Epilepsy in Hypothalamic Hamartoma: Clinical and EEG Features

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Hypothalamic hamartoma (HH) is a congenital malformation of the hypothalamus that may be asymptomatic or manifest with precocious puberty or seizures. Gelastic seizures often begin early in life, even in the newborn period, being manifest by frequent attacks of inappropriate laughter resulting from seizure activity in the HH. The scalp electroencephalogram (EEG) is often normal in children with gelastic seizures, such that the diagnosis of epilepsy and the finding of a HH are often delayed. In a proportion of children with HH, there is an epileptic progression, in which complex partial seizures with frontal, temporal, and lateralized clinical features appear, usually with the appearance of focal slowing and epileptiform activity on the interictal EEG. Further progression may ensue with the appearance of tonic or atonic drop attacks, generalized tonic-clonic seizures, and epileptic spasms; rarely, infantile spasms may be the presenting seizure type. With the appearance of generalized seizures, the interictal EEG shows bilaterally synchronous and generalized epileptiform activity, often in abundance. The mechanism of this evolution is incompletely understood but neocortical seizure propagation and secondary epileptogenesis are believed to be important. Paralleling the development of the focal and generalized electroclinical manifestations in children with HH is usually slowing of development and the appearance of behavioral problems. Fortunately, many of these neurologic manifestations can be arrested, or reversed, with effective surgical treatment directed at the HH.

Section snippets

Gelastic Seizures

Gelastic seizures are epileptic events characterized by bouts of laughter.4 In HH, laughter-like vocalization is usually combined with facial contraction in the form of a smile.5 In some children, the vocalization has a crying quality and the facial contraction resembles a grimace; these are referred to as dacrystic seizures. There may be a combination of gelastic and dacrystic seizures in the same patient6 and gelastic and dacrystic features in the same seizure,7 such that these are generally

Complex Partial Seizures

In many children with gelastic seizures and HH, other clinical seizure characteristics develop. When impairment of consciousness is prominent or the child is witnessed to have automatisms or focal motor manifestations, the attacks are often described as complex partial seizures. The distinction between gelastic and complex partial seizures can be difficult on history and on video analysis. Gelastic features are often retained in so-called complex partial seizures. In other patients in whom the

Generalized Seizures

The most dramatic and disabling seizure manifestation of HH is the emergence of generalized seizures, particularly tonic seizures and drop attacks. Generalized seizures are reported in approximately 70% of patients in larger surgical series.15, 43, 44 However, the exact prevalence of specific generalized seizure types in patients with HH is uncertain because of the bias in surgical series to more severely affected patients and the absence of adequate clinical descriptions in most studies.

Determinants of Electroclinical Manifestations of Hypothalamic Hamartoma

The variability in clinical manifestations of HH is incompletely understood. There is some evidence to suggest that the size of HHs and their attachment to the hypothalamus are important determinants. HHs associated with epilepsy almost universally have an intraventricular attachment to the medial hypothalamus or mammillary bodies,48 the latter being an important functional connection in terms of seizures. As previously mentioned, asymmetry of HH attachment generally correlates with asymmetries

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