Seizure control after chronic pharmacotherapy in epileptic disorders beginning after 40 years of age

Few studies have been published on the pharmacologic response to treatment of patients whose seizures begin after 40 years of age. The purpose of this study was to assess the impact of chronic pharmacotherapy on the seizure control of such patients. We retrospectively studied the seizure frequency recorded during a 12-month period in a group of 94 outpatients whose seizure disorders began after 40 years of age (median age of seizure onset 56.5 years) and who had been treated with anticonvulsant medication for a median period of 6 years (range 18 months to 12 years). We assessed the relationship between the patients' seizure frequency during the last 12 months of treatment using (a) the present and previously prescribed pharmacologic regimens, (b) anticonvulsant blood levels of present regimen, (c) etiology and duration of seizure disorder, (d) age at onset of seizures, and (e) presence of electrographic (EEG) and neuroradiologic abnormalities. We only identified side effects occurring at blood levels within or below the drug's therapeutic range. Seventy-eight patients (83%) were seizure free during the last 12 months of treatment, 11 (11%) had rare seizures, and five (6%) had more than four seizures per year. Seizure frequency was not affected by duration and etiology of seizure disorder, age at onset of seizures, seizure type, neuroradiologic or electroencephalographic abnormalities, and present or previously prescribed pharmacologic regimens. Persistent side effects were reported in seven of 76 (9%) monotherapy regimens and in two of 12 (17%) polytherapy regimens. Our data suggest that seizures beginning after the age of 40 have a favorable prognosis after chronic pharmacotherapy.