Specific profiles of neurocognitive and reading functions in a sample of 42 Italian boys with Duchenne Muscular Dystrophy

Abstract

A group of 42 Italian boys with Duchenne Muscular Dystrophy was compared with a control group of 10 boys with Spinal Muscular Atrophy and Osteogenesis Imperfecta on tests assessing general intellectual ability, language, neuropsychological functions, and reading skills with the aim of describing a comprehensive profile of the various functions and investigating their interrelationships. The influence of general intellectual level on performance was analyzed. Further, correlations between various neuropsychological measures and language performances were computed for the group with Duchenne Muscular Dystrophy, as well as the correlations between reading scores and other cognitive and linguistic measures.

A general lowering in VIQ, PIQ, and FSIQ scores was found to characterize the group with Duchenne Muscular Dystrophy. Expressive language skills were within the normal range, while syntactic and grammatical comprehension were significantly impaired.

The presence of below-average reading performances was further confirmed. However, unlike previous studies on irregular orthographies, the present results show that (a) the mild reading difficulties found in the sample essentially concern speed rather than accuracy; (b) they concern word rather than nonword reading; (c) lower reading performances are related to lower scores in general IQ; (d) no correlations emerge with phonological abilities, verbal short-term memory, or working memory, but rather with long-term memory and lexical skills. This may suggest that language-specific effects modulate the cognitive expressions of Duchenne Muscular Dystrophy and raises the possibility that the dysfunctions underlying the reading difficulties observed in affected readers of regular orthographies involve different neurocognitive systems than the cortico-cerebellar circuits usually invoked.

Keywords:

• Dystrophin
• Duchenne Muscular Dystrophy
• Language
• Reading
• Cerebellum
• Hippocampus
• Orthography

Acknowledgments

The present study was supported by a Telethon-UILDM grant, GUP04001. The authors wish to thank Rasmus Petersen, Manchester University, for help revising the manuscript.

Notes

¹ The WISC-R version of the Wechsler scales was used because it was the only version currently adapted and normed for the Italian population at the beginning of the study.

² Missing data are related either to an optional subtest of the WISC-R not having been administered or to unreliability of the collected data due to technical administration, scoring, or recording problems.

³ It was ensured that the variables averaged into a single composite score were indeed part of the same domain, both on grounds of theoretical reasons and of high intercorrelations.

⁴ Due to variation in the number of participants for the various subtests, the analysis of correlations has been repeated on the subset of subjects for whom all test scores were available (n = 24), yielding substantially comparable results.