Prognostic accuracy of transcranial magnetic stimulation-induced motor evoked potentials on recovery of upper limb: a systematic review

Background Prospective prognostic studies examining transcranial magnetic stimulation-induced motor evoked potentials (TMS-MEP) as predictors of upper limb (UL) motor function and capacity following stroke are influenced by variations in TMS procedures, outcome measures, and the timing of assessments. This prognostic review investigated three key areas: 1) the technical and methodological quality of TMS-MEP studies; 2) the prognostic accuracy for outcome related to muscle strength, muscle synergies and UL-capacity; and 3) the influence of the timing of TMS-MEP on outcomes. Methods With the QUAPAS (Quality Assessment of Prognostic Accuracy Studies) tool and Chipchase checklist the risk of bias (RoB) and technical quality of TMS-MEP studies were assessed, respectively. Sensitivity, specificity, negative predicted values (NPV), and positive predicted values (PPV) were analyzed for muscle strength, muscle synergies, and UL-capacity. Results Sixteen prospective TMS-MEP studies were included, all of which showed low RoB. Three studies reported all the recommended technical items for TMS testing. After pooling the data, muscle strength showed a sensitivity of 0.76 (95% CI: 0.64–0.85), specificity of 0.96 (95% CI: 0.55–1.00), PPV of 0.96 (95% CI: 0.85–0.99) and NPV of 0.62 (95% CI: 0.43–0.78). For muscle synergies, sensitivity was 0.70 (95% CI: 0.57–0.81), specificity was 0.98 (95% CI: 0.65–1.00), PPV was 0.98 (95% CI: 0.54–1.00) and NPV was 0.69 (95% CI: 0.42–0.87). For UL-capacity, the sensitivity was 0.84 (95% CI: 0.76–0.89), specificity was 0.91 (95% CI: 0.78–0.96), positive predictive value (PPV) was 0.91 (95% CI: 0.79–0.97), and negative predictive value (NPV) was 0.81 (95% CI: 0.65–0.91). No significant differences in accuracy were observed between type of outcome measures (i.e., muscle strength, muscle synergies or UL-capacity) and no differences were found between groups application of TMS-MEP before or beyond the seventh day after stroke onset. Conclusion TMS-MEP accurately predicts favorable UL-motor recovery regarding muscle strength, muscle synergy, and UL-capacity. However, its accuracy in identifying individuals who do not regain UL motor function and capacity remains limited early post-stroke.