Vigabatrin-Induced Generalized Epileptiform Discharges in a Patient with Focal Epilepsy
A 21-year-old man has been treated for a seizure disorder in the Department of Neurology since he was 15 years old. At the age of nine years old, he suffered the first seizure attack. The beginning of his seizures was a visual aura, right side hemianopsia, usually accompanied by a headache, and then he stares vacantly and does not respond to verbal commands. The frequency of the seizures was two to three times per year.\nWhen he was 13 years old, he had started to take an unknown species of antiepileptic drug. But because of the bankruptcy of the hospital he was treated in, he stopped the medication when he was 14 years old. He suffered a generalized tonic-clonic seizure under the drug withdrawal state. Just after the seizure he visited another hospital. Valproic acid (VPA) monotherapy did not change the seizure frequency under poor drug compliance. He heard that there were no abnormal findings on the two EEGs checked in that hospital.\nThe patient visited the pediatric department of our hospital when he was 15 years old. There were no abnormal findings in the brain MRI taken at that age; VGB was added on and VPA was tapered; his prescription was adjusted to high dosage of VGB (3,500 mg/day) by a pediatrician. Five months after his visit to the pediatric department, he suffered another complex partial seizure, and the pediatrician in charge referred the patient to the department of Neurology. Since then, he had been seizure free for four years and eight months while taking 3,000 mg/day of VGB. He also did not report any absence attack during that period. However, he had another complex partial seizure starting with visual aura when he was 20 years old; that was his last seizure.\nEEGs were recorded periodically in our hospital after the use of VGB since the first visit in the pediatric department. In eight of the consecutive nine EEGs recorded over approximately four years, the diffuse bursts of 2–2.5 Hz spike-and-wave complexes were observed repetitively (). The occurrences of the abnormal discharges in each EEG were several to frequent during the 30 min recording. In another EEG recorded five months after the last seizure at when he was 20 years old, the generalized epileptiform discharges were also observed intermittently. Just after that EEG recording, 600 mg/day of VPA was added to his medication, and the tapering of VGB was started.\nFour months after starting of the drug changes, another EEG was done. The patient’s prescription at that time was 600 mg/day of VPA plus 1,000 mg/day of VGB. In the EEG recorded under that medication, several clusters of spikes on the occipital area of the left hemisphere were observed (). There was no burst of the 2–2.5 Hz spike-and-wave complexes on that EEG. One month after the EEG recording, the VGB medication was stopped after tapering. When the patient was 21 years old, four months after the EEG recording, another EEG was recorded; no epileptiform discharges were observed in that EEG. The medication at that time was 600 mg/day of VPA.