Differential diagnosis of gelastic seizures beside hypothalamic hamartoma

Background: Gelastic seizures are considered to be pathognomonic for hypothalamic hamartoma (HT). Compared to HT the number of reported cases with different aetiology, mainly frontal or temporal tumours or focal cortical dysplasia (FCD), described so far is small.

We report 8 consecutive patients suffering from gelastic seizures and their clinical presentation, aetiology and results of long-term video-EEG.

Patients: Since 01/2000 about 600 patients with epilepsy (age 2 weeks up to 26 years) were investigated by long-term video-EEG monitoring for presurgical evaluation or syndrome diagnosis in our institution. About 75% of these patients had focal epilepsies. Gelastic seizures occurred in 8 patients (3 f, 5 m age; 2.5–18yrs).

Epilepsy syndromes, aetiology and clinical course: HT was diagnosed in two male patients (7 and 10,4yrs). Seizure semiology comprised gelastic, clonic, tonic and psychomotor symptoms. Both children were treated by interstitial stereotactic radiosurgery. MRI was suspect for right frontal FCD in two patients (m, 5.5yrs; f, 15yrs). Gelastic seizures were accompanied by left-sided cloni. Epilepsy surgery is planned in both cases. One boy with a low-grade ganglioglioma in the right parietal lobe laughed during psychomotor seizures. However, laughing was not the dominant semiological pattern. He became seizure free after lesionectomy. During the course of a cryptogenic focal epilepsy with mainly hypomotor seizures, one girl (5.5yrs) developed gelastic seizures. Bilateral ictal EEG patterns were localized in both temporal and frontal lobes. In a 3 year old boy epilepsy started at 4 weeks of age with myoclonic and tonic seizures. Aetiology remained unclear. In addition, infrequent gelastic seizures occurred at the age of 13 months and were accompanied by diffuse bilateral EEG patterns. Finally, a girl with complex I deficiency and repetitive complex partial status epilepticus presented with gelastic seizures at the age of 5 years. Ictal EEG revealed diffuse bilateral sharp-wave patterns.

Conclusions: Gelastic seizures are rare. However, they are not pathognomonic for hypothalamic hamartoma.