title: Biomarkers in a Taurine Trial for Succinic Semialdehyde Dehydrogenase Deficiency.
abstract: OBJECTIVE
  We tested the hypothesis that patients with succinic semialdehyde dehydrogenase (SSADH) deficiency on taurine would have decreased cortical excitability as measured by transcranial magnetic stimulation (TMS) and improved cognition, due to taurine's partial GABA(A and B) receptor agonist effects and rescue in the null mouse model from status epilepticus and premature lethality.
  
  
  METHODS
  Biomarkers including neuropsychological testing, TMS, and CSF metabolites were studied in a cohort of patients on and off three months' taurine treatment.
  
  
  RESULTS
  Seven patients (5M/2F; age range 12-33 years) were enrolled in this open-label crossover study. Baseline average full-scale IQ (FSIQ) was 44.1 (range 34-55). Of six who returned at 6-month follow-up, five completed cognitive testing (3M/2F) on therapy; average FSIQ = 43.4 (range 33-51). CSF biomarkers (n = 4 subjects) revealed elevation in taurine levels but no change in free or total GABA. Baseline cortical excitability measured with TMS agreed with previous findings in this population, with a short cortical silent period and lack of long-interval intracortical inhibition. Patients on taurine showed a decrease in cortical silent period and short-interval intracortical inhibition compared to their off taurine study.
  
  
  CONCLUSIONS
  TMS demonstrated decreased inhibition in patients on taurine, in contrast to the study hypothesis, but consistent with its failure to produce clinical or cognitive improvement. TMS may be a useful biomarker for therapy in pediatric neurotransmitter disorders.
authors.affiliation: Clinical Epilepsy Section, Bethesda, MD, USA. jschreib@childrensnational.org.
authors.forename: John M
authors.initials: JM
authors.lastname: Schreiber
authors.affiliation: Department of Child Neurology, Children's National Medical Center (CNMC), Washington, DC, USA.
authors.forename: Phillip L
authors.initials: PL
authors.lastname: Pearl
authors.affiliation: Clinical Epilepsy Section, Bethesda, MD, USA.
authors.forename: Irene
authors.initials: I
authors.lastname: Dustin
authors.affiliation: Clinical Epilepsy Section, Bethesda, MD, USA.
authors.forename: Edythe
authors.initials: E
authors.lastname: Wiggs
authors.affiliation: Department of Child Neurology, Children's National Medical Center (CNMC), Washington, DC, USA.
authors.forename: Emily
authors.initials: E
authors.lastname: Barrios
authors.affiliation: Cognitive Neuroscience Section, NINDS, NIH, Bethesda, MD, USA.
authors.forename: Eric M
authors.initials: EM
authors.lastname: Wassermann
authors.affiliation: Experimental and Systems Pharmacology, Washington State University (WSU), Spokane, WA, USA.
authors.forename: K Michael
authors.initials: KM
authors.lastname: Gibson
authors.affiliation: Clinical Epilepsy Section, Bethesda, MD, USA.
authors.forename: William H
authors.initials: WH
authors.lastname: Theodore