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OVERVIEW

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Hypothalamic hamartomas (HHs) are congenital mass lesions in the region of the third ventricle and tuber cinereum. Their true prevalence is unknown and is approximated to be 1 in 100,000. This estimated prevalence appears high but may actually be an underestimate as the diagnosis is often missed or at least significantly delayed.1

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Two "main" clinical syndromes are recognized: precocious puberty and intractable epilepsy, including gelastic (laughing) seizures. Gelastic seizures are usually followed by the development of other seizure types including tonic, tonic–clonic, and complex partial.2 Predominantly gelastic seizures, but also all other seizure types are often extremely refractory to antiepileptic drugs (AEDs). Associated clinical problems with the intrahypothalamic (sessile) subtype include developmental retardation, cognitive decline, and psychiatric symptoms such as mood liability and rage behavior.3 Pedunculated lesions, which hang inferiorly from the tuber cinereum, are most likely to cause central precocious puberty, although many patients have both clinical syndromes.

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There are several classifications of HHs. Arita et al classified lesions into two types on the basis of magnetic resonance imaging (MRI) characteristics. These include (1) a parahypothalamic type in which the HH is attached to the floor of the third ventricle or is pedunculated (and associated with precocious puberty) and (2) a intrahypothalamic type in which the HH is enveloped by the hypothalamus and distorts the third ventricle (more commonly associated with gelastic epilepsy, with or without precocious puberty, mental retardation, and behavioral problems).4 The sessile or intrahypothalamic types of HHs have a prominent intraventricular component and are strongly associated with gelastic epilepsy probably because of their juxtaposition to the body of the hypothalamus and central connections.

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Various therapies to control seizures have met with only limited success. These include vagal nerve stimulation, gamma-knife therapy (probably most successful), stereotactic destruction of the lesion through radio frequency, and even GnRH analogue (standard treatment for precocious puberty).5 Initially, only single-case reports and small series reported favorable seizure control after surgical resection of the HH.6 Subsequently, two surgical techniques have proven to be beneficial, often leading to curative results in the treatment of HH patients. These include surgical resection via an anterior transcallosal interforniceal approach and an endoscopic transventricular approach.7,8,9 Although complete resection of the HH is preferential, incomplete resection with presumed complete disconnection of the HH from its attachment to the hypothalamus can also achieve seizure freedom.

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CLINICAL FEATURES

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EPILEPSY

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Gelastic seizures are the hallmark of HH. Gelastic seizures were first described by Daly and Mulder in 1957.10 They are usually quite brief, typically lasting less than 30 seconds, and more often lasting just a few seconds in duration. They may be associated with little or no change in consciousness, particularly early in the course. They are very frequent, up to multiple seizure events hourly in severely affected patients.

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