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Comparisons of intellectual capacities between mild and classic adult-onset phenotypes of myotonic dystrophy type 1 (DM1)

Jean Stéphane, Richer Louis, Laberge Luc et Mathieu Jean. (2014). Comparisons of intellectual capacities between mild and classic adult-onset phenotypes of myotonic dystrophy type 1 (DM1). Orphanet Journal of Rare Diseases, 9, (1), p. 1-10.

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Background : Myotonic dystrophy type 1 (DM1) is an autosomal dominant genetic multisystem disorder and the commonest adult-onset form of muscular dystrophy. DM1 results from the expansion of an unstable trinucleotide cytosine-thymine-guanine (CTG) repeat mutation. CTG repeats in DM1 patients can range from 50 to several thousands, with a tendency toward increased repeats with successive generations (anticipation). Associated findings can include involvements in almost every systems, including the brain, and cognitive abnormalities occur in the large majority of patients. The objectives are to describe and compare the intellectual abilities of a large sample of DM1 patients with mild and classic adult-onset phenotypes, to estimate the validity of the Wechsler Adult Intelligence Scale-Revised (WAIS-R) in DM1 patients with muscular weakness, and to appraise the relationship of intelligence quotient (IQ) to CTG repeat length, age at onset of symptoms, and disease duration.

Methods : A seven-subtest WAIS-R was administered to 37 mild and 151 classic adult-onset DM1 patients to measure their Full-Scale (FSIQ), Verbal (VIQ) and Performance IQ (PIQ). To control for potential bias due to muscular weakness, Standard Progressive Matrices (SPM), a motor-independent test of intelligence, were also completed.

Results : Total mean FSIQ was 82.6 corresponding to low average IQ, and 82% were below an average intelligence. Mild DM1 patients had a higher mean FSIQ (U=88.7 vs 81.1, p<0.001), VIQ (U=87.8 vs 82.3, p=0.001), and PIQ (U=94.8 vs 83.6, p<0.001) than classic adult-onset DM1 patients. In both mild and classic adult-onset patients, all subtests mean scaled scores were below the normative sample mean. FSIQ also strongly correlate with SPM (r s =0.67, p<0.001), indicating that low intelligence scores are not a consequence of motor impairment. FSIQ scores decreased with both the increase of (CTG)n (r s =−0.41, p<0.001) and disease duration (r s =−0.26, p=0.003).

Conclusions : Results show that intellectual impairment is an extremely common and important feature in DM1, not only among the classic adult-onset patients but also among the least severe forms of DM1, with low IQ scores compared to general reference population. Health care providers involved in the follow-up of these patients should be aware of their intellectual capacities and should adapt their interventions accordingly.

Type de document:Article publié dans une revue avec comité d'évaluation
Pages:p. 1-10
Version évaluée par les pairs:Oui
Date:Novembre 2014
Sujets:Sciences sociales et humaines > Sciences sociales > Psychologie
Sciences de la santé
Sciences de la santé > Sciences médicales > Génétique
Sciences de la santé > Sciences médicales > Neurosciences
Département, module, service et unité de recherche:Départements et modules > Département des sciences de la santé > Module de psychologie
Mots-clés:Myotonic dystrophy, phenotype, central nervous system, neuropsychology, intellectual disability, DM1, dystrophie myotonique de type 1, phénotype, système nerveux central, neuropsychologie, déficience intellectuelle
Déposé le:20 avr. 2016 22:13
Dernière modification:25 nov. 2016 18:22
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