<P> The main sign of a gelastic seizure is a sudden outburst of laughter or crying with no apparent cause . The laughter may sound unpleasant and sardonic rather than joyful . The outburst usually lasts for less than a minute . During or shortly after a seizure, an individual might display some twitching, strange eye movements, lip smacking, fidgeting or mumbling . If a person who suffers from the seizures is hooked up to an electroencephalogram, it will reveal interictal epileptic discharges . This syndrome usually manifests itself before the individual reaches the age of three or four . The temporal lobes, and the hypothalamus are the areas of the brain with the most involvement with these seizures . This may cause learning disabilities, and faulted cognitive function as well . It is not uncommon for children to have tonic - clonic seizures, and atonic seizures directly following the seizure . Those that are associated with hypothalamic hamartomas may occur as often as several times hourly and typically begin during infancy . Seizures that occur in infancy may include bursts of cooing, respirations, giggling, and smiling . Due to early hypothalamic - pituitary - gonadal axis activation in girls who suffer from the seizures, it is not uncommon for them to display secondary sex characteristics before the age of eight . </P> <P> A gelastic seizure is typically caused by a hypothalamic hamartoma, or a brain tumor . A hypothalamic hamartoma is defined as a benign mass of glial tissue on or near the hypothalamus . The size of the hamartoma can vary from one centimeter to larger than three centimeters . They can cause several different types of seizures including a Gelastic Seizure . These structures can be detected with different imaging modalities such as computed tomography and magnetic resonance imaging . A computed tomography scan of an individual with a hypothalamic hamartoma would reveal an suprasellar mass with the same density as brain tissue . Images of these masses are not enhanced with the use of contrast . However, although a computed tomography scan may be useful in diagnosing the cause of a seizure, in the case of a hypothalamic hamartoma, magnetic resonance imaging is the tool of choice due to the cerebrospinal fluid which defines these masses . Photon emission computed tomography may also be used . This involves the use of a radiotracer which is taken up by the ictal region of the brain which is typically where the tumor lies . Gelastic seizures have been observed after taking a birth control pill (Maxim (R)). </P> <P> Optic nerve hypoplasia is the only reported condition with gelastic seizures without hypothalamic hamartomas, suggesting that hypothalamic disorganization alone can cause gelastic seizures . </P> <P> A diagnosis is difficult, especially in children, due to the difficulty in differentiating between actual laughing or crying, versus a seizure that involves laughing and crying . In pre-verbal infants, a diagnosis may be impossible . A long history must be taken with a description of all the signs leading to and during the seizure . The episodes can also be confused with behavioral and emotional disorders . Some doctors ask parents to videotape the children's outbursts . The tapes may be difficult to obtain, but can be very helpful in speeding up the difficult diagnosis process . Diagnosis is also complicated due to the many possible causes of the seizures . Imaging is always helpful in an attempt to diagnose seizures caused by hypothalamic hamartoma . If there is evidence of this, the diagnosis takes much less time . </P>

What causes a person to laugh for no reason