Brain Advance Access originally published online on March 31, 2009
Brain 2009 132(6):1577-1588; doi:10.1093/brain/awp056
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Prevalence of hereditary ataxia and spastic paraplegia in southeast Norway: a population-based study
1 Department of Neurology, Ullevål University Hospital, Oslo, Norway 2 Faculty of Medicine, University of Oslo, Norway 3 Department of Medical Genetics, Ullevål University Hospital, Norway 4 Centre of clinical research, Unit of Epidemiology and Biostatistics, Ullevål University Hospital, Oslo, Norway
Correspondence to: Anne Kjersti Erichsen, Department of Neurology, Ullevål University Hospital, Oslo, Norway E-mail: annekjersti_e{at}yahoo.no
A population-based, cross-sectional study was performed in southeast Norway, between January 2002 and February 2008, to identify subjects with hereditary ataxia and hereditary spastic paraplegia, and to estimate the prevalence of these disorders. Patients were recruited through colleagues, families, searches in computerized hospital archives and the National Patients’ Association for Hereditary Ataxia and Spastic Paraplegia. Strict criteria were used for inclusion of familial and isolated subjects. A project neurologist examined all index subjects and clinical and genetic data were registered. The source population on January 1, 2008 was 2.63 million and the prevalence day was set as February 1, 2008. One hundred seventy-one subjects from 87 unrelated families with hereditary ataxia and 194 subjects from 65 unrelated families with hereditary spastic paraplegia were included. The total prevalence was estimated at 13.9/100 000. Hereditary ataxia prevalence in the region was estimated at 6.5/100 000: 4.2/100 000 for autosomal-dominant and 2.3/100 000 for autosomal recessive, 0.15/100 000 for Friedreich's ataxia and 0.4/100 000 for ataxia telangiectasia. Hereditary spastic paraplegia prevalence was 7.4/100 000: 5.5/100 000 for autosomal dominant-hereditary spastic paraplegia, 0.6/100 000 for autosomal recessive-hereditary spastic paraplegia and 1.3/100 000 for isolated subjects. Marked differences were found in the frequencies of hereditary ataxia subtypes compared with other countries, while those of the most common autosomal dominant-hereditary spastic paraplegia genotypes, SPG4, SPG3 and SPG31, were similar to those previously reported. Clear variations between age groups and counties were observed, but no gender differences. Mean age on prevalence day was 48 years, mean age at onset was 24 years. We present the largest population study performed on hereditary ataxia and hereditary spastic paraplegia prevalence and report a higher prevalence than expected. Better inclusion criteria and multiple search strategies may explain the observed differences.
Key Words: ataxia telangiectasia; Friedreich's ataxia; hereditary ataxia; hereditary spastic paraplegia; prevalence; SCA; SPG3; SPG4; SPG11; SPG31
Abbreviations: AD = autosomal dominant, ; AR = autosomal recessive, ; AOA1 and AOA2 = ataxia with ocular apraxia type 1 and 2, ; FRDA = Friedreich's ataxia, ; A-T = ataxia telangiectasia, ; HA = hereditary ataxia, ; HSP = hereditary spastic paraplegia, ; MLPA = multiplex ligation probe amplification, ; RR = rate ratio, ; SCA = spinocerebellar ataxias,
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Received September 15, 2008. Revised January 4, 2009. Accepted February 15, 2009.
*These authors contributed equally to this work.