IS case 478: Hypothalamic hamartoma
Imaging Sciences URMC 2010
Publication Date: 2010-08-30
Patient is an-11-year-old male presenting with gelastic seizures.
Axial and sagittal T1, coronal T2 and axial T1 fat saturation post-contrast images demonstrated an ovoid, mass measuring in the region of the tuber cinereum of the hypothalamus between the infundibular stalk, anteriorly, and the mamillary body, posteriorly, which extends upward within the third ventricle. There was no evidence of enhancement of the mass on post-contrast image.
Hypothalamic hamartomas are developmental malformations located in the tuber cinereum of the hypothalamus. Most of the neurons in a hamartoma are similar to normal hypothalamic neurons. Most patients present in the first or second decade of life, with boys being more commonly affected than girls. Boyko, et al.  classified hypothalamic hamartomas into two types: the pedunculated type which is more likely to be associated with precocious puberty, and the sessile type often associated with gelastic seizures. Hypothalamic hamartomas < 1 cm usually present with precocious puberty, whereas lesions >1 cm usually present with gelastic seizures. The most common tumoral cause of central precocious puberty is hypothalamic hamartoma, the incidence ranging from 14–58%.
Findings on MRI include well-defined pedunculated or sessile lesions at the tuber cinereum and are isointense or mildly hypointense on T1-weighted images and iso- to hyperintense on T2-weighted images, with no contrast enhancement or calcification. Proton MR spectroscopy shows normal choline and creatine but mildly to moderately decreased NAA.The absence of any long-term change in the size, shape, or signal intensity of the lesion strongly supports the diagnosis of hypothalamic hamartoma.
Differential diagnosis of hypothalamic hamartoma may include craniopharyngioma and optic-hypothalamic gliomas
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