HYPOTHALAMIC HAMARTOMAS AND GELASTIC EPILEPSY - A SPECTROSCOPIC STUDY

Background. Patients with hypothalamic hamartomas present with epilept ic attacks of laughter and later experience multiple seizure types and cognitive decline, suggestive of secondary generalized epilepsy. It h as been suggested in the past that gelastic seizures originate in the temporal lobes rather than in the hamartoma, but temporal resections h ave been ineffective. Recent electrophysiologic evidence suggests that the epileptogenic discharges may originate in the hamartoma itself. M ethods: We used proton magnetic resonance spectroscopic imaging to qua ntify the amount of neuronal damage in the temporal lobes and hamartom as of patients with hypothalamic hamartomas and gelastic seizures. Fiv e patients were studied and the relative intensity of N-acetylaspartat e to creatine (NAA/Cr) was determined for both temporal lobes as well as for the hamartoma. These values were compared with signals from the temporal lobes and hypothalami of normal control subjects. Results: N AA/Cr was not significantly different from normal control subjects for either temporal lobe, nor was there a significant asymmetry between t he two temporal lobes for any of the patients. NAA resonance signals w ere present in the hamartomas, and the ratio of NAA to Cr was decrease d in the hamartomas compared with the hypothalami of normal control su bjects (t = 4.5, p = 0.005). Conclusions: We found no detectable neuro nal damage in the temporal lobes of patients with hypothalamic hamarto mas and gelastic epilepsy. This is further evidence that gelastic seiz ures do not originate in the temporal lobes of these patients.