Abstract

Inherited ataxias are a group of genetically heterogeneous neurodegenerative disorders. The chances of obtaining a diagnosis in individuals with rare ataxias increase with evaluation at dedicated Ataxia clinics with comprehensive neurological assessment.

At the National Ataxia Clinic, Tallaght Hospital, from December 2014–April 2016, 137 patients with inherited ataxias were assessed. In December 2014, 53% of 133 patients had a genetically confirmed diagnosis. The commonest in the autosomal-recessive (AR) group were Friedreich's ataxia, Ataxia-telangiectasia (AT), Ataxia with oculomotor apraxia 1&2 (AOA1&2) and, in the autosomal-dominant group, SCA2, SCA3 and SCA14.

Over a 16 month-period a number of undiagnosed patients were tested, some with next generation sequencing (NGS) gene panels. As a result, currently 65% of 137 patients have a genetic diagnosis. Interestingly, in the AR group most common non-Friedreich's ataxias are SPG7 (5 unrelated individuals) and ANO10-associated ataxia in 5 individuals from 2 families.

A commercial panel approach using NGS has increased the rate of positive genetic results where traditional methods were unsuccessful in early and late-onset ataxia patients. These results are likely to change previous assumptions about the prevalence of certain non-Friedreich's ataxias, as SPG7 and ANO10 now outnumber AOA1&2 and AT in our AR cohort.