Myotonic dystrophy: practical issues relating to assessment of strength.
BACKGROUND
Myotonic dystrophy type 1 is a slowly progressive multisystem disease in which skeletal muscle involvement is prominent. As novel physical and pharmacological treatments become available, it is crucial to be able to measure their efficacy accurately.


METHODS
158 consecutive patients with myotonic dystrophy were assessed annually in a specialist muscle clinic. Strength was measured using both the Medical Research Council (MRC) scale and a hand-held dynamometer. Dynamometer readings were obtained from 108 normal subjects (controls).


RESULTS
The movements showing the greatest rate of change in strength were ankle dorsiflexion and pinch grip. Both of these showed a decline of only 0.06 points/year on the MRC scale. Using a hand-held dynamometer, a change in strength of 1.18 kgN/year for women and 1.61 kgN/year for men was detected.


CONCLUSIONS
The MRC scale is unsuitable for detecting the small changes in strength seen in a slowly progressive disease such as myotonic dystrophy. Dynamometry provides a simple alternative that can give meaningful data over the duration of a typical clinical trial.
Whittaker
R G
RG
Mitochondrial Research Group, School of Neurology, Neurobiology and Psychiatry, University of Newcastle upon Tyne, Framlington Place, Newcastle upon Tyne NE2 4HH, UK. r.whittaker@ncl.ac.uk
Ferenczi
E
E
Hilton-Jones
D
D
D000328:Adult; D000368:Aged; D023381:Endpoint Determination; D005260:Female; D018737:Hand Strength; D006801:Humans; D008297:Male; D008875:Middle Aged; D018908:Muscle Weakness / Q000175:diagnosis / Q000209:etiology; D009223:Myotonic Dystrophy / Q000150:complications* / Q000188:drug therapy; D012016:Reference Values; D012720:Severity of Illness Index; D012737:Sex Factors