What type of seizure is uniquely seen in patients with hypothalamic hamartomas?
Gelastic (laughing) phenotype.
How are hypothalamic hamartomas differentiated from chiasmatic/hypothalamic astrocytomas on imaging?
Chiasmatic/hypothalamic astrocytomas are typically of higher signal on T2/FLAIR and often show enhancement. Additionally, astrocytomas are more likely to extend into the optic pathways and are more common in patients with neurofibromatosis.
How do hypothalamic hamartomas typically present?
Clinically, these patients may have precocious puberty or epilepsy. Specifically, hypothalamic hamartomas are classically associated with gelastic seizures (recurrent bursts of laughter without loss of consciousness).
MRI of the brain shows a lobular mass centered at the tuber cinereum. The mass is solid and isointense to gray matter on all sequences without evidence of enhancement. The mass abuts the optic chiasm and gently molds against the dorsum sella. Posteriorly, the mass splays the cerebral peduncles. The mass contacts the optic tracts superolaterally and mildly elevates the third ventricle.