Correlation of DTI-Derived Measures to Therapy-Mediated Recovery after Stroke: Preliminary Findings

Corticospinal tracts (CST) forms the basis of motor neurophysiology after stroke. Motor skill recovery has been correlated well to the microstructural properties of CST in both hemispheres. Functional imaging has opened up new possibilities of imaging functionality of cortex and fiber tracts in the brain. We studied therapy-induced changes in blood oxygenation level-dependent (BOLD) and DTI imaging on 20 chronic stroke patients at baseline, 8, and 24 weeks.

All the patients were subjected to MR imaging on a 1.5 T MR scanner. We used block design for BOLD with alternate baseline and activation cycles (repetition time (TR) =4520 ms, echo time (TE) = 44 ms, slices = 31, slice thickness = 4 mm). DTI parameters were as follows: TE = 76 ms, TR = 10,726 ms, EPI factor = 127, resolution = 128 × 128 matrix, field of view = 230 mm and a slice thickness of 4.0 mm.

The data was analyzed on SPSS software and tractography/DTI processing software (M/s. Siemens Medical Solutions, Erlangen Germany.

The mean axial diffusivity (λ[INSIDE:1]) and radial diffusivity (λ[INSIDE:2]) in the affected hemisphere were 0. 30 and 0.18, respectively. The mean number (FN) ratio (± SD) was 0.27 ± 0.14 at baseline, 0.33 ± 0.19 at 8 weeks, and 0.41 ± 0.23 at 24 weeks. Multivariate regression analysis at baseline showed that rFA was well-correlated to the Fugl-Meyer score (regression coefficient: 0.198, F = 10.382, P = 0.001), MI followed by signal intensity.

All patients had high % signal intensity after 8 weeks of physiotherapy regime with a greater percentage change in rFA as compared at follow-up suggesting that a focused exercise regime in stroke patients helps in the reconnection of neural and myelin networks.

Clinical and functional recovery after stroke is well-correlated with the DTI and BOLD parameters i.e., rFA ratios, CST involvement fiber numbers, and % signal intensity of the ipsilesional cortex.