Giant subcortical high-frequency SEPs in idiopathic generalized epilepsy: a protective mechanism against seizures?
OBJECTIVE
Recently, we found that high-frequency somatosensory evoked potentials (HF-SEPs), which are modulated by arousal-related structures, were abnormally enhanced during N-REM sleep in two seizure-free IGE patients [Restuccia D, Rubino M, Valeriani M, Della Marca G. Increase of brainstem high-frequency SEP subcomponents during light sleep in seizure-free epileptic patients. Clin Neurophysiol 2005; 116: 1774-1778]. Here, we aimed at verifying whether similar HF-SEP abnormalities were significantly correlated to the clinical outcome in a larger population of untreated IGE patients.


METHODS
Patients were classified as Juvenile Myoclonic epilepsy (JME; six patients) and Childhood or Juvenile Absence epilepsy (CAE and JAE, six patients). They were untreated because newly diagnosed, or because seizure-free. HF-SEPs from patients were compared with those obtained from 21 healthy volunteers.


RESULTS
HF-SEPs were abnormally enhanced in all seizure-free CAE-JAE patients, whereas they were normal in all JME patients and in CAE-JAE patients with frequent seizures. Not only scalp distribution, but also dipolar source analysis suggested a subcortical origin for these enhanced subcomponents, possibly in the brainstem.


CONCLUSIONS
The enhancement of HF-SEPs might reflect the hyperactivity of arousal-related brainstem structures; such an enhancement was found in all seizure-free CAE-JAE patients, while it was never observed in JME patients.


CONCLUSIONS
We speculate that the hyperactivity of arousal-related brainstem structures might account for the different clinical outcome among IGE subsyndromes.
Restuccia
Domenico
D
Scientific Institute E. MEDEA, Polo Friuli Venezia Giulia, Udine, Italy. restuccia@pp.lnf.it
Valeriani
Massimiliano
M
Della Marca
Giacomo
G
D000293:Adolescent; D000328:Adult; D001931:Brain Mapping; D001933:Brain Stem / Q000503:physiopathology*; D004569:Electroencephalography / Q000379:methods; D004832:Epilepsy, Absence / Q000503:physiopathology*; D005073:Evoked Potentials, Somatosensory / Q000502:physiology*; D005260:Female; D007839:Functional Laterality; D006801:Humans; D008297:Male; D020190:Myoclonic Epilepsy, Juvenile / Q000503:physiopathology*