Answer of March 2009

Clinical History:

A 17-years-old boy presented with repeated episode of gelastic seizure. Contrast CT brain and EEG were unremarkable. MRI brain (Sagittal T1W, Sagittal T1W+C and axial T1W) was obtained.

Diagnosis:

Hypothalamic hamartoma

Discussion:

MRI brain showed a well defined mass at the tuber cinereum of hypothalamus. It is isointense to grey matter on T1W images and iso- or slightly hyperintense on T2-weighted images, with no contrast enhancement.

Hypothalamic hamartomas are developmental malformations consisting of tumor-like masses located in the tuber cinereum of the hypothalamus. It is the most common tumoral cause of central precocious puberty, incidence ranging from 14-58%. Histologically it contains nerve cells that resemble those of the normal hypothalamus, along with normal glial cells.

Most patients present in the first or second decade of life, with boys being more commonly affected than girls. Hypothalamic hamartomas are classified into two types: the pedunculated type is more likely to be associated with precocious puberty, and the sessile type is often associated with gelastic seizures. Hypothalamic hamartomas less than 1cm usually present with precocious puberty, whereas lesions more than 1cm usually present with gelastic seizures. 

Treatment options for precocious puberty associated with hypothalamic hamartoma may be surgical or medical. Surgical excision of hamartoma is recommended in young children. Medical treatment of precocious puberty includes use of a long-acting GnRH analogue or antagonists.