Artikel
Language shift to the right hemisphere in patients with language eloquent lesions of the dominant left hemisphere
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Autoren
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Nico Sollmann
- Department of Neurosurgery, Technische Universität München, Munich, Germany
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Theresa Hauck
- Department of Neurosurgery, Technische Universität München, Munich, Germany
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Bernhard Meyer
- Department of Neurosurgery, Technische Universität München, Munich, Germany
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Florian Ringel
- Department of Neurosurgery, Technische Universität München, Munich, Germany
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Sandro M. Krieg
- Department of Neurosurgery, Technische Universität München, Munich, Germany
| Veröffentlicht: | 21. Mai 2013 |
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Gliederung
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Objective: Human language function is known to be located within the left hemisphere especially in right-handed subjects. Thus, left-sided perisylvian lesions usually cause dysarthria or aphasia. However, recent reports demonstrated changes of language organization in such cases. Moreover, there are several reports in which fMRI showed increase activation of the right hemisphere in patients with left-sided perisylvian lesions. But as fMRI is frequently impaired by intracerebral lesions, this study was designed to provide evidence for human language plasticity by a virtual lesion model.
Method: Fourteen right-handed and one left-handed patient suffering from tumors within language-eloquent brain areas underwent nTMS language mapping by an object naming task of both hemispheres. All patients were proved to be left-dominant in terms of language function by awake surgery. Moreover, 50 healthy and purely right-handed subjects were also examined via nTMS language mapping of both hemispheres. The induced speech errors were categorized into six different error types. The error ratio (induced errors/number of stimulations) was then determined for each CPS region of the left and right hemisphere. Moreover, a hemispheric dominance ratio was defined for each region which is defined as the quotient of the error ratio (left/right) of the corresponding area of both hemispheres (ratio >1 = left dominant; ratio <1 = right dominant).
Results: Over all, patients with language-eloquent tumors showed a significant lower ratio than healthy subjects concerning „all errors“ and „all errors without hesitations“, which means a higher participation of the right hemisphere in language function. Yet, there was no CPS region with pronounced difference in language dominance compared to the whole hemisphere. Thus, language switch seems to show a more diffuse rather than focused pattern.
Conclusions: This is the first study that shows cortical plasticity as a shift of language function to the non-dominant hemisphere by using a virtual lesion model.
