Abstracts

Rationale:
Childhood absence epilepsy (CAE) is a self-limited epileptic syndrome that resolves by 12 years of age.  Yet, for some (10-20%), seizure resolution stalls.  For this project, we studied teenagers with classic 3 Hz CAE and examined their clinical course and EEGs to understand why seizure resolution failed.  We wanted to address 3 questions.  First, was there one EEG pattern that predominated in this cohort of failed seizure remission?  Second, can we identify the specific factor(s), either intrinsic or extrinsic, that caused the resolution delay?  Third, have these teenagers missed their window of opportunity to have their seizures resolve?
Method:
Patients were selected that a) met standard criteria for CAE, b) responded well to initial anti-epilepsy treatment and c) had seizure activity persist > 14 years of age.  They were followed prospectively with serial, biannual EEGs over the course of their disorder.  Both routine and 24-hour continuous video-EEG monitoring were used to ensure comprehensive review of both wakefulness and sleep.
Results:
We identified 12 teenagers with CAE from our pool of 78 CAE patients (15%) seen over the past 8 years.  Their ages ranged from 14.1-19.5 years (mean= 15.5) and seizure onset ranged from 4.5-11 years (mean= 8.1). None of the patients had myoclonic seizures and only 2/12 of the patients had 1-2 isolated tonic-clonic seizures. Despite recent seizure control, their EEGs showed persistent abnormalities.  In the latest EEGs, 66% of patients (6/9) showed isolated bifrontal spike and wave discharges (SWD) during sleep.  These discharges lasted 0.5-1.5 seconds and had weak propagation to caudal areas.  Other patients showed increased vertex wave activity or recurrent K-complexes.  Patients fit into one of 3 causation categories: delay in diagnosis, poorly controlled seizures or extrinsic/intrinsic factors.  Six patients had delays in diagnosis ranging from 1-7 years (mean= 3.1). In the second group, treatment was started in a timely manner, but seizures were never completely suppressed.  In the third group, 3 patients had mild mental retardation and one had serious depression treated with psychotropic medication.  Since most patients in our cohort (75%) still require anti-seizure medication, it is too early to determine if seizure resolution is delayed or failed.
Conclusion:
Teenagers with CAE provide a unique opportunity to study seizure resolution.  Isolated nocturnal bifrontal SWD was the most common EEG finding and lack of early and consistent seizure control explained seizure failure in 67% of patients. Full seizure resolution may still be possible.  Understanding the delayed seizure resolution in these patients will help improve seizure control for other CAE patients.
Funding:
:No special funding