Limits...
The structural plasticity of white matter networks following anterior temporal lobe resection.

Yogarajah M, Focke NK, Bonelli SB, Thompson P, Vollmar C, McEvoy AW, Alexander DC, Symms MR, Koepp MJ, Duncan JS - Brain (2010)

Bottom Line: These findings were confirmed on analysis of the native clusters and hand drawn regions of interest.The mean pre- and postoperative fractional anisotropy and parallel diffusivity in this cluster were significantly correlated with postoperative verbal fluency and naming test scores.These findings have important implications for our understanding of brain injury and rehabilitation, and may also prove useful in the prediction and minimization of postoperative language deficits.

View Article: PubMed Central - PubMed

Affiliation: Department of Experimental and Clinical Epilepsy, UCL Institute of Neurology, London, WC1N 3BG, UK.

ABSTRACT
Anterior temporal lobe resection is an effective treatment for refractory temporal lobe epilepsy. The structural consequences of such surgery in the white matter, and how these relate to language function after surgery remain unknown. We carried out a longitudinal study with diffusion tensor imaging in 26 left and 20 right temporal lobe epilepsy patients before and a mean of 4.5 months after anterior temporal lobe resection. The whole-brain analysis technique tract-based spatial statistics was used to compare pre- and postoperative data in the left and right temporal lobe epilepsy groups separately. We observed widespread, significant, mean 7%, decreases in fractional anisotropy in white matter networks connected to the area of resection, following both left and right temporal lobe resections. However, we also observed a widespread, mean 8%, increase in fractional anisotropy after left anterior temporal lobe resection in the ipsilateral external capsule and posterior limb of the internal capsule, and corona radiata. These findings were confirmed on analysis of the native clusters and hand drawn regions of interest. Postoperative tractography seeded from this area suggests that this cluster is part of the ventro-medial language network. The mean pre- and postoperative fractional anisotropy and parallel diffusivity in this cluster were significantly correlated with postoperative verbal fluency and naming test scores. In addition, the percentage change in parallel diffusivity in this cluster was correlated with the percentage change in verbal fluency after anterior temporal lobe resection, such that the bigger the increase in parallel diffusivity, the smaller the fall in language proficiency after surgery. We suggest that the findings of increased fractional anisotropy in this ventro-medial language network represent structural reorganization in response to the anterior temporal lobe resection, which may damage the more susceptible dorso-lateral language pathway. These findings have important implications for our understanding of brain injury and rehabilitation, and may also prove useful in the prediction and minimization of postoperative language deficits.

Show MeSH

Related in: MedlinePlus

Threshold-free cluster-enhanced corrected (P < 0.05) results of the whole-brain tract-based spatial statistics analysis of fractional anisotropy after left anterior temporal lobe resection. The left side of the brain is on the right side of the image. R = right. Significant clusters representing increases (red to yellow) and decreases (blue to light blue) in fractional anisotropy after surgery are projected onto the mean fractional anisotropy template derived from all pre- and postoperative left temporal lobe epilepsy patients. For clarity, the group fractional anisotropy skeleton is not shown. The area of resection is visible inferiorly in the left temporal lobe where the white matter bundles are absent. Fractional anisotropy reduction after left anterior temporal lobe resection is apparent in the left temporal and occipital lobes, fornix, splenium and anterior commissure. There are also decreases in fractional anisotropy to a lesser extent in the contralateral hemisphere. Fractional anisotropy increases are present in the external capsule, posterior limb of the internal capsule and corona radiata. See Table 2 for more details regarding the anatomical location of local maxima.
© Copyright Policy - creative-commons
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC3198261&req=5

Figure 1: Threshold-free cluster-enhanced corrected (P < 0.05) results of the whole-brain tract-based spatial statistics analysis of fractional anisotropy after left anterior temporal lobe resection. The left side of the brain is on the right side of the image. R = right. Significant clusters representing increases (red to yellow) and decreases (blue to light blue) in fractional anisotropy after surgery are projected onto the mean fractional anisotropy template derived from all pre- and postoperative left temporal lobe epilepsy patients. For clarity, the group fractional anisotropy skeleton is not shown. The area of resection is visible inferiorly in the left temporal lobe where the white matter bundles are absent. Fractional anisotropy reduction after left anterior temporal lobe resection is apparent in the left temporal and occipital lobes, fornix, splenium and anterior commissure. There are also decreases in fractional anisotropy to a lesser extent in the contralateral hemisphere. Fractional anisotropy increases are present in the external capsule, posterior limb of the internal capsule and corona radiata. See Table 2 for more details regarding the anatomical location of local maxima.

