Responsiveness of outcome measures in myotonic dystrophy type 1.

OBJECTIVE: As myotonic dystrophy type 1(DM1) evolves slowly and interventional trials often have a short duration, responsive outcomes in DM1 are needed. The objective of this study was to determine the responsiveness of muscle strength, balance, and functional mobility measurements after a 1-year follow-up period in individuals with DM1. METHODS: Sixty-three adults with noncongenital DM1 completed the following assessments at baseline and at 1-year follow-up: Handheld dynamometry (lower limbs), stationary dynamometry (lower limbs), step test, timed-up-and-go test (TUG), modified clinical test of sensory integration and balance (mCTSIB), feet-together stance, tandem stance, one-leg stance, 10-meter walk test, and sit-to-stand test. RESULTS: Change was captured by stationary dynamometry (proximal flexor and extensor muscles), handheld dynamometry (proximal flexor and distal extensor muscles), TUG, and mCTSIB (P ≤ 0.04). Ceiling or floor effects were shown for most static balance tests. INTERPRETATION: Overall, adequate responsiveness was shown for both muscle strength dynamometers, TUG and mCTSIB. These outcomes are therefore likely candidate endpoints for clinical trials lasting 1 year. Most static balance tests are not responsive and not recommended in a heterogeneous DM1 population.

Intrarater reliability and validity of outcome measures in myotonic dystrophy type 1.

OBJECTIVE: To investigate intrarater reliability and concurrent and construct validity of muscle strength, balance, and functional mobility measures in individuals with noncongenital myotonic dystrophy type 1 (DM1). METHODS: Seventy-eight adults with noncongenital DM1 participated in visit 1, and 73 of the them participated in visit 2 separated by 1 to 2 weeks. The assessments consisted of muscle strength tests with handheld dynamometry (HHD) and stationary dynamometry in the lower limb. The balance tests consisted of the step test, Timed Up and Go test, feet-together stance, tandem stance, 1-leg stance, and modified Clinical Test of Sensory Integration and Balance on a balance platform. The functional mobility tests consisted of the 10-m walk test (10mWT) and 10-times Sit-to-Stand test. RESULTS: The HHD and stationary dynamometry had sufficient intrarater reliability for most muscle groups on a group (SEM% ≤15%) and individual (minimal detectable difference [MDD95%] ≤30%) level, but the HHD was most reliable. Stationary dynamometry measured a higher torque than HHD for all extensor muscles, but for single individuals, none of the devices were favored. Overall, intrarater reliability and validity were sufficient only for the dynamic balance tests, not the static balance tests. Both functional mobility tests were sufficiently reliable and valid, but the 10mWT was most reliable. CONCLUSION: Overall, HHD is recommended as a reliable and valid tool for single individuals and for flexor muscles on a group level. For balance assessments, the dynamic balance tests are recommended as the most valid and reliable balance tests. Both functional mobility tests are recommended for valid and reliable outcomes, but the 10mWT was superior for reliability.

Muscle Strength and Aerobic Capacity in Patients with CIDP One Year after Participation in an Exercise Trial.

BACKGROUND: We have previously shown that patients with chronic inflammatory demyelinating polyneuropathy (CIDP) improve muscle strength and aerobic capacity after resistance and aerobic exercise. OBJECTIVE: The purpose of this study was to determine if muscle strength and aerobic capacity are preserved one year after discontinuation of regular exercise. METHODS: All patients in the previous exercise study were eligible for a one-year follow-up with measurement of combined isokinetic muscle strength (cIKS) by dynamometry and maximal oxygen consumption velocity (VO2-max). Data are presented as median (ranges). RESULTS: Ten of 17 patients accepted to participate in the follow-up study. Following the exercise study six patients discontinued exercise and at one-year follow-up cIKS had decreased by -13.0 % (-25.8 to -2.9) (p = 0.03) and VO2-max by -16.6 % (-18.8 to -12.6) (p = 0.06). Four patients continued exercise (three with aerobic training and one with resistance training) and at one-year follow-up cIKS and VO2-max were preserved compared to the end of the exercise study (11.6 % (-8.9 to 32.1) (p = 0.88) and -8.4 % (-34.5 to -2.2) (p = 0.13), respectively). CONCLUSIONS: Continuation of aerobic and resistance exercise may preserve gains in muscle strength and aerobic capacity in patients with CIDP.

Does grip strength reflect isokinetic muscle strength in lower limbs in patients with chronic inflammatory demyelinating polyneuropathy?

INTRODUCTION: Grip strength (GS) is a common measure of general muscle strength in patients with chronic inflammatory demyelinating polyneuropathy (CIDP). However, it is important to investigate the correlation and responsiveness of GS compared with isokinetic muscle strength (IKS) and function of the lower limbs. METHODS: Seventy patients with CIDP were evaluated with GS, IKS, and functional measures of the lower limbs. Reevaluation was performed after 2 and 10/12 weeks. Correlation and response analyses were performed. RESULTS: GS correlated with IKS at the ankle (IKSankle ; maximum Spearman's rank-order correlation [RS ] = 0.58) and with walking performance (maximum RS = -0.38). IKSankle was more responsive to detect change (standardized response mean [SRM] = 0.57) than GS (SRM = 0.27). DISCUSSION: GS does not seem to be an appropriate surrogate measure of IKS and function of the lower limbs in patients with CIDP. Muscle Nerve 58: 449-452, 2018.

Aerobic anti-gravity exercise in patients with Charcot-Marie-Tooth disease types 1A and X: A pilot study.

Background: Charcot-Marie-Tooth (CMT) disease is a hereditary neuropathy associated with impaired walking capacity. Some patients are too weak in the lower extremity muscles to walk at gravity with sufficient intensity or duration to gain benefit. Aim: The aim was to investigate the effect of aerobic anti-gravity exercise in weak patients with CMT 1A and X. Methods: Five adult patients performed moderate-intensity aerobic anti-gravity exercise 3/week for 10 weeks. Results: There was a significant positive difference in Berg balance scale and postural stability test between test occasions, and walking distance in the 6-min walk test trended to increase. Conclusions: The study indicates that the anti-gravity treadmill training of patients with CMT should be pursued in larger CMT cohorts.