Affiliations: Department of Neurology, University Hospital
Eppendorf, Hamburg, Germany
Note: [] Corresponding author: Prof. Dr. J. Liepert, Department of
Neurology, University Hospital Eppendorf, Martinistr. 52, D-20246 Hamburg,
Germany. Tel.: +49 40 4280 33772; Fax: +49 40 4280 35623; E-mail:
liepert@uke.uni-hamburg.de
Abstract: Introduction: A stroke may modulate motor cortex excitability. We
examined if distinct ischemic brain lesions are associated with a specific
pattern of excitability changes. We also investigated the effects of a
rehabilitative therapy on motor excitability. Methods: In stroke patients, the consequences of a) a lesion in the
central somatosensory system, b) a cerebellar lesion and c) a two week period
of Constraint-induced movement therapy (CIMT), on motor cortex excitability
were studied. Transcranial magnetic stimulation techniques and functional
magnetic resonance imaging (fMRI) were employed. Results: Patients with a lesion in the primary somatosensory cortex
or in the ventroposterolateral nucleus of the thalamus had a decreased
intracortical inhibition on the affected side. Patients with lesions in the
territory of the superior cerebellar artery had a loss of intracortical
facilitation and an increase of intracortical inhibition. Patients with
cortical lesions undergoing CIMT had a loss of intracortical inhibition prior
to therapy. After CIMT, changes of ICI were stronger in the lesioned than in
the non-lesioned hemisphere but could result either in an increase of ICI or a
reduction of ICI. In three patients fMRI results showed that cortical
activation was less post CIMT as compared to pre-treatment activation. In
parallel, ICI was reduced after treatment. Conclusions: Our results suggest that, physiologically, central
somatosensory influence on the motor cortex is inhibitory. In contrast, the
cerebellum normally exerts a facilitatory influence on the motor cortex. CIMT
induces changes of intracortical excitability mainly in the affected
hemisphere.
Keywords: stroke, motor cortex excitability, Constraint-induced movement therapy, transcranial magnetic stimulation, functional magnetic resonance imaging
