VIGABATRIN THERAPY IN 6 PATIENTS WITH SUCCINIC SEMIALDEHYDE DEHYDROGENASE-DEFICIENCY

The antiepileptic vigabatrin (gamma-vinyl GABA; 4-amino-5-hexenoic aci d; Sabril) is an irreversible inhibitor of GABA-transaminase, the enzy me responsible for the degradation of the neurotransmitter GABA. Vigab atrin has been used therapeutically in five patients with succinic sem ialdehyde dehydrogenase (SSADH) deficiency, a rare inborn error of GAB A metabolism (McKusick 271980; Gibson et al 1989; Jaeken et al 1989; B randt et al 1992; Howells et al 1992; Jakobs et al 1992; Uziel et al 1 993). SSADH-deficient patients accumulate increased quantities of 4-hy droxybutyric acid (4-HBA) in physiological fluids. Inhibition of GABA- transaminase by vigabatrin should yield a decrease in the accumulation of 4-HBA in patient physiological fluids and may lead to clinical imp rovement. In the five patients previously treated, there was an expect ed increase in the cerebrospinal fluid (CSF) GABA/4-HBA ratio. Clinica lly, there was improvement in ataxia, hypotonia, speech, behaviour, co ncentration and cooperativity to differing degrees; one patient did no t respond to therapy. We report our results of vigabatrin therapy in s ix additional SSADH-deficient patients.