Ramdharry G.1,2, Dudziec M.1, Laura M.3, Tropman D.4, Reilly M.M.3
1Kingston University, Faculty of Health, Social Care and Education, London, United Kingdom, 2University College Hospitals NHS Foundation Trust, Queen Square Centre for Neuromuscular Diseases, London, United Kingdom, 3UCL, Queen Square Centre for Neuromuscular Diseases, London, United Kingdom, 4St George's Hospital NHS FoundationTrust, Medical Physics, London, United Kingdom
Background: Charcot Marie Tooth disease (CMT) is an inherited polyneuropathy that presents with distal lower motor neuron muscle weakness, atrophy and sensory impairment. Falls were reported by 89% of people with CMT in our previous study. To date laboratory studies of balance in people with CMT have focused on static and reactive balance performance. Anticipatory balance strategies for self-generated dynamic tasks has not been explored. Forward and lateral reach tests can predict falls in other neurological conditions and older people.
Purpose: This study explores whether dynamic balance tests can predict falls and which impairments relate to performance of these tests.
Methods: We measured isokinetic lower limb muscle strength (peak torque; average power), sensory impairment, disease severity (CMT examination Score) and balance confidence (Modified Falls Self Efficacy scale). Falls events were recorded over 6 months using weekly postcards. Dynamic balance was tested in the movement laboratory using kinematic analysis of a forward and lateral reach task. An infrared marker was placed on the right ulnar styloid and participants were asked to maximally reach forward and to the side without stepping. The distance reached was recorded for three trials, then averaged and divided by the persons height to normalise for stature. A reach ratio was expressed to explore the reach distance as a percentage of the persons height. Static standing balance was also measured by the velocity and path length of the centre of pressure (COP) using a force plate. Negative binomial regression analysis explored whether forward reach, lateral reach and static balance performance predicted falls. Linear regression analysis explored the impairments that predicted performance of the reach tests.
Results: Twenty-eight participants completed the reach tests. The median number of reported falls in 6 months was 4 (mean 8.9; range 0-54). The mean normalised forward reach distance was 157.17mm/m (±36.33), a mean reach ratio of 15.7% of the persons height. The mean normalised lateral reach distance was 124.41mm/m (±35.11) which was a mean reach ratio of 12.4%. The most frequent fallers (>10) had a reach ratio below 14%. The negative binomial multiple regression indicated that forward reach and COP velocity significantly predicted falls (R2 =0.12, P=0.006; falls in 6 months = 4.36 + (0.003*COP velocity) 0.02*forward reach)). Performance of forward reach was predicted by knee extension average power generation (R2 =0.15, P=0.04; forward reach = 128 + 0.5*knee extension power) and lateral reach by ankle inversion average power generation (R2=0.34, P P 0.001; lateral reach = 79 + 7.9*inversion power).
Conclusion(s): Dynamic balance, as measured by functional reach distance, and static balance can partially predict falls in six months, but the low R2 value indicates additional factors may be. Proximal and distal lower limb muscle function are important in predicting how far people will voluntarily reach.
Implications: Dynamic balance testing may contribute to understanding potential falls risk in people with CMT. Functional reach tests may be an informative addition to balance assessment for people with CMT. Proximal muscle strength training may be important to include in balance training approaches.
Funding acknowledgements: This work was funded by the National Institute for Health Research, Clinical Academic Training Clinical Lectureship CL09.
Topic: Neurology
Ethics approval: This study was approved by the City and East NRES research ethics committee, reference 12/LO/0156
All authors, affiliations and abstracts have been published as submitted.
