9 research outputs found
Connectivity-based parcellation of the amygdala and identification of its main white matter connections.
Constrained-Spherical Deconvolution Tractography in the Evaluation of the Corticospinal Tract in Glioma Surgery
Introduction: Tractography has demonstrated utility for surgical resection in the setting of primary brain tumors involving eloquent white matter (WM) pathways. Methods: Twelve patients with glioma in or near eloquent motor areas were analyzed. The motor status was recorded before and after surgery. Two different tractography approaches were used to generate the motor corticospinal tract (CST): Constrained spherical deconvolution probabilistic tractography (CSD-Prob) and single tensor deterministic tractography (Tens-DET). To define the degree of disruption of the CST after surgical resection of the tumor, we calculated the percentage of the CST affected by surgical resection, which was then correlated with the postoperative motor status. Moreover, the fractional anisotropy (FA), mean diffusivity (MD), axial diffusivity (AD), and radial diffusivity (RD) of the CST generated by the CSD-Prob and the Tens-DET was measured and compared between the ipsilesional and contralesional side. Results: The CST was identified in all patients and its trajectory was displaced by the tumor. Only the CSD-Prob approach showed the CST with the characteristic fan-like projections from the precentral gyrus to the brainstem. Disruption of the CST was identified in 6/6 with postoperative motor deficit by CSD-Prob approach and in 5/6 in the Tens-DET. The degree of disruption was significantly associated with the motor deficit with the CSD-Prob approach (rho = −0.88, p = 0.021). However, with the Tens-DET approach the CST disruption did not show significant association with the motor function (rho = −0.27, p = 0.6). There was a significant decrease in FA (p = 0.006) and a significant increase in MD (p = 0.0004) and RD (p = 0.005) on the ipsilesional CST compared with the contralesional CST only with the CSD-Prob approach. Conclusion: CSD-Prob accurately represented the known anatomy of the CST and provided a meaningful estimate of microstructural changes of the CST affected by the tumor and its macrostructural damage after surgery. Newer surgical planning stations should include advanced models and algorithms of tractography in order to obtain more meaningful reconstructions of the WM pathways during glioma surgery.ISSN:2296-875
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Connectivity-based parcellation of the amygdala and identification of its main white matter connections
The amygdala plays a role in emotion, learning, and memory and has been implicated in behavioral disorders. Better understanding of the amygdala circuitry is crucial to develop new therapies for these disorders. We used data from 200 healthy-subjects from the human connectome project. Using probabilistic tractography, we created population statistical maps of amygdala connectivity to brain regions involved in limbic, associative, memory, and reward circuits. Based on the amygdala connectivity with these regions, we applied k-means clustering to parcellate the amygdala into three clusters. The resultant clusters were averaged across all subjects and the main white-matter pathways of the amygdala from each averaged cluster were generated. Amygdala parcellation into three clusters showed a medial-to-lateral pattern. The medial cluster corresponded with the centromedial and cortical nuclei, the basal cluster with the basal nuclei and the lateral cluster with the lateral nuclei. The connectivity analysis revealed different white-matter pathways consistent with the anatomy of the amygdala circuit. This in vivo connectivity-based parcellation of the amygdala delineates three clusters of the amygdala in a mediolateral pattern based on its connectivity with brain areas involved in cognition, memory, emotion, and reward. The human amygdala circuit presented in this work provides the first step for personalized amygdala circuit mapping for patients with behavioral disorders
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A structural connectivity atlas of limbic brainstem nuclei.
BACKGROUND: Understanding the structural connectivity of key brainstem nuclei with limbic cortical regions is essential to the development of therapeutic neuromodulation for depression, chronic pain, addiction, anxiety and movement disorders. Several brainstem nuclei have been identified as the primary central nervous system (CNS) source of important monoaminergic ascending fibers including the noradrenergic locus coeruleus, serotonergic dorsal raphe nucleus, and dopaminergic ventral tegmental area. However, due to practical challenges to their study, there is limited data regarding their in vivo anatomic connectivity in humans. OBJECTIVE: To evaluate the structural connectivity of the following brainstem nuclei with limbic cortical areas: locus coeruleus, ventral tegmental area, periaqueductal grey, dorsal raphe nucleus, and nucleus tractus solitarius. Additionally, to develop a group average atlas of these limbic brainstem structures to facilitate future analyses. METHODS: Each nucleus was manually masked from 197 Human Connectome Project (HCP) structural MRI images using FSL software. Probabilistic tractography was performed using FSLs FMRIB Diffusion Toolbox. Connectivity with limbic cortical regions was calculated and compared between brainstem nuclei. Results were aggregated to produce a freely available MNI structural atlas of limbic brainstem structures. RESULTS: A general trend was observed for a high probability of connectivity to the amygdala, hippocampus and DLPFC with relatively lower connectivity to the orbitofrontal cortex, NAc, hippocampus and insula. The locus coeruleus and nucleus tractus solitarius demonstrated significantly greater connectivity to the DLPFC than amygdala while the periaqueductal grey, dorsal raphe nucleus, and ventral tegmental area did not demonstrate a significant difference between these two structures. CONCLUSION: Monoaminergic and other modulatory nuclei in the brainstem project widely to cortical limbic regions. We describe the structural connectivity across the several key brainstem nuclei theorized to influence emotion, reward, and cognitive functions. An increased understanding of the anatomic basis of the brainstems role in emotion and other reward-related processing will support targeted neuromodulatary therapies aimed at alleviating the symptoms of neuropsychiatric disorders
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Structural correlates of emotional response to electrical stimulation of the amygdala in subjects with PTSD.
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Deep brain stimulation of the amygdala for treatment-resistant combat post-traumatic stress disorder: Long-term results.
Deep brain stimulation (DBS) holds promise for neuropsychiatric conditions where imbalance in network activity contributes to symptoms. Treatment-resistant Combat post-traumatic stress disorder (TR-PTSD) is a highly morbid condition and 50% of PTSD sufferers fail to recover despite psychotherapy or pharmacotherapy. Reminder-triggered symptoms may arise from inadequate top-down ventromedial prefrontal cortex (vmPFC) control of amygdala reactivity. Here, we report long-term data on two TR-PTSD participants from an investigation utilizing high-frequency amygdala DBS. The two combat veterans were implanted bilaterally with quadripolar electrodes targeting the basolateral amygdala. Following a randomized staggered onset, patients received stimulation with adjustments based on PTSD symptom severity for four years while psychiatric and neuropsychiatric symptoms, neuropsychological performance, and electroencephalography were systematically monitored. Evaluation of vmPFC-Amygdala network engagement was assessed with 18FDG positron emission tomography (PET). CAPS-IV scores varied over time, but improved 55% from 119 at baseline to 53 at 4-year study endpoint in participant 1; and 44%, from 68 to 38 in participant 2. Thereafter, during 5 and 1.5 years of subsequent clinical care respectively, long-term bilateral amygdala DBS was associated with additional, clinically significant symptomatic and functional improvement. There were no serious stimulation-related adverse psychiatric, neuropsychiatric, neuropsychological, neurological, or neurosurgical effects. In one subject, symptomatic improvement was associated with an intensity-dependent reduction in amygdala theta frequency power. In our two participants, FDG-PET findings were inconclusive regarding the hypothesized mechanism of suppression of amygdala hyperactivity. Our findings encourage further research to confirm and extend our preliminary observations