Background/Objectives: The paretic wrist after stroke may exhibit median nerve conduction abnormalities, but factors underlying hemiplegic–contralateral asymmetry remain uncertain. We compared electrodiagnostic and ultrasonographic wrist measures between sides and assessed predictors of side-to-side differences in distal motor latency (ΔDML) and distal sensory latency (ΔDSL). Methods: We retrospectively analyzed 85 patients with stroke. Distal motor latency (DML), distal sensory latency (DSL), wrist-to-forearm ratio (WFR), and median nerve inlet cross-sectional area (CSA) were measured bilaterally. Paired t-tests evaluated hemiplegic–contralateral differences, and Wilcoxon signed-rank tests were performed as sensitivity analyses. Multivariable linear regression with robust (HC3) standard errors modeled ΔDML as the primary outcome and ΔDSL as the secondary outcome, with wrist flexor spasticity (Modified Ashworth Scale, MAS) specified a priori as the primary explanatory variable; extended models additionally included ΔWFR. Sensitivity analyses re-specified MAS as an ordered category, and complementary linear mixed-effects models using raw bilateral latency values were fitted to assess the robustness of Δ-based modeling. Results: The hemiplegic side showed higher DML (5.51 ± 0.79 vs. 4.81 ± 0.42 ms; mean difference 0.694; p < 0.001), DSL (4.51 ± 0.88 vs. 3.66 ± 0.45 ms; mean difference 0.852; p < 0.001), WFR (1.21 ± 0.30 vs. 1.07 ± 0.16; p = 0.008), and CSA (11.16 ± 3.67 vs. 9.69 ± 2.04 mm2; p = 0.032). MAS was associated with ΔDML (β = 0.336; p < 0.001) and ΔDSL (β = 0.238; p = 0.015). ΔWFR remained significant for ΔDML (β = 1.314; p < 0.001) and ΔDSL (β = 1.371; p = 0.001), improving adjusted R2 from 0.251 to 0.370 for ΔDML and from 0.142 to 0.253 for ΔDSL. Findings remained directionally consistent when MAS was modeled as an ordered category. Complementary mixed-effects models using raw bilateral latency values showed significant hemiplegic-side-by-MAS interactions for both DML (β = 0.425; 95% CI 0.275 to 0.575; p < 0.001) and DSL (β = 0.366; 95% CI 0.195 to 0.537; p < 0.001). Conclusions: In chronic stroke hemiplegia, median nerve latencies and wrist morphology may differ between sides. Wrist flexor spasticity and side-to-side increases in WFR may be independently associated with greater latency asymmetry. These interlimb latency differences should be interpreted as physiological markers of side-to-side median nerve involvement at the wrist rather than as stand-alone diagnostic criteria for carpal tunnel syndrome.
Ku et al. (Fri,) studied this question.