Elisabet Hammarén

Muscle force, balance and falls in muscular impaired individuals with myotonic dystrophy type 1: A five-year prospective cohort study

Individuals with myotonic dystrophy type 1 (DM1) have progressive muscle weakness with gait and balance impairments. We explored prospectively the natural history of muscle force, gait, balance, balance confidence and walking ability in muscular affected individuals with DM1. After five years data from 43 individuals (m/f:18/25) were analysed. All measures of balance showed statistically significant deterioration (p < 0.001) with averaged yearly loss of function by 3-4%. In the group as a whole, loss of muscle force was statistically significant in all lower limb muscles measured after five years: changes relative to baseline force were median -6% to -18%. For males muscle force loss was statistically significant in all leg muscles, but only in hip flexors for women. After five years 100% of the men had fallen during the previous year and 67% three times or more, in contrast only 60% of the women had fallen in the previous year and 36% three times or more. The proportion of individuals seeking medical care the previous year, after falling, was more than doubled after five years, albeit the number of falls had not changed. Awareness of this increased risk of falls is important for caregivers and patients.

Factors of importance for dynamic balance impairment and frequency of falls in individuals with myotonic dystrophy type 1 – A cross-sectional study – Including reference values of Timed Up & Go, 10 m walk and step test

Patients with myotonic dystrophy type 1 suffer from gait difficulties including stumbles and falls. To identify factors of importance for balance impairment and fall-risk a mapping of functional balance was performed, in a cross-sectional study of 51 adults. Walking, balance, falls and muscle force were self-assessed and measured. Reference values of balance were established through measurements of 220 healthy subjects. Falls were more frequently observed in the patients who were more severely affected of muscle weakness than in mildly affected patients, p=0.014. The number of falls showed negative correlation with balance confidence (rs=-0.516, p<0.001). The ankle dorsiflexor force together with the time difference between comfortable and maximum speed in 10m-walk proved to be significant factors for fall frequency. A ten Newton muscle force decrease showed 15% increase in odds ratio for frequent falls. One-second increase in time difference between comfortable and maximum walking speed showed 42% increase in odds ratio for frequent falls. In conclusion, assessing the ankle muscle force and the time difference in different walking speeds is important to detect risk of falling. The activities-specific balance confidence score reflects the consequences of the muscle force decrease. Certain patient strategies to diminish risk of falling could be due.

Quantification of mobility impairment and self-assessment of stiffness in patients with myotonia congenita by the physiotherapist

We investigated test-retest reliability and responsiveness in two functional measuring instruments, Timed Up&Go (TUG) and Timed-Stands Test (TST), and in three self-assessment scales, Visual Analogue Scale (VAS), Borgs Category-Ratio Scale (BorgCR10) and Myotonia Behaviour Scale (MBS) when quantifying myotonic stiffness and mobility impairment. These methods were used in the assessment of treatment efficacy of mexiletine. Six male patients with myotonia congenita followed a standardised protocol with time scoring and rest on two occasions, with and without mexiletine. Time scoring of TUG and TST and self-assessments of stiffness were performed. A 14-day stiffness diary was used at home. Timed Up&Go and TST showed very good test-retest agreement (ICC=0.87-0.95) and significant to change (P=0.005 and 0.001, respectively). All self-assessment scales revealed excellent responsiveness and good test-retest reliability. The measurement instruments possess great capacity to detect functional impairment in the myotonia congenita patient group, and sensibility to identify true changes due to treatment. When considering the results, three instruments are favoured; Timed Up&Go and BorgCR10 for short, and MBS for long-term evaluations.

Modified Exercise Test in Screening for Mitochondrial Myopathies – Adjustment of Workload in Relation to Muscle Strength

The aim of this study was to evaluate the usefulness of a modification of the bicycle ergometer test, the subanaerobic threshold exercise test (SATET), as a screening test for patients with mitochondrial myopathies. Since the original SATET is frequently found to be strenuous for weak patients, a new variable (relative muscle strength) was added to the workload formula. Plasma lactate levels were recorded at rest, then after 5 and 15 min of cycling on an ergometer, with constant workload. Nine patients with mitochondrial myopathy, 10 patients with other neuromuscular diseases and 9 healthy but sedentary volunteers undertook the test. An upper reference limit after exercise for plasma lactate was settled at 2.9 mmol/l. The modified SATET showed a sensitivity of 78% and a specificity compared to the healthy subjects of 100%. Compared to patients with other neuromuscular diseases, the specificity was lower (60%). All subjects completed the test without severe fatigue or pain.

Effects of a balance exercise programme in myotonic dystrophy type 1: A pilot study

Abstract This pilot study aimed to evaluate the effects of balance exercises in adults with classical myotonic dystrophy type 1 (DM1) directly after intervention and at follow-up after 12 weeks. Eleven outpatients (median age 49 years, range 36–60 years) with balance difficulties participating in a 10 week intervention were assessed before, after and at follow-up. The primary outcome measure was balance confidence, measured with the Activities-specific Balance Confidence (ABC) scale. Secondary outcome measures were the Step Test, Timed Up and Go test, Timed 10 m Walk at maximum pace, isometric muscle force in legs and number of falls. The most important findings directly after the intervention were that nine of the 11 patients scored higher on the ABC scale (p = 0.02), and that the number of steps in the Step Test increased in nine of 10 participants. The increased number of steps remained increased at follow-up, but the increased confidence was not maintained for all patients. Timed Up and Go was unchanged but the time to walk 10 m increased. The knee extensor force and number of falls did not show any statistically significant changes. Unexpectedly, all patients deteriorated in the ankle dorsiflexor force (mean –17%) after intervention. The study showed that self-assessed balance confidence is likely to increase following an individualized balance exercise programme in outpatients with DM1.

Muscle force and other factors for falls in myotonic dystrophy type 1: studies of persons with a rare disease

Muscle force and other factors for falls in myotonic dystrophy type 1: studies of persons with a rare disease E. Hammar en, G. Kjellby-Wendt and C. Lindberg Department of Physiotherapy, Sahlgrenska University Hospital, G€oteborg, Sweden; Department of Clinical Neuroscience and Rehabilitation, Institute of Neuroscience and Physiology, Sahlgrenska Academy at University of Gothenburg, G€oteborg, Sweden; Department of Clinical Genetics, Sahlgrenska University Hospital, G€oteborg, Sweden