Comparing Endophenotypes in Adult-Onset Primary Torsion Dystonia

Adult-onset primary torsion dystonia (AOPTD) has an autosomal dominant pattern of inheritance with markedly reduced penetrance. the genetic causes of most forms of AOPTD remain Unknown Endophenotypes, markers of sub-clinical gene carriage. may be of use detecting non-manifesting gene carriers of relatives of AOPTD patients. The aim of tills study was 10 compare the utility Of the spatial discrimination threshold (SDT) and temporal discrimination threshold (TDT) as potential endophenotypes in AOPTD Data oil other published candidate endophenotypes are also considered Both sur and TDT testing were performed ill 24 AOPTD patients and 34 of their unaffected first degree relatives. results were compared with normal values from a control population Of the 24 AOPFD patients 5 (21%) had abnormal SDTs and 20 (83%) had abnormal TDTs of the 34 first degree relatives 17 (50%) had abnormal SDTs and 14 (41%) had abnormal TDTs Discoidant results on SDT and TDT testing were found in 16 (67%) AOPTD Patients and 21 (62%.) first degree relatives TDT testing has superior sensitivity compared to SDT testing ill AOPTD patients, although fake positive TDTs are recognised. the specificity of TDT testing in unaffected relatives IS not determinable The high level of discordance between the two tests probably relates methodological difficulties with SDT testing The SDT is an unreliable endophenotype, TDT testing Fulfils criteria for I reliable endophenotype with a high Sensitivity (C) 2009 Movement Disorder Society