Cognitive impairment and (CTG)n expansion in myotonic dystrophy patients

Giulia I. Perini, Elisabetta Menegazzo, Mario Ermani, Michele Zara, Andrea Gemma, Emilia Ferruzza, Massimo Gennarelli, Corrado Angelini

Research output: Contribution to journalArticlepeer-review

Abstract

Background: Myotonic dystrophy (DM) is a genetic multisystemic disease with muscular, endocrine, ocular, cardiac and cognitive impairment. The molecular basis of the disease has been identified in an unstable base triplet (CTG)n repeat located in the 3' untranslated region of the miotonin protein-kinase (MT-PK) gene on the long arm of chromosome 19. Cognitive impairment could be a direct expression of this genetic alteration at the central nervous system (CNS) level rather than a consequence of the neuromuscular impairment. To explore this hypothesis, we tested a group of genetically diagnosed, adult onset DM, of their nonaffected relatives (NAR), of patients with spinal muscle atrophy (SMA), and of normal controls using the Wechsler Adult Intelligence Scale (WAIS). Methods: Seventeen adult-onset DM patients, 9 NAR, 10 SMA patients and 20 unrelated normal controls (NC) were studied. Clinical, neuromuscular and neuropsychiatric evaluation, which included WAIS and the Schedule for Affective Disorders and Schizophrenia (SADS), were performed on the four groups. DM, NAR and NC were also assessed by a neurophysiological (P300) evaluation. A DNA analysis was performed in DM and in NAR to measure presence and magnitude of CTG expansion. Results: We found a statistically significant difference between verbal (p <.0003), nonverbal (p <.0001) and total (p <.0001) IQ of DM patients compared to IQs of NAR, SMA and NC. Seven out of 11 WAIS subtests were significantly and consistently lower in DM patients compared to SMA and/or NC. In DM patients there was a statistically significant negative correlation between nonverbal (r = - .68; p <.002) and total (r = .59; p <.01) IQ and (CTG)n. Patients with DM had a significantly lower P300 amplitude compared to NAR and NC. Conclusions: Our study indicates that in DM there is a mild but significant cognitive impairment which correlates with the degree of CTG expansion and it is not dependent on the neuromuscular impairment; however further studies with larger groups of patients and controls are suggested to confirm our results, due to the small sample size and to a possible effect of educational level in our patients. Copyright (C) 1999 Society of Biological Psychiatry.

Original languageEnglish
Pages (from-to)425-431
Number of pages7
JournalBiological Psychiatry
Volume46
Issue number3
DOIs
Publication statusPublished - Aug 1 1999

Keywords

  • Cognitive deficits
  • Evoked potential CTG amplification
  • Myotonic dystrophy
  • Spinal muscle atrophy

ASJC Scopus subject areas

  • Biological Psychiatry

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