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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.

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Scatterplot and regression line of percentage change in λ ∥ in the cluster showing an increase in fractional anisotropy after left anterior temporal lobe resection against interval between surgery and imaging. The circled point is an outlier, and when removed from the analysis, the correlation is significant (r = 0.400, P = 0.024).
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Figure 4: Scatterplot and regression line of percentage change in λ ∥ in the cluster showing an increase in fractional anisotropy after left anterior temporal lobe resection against interval between surgery and imaging. The circled point is an outlier, and when removed from the analysis, the correlation is significant (r = 0.400, P = 0.024).

Mentions: There was also a significant correlation between pre- and postoperative λ ∥ in this cluster and the postoperative graded naming test score (r = 0.388, P = 0.030 and r = 0.480, P = 0.009, respectively), but not the preoperative graded naming test score. In view of the apparent importance of λ ∥, we tested for a correlation between the percentage increase in this parameter and the interval between temporal lobe resection and postoperative scanning. Although there was a positive trend this was not significant due to the presence of an outlier who was the only patient with an ILAE outcome of Class V in this group (Fig. 4). After exclusion of this outlier, this trend was significant (r = 0.400, P = 0.024), and the correlations between the diffusion parameters and verbal fluency and graded naming test scores remained significant.Figure 4


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)

Scatterplot and regression line of percentage change in λ ∥ in the cluster showing an increase in fractional anisotropy after left anterior temporal lobe resection against interval between surgery and imaging. The circled point is an outlier, and when removed from the analysis, the correlation is significant (r = 0.400, P = 0.024).
© Copyright Policy - creative-commons
Related In: Results  -  Collection

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

Figure 4: Scatterplot and regression line of percentage change in λ ∥ in the cluster showing an increase in fractional anisotropy after left anterior temporal lobe resection against interval between surgery and imaging. The circled point is an outlier, and when removed from the analysis, the correlation is significant (r = 0.400, P = 0.024).
Mentions: There was also a significant correlation between pre- and postoperative λ ∥ in this cluster and the postoperative graded naming test score (r = 0.388, P = 0.030 and r = 0.480, P = 0.009, respectively), but not the preoperative graded naming test score. In view of the apparent importance of λ ∥, we tested for a correlation between the percentage increase in this parameter and the interval between temporal lobe resection and postoperative scanning. Although there was a positive trend this was not significant due to the presence of an outlier who was the only patient with an ILAE outcome of Class V in this group (Fig. 4). After exclusion of this outlier, this trend was significant (r = 0.400, P = 0.024), and the correlations between the diffusion parameters and verbal fluency and graded naming test scores remained significant.Figure 4

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