Taurine Therapy for SSADH Deficiency

Background: \- Succinic semialdehyde dehydrogenase (SSADH) deficiency is a rare genetic disease that results in changes to certain brain chemicals. These chemicals may affect brain excitability, or how likely nerve cells are to turn on. Changes in brain excitability may help to explain the symptoms of the disease, including learning and memory problems, seizures, and poor balance. A supplement called taurine may help people with SSADH deficiency by working on the brain chemical GABA. GABA helps to regulate brain activity. Researchers want to see if taurine can help people with SSADH deficiency. Objectives: \- To learn more about how taurine affects the brain in people with SSADH deficiency. Eligibility: \- Individuals at least 12 years of age who have SSADH deficiency. Design: * Participants will be screened with a physical exam and medical history. They will provide blood and urine samples. They will also take taurine supplements as part of this protocol. * Participants will have two sets of study tests. One set will be given while participants are taking taurine. The second will be given when they are not taking it. Each testing session will take about 2 days to complete. * Half of the participants will have the "off taurine" testing before starting on the taurine supplement. The other half will start taking taurine first, have the "on taurine" testing, and have the "off taurine" testing about 3 months after stopping taurine. Participants may decide the order in which they will have the testing done. * Participants will have the following tests at the two test visits: * Paper and pencil tests of learning and memory. * Transcranial magnetic stimulation to study the excitability of nerve cells. * Imaging studies to show GABA receptors in the brain and measure their activity. * Electroencephalogram to measure brain waves. * Lumbar puncture to collect spinal fluid. * Participants will be monitored with regular study visits while they receive the taurine supplement treatment.