Abstracts

RATIONALE: The Idiopathic Generalized Epilepsies (IGE) include a wide range of syndromes with heterogeneous pathophysiologic mechanisms. Seizures in most IGE patients are readily controlled by appropriate anticonvulsants but some patients have an unfavorable course and drug resistance. The objective of this study is to further define the causes of medical intractability in IGE patients. This may be helpful in devising optimal therapeutic strategies.
METHODS: Twenty-seven patients fulfilling the major diagnostic criteria for IGE but whom were medically intractable were studied. Clinical, EEG, neuroradiologic and neuropsychological data were reviewed.
RESULTS: Seventeen patients were women, mean age at seizure onset was 9 years (range, 3-17) and mean duration of disease was 25 years (range, 7-46). A family history of epilepsy with affected first or second-degree relatives was present in 16 (58%) patients. An antecedent of febrile convulsions was reported in two, and seven had a history of risk factors such as head trauma, encephalitis and meningitis. All patients had more than one seizure type except three whom had only absences. Two seizure types were reported in 13, three in nine and four in two patients. The first seizure type at onset of disease was absence in 19, generalized tonic-clonic seizures in four and myoclonus in four patients. Five patients had other types of seizure as well including petit mal status (2), atonic seizures (2) and seizures with focal features (1). All patients received polytherapy with VPA or LTG, the drugs most frequently taken at last follow-up. Initial treatment with phenytoin, carbamazepine or gabapentin was reported in 20 patients. Precipitating seizure factors were found in 17 patients: sleep deprivation (10), fatigue (3), poor compliance (3), alcohol (2) and drug intoxication (1) were reported in 17 patients. EEG background activity was normal and all had generalized epileptiform discharges ranging from 2.5 to 5 Hz. Only two patients showed photosensitivity. Additional focal epileptiform (9) and non-epileptiform (2) abnormalities were found in eleven cases. MRI study was normal in 21 (78%) patients; the remains patients had subcortical atrophy (2), limited encephalomalacia (2), hippocampal atrophy (1) and asymmetry of insular cortex (1). Neuropsychological examination showed generalized or bifrontal dysfunction in 12/19 (63%) patients, and one had temporal lobe dysfunction.
CONCLUSIONS: Reasons for intractability was inadequate initial antiepileptic drug treatment (74%) and presence of precipitating factors (63%). Focal features also contributed to intractability (52%). Control was difficult to re-establish once lost even with adequate drug regimen. Complete investigation of intractable patients and elimination of correctable aggravating factors should reduce intractability and provide clarification of the apparent increased severity in some patients.
[Supported by: Canadian Institutes of Health Research (CIHR)]