This double-blind placebo-controlled parallel design protocol will investigate the effects of gamma-vinyl-GABA (vigabatrin--GVG) an experimental antiepileptic drug, on cerebral glucose metabolism (LCMRglc), blood flow (CBF), and seizure frequency, in patients with uncontrolled complex partial (CPS) and secondary generalized seizures (GTCS). Positron Emission Tomography (PET) will be used to measure CBF and LCMRglc.