title: Development of a disability scale for myotonic dystrophy type 1.
abstract: OBJECTIVE
  Myotonic dystrophy type 1 (DM1) is a multisystem disorder. Many tests in the literature have evaluated single aspects of DM1 patients, mainly focusing on muscular impairment, without an overall quantification of the different disease-specific neurological features. We developed and validated a new functional scale for DM1 patients based on neuromuscular impairment (NI) and disability.
  
  
  METHODS
  Thirty-three patients were tested in basal condition, 18 were re-evaluated after therapeutic intervention with mexiletine, and 13 at one year follow-up without treatment. The scale includes 21 ordinal items in four areas: neuropsychology, motricity, myotonia and daily life activities. We evaluated inter- and intra-observer reliability (intraclass correlation coefficient, ICC and Spearman correlations, respectively), internal consistency (Cronbach's alpha), external validity (Spearman correlations between each area and other clinical and objective measurements and scales), and sensitivity to clinical changes after treatment or at follow-up.
  
  
  RESULTS
  Our analysis provided good results for inter-observer agreement (ICC = 0.72-0.97), intra-observer reliability, and internal consistency for all areas (Cronbach's α > 0.73). Total score and single area subscores were significantly correlated to objective measurements, disease duration and multisystem involvement. Finally, the scale was sensitive to clinical changes disclosing a significant improvement after treatment in the items assessing myotonia, and also to disease progression showing a significant worsening in all areas but myotonia in untreated patients.
  
  
  CONCLUSIONS
  Our scale provides a new practical measure to evaluate NI and disability of DM1 patients. Further longitudinal studies are warranted to confirm its reliability in tracking disease progression and severity over a longer period of time.
authors: Department of Neurological Sciences, University of Bologna, Italy.
authors: S
authors: S
authors: Contardi
authors: F
authors: F
authors: Pizza
authors: F
authors: F
authors: Falzone
authors: R
authors: R
authors: D'Alessandro
authors: P
authors: P
authors: Avoni
authors: V
authors: V
authors: Di Stasi
authors: P
authors: P
authors: Montagna
authors: R
authors: R
authors: Liguori
mesh_terms: D000203:Activities of Daily Living; D000328:Adult; D004185:Disability Evaluation; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008875:Middle Aged; D009223:Myotonic Dystrophy / Q000503:physiopathology* / Q000523:psychology; D015203:Reproducibility of Results; D012720:Severity of Illness Index; D055815:Young Adult