Mentions: Following left anterior temporal lobe resection, there were significant decreases in FA in the main fibre tracts ipsilateral to the side of surgery, and also to a lesser extent in the contralateral hemisphere (Fig. 1). The areas of decreased FA corresponded to one contiguous, large cluster of 15 240 voxels (P < 0.001). The local maxima of this cluster were determined in order to investigate the anatomy of this cluster further (Table 2). The most significant decreases in FA were on the left side in the geniculo-calcarine tract and its projection to the lingual/occipital fusiform gyri, and intracalcarine cortex, part of the inferior longitudinal fasciculus, parahippocampal gyrus, crura of the fornix, anterior commissure and the anterior temporal portions of the superior longitudinal fasciculus. There were also significant decreases of FA in the temporal portion of the left uncinate fasciculus that connects to the temporal pole and the anterior floor of the external capsule. The latter structure contains fibres of the uncinate and inferior fronto-occipital fasciculi. Less-significant decreases in FA were also noted on the contralateral side in the fornix, anterior commissure and temporal portion of the inferior longitudinal fasciculus. Analysis of the de-projected, pre- and postoperative native clusters (Table 3) confirmed that there was a significant mean 7.08% decrease in FA in these areas postoperatively (z = −3.845, P < 0.001) due mainly to a mean 7.77% increase in λT (z = −3.883, P < 0.001). M.D. was also significantly increased by a mean 4.75% postoperatively in these areas (z = −3.735, P < 0.001).Figure 1


The structural plasticity of white matter networks following anterior temporal lobe resection.

Yogarajah M, Focke NK, Bonelli SB, Thompson P, Vollmar C, McEvoy AW, Alexander DC, Symms MR, Koepp MJ, Duncan JS - Brain (2010)

Threshold-free cluster-enhanced corrected (P < 0.05) results of the whole-brain tract-based spatial statistics analysis of fractional anisotropy after left anterior temporal lobe resection. The left side of the brain is on the right side of the image. R = right. Significant clusters representing increases (red to yellow) and decreases (blue to light blue) in fractional anisotropy after surgery are projected onto the mean fractional anisotropy template derived from all pre- and postoperative left temporal lobe epilepsy patients. For clarity, the group fractional anisotropy skeleton is not shown. The area of resection is visible inferiorly in the left temporal lobe where the white matter bundles are absent. Fractional anisotropy reduction after left anterior temporal lobe resection is apparent in the left temporal and occipital lobes, fornix, splenium and anterior commissure. There are also decreases in fractional anisotropy to a lesser extent in the contralateral hemisphere. Fractional anisotropy increases are present in the external capsule, posterior limb of the internal capsule and corona radiata. See Table 2 for more details regarding the anatomical location of local maxima.
© Copyright Policy - creative-commons
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3198261&req=5

