Figure 5.

Correlations with clinical status—changes with time. Correlation coefficients between the physiological parameters measured and clinical outcome scores are presented for the 3 phases of stroke recovery studied. Significant correlations are denoted by filled symbols (P < 0.05). Because of the respective floor and ceiling effects seen in NHPT and ARAT scores in the early and late stages, the correlations in the acute period are with ARAT scores and those at later time points are with NHPT scores. The complete correlation coefficients are given in Table 3, and the plots can be seen in Supplementary Figures 4–8. (A) Physiological parameters reflecting integrity of the corticospinal tract are shown. rMTs and aMTs show negative clinical correlations, whereas RC gradients show positive correlations. Thus, poor clinical performance is associated with depressed RC gradients and raised motor thresholds. These correlations are significant for both resting and active thresholds in the acute period and for rMT at 3 months and aMT at 6 months. RC gradients show significant correlations in the acute period. (B) Measures of intracortical excitability are shown, as assessed by paired pulse TMS in each hemisphere . No significant/trend clinical correlations were seen with ICF in the AH, which is not shown. In the acute period, LICI in the AH showed a negative clinical correlation—weaker inhibition associated with worse clinical status—but no other measures showed significant correlations. At 3 months, however, all these measures showed significant negative clinical correlations except for SICI in the AH (which showed a trend correlation, P = 0.063)—weaker SICI/LICI or stronger ICF at this stage was associated with poorer motor function. By 6 months, none of the intracortical excitability measures showed significant or trend clinical correlations. Thus, although clinical status relates closely to corticospinal excitability in the acute period (but less so beyond), intracortical excitability measures become important by 3 months—this relationship is lost by 6 months.