Intraventricular glioneuronal hamartoma: histopathological correlation with magnetic resonance spectroscopy.

Intraventricular hamartomas are extremely uncommon lesions outside of a setting of tuberous sclerosis. The second case of its kind in medical literature is presented and its possible aetiopathogenesis, imaging characteristics, pathognomonic magnetic resonance spectroscopy (MRS) and histopathology are discussed. An 11-year-old male presented with a seizure disorder for one year, with headache and vomiting for 15 days. Computerized tomography (CT) revealed a non-enhancing, heterogeneous, left-sided, trigonal lesion with areas of calcification trapping the left frontal horn. Magnetic resonance imaging (MRI) indicated that the lesion was iso to hypointense on T1 weighted images (T1WI) and iso to hyperintense on T2 weighted images (T2WI). A pathognomonic neurochemical signature was elicited on (1)H MRS showing low N-acetylaspartate resonance and normal creatine:choline ratios. Radical decompression of the tumor resulted in an excellent outcome. The diagnosis was established by positive immunohistochemical reactivity for synaptophysin, glial fibrillary acidic protein (GFAP) and myelin basic protein. This is the first case report in existing medical literature in which a histopathological correlation is available for a hamartoma with an unequivocal MRS signal. The authors advocate the use of MRS in patients with tuberous sclerosis or neurofibromatosis with suspected hamartomas to distinguish these benign lesions from gliomas prior to a surgical exploration.