ORIGINAL ARTICLE A comprehensive clinical and genetic study of a large Mexican population with spinocerebellar ataxia type 7 L. Velázquez-Pérez & C. M. Cerecedo-Zapata & O. Hernández-Hernández & E. Martínez-Cruz & Y. S. Tapia-Guerrero & R. González-Piña & J. Salas-Vargas & R. Rodríguez-Labrada & R. Gurrola-Betancourth & N. Leyva-García & B. Cisneros & J. J. Magaña Received: 23 April 2014 /Accepted: 8 September 2014 # Springer-Verlag Berlin Heidelberg 2014 Abstract Spinocerebellar ataxia type 7 (SCA7) is an inherited neurodegenerative disorder characterized by pro- gressive cerebellar ataxia associated with macular degenera- tion. We recently described one of the largest series of patients with SCA7 that originated from a founder effect in a Mexican population, which allowed us to perform herein the first comprehensive clinical, neurophysiological, and genetic char- acterization of Mexican patients with SCA7. In this study, 50 patients, categorized into adult or early phenotype, were clin- ically assessed using standard neurological exams and geno- typed using fluorescent PCR and capillary electrophoresis. Patients with SCA7 exhibited the classical phenotype of the disease characterized by cerebellar ataxia and visual loss; however, we reported, for the first time, frontal-executive disorders and altered sensory-motor peripheral neuropathy in these patients. Semiquantitative analysis of ataxia-associated symptoms was performed using Scale for the Assessment and Rating of Ataxia (SARA) and the Brief Ataxia Rating Scale (BARS) scores, while extracerebellar features were measured employing the Inventory of Non-ataxia Symptoms (INAS) scale. Ataxia rating scales confirmed the critical role size of cytosine-adenine-guanine (CAG) repeat size on age at onset and disease severity, while analysis of CAG repeat instability showed that paternal rather than maternal transmission led to greater instability. Keywords Ataxia rating scales . Autosomal dominant cerebellar ataxia . CAG repeats . Electrophysiological findings . Intergenerational transmission . Spinocerebellar ataxia type 7 Introduction Spinocerebellar ataxia type 7 (SCA7) is an autosomal domi- nant genetic disease characterized by cerebellar dysfunction associated with gait ataxia, dysarthria, dysmetria, dysdiadochokinesia, hyperreflexia, sensory loss, postural Electronic supplementary material The online version of this article (doi:10.1007/s10048-014-0424-y) contains supplementary material, which is available to authorized users. L. Velázquez-Pérez : C. M. Cerecedo-Zapata : O. Hernández-Hernández : Y. S. Tapia-Guerrero : N. Leyva-García : J. J. Magaña (*) Laboratory of Genomic Medicine, Department of Genetics, National Rehabilitation Institute (INR), Mexico City, Mexico e-mail: maganasm@hotmail.com L. Velázquez-Pérez : B. Cisneros (*) Department of Genetics and Molecular Biology, Center of Research and Advanced Studies (CINVESTAV-IPN), Av. Instituto Politécnico Nacional No. 2508, Col. San Pedro Zacatenco, 07360 Mexico City, Mexico e-mail: bcisnero@cinvestav.mx L. Velázquez-Pérez : R. Rodríguez-Labrada Center for Research and Rehabilitation of the Hereditary Ataxias (CIRAH), Holguín, Cuba C. M. Cerecedo-Zapata : E. Martínez-Cruz : J. Salas-Vargas : R. Gurrola-Betancourth Rehabilitation and Social Inclusion Center of Veracruz (CRIS-DIF), Xalapa, Veracruz, Mexico R. González-Piña Department of Brain Plasticity, INR, Mexico City, Mexico Neurogenetics DOI 10.1007/s10048-014-0424-y