RT Journal Article
SR Electronic
T1 Muscle strength and motor function in adolescents and adults with spinal muscular atrophy
JF Neurology
JO Neurology
FD Lippincott Williams & Wilkins
SP e1988
OP e1998
DO 10.1212/WNL.0000000000010540
VO 95
IS 14
A1 Wijngaarde, Camiel A.
A1 Stam, Marloes
A1 Otto, Louise A.M.
A1 Bartels, Bart
A1 Asselman, Fay-Lynn
A1 van Eijk, Ruben P.A.
A1 van den Berg, Leonard H.
A1 Goedee, H. Stephan
A1 Wadman, Renske I.
A1 van der Pol, W. Ludo
YR 2020
UL http://n.neurology.org/content/95/14/e1988.abstract
AB Objective To assess longitudinal patterns of muscle strength, motor function, and maximal compound muscle action potential amplitudes (CMAPMAX) in older patients with spinal muscular atrophy (SMA), hypothesizing a continued decline of motor function parameters throughout life.Methods We measured muscle strength (Medical Research Council), motor function (Hammersmith Functional Motor Scale Expanded [HFMSE] and Motor Function Measure), and CMAPMAX in treatment-naive patients. We used both longitudinal and cross-sectional data in mixed models to analyze natural history patterns.Results We included 250 patients with SMA types 1c through 4. Median patient age at assessment was 26.8 years, the number of assessments per patient ranged from 1 to 6. Baseline muscle strength and motor function scores differed significantly between SMA types, but annual rates of decline were largely similar and mostly linear. HFMSE floor effects were present for all patients with SMA type 1c, and adolescents and adults with types 2 and 3a. CMAPMAX differed significantly between SMA types but did not decline significantly with increasing age. Muscle strength correlated very strongly with motor function (τ ≥ 0.8) but only moderately with CMAPMAX (τ ≈ 0.5–0.6).Conclusion Muscle strength and motor function decline in older patients with SMA are constant without periods of slower progression or a plateau phase. The floor effects of the HFMSE preclude its use for long-term follow-up of adult patients with SMA types 1c through 3a. Muscle strength sum scores represent an alternative, feasible outcome measure for adolescent and adult patients with SMA.CI=confidence interval; CMAPMAX=maximal compound muscle action potential amplitudes; HFMSE=Hammersmith Functional Motor Scale Expanded; LMM=linear mixed-effects model; MFM=Motor Function Measure; MRC=Medical Research Council; SMA=spinal muscular atrophy; SMN=survival motor neuron