Association Between Electrophysiological Evaluation and Muscle Quality Changes in the Lower Limb of Subacute Stroke Patients: A Pilot Longitudinal Observational Study

<b>Background:</b> This pilot longitudinal observational study investigated 4-week changes in lower limb muscle quantity and quality in patients with subacute stroke and explored risk factors associated with these changes. <b>Methods:</b> Twenty-six patients with hemiplegia following subacute stroke underwent assessment at baseline and 4-week follow-up. Muscle quantity was evaluated by ultrasound muscle thickness and bioelectrical impedance analysis, while muscle quality was assessed by shear-wave elastography in seven muscles (rectus femoris, vastus intermedius, vastus lateralis [VL], vastus medialis, tibialis anterior, gastrocnemius [GCM], and soleus). Electrophysiological assessments included motor-evoked potential (MEP), somatosensory-evoked potential (SEP), nerve conduction studies (NCSs), and central motor conduction time (CMCT). <b>Results:</b> Muscle thickness and bioimpedance did not significantly change between baseline and follow-up. In contrast, shear modulus increased in the paretic-side VL and GCM muscles (<i>p</i> < 0.001 and <i>p</i> = 0.049), with no differences in the non-paretic side. Greater deterioration in GCM quality was observed in patients with abnormal lower-limb MEP, and increased VL stiffness correlated with prolonged CMCT. Multivariable analyses were performed adjusting for age, sex, National Institutes of Health Stroke Scale, and comorbidity burden; however, due to the small electrophysiology sample (<i>n</i> = 11), these results should be interpreted as exploratory. <b>Conclusions:</b> In subacute stroke, early deterioration in muscle quality can occur despite stable quantity and appears linked to corticospinal integrity. Integrating electrophysiological evaluation with elastography may help identify patients who could benefit from early, targeted neuromuscular rehabilitation. These exploratory findings require validation in larger cohorts.