A Giant Hamartoma of Tuber Cinerium : Conventional MR Imaging and MR Spectroscopy Findings

Hypothalamic hamartoma is a developmental malformation in the region of tuber cinereum and mamillary bodies. It presents the most commonly detectable lesion in patients with precocious puberty and is associated with gelastic seizures. As well as, it can be completely silent to be found only incidentally. Computed tomography (CT) and magnetic rezonans (MR) imaging are preferred imaging modalities in diagnose of hypothalamic hamartomas. The aim of this study is to present the radiologic imaging findings of a rare hypothalamic hamartoma case.


INTRODUCTION
Hypothalamic hamartomas (HH) are rare, congenital, nonneoplastic heterotopias that are originating from tuber sinerium and mamillar bodies.Prevalence of HH is between 50,000 to 100,000 (1).The characteristic clinical symptoms are precocious puberty, gelastic seizure, cognitive and behavioral abnormalities in children and, jeneralize seuzire accompanying with tonic, atonic and other convulsions in adults (2).The radiological presentation can also vary.HH usulally determined in the form of a suprasellar, non-enhanced mass in the hypothalamus.Epilepsy in patients with HH is usually resistant to medical treatment, therefore surgery should always be considered in treatment.The largest HH that was reported is 5 cm dimension (3).The aim of this study is to present the radiologic imaging findings with huge dimension of a rare HH case.

CASE
A 17 year old boy presented with generalized tonicclonic seizures since the age of 1 year.Neuroimaging findings were atypical, showing the large tumor (maximum diameter, 56 mm) with a cystic component and calcification.In physical examination, there are no findings other than speech aphasia and assisted walking.Brain magnetic resonance (MR) imaging revealed that, 5,6x4x2 cm dimension, izointens with grey matter on T1 and T2 weighted images, no contrast enhacement mass in tuber sinerium is present (Figure 1).The lesion pressed to 5, 6. and.8. kranial nerves because of its localization.On Diffusion MR imaging, it's seen that, lesions signal caracterization is similar to neural parenchyma (Figure 2).The imaging findings are compatible with hamartoma.In single-voxel proton MR spectroscopy of the mass lesion, metabolic distribution revealed  3).The patient is followed with medical treatment, surgical treatment was not considered.

DISCUSSION
Hypothalamic hamartomas are relatively rare, nonneoplastic congenital malformations.They may be pedunculated, adjacent to the mamillary bodies or tuber cinerium by a thin stalk, or sessile (4).The character-istic clinical symptoms are precocious puberty, gelastic seizure, cognitive and behavioral abnormalities jeneralize seuzire accompanying with tonic, atonic and other convulsions (5).Seizure is the main neurologic manifestation of HH and gelastic seizures beginning early in life are the classical epileptic presentation.Gelastic seizures are epileptic events characteristic by bouts of laughter and they are rarely diagnosed at onset.They may be mistaken for normal laughter (6).
Computed tomography (CT) and MR imaging are used to diagnose of HH.CT is not sensitive to the presence of the HH.MR imaging is the study of choice for patients with clinical suspicion of HH.These lesions have typically been described as isointense to gray matter on T2-weighted and T1-weighted images (7).The characteristic location, isointensity to normal brain, lack of contrast enhancement of the solid compartment of the mass, the absence of hemorrhage and calcification and absence of change in size and morphology of the mass at the follow-up.In MR spectroscopy, metabolic distribution shows decreased NAA, increased MI, and elevated Cho levels.In literature, the largest HH size is 5 cm (3).HH in our patients is size of 5,6 cm.Classification of the lesion is important for treatment and accuratly predict of it's prognosis.Also type and size of the lesion is important.Precocious puberty is more common in the pedunculated type and <1 cm size of lesion.On the other hand gelastic seizures are more common in the sessile  type and >1 cm size of lesion (8).Differential diagnosis of HH may include craniopharyngioma, chiasmatic/ hypotalamic astrositoma, optic/hypotalamic astrositoma, rathke cleft cyst ectopic posterior pituitary, germinomas, langerhans cell histiocytosis and lipoma (1)(2)(3)(4)(5)(6)(7)(8).Treatment options in HH are surgical or medical.Medical treatment contains use GnRH analogue or antagonists until puberty.Surgical treatment is considered in young children, whereas in children close to puberty, surgical treatment is not required.In conclusion, typical clinical presentation, uncommon location and characteristic conventional MR imaging and MR spectroscopy findings help the diagnosis of HH.Early diagnosis and treatment, the seizures are improved and the reduction in their cognitive abilities are avoided.

Figure 3 .
Figure 3. MR spectroscopy of the mass shows metabolic distribution decreased NAA, increased MI, and slightly elevated Cho.

Figure 2 .
Figure 2. In diffusion weighted images show that lesionsignal caracterization is similar to neural parenchyma.