Radiological Case: Giant Hypothalamic Hamartoma

Mougnyan Cox, MD; Julia Ahn, DO; Vinay Kandula, MD; and Joseph Piatt, MD

Disclosures

Appl Radiol. 2017;46(5):31A-31B. 

In This Article

Discussion

Hypothalamic hamartomas are congenital malformations characterized by disorganized but normal neural tissue in the hypothalamic region.[1] Patients with hypothalamic hamartomas classically present with gelastic seizures (laughing seizures), but other seizures types may also occur.[2] Hypothalamic hamartomas are also an important structural cause of precocious puberty, and have been reported to be the most common cause of central precocious puberty.[3] Treatment is usually medical, with a focus on correcting any associated endocrinologic abnormalities or controlling seizures. Surgery is usually reserved for medically refractory seizures, or precocious puberty in some cases.[4,5]

On imaging, hypothalamic hamartomas are similar in appearance to distorted but normal brain tissue.[6] Hypothalamic hamartomas arise from the floor of the third ventricle and project into the suprasellar cistern. When large, these lesions can distort the suprasellar cistern and compress or displace multiple structures including the optic chiasm and prechiasmatic optic nerves, internal carotid arteries, and pituitary stalk. On CT, these lesions appear isodense to the normal brain parenchyma, and do not enhance after contrast administration. Hemorrhage and calcification within hypothalamic hamartomas are exceedingly rare. MRI imaging shows a soft tissue mass in the hypothalamic region that is isointense to brain on T1 and T2, without abnormal enhancement.

The differential diagnosis for a suprasellar mass in a pediatric patient is extensive,[7] but the majority of the lesions are uncommon. Major considerations for a solid suprasellar mass would include a craniopharyngioma, pituitary macroadenoma, or a germ cell tumor (including teratomas). Craniopharyngiomas in pediatric patients are usually of the adamantinomatous type. These lesions are typically cystic, contain calcifications, and enhance after contrast administration.[8] Pituitary macroadenomas usually expand the sella, and may extend into the suprasellar cistern when large. These lesions have a propensity to invade the cavernous sinus, and may encase the internal carotid artery without causing significant narrowing. Suprasellar germ cell tumors (most commonly germinomas) arise from the hypothalamic region and grow along the pituitary stalk. When large, they present as heterogeneous masses with enhancement and mild restricted diffusion. These tumors have a tendency for cerebrospinal fluid dissemination, and additional enhancing foci elsewhere in the ventricles should be viewed with suspicion and considered to be metastases until proven otherwise.

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