Prediction of motor recovery using initial impairment and fMRI 48 h poststroke

Abstract

There is substantial interpatient variation in recovery from upper limb impairment after stroke in patients with severe initial impairment. Defining recovery as a change in the upper limb Fugl-Meyer score (ΔFM), we predicted ΔFM with its conditional expectation (i.e., posterior mean) given upper limb Fugl-Meyer initial impairment (FM(ii)) and a putative functional magnetic resonance imaging (fMRI) recovery measure. Patients with first time, ischemic stroke were imaged at 2.5 ± 2.2 days poststroke with 1.5-T fMRI during a hand closure task alternating with rest (fundamental frequency = 0.025 Hz, scan duration = 172 s). Confirming a previous finding, we observed that the prediction of ΔFM by FM(ii) alone is good in patients with nonsevere initial hemiparesis but is not good in patients with severe initial hemiparesis (96% and 16% of the total sum of squares of ΔFM explained, respectively). In patients with severe initial hemiparesis, prediction of ΔFM by the combination of FM(ii) and the putative fMRI recovery measure nonsignificantly increased predictive explanation from 16% to 47% of the total sum of squares of ΔFM explained. The implications of this preliminary negative result are discussed.

Figure 1.

Schematic of patient sample composition.

Figure 2.

Cumulative correlation coefficient (see text for description) versus FM_ii for the nonimaged sample. The arrow marks where we specified the (inclusive) threshold (which corresponds to FM_ii ≥ 56) for defining severe FM_ii based on where the cumulative correlation coefficient begins to decrease. We chose to place this threshold slightly before the apparent decrease so as to be less likely to misclassify severe strokes as nonsevere.

Figure 3.

Predicted (posterior mean) versus observed ΔFM when using either 1) FM_ii (patients with nonsevere FM_ii: white squares; patients with severe FM_ii: black squares) or 2) FM_ii and Z (patients with nonsevere FM_ii: red circles; patients with severe FM_ii: blue circles) as the information in determining the posterior density of ΔFM. The SPE for a given datum is the (vertical distance to the identity line)². All data plotted correspond to the imaged sample.