Idiopathic epilepsy with generalized tonic-clonic seizures only versus idiopathic epilepsy with phantom absences and generalized tonic-clonic seizures: one or two syndromes?
OBJECTIVE
To define the relationship between two syndromes of idiopathic generalized epilepsy (IGE) with apparently similar phenotypes: The form with generalized tonic-clonic seizures only (IGE-GTCS) and that with phantom absences (IGE-PA).


METHODS
We compared the electroclinical features of 33 consecutive patients with GTCS and generalized spike wave (GSW); 18 had only GTCS and were diagnosed as IGE-GTCS, and 15 had hitherto unnoticed mild absences on the electroencephalography (EEG) and were diagnosed as IGE-PA. All patients were subjected to the same diagnostic workout, including video EEG during hyperventilation with breath counting (HBC). Patients with a clinical history of absences or myoclonic seizures were excluded.


RESULTS
PA were easily identified with the first or second EEG in 14 of 15 patients with IGE-PA and always with sleep-deprived EEGs; conversely, PA did not occur in the IGE-GTCS patients despite using more EEGs. GTCS were twice as frequent in the IGE-GTCS group and tended to occur on awakening, whereas episodes of absence status affected twice as many patients with IGE-PA. The hereditary risk was 30% in the IGE-GTCS and 6.7% in IGE-PA. GSW had a strong polyspike component in IGE-PA and were briefer in IGE-GTCS. There is no evidence for a maturational influence on the duration of GSW in either syndrome.


CONCLUSIONS
Our findings clearly indicate that IGE-GTCS and IGE-PA are two distinct IGE syndromes and emphasize the role of PA for patients' diagnosis and management and for syndromic classification. They also appear to validate HBC as a simple, sensitive, and pragmatic method for the clinical identification of typical absences.
Koutroumanidis
Michael
M
Department of Clinical Neurophysiology and Epilepsies, Guy's, St. Thomas' and Evelina NHS Foundation Trust, London, United Kingdom. michael.koutroumanidis@gstt.nhs.uk
Aggelakis
Konstantinos
K
Panayiotopoulos
Chrysostomos P
CP
D000293:Adolescent; D000328:Adult; D017668:Age of Onset; D000368:Aged; D003072:Cognition Disorders / Q000209:etiology; D003937:Diagnosis, Differential; D004831:Epilepsies, Myoclonic / Q000150:complications / Q000175:diagnosis*; D004832:Epilepsy, Absence / Q000175:diagnosis; D004829:Epilepsy, Generalized / Q000150:complications / Q000175:diagnosis*; D005260:Female; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D012640:Seizures / Q000150:complications / Q000175:diagnosis*; D012892:Sleep Deprivation; D014741:Video Recording; D055815:Young Adult