific for the diagnosis. All craniopharyngiomas showed a dominant peak at 1 to 2 ppm, consistent with lactate or lipids, with trace amounts of other metabolites. This was confirmed using high-resolution spectroscopy. Chiasmatic gliomas showed a profile of choline, N-acetylaspartate, and creatine, and the choline:N-acetylaspartate ratio was 2.6 +/- 1.3, compared with 0.7 +/- 0.3 for samples of healthy brain (t test, P = 0.0003). Pituitary adenomas showed only a choline peak or no metabolites at all. Conclusion Proton spectroscopy may be helpful in supplementing standard imaging for the preoperative diagnosis of three types of suprasellar tumors that are common in pediatric patients.

We report three patients with gangliogliomas involving the optic chiasm via distinct mechanisms.The ganglioglioma in one patient likely originated in the temporal lobe and spread medially to involve the chiasm, and diffuse spinal cord dissemination also occurred. Chiasmal involvement in this manner and dissemination at presentation are unusual for gangliogliomas. The tumor in a second patient was intrinsic to the hypothalmus and chiasm, while in the third patient, it involved both optic tracts, and a cyst compressed the chiasm laterally. Two patients developed severe bilateral visual loss, while the other had a stable bitemporal hemianopsia. Two patients received radiotherapy, but one continued to lose vision. Although gangliogliomas rarely involve chiasm, the mechanisms by which they produce chiasmal visual loss may be diverse, and the long-term visual prognosis is variable.NEUROLOGY 1996;46: 1669-1673