After an earlier attempt by Gumpert et al.,³² Gascon and Lombroso²⁹ suggested the following criteria for the diagnosis of gelastic epilepsy: Stereotyped recurrence of pathologic laughter; absence of external precipitants; concomitance of other manifestations generally accepted as epileptic (such as tonic or clonic movements, loss of consciousness, automatisms); presence of interictal and, where it can be recorded, ictal electroencephalographic (EEG) epileptiform discharges; and absence of other neuropathology that could explain pathologic laughter. Loiseau et al.⁴⁸ insisted on the now-accepted distinction between a seizure symptom or type and an epilepsy syndrome, arguing that there was no basis for the concept of “gelastic epilepsy,” an example, in their opinion, of the futility of classifications based on a single symptom.

Laughter is the principal clinical manifestation and defines the gelastic seizure type. Whether there are features of the laughter or other ictal manifestations that can distinguish between different gelastic seizure foci has been a matter of much discussion, and the issue remains controversial. Gascon and Lombroso²⁹ noted that patients with probable temporal lobe seizure origin had either a pleasurable aura or a mirthful quality to their laughter, and Loiseau et al.⁴⁸ agreed that the laughter in such cases was an expression of emotion. Exceptions have been noted, however, including patients with temporal lobe tumors whose ictal laughter either sounded forced or did not have an infectious quality.^4,64 Conversely, gelastic seizures of frontal lobe origin are said to present a more uniform picture, in which laughter sounds unnatural, appears forced, is devoid of emotional content, and is not associated with feelings of mirth.^8,71 The clouding of consciousness and impairment of memory that often accompany gelastic seizures of temporal and frontal lobe origin make separation of the affective and motor components of ictal laughter fraught with difficulty. Furthermore, previous reviews of gelastic seizures not associated with hypothalamic hamartoma have included many cases described before the use of magnetic resonance imaging (MRI) and in which localization of the ictal onset zone was based primarily on scalp EEG abnormalities.⁷¹ As is discussed further in Chapter 250, localized interictal EEG abnormalities and even invasive ictal recordings can be misleading in patients with hypothalamic hamartoma.¹³ In addition, the diagnosis can easily be missed with computed tomographic imaging.^1,34,49

The laughter in gelastic seizures associated with hypothalamic hamartoma has been described variously as “unnatural,”^21,69 “mechanical,”^13,70 “mirthless,”⁴⁴ “bubbling,”²⁰ “pleasant,”^5,70 or “normal.”¹ Delay in diagnosis of gelastic seizures in patients with hypothalamic hamartoma (see Chapter 250) attests to the fact that the laughter may sound real¹¹ and be indistinguishable from the person’s normal laughter.^1,3,54 The best-known example of this is the patient reported by Berkovic et al.⁵ who won a happy baby contest. As the patient grows older, however, the quality of the vocalization may become increasingly less like normal laughter.⁵

As to the question of mirth associated with gelastic seizures in hypothalamic hamartoma, reports are limited in number because of the typically young age of patients and the frequent presence of intellectual impairment. Striano et al.⁶⁷ observed that older patients do not feel amused during gelastic seizures but, rather, are so embarrassed that they try to conceal them (e.g., by feigning a sneeze). On the other hand, Sturm et al.⁶⁸ described three adult patients who experienced a strong desire or “pressure to laugh” either separately from or just prior to typical gelastic seizures; one described this as a pleasant and emotional feeling in the chest, and another said it was a pleasant, nonsexual feeling that made him happy and would allow himself to laugh when this was socially appropriate.

Gelastic seizures may be closely related to seizures with epileptic crying, termed “dacrystic”⁵⁶ or “quiritarian.”⁶⁴ Ictal crying has been noted in many patients with gelastic- seizures, mostly in association with hypothalamic hamar-toma^{12,31,41,47,60,65,67,72,73} and less often associated with other
localized pathology.⁶⁴ By contrast, dacrystic seizures have rarely been reported in the absence of gelastic seizures.^17,18

Gelastic seizures in patients with hypothalamic hamartoma are typically brief, lasting <30 seconds and often are just a few seconds in duration. Consciousness is said to be preserved during these brief events.⁷¹ This appears to be based on the rapid resumption of previous activity in infants and young children and from interviews with adult patients; ictal cognitive testing, however, has not been undertaken. By contrast, laughter is said to be longer lasting in patients with frontal and temporal gelastic seizures and is associated with impairment of consciousness in temporal gelastic seizures.⁷¹ Very frequent gelastic seizures that occur in wakefulness and from sleep are typical of infants with hypothalamic hamartoma.^22,62,65 Occasional cases of gelastic status epilepticus or “status gelasticus” have been reported, both in patients with hypothalamic hamartoma^55,59,73 and in one without it.³⁰

Associated with the ictal laughter are other motor manifestations that have not been well characterized. Facial contraction resembling a grimace or smile is reported,^47,61 as are clonic buccal, palpebral, and ocular movements, producing a grimacing appearance.²⁰ Autonomic features including facial flushing, lacrimation, and pupillary dilation are known to occur in patients with hypothalamic hamartoma,^5,68 but whether these are unique to patients with hypothalamic hamartoma is uncertain. Cerullo et al.¹⁴ demonstrated a rise in systolic and diastolic blood pressure, increased heart rate, facial flushing without diaphoresis, flattening of the plethysmogram, and modification of respiratory activity during gelastic seizures of two patients with hypothalamic hamartoma.

Interictal clinical features in patients with gelastic seizures depend on the underlying syndrome diagnosis. There is insufficient knowledge of such clinical features in patients with gelastic seizures due to temporal or frontal lobe epilepsy. The interictal clinical features associated with hypothalamic hamartoma are discussed in relation to diagnostic considerations later in this chapter and in Chapter 250.

Postictal features of gelastic seizures have not been well characterized. In older patients with hypothalamic hamartoma, gelastic seizures may be associated with impaired consciousness. In addition, gelastic seizures in hypothalamic hamartoma may be followed by nongelastic seizures, and the postictal features of these other seizure types may dominate the clinical picture. Whether these nongelastic seizures represent seizure spread from the hypothalamic hamartoma¹³ or are otherwise “triggered” by the gelastic seizure⁴¹ is unresolved, but both situations are possible.