Comparison of different stimulation parameters of repetitive transcranial magnetic stimulation for unilateral spatial neglect in stroke patients

Abstract

Objective: In this study three different stimulation parameters of repetitive transcranial magnetic stimulation (rTMS) were tested to compare the efficacy of continuous theta burst stimulation (continuous TBS) for rehabilitation of unilateral spatial neglect (USN) in stroke patients.

Methods: Carefully selected cohort of thirty-eight stroke patients were randomly assigned to three treatment groups (1 Hz group, 10 Hz group and continuous TBS group) and sham group. Intervention in patients in the treatment group consisted of rTMS, while patients in the sham group received pseudo-stimulation for two weeks. All patients were administered star cancellation and line bisection tests at 4 different time points of the study. Further, all study subjects in the three treatment groups and sham group underwent diffusion-tensor imaging (DTI) at the beginning and at the end of treatment to calculate fractional anisotropy (FA) and mean diffusivity (MD).

Results: Among the three stimulation parameters, star cancellation and line bisection tests revealed significant differences in outcomes at the end of treatments and one month after the end of treatments, compared to beginning of the treatments. Importantly, continuous TBS group patients displayed the best curative effect, based on behavioral scoring, at one month after end of the treatments, followed by the 1Hz group and 10 Hz group. DTI results showed a significant increase in FA and MD in superior longitudinal fasciculus, superior occipitofrontal fascicle and inferior fronto-occipital fasciculus on the left side, as well as the capsula external and inferior fronto-occipital fasciculus on the right side, in patients after continuous TBS. In addition, compared to the sham group, patients stimulated with continuous TBS exhibited a dramatic increase in FA in the left external capsule.

Conclusion: Our study presents strong evidence that rTMS significantly improves neurocognitive functions in USN, with continuous TBS showing the best curative effect. Enhanced connections in the white matter tract network related to visual attention, as assessed by DTI, might be the potential mechanism for the observed recovery in USN using continuous TBS.

Keywords: Continuous theta burst stimulation; Diffusion-tensor imaging; Fractional anisotropy; Mean diffusivity; Neural regulation; Repetitive transcranial magnetic stimulation; Stroke; Unilateral spatial neglect.