Characterisation of the Cognitive Profile of Patients Suffering From Friedreich's Ataxia

Overview

Friedreich's Ataxia (FA) Friedreich's Ataxia is a neurodegenerative disease caused by a homozygous expansion of the GAA triplet repeats of the frataxin gene (FXN). FA usually begins in childhood or adolescence. It affects both boys and girls. At the neurophysiological level, FA is characterised by neuronal loss affecting the dorsal root ganglia, spinal cord and cerebellum. At present, daily exercise is the only way to combat the disease. There is no cure for Friedreich's ataxia. Clinically, FA mainly combines balance, movement coordination, articulation (dysarthria) with cardiac involvement and sometimes diabetes . After a few years of evolution, walking is no longer possible. Recent data ; also indicate disturbances in information processing and cognitive functioning. In short, FA involves adolescents who progressively lose walking, writing and speech for some; however, each patient progresses differently with respect to the disease, and this is the case with respect to motor and cognitive symptoms.

The role of behavioural and cognitive assessment in the clinical trial The effectiveness of a treatment is ultimately determined by the elimination of the physiological cause of the disease and the alleviation of the symptoms that patients suffer. However, new treatments rarely eliminate all causes and symptoms of the disease. As long as the effectiveness of a treatment is unknown, it is subtle changes in parameters that decide whether the approach taken is worth pursuing. For a clinical trial which is supposed to evaluate the effectiveness of a treatment for Friedreich's Ataxia, it is therefore necessary to evaluate subtle changes in the functioning of the motor and cognitive system induced by the treatment. For this reason, the project is assembling a battery of tests that quantify the most important aspects of motor, cognitive and speech function in patients with FA. These tests are designed with the specific needs of FA patients in mind, i.e. on the one hand, the tests assess functions that are particularly important in view of the symptoms of Friedreich's disease indicated in the scientific literature, and on the other hand, the psychometric characteristics of the tests are adapted to the general abilities of FA patients. In this respect, it is important to point out that the expansion of the GAA repetition in people with Friedreich's disease varies from 150 to 1,000 triples (compared to 7 to 25 in the rest of the population), and that this large variation in the genotype of FA patients could potentially influence the cognitive profile of the participants. Previous studies have suggested the relationship between the number of repeats of the GAA triplet of the FXN gene and performance in cognitive assessment tests. Specifically, while in FA patients both alleles of the FXN gene contain an unusually high number of GAA repeats, performance in cognitive tests would correlate with the number of GAA repeats in the allele that contains fewer such repeats. Using this test battery, we are therefore able to achieve our main objective, i.e. to characterise the cognitive profile of FA patients as a function of the number of GAA triplet repeats of the FXN gene. Specifically, the test battery will establish whether motor, executive and speech symptoms affect patients differently according to their particular genetic characteristics.