Ultrasound Assessment of Changes in Muscle Architecture of the Brachialis Muscle After Stroke-A Prospective Study.

Objective: To investigate changes in ultrasound-derived muscle architecture parameters of the brachialis and correlations in patients with subacute stroke.

Design: Prospective longitudinal observational study.

Setting: Tertiary inpatient rehabilitation center.

Participants: Fifty adult patients (N=50) who were recruited within the first month poststroke. The patients had a mean age of 57.2±12.3 years and 68.0% were male. The majority of patients had significant upper limb weakness with a low mean Motricity Index of 18.5±24.7 and median elbow flexor strength of grade 0.

Intervention: Not applicable.

Main Outcome Measures: Ultrasound of the intact and hemiparetic brachialis was performed at 3-time intervals: within 1 month of stroke onset and at 1 and 6 months after first assessment. Clinical variables captured included upper limb motor power and elbow flexor spasticity.

Results: Compared to the intact brachialis, there was reduced muscle thickness (1.93 cm vs 2.07 cm, 1.86 cm vs 2.08 cm, 1.85 cm vs 2.05 cm; =.022) and increased echo intensity (63.3 arbitrary units [AU] vs 56.8 AU, 69.4 AU vs 56.6 AU, 77.4 AU vs 58.2 AU; <.001) in the hemiparetic brachialis at all assessment intervals (baseline, 1 month, 6 months). Reduction in muscle mass was greater in older patients, with the correlation coefficient ranging from -0.30 (=.03) at baseline to -0.50 (<.001) at 6 months. Presence of elbow flexor spasticity at 1-month assessment interval was associated with lower muscle mass reduction (1.93 cm vs 1.74 cm; =.017), lower echo intensity (65.1 AU vs 75.1 AU; =.023), and longer fascicle lengths (12.92 cm vs 9.83 cm; =.002).

Conclusions: Changes including decreased muscle thickness and increased echo intensity of the hemiparetic brachialis were noted over time. Elbow flexor spasticity at 1-month assessment interval appears to mitigate against these changes.