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Complete hemispherotomy leads to lateralized functional organization and lower level of consciousness in the isolated hemisphere

(2020) EPILEPSIA OPEN. 5(4). p.537-549
Author
Organization
Abstract
Objective To quantify whole‐brain functional organization after complete hemispherotomy, characterizing unexplored plasticity pathways and the conscious level of the dissected hemispheres. Methods Evaluation with multimodal magnetic resonance imaging in two pediatric patients undergoing right hemispherotomy including complete callosotomy with a perithalamic section. Regional cerebral blood flow and fMRI network connectivity assessed the functional integrity of both hemispheres after surgery. The level of consciousness was tested by means of a support vector machine classifier which compared the intrinsic organization of the dissected hemispheres with those of patients suffering from disorders of consciousness. Results After hemispherotomy, both patients showed typical daily functionality. We found no interhemispheric transfer of functional connectivity in either patient as predicted by the operation. The healthy left hemispheres displayed focal blood hyperperfusion in motor and limbic areas, with preserved network‐level organization. Unexpectedly, the disconnected right hemispheres showed sustained network organization despite low regional cerebral blood flow. Subcortically, functional connectivity was increased in the left thalamo‐cortical loop and between the cerebelli. One patient further showed unusual ipsilateral right cerebello‐cortical connectivity, which was explained by the mediation of the vascular system. The healthy left hemisphere had higher probability to be classified as in a minimally conscious state compared to the isolated right hemisphere. Significance Complete hemispherotomy leads to a lateralized whole‐brain organization, with the remaining hemisphere claiming most of the brain's energetic reserves supported by subcortical structures. Our results further underline the contribution of nonneuronal vascular signals on contralateral connectivity, shedding light on the nature of network organization in the isolated tissue. The disconnected hemisphere is characterized by a level of consciousness which is necessary but insufficient for conscious processing, paving the way for more specific inquiries about its role in awareness in the absence of behavioral output.
Keywords
brain connectivity, epilepsy, functional connectivity, fMRI, arterial spin labelling, consciousness, functional MRI, hemispherotomy, networks

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MLA
Blauwblomme, Thomas, et al. “Complete Hemispherotomy Leads to Lateralized Functional Organization and Lower Level of Consciousness in the Isolated Hemisphere.” EPILEPSIA OPEN, vol. 5, no. 4, 2020, pp. 537–49, doi:10.1002/epi4.12433.
APA
Blauwblomme, T., Demertzi, A., Tacchela, J., Fillon, L., Bourgeois, M., Losito, E., … Nabbout, R. (2020). Complete hemispherotomy leads to lateralized functional organization and lower level of consciousness in the isolated hemisphere. EPILEPSIA OPEN, 5(4), 537–549. https://doi.org/10.1002/epi4.12433
Chicago author-date
Blauwblomme, Thomas, Athena Demertzi, Jean‐Marc Tacchela, Ludovic Fillon, Marie Bourgeois, Emma Losito, Monika Eisermann, et al. 2020. “Complete Hemispherotomy Leads to Lateralized Functional Organization and Lower Level of Consciousness in the Isolated Hemisphere.” EPILEPSIA OPEN 5 (4): 537–49. https://doi.org/10.1002/epi4.12433.
Chicago author-date (all authors)
Blauwblomme, Thomas, Athena Demertzi, Jean‐Marc Tacchela, Ludovic Fillon, Marie Bourgeois, Emma Losito, Monika Eisermann, Daniele Marinazzo, Federico Raimondo, Sarael Alcauter, Frederik Van de Steen, Nigel Colenbier, Steven Laureys, Volodia Dangouloff-Ros, Lionel Naccache, Nathalie Boddaert, and Rima Nabbout. 2020. “Complete Hemispherotomy Leads to Lateralized Functional Organization and Lower Level of Consciousness in the Isolated Hemisphere.” EPILEPSIA OPEN 5 (4): 537–549. doi:10.1002/epi4.12433.
Vancouver
1.
Blauwblomme T, Demertzi A, Tacchela J, Fillon L, Bourgeois M, Losito E, et al. Complete hemispherotomy leads to lateralized functional organization and lower level of consciousness in the isolated hemisphere. EPILEPSIA OPEN. 2020;5(4):537–49.
IEEE
[1]
T. Blauwblomme et al., “Complete hemispherotomy leads to lateralized functional organization and lower level of consciousness in the isolated hemisphere,” EPILEPSIA OPEN, vol. 5, no. 4, pp. 537–549, 2020.
@article{8675174,
  abstract     = {Objective
To quantify whole‐brain functional organization after complete hemispherotomy, characterizing unexplored plasticity pathways and the conscious level of the dissected hemispheres.

Methods
Evaluation with multimodal magnetic resonance imaging in two pediatric patients undergoing right hemispherotomy including complete callosotomy with a perithalamic section. Regional cerebral blood flow and fMRI network connectivity assessed the functional integrity of both hemispheres after surgery. The level of consciousness was tested by means of a support vector machine classifier which compared the intrinsic organization of the dissected hemispheres with those of patients suffering from disorders of consciousness.

Results
After hemispherotomy, both patients showed typical daily functionality. We found no interhemispheric transfer of functional connectivity in either patient as predicted by the operation. The healthy left hemispheres displayed focal blood hyperperfusion in motor and limbic areas, with preserved network‐level organization. Unexpectedly, the disconnected right hemispheres showed sustained network organization despite low regional cerebral blood flow. Subcortically, functional connectivity was increased in the left thalamo‐cortical loop and between the cerebelli. One patient further showed unusual ipsilateral right cerebello‐cortical connectivity, which was explained by the mediation of the vascular system. The healthy left hemisphere had higher probability to be classified as in a minimally conscious state compared to the isolated right hemisphere.

Significance
Complete hemispherotomy leads to a lateralized whole‐brain organization, with the remaining hemisphere claiming most of the brain's energetic reserves supported by subcortical structures. Our results further underline the contribution of nonneuronal vascular signals on contralateral connectivity, shedding light on the nature of network organization in the isolated tissue. The disconnected hemisphere is characterized by a level of consciousness which is necessary but insufficient for conscious processing, paving the way for more specific inquiries about its role in awareness in the absence of behavioral output.},
  author       = {Blauwblomme, Thomas and Demertzi, Athena and Tacchela, Jean‐Marc and Fillon, Ludovic and Bourgeois, Marie and Losito, Emma and Eisermann, Monika and Marinazzo, Daniele and Raimondo, Federico and Alcauter, Sarael and Van de Steen, Frederik and Colenbier, Nigel and Laureys, Steven and Dangouloff-Ros, Volodia and Naccache, Lionel and Boddaert, Nathalie and Nabbout, Rima},
  issn         = {2470-9239},
  journal      = {EPILEPSIA OPEN},
  keywords     = {brain connectivity,epilepsy,functional connectivity,fMRI,arterial spin labelling,consciousness,functional MRI,hemispherotomy,networks},
  language     = {eng},
  number       = {4},
  pages        = {537--549},
  title        = {Complete hemispherotomy leads to lateralized functional organization and lower level of consciousness in the isolated hemisphere},
  url          = {http://dx.doi.org/10.1002/epi4.12433},
  volume       = {5},
  year         = {2020},
}

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