Affiliations: Perception and Eye Movement Laboratory, Department of
Neurology, Department of Clinical Research, Inselspital, Bern University
Hospital, and University of Bern, Bern, Switzerland
Note: [] Corresponding author: Th. Nyffeler, MD; Perception and Eye
Movement Laboratory, Department of Neurology, Department of Clinical Research,
Inselspital, Freiburgstrasse 10, 3010 Bern, Switzerland. Tel.: +41 31 632 30
83; Fax: +41 31 632 97 70; E-mail: thomas.nyffeler@insel.ch
Abstract: Hemispatial neglect – defined as the failure to attend, explore,
and act upon the contralesional side of space – is a frequent and disabling
neurological syndrome. Interhemispheric rivalry is considered as a major
pathophysiological mechanism underlying hemispatial neglect. According to this
account, the contralesional, intact hemisphere undergoes a pathological
hyperactivity due to a deficient transcallosal inhibition from the damaged
hemisphere. This model offers a framework for possible therapeutic
interventions with repetitive transcranial magnetic stimulation (rTMS), i.e. a
reduction of the pathological hyperactivity with a rTMS protocol that has
lasting inhibitory effects. In the present work, we will first review evidence
for the interhemispheric rivalry account coming from animals and humans. We
will then describe studies showing the possibility to perturb and to restore
interhemispheric balance in healthy subjects as a proof of concept for
therapeutic rTMS application. Finally, we will consider studies applying rTMS
as a therapeutic approach in hemispatial neglect. We conclude that rTMS is a
promising approach to reduce the interhemispheric imbalance in neglect patients
and to ameliorate symptoms. Newly developed protocols such as Theta Burst
Stimulation (TBS) – with short stimulation times and long offline effects –
seem to be particularly convenient. However, future studies should assess
stimulation effects not only in clinical testing, but also on disability,
considering combination with traditional therapies as well.