Figure 1: Threshold-free cluster-enhanced corrected (P < 0.05) results of the whole-brain tract-based spatial statistics analysis of fractional anisotropy after left anterior temporal lobe resection. The left side of the brain is on the right side of the image. R = right. Significant clusters representing increases (red to yellow) and decreases (blue to light blue) in fractional anisotropy after surgery are projected onto the mean fractional anisotropy template derived from all pre- and postoperative left temporal lobe epilepsy patients. For clarity, the group fractional anisotropy skeleton is not shown. The area of resection is visible inferiorly in the left temporal lobe where the white matter bundles are absent. Fractional anisotropy reduction after left anterior temporal lobe resection is apparent in the left temporal and occipital lobes, fornix, splenium and anterior commissure. There are also decreases in fractional anisotropy to a lesser extent in the contralateral hemisphere. Fractional anisotropy increases are present in the external capsule, posterior limb of the internal capsule and corona radiata. See Table 2 for more details regarding the anatomical location of local maxima.
Mentions: Following left anterior temporal lobe resection, there were significant decreases in FA in the main fibre tracts ipsilateral to the side of surgery, and also to a lesser extent in the contralateral hemisphere (Fig. 1). The areas of decreased FA corresponded to one contiguous, large cluster of 15 240 voxels (P < 0.001). The local maxima of this cluster were determined in order to investigate the anatomy of this cluster further (Table 2). The most significant decreases in FA were on the left side in the geniculo-calcarine tract and its projection to the lingual/occipital fusiform gyri, and intracalcarine cortex, part of the inferior longitudinal fasciculus, parahippocampal gyrus, crura of the fornix, anterior commissure and the anterior temporal portions of the superior longitudinal fasciculus. There were also significant decreases of FA in the temporal portion of the left uncinate fasciculus that connects to the temporal pole and the anterior floor of the external capsule. The latter structure contains fibres of the uncinate and inferior fronto-occipital fasciculi. Less-significant decreases in FA were also noted on the contralateral side in the fornix, anterior commissure and temporal portion of the inferior longitudinal fasciculus. Analysis of the de-projected, pre- and postoperative native clusters (Table 3) confirmed that there was a significant mean 7.08% decrease in FA in these areas postoperatively (z = −3.845, P < 0.001) due mainly to a mean 7.77% increase in λT (z = −3.883, P < 0.001). M.D. was also significantly increased by a mean 4.75% postoperatively in these areas (z = −3.735, P < 0.001).Figure 1

Bottom Line: These findings were confirmed on analysis of the native clusters and hand drawn regions of interest.The mean pre- and postoperative fractional anisotropy and parallel diffusivity in this cluster were significantly correlated with postoperative verbal fluency and naming test scores.These findings have important implications for our understanding of brain injury and rehabilitation, and may also prove useful in the prediction and minimization of postoperative language deficits.

View Article: PubMed Central - PubMed

Affiliation: Department of Experimental and Clinical Epilepsy, UCL Institute of Neurology, London, WC1N 3BG, UK.

ABSTRACT
Anterior temporal lobe resection is an effective treatment for refractory temporal lobe epilepsy. The structural consequences of such surgery in the white matter, and how these relate to language function after surgery remain unknown. We carried out a longitudinal study with diffusion tensor imaging in 26 left and 20 right temporal lobe epilepsy patients before and a mean of 4.5 months after anterior temporal lobe resection. The whole-brain analysis technique tract-based spatial statistics was used to compare pre- and postoperative data in the left and right temporal lobe epilepsy groups separately. We observed widespread, significant, mean 7%, decreases in fractional anisotropy in white matter networks connected to the area of resection, following both left and right temporal lobe resections. However, we also observed a widespread, mean 8%, increase in fractional anisotropy after left anterior temporal lobe resection in the ipsilateral external capsule and posterior limb of the internal capsule, and corona radiata. These findings were confirmed on analysis of the native clusters and hand drawn regions of interest. Postoperative tractography seeded from this area suggests that this cluster is part of the ventro-medial language network. The mean pre- and postoperative fractional anisotropy and parallel diffusivity in this cluster were significantly correlated with postoperative verbal fluency and naming test scores. In addition, the percentage change in parallel diffusivity in this cluster was correlated with the percentage change in verbal fluency after anterior temporal lobe resection, such that the bigger the increase in parallel diffusivity, the smaller the fall in language proficiency after surgery. We suggest that the findings of increased fractional anisotropy in this ventro-medial language network represent structural reorganization in response to the anterior temporal lobe resection, which may damage the more susceptible dorso-lateral language pathway. These findings have important implications for our understanding of brain injury and rehabilitation, and may also prove useful in the prediction and minimization of postoperative language deficits.

Show MeSH
Related in: MedlinePlus