P 522. Measuring Grip and Finger Flexion Strength in Children and Adolescents with Neuromuscular Disorders
30 October 2018 (online)
Background: The principal characteristic of a genetically determined neuromuscular disorder is weakness in the proximal and/or distal musculature. There are various clinical testing methods for establishing muscular strength and function in cases of neuromuscular disorders. A majority of the available measuring methods are based on the measurement of strength in the lower extremities. There are few tests available for determining the loss of strength in the upper extremities.
Aims: The aim of this study is to measure the maximum voluntary grip strength and finger flexion strength among children, adolescents, and young adults with neuromuscular disorders.
Issue Under Investigation: Voluntary grip and finger flexion strength is an important parameter for clinically assessing the progress of hereditary neuromuscular disorders during childhood. The standardized measurement of grip strength and finger flexion strength can be used to identify markers for the progression and prognosis of a neuromuscular disorder, and to establish outcome parameters or targets for therapeutic interventions and future treatment studies in patients with neuromuscular disorders during the phase when the ability to walk has been lost.
Methods: To check the feasibility of the proposed tests, grip strength and finger flexion strength were measured in n = 11 children and adolescents with neuromuscular disorders. These were n = 3 boys with Duchenne muscular dystrophy (8, 9, and 16 years), n = 1 boy with Becker muscular dystrophy (15 years), n = 1 boy with FSHD (14 years), n = 1 girl with Emery–Dreifuss muscular dystrophy Type 2 (18 years), n = 1 girl with myotonic dystrophy, n = 1 boy with congenital myopathy, and n = 3 patients with spinal muscular atrophy (SMA) II (n = 2 boys, 7 years and n = 1 girl, 17 years). Measurement of grip strength and finger flexion strength was performed under standardized, biomechanically precise and isometric measuring conditions using an HFD 200 hand and finger dynamometer. The strength parameters used were maximum voluntary grip strength in the distal (II-V2) and intermediate (II-V4) phalanges, as well as maximum voluntary finger flexion strength in the distal (III2) and intermediate phalanges (III4) of the middle finger of both the right and left hands. In the patients with SMA, the strength parameters were measured before and after administration of intrathecal nusinersen. The strength parameters obtained from the patients were compared with the age- and gender-specific standard values.
Findings: As was to be expected, all children with neuromuscular disorders produced lower strength values in comparison with the age- and gender-specific standard values. This was most clearly evident in the 16-year-old patient with Duchenne muscular dystrophy. The strength values of this patient were found to be 2 to 7% of the standard values for the corresponding age group. The smallest deviation of the strength values from the standard values were found in the patient with FSHD. The strength values obtained in the patients with SMA II were also considerably lower (2–30% of the standard values for the corresponding age group). The 7-year-old patients with SMA II showed a clear increase in strength after the administration of nusinersen. After the first dose of nusinersen, an increase in strength of up to 80 to 100% compared with the initial value was already measurable. The greatest increase in strength values was measured in the grip strength of the intermediate phalanges. In one of the patients, these values increased by 47.3 Newton (from 60.8 to 108 Newton).
Conclusion: The measurement of voluntary grip strength and finger flexion strength in patients with neuromuscular disorders facilitates the objective quantification of muscular weakness. Grip and finger flexion strength can be used as parameters for assessing the efficacy of treatment studies.