One session of repeated parietal theta burst stimulation trains induces long-lasting improvement of visual neglect

Visual neglect is a frequent disability in stroke and adversely affects mobility, discharge destination, and length of hospital stay. It is assumed that its severity is enhanced by a released interhemispheric inhibition from the unaffected toward the affected hemisphere. Continuous theta burst transcranial magnetic stimulation (TBS) is a new inhibitory brain stimulation protocol which has the potential to induce behavioral effects outlasting stimulation. We aimed to test whether parietal TBS over the unaffected hemisphere can induce a long-lasting improvement of visual neglect by reducing the interhemispheric inhibition.

Eleven patients with left-sided visual neglect attributable to right hemispheric stroke were tested in a visual perception task. To evaluate the specificity of the TBS effect, 3 conditions were tested: 2 TBS trains over the left contralesional posterior parietal cortex, 2 trains of sham stimulation over the contralesional posterior parietal cortex, and a control condition without any intervention. To evaluate the lifetime of repeated trains of TBS in 1 session, 4 trains were applied over the contralesional posterior parietal cortex.

Two TBS trains significantly increased the number of perceived left visual targets for up to 8 hours as compared to baseline. No significant improvement was found with sham stimulation or in the control condition without any intervention. The application of 4 TBS trains significantly increased the number of perceived left targets up to 32 hours.

The new approach of repeating TBS at the same day may be promising for therapy of neglect.