The syndrome gelastic seizures-hypothalamic hamartoma: severe, potentially reversible encephalopathy.

Hypothalamic hamartoma (HH) is the pathologic hallmark of a spectrum of epileptic conditions, ranging from a mild form of epilepsy, whose seizures are an urge to laugh without cognitive defects, to the fully developed syndrome of early onset gelastic seizures (GS) associated with precocious puberty and the evolution to a catastrophic epilepsy syndrome. However, a refractory focal or generalized epilepsy develops during the clinical course in nearly all cases. Neurophysiologic and neuroimaging studies have assessed the role of HH in the generation of the GS as well as in the process of secondary epileptogenesis. Electrophysiologic properties of small gamma-aminobutyric acid (GABA)ergic, spontaneously firing neurons might explain the intrinsic epileptogenicity of HH. Surgical ablation of the HH can reverse both epilepsy and encephalopathy. Gamma-knife radiosurgery and image-guided robotic radiosurgery can be useful and safe approaches for treatment, in particular of small HH.