Matthieu Vassal, Emmanuelle Le Bars, S.T. Sylvie Moritz-Gasser, Nicolas Menjot and Hugues Duffau
Crossed aphasia (aphasia resulting from a right hemispheric lesion among right-handed patients) is rare. The authors describe for the first time transient crossed aphasia elicited by intraoperative electrostimulation of both cortex and white matter pathways in awake patients.
Three right-handed adults underwent surgery for a right-sided glioma. Because slight language disorders occurred during partial seizures or were identified on preoperative cognitive assessment, with right activations detected on language functional MR imaging in 1 patient, awake craniotomy was performed using intraoperative cortico-subcortical electrical functional mapping.
Transient language disturbances were elicited by stimulating discrete cortical areas (inferior frontal gyrus and posterior part of the superior temporal gyrus) and white matter pathways (inferior frontooccipital fasciculus and arcuate fasciculus). A subtotal resection was achieved in all cases, according to functional boundaries. Postoperatively, 1 patient experienced a transient dysphasia, which resolved after speech rehabilitation, with no permanent deficit.
These original findings highlight the possibility of finding crucial cortico-subcortical language networks in the right hemisphere in a subgroup of atypical right-handed patients. These findings provide new insights into the neural basis of language, by underlining the role of the right inferior occipitofrontal fasciculus in semantics and that of the right arcuate fasciculus in phonology, and by supporting the hypothesis of a mirror organization between the right and left hemispheres. The authors suggest that, in right-handed patients, if language disturbances are detected during seizures or on presurgical neuropsychological assessment, especially when right activations are observed on language functional MR imaging, awake craniotomy with intraoperative language mapping should be considered.
Matthieu Vassal, Céline Charroud, Jérémy Deverdun, Emmanuelle Le Bars, François Molino, Francois Bonnetblanc, Anthony Boyer, Anirban Dutta, Guillaume Herbet, Sylvie Moritz-Gasser, Alain Bonafé, Hugues Duffau and Nicolas Menjot de Champfleur
The supplementary motor area (SMA) syndrome is a well-studied lesional model of brain plasticity involving the sensorimotor network. Patients with diffuse low-grade gliomas in the SMA may exhibit this syndrome after resective surgery. They experience a temporary loss of motor function, which completely resolves within 3 months. The authors used functional MRI (fMRI) resting state analysis of the sensorimotor network to investigate large-scale brain plasticity between the immediate postoperative period and 3 months' follow-up.
Resting state fMRI was performed preoperatively, during the immediate postoperative period, and 3 months postoperatively in 6 patients with diffuse low-grade gliomas who underwent partial surgical excision of the SMA. Correlation analysis within the sensorimotor network was carried out on those 3 time points to study modifications of its functional connectivity.
The results showed a large-scale reorganization of the sensorimotor network. Interhemispheric connectivity was decreased in the postoperative period, and increased again during the recovery process. Connectivity between the lesion side motor area and the contralateral SMA rose to higher values than in the preoperative period. Intrahemispheric connectivity was decreased during the immediate postoperative period and had returned to preoperative values at 3 months after surgery.
These results confirm the findings reported in the existing literature on the plasticity of the SMA, showing large-scale modifications of the sensorimotor network, at both inter- and intrahemispheric levels. They suggest that interhemispheric connectivity might be a correlate of SMA syndrome recovery.