Corpus Callosum Diffusion and Language Lateralization in Patients with Brain Tumors: A DTI and fMRI Study

Abstract

BACKGROUND AND PURPOSE Examining how left-hemisphere brain tumors might impact both the microstructure of the corpus callosum (CC) as measured by fractional anisotropy (FA) values in diffusion tensor imaging (DTI) as well as cortical language lateralization measured with functional MRI (fMRI). METHODS fMRI tasks (phonemic fluency and verb generation) were performed in order to detect activation in Broca’s and Wernicke’s area. Twenty patients with left-hemisphere brain tumors were investigated. fMRI results were divided into left dominant (LD), right dominant (RD), or codominant (CD) for language function. DTI was performed to generate FA maps in the anterior and posterior CC. FA values were correlated with the degree of language dominance. RESULTS Patients who were LD or RD for language in Broca’s area had lower FA in the anterior CC than those who were CD for language (median for CD = .72, LD = .66, RD = .65, P < .09). Lateralized versus CD group level analysis also showed that CD patients had higher FA in the anterior CC than patients who displayed strong lateralization in either hemisphere (median for CD = .72, lateralized = .65, P < .05). CONCLUSION Our preliminary observations indicate that the greater FA in CD patients may reflect a more directional microstructure for the CC in this region, suggesting a greater need for interhemispheric transfer of information. Because brain tumors can cause compensatory codominance, our findings may suggest a mechanism by which interhemispheric transfer is facilitated during plasticity in the presence of a tumor.

Diffusion Tensor Imaging Shows Corpus Callosum Differences between High‐Grade Gliomas and Metastases

“…This is in line with the recent study done by Tantillo et al, which observed that FA values were higher in left‐hemispheric brain tumor patients that were codominant for language tasks than those that were left‐dominant, and this was suspected to be due to contralateral brain reorganization in the codominant group. Although contralateral reorganization is usually associated with low‐grade gliomas because of their typically longer median survival time compared to HGGs, contralateral reorganization has been suggested to occur in HGG patients as well . In addition, the median survival time for HGG patients is known to be longer than that for MET patients, so our results provide further evidence that a higher degree of contralateral brain reorganization can occur if the brain is given more time to undergo reorganization.…”

“…Since this seems to occur more in the patients of the HGG group according to their DTI characteristics, this raises the possibility that the increase in interhemispheric transfer would be due to more excitatory signals being sent to the contralateral side through the CC . Higher FA values of the CC have been shown to occur in those with bimanual motor skills or codominant language tasks as compared to more lateralized individuals, which further supports this speculation …”

“…A previous study by Saksena et al found that FA values were lower and MD values were higher in brain cancer patients compared to healthy controls, but they were unable to find significant differences in DTI characteristics between patient groups . However, Tantillo et al studied a population of brain cancer patients alone with functional magnetic resonance imaging (fMRI) and DTI data and found differences in FA values among two groups of patients . Left‐hemispheric brain tumor patients who exhibited codominance of language function had higher FA values in the anterior CC compared to those who exhibited lateralized language function; this was suspected to occur due to higher interhemispheric transfer of excitatory signals for contralateral brain reorganization in the former group of patients .…”

Corpus callosum demyelination associated with acquired stuttering

“…Structural changes have been demonstrated within the corpus callosum in functional MRI in patients with left hemispheric brain tumours impacting normal centres of language processing and production. These differences suggest network plasticity resulting in dysfunctional recruitment of the non-dominant hemisphere 4. Peters et al 2 presented a patient with new onset stuttering after recurrence of a right temporoparietal anaplastic astrocytoma, suggesting an additional complex interplay between cortical and subcortical structures in the role of language.…”

Infiltration of the basal ganglia by brain tumors is associated with the development of co-dominant language function on fMRI

“…Lastly, it is possible that the involvement of varying degrees of white matter surrounding the basal ganglia could factor in establishing co-dominance for language. The corpus callosum for example, has been correlated with co-dominance in brain tumor patients (Tantillo et al, 2015). However, the corpus callosum specifically was only involved in two of our thirty-five co-dominant cases, lessening its contribution.…”