Tag: diffusion tensor imaging tractography

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Tractography-Based Surgical Targeting for Thalamic Deep Brain Stimulation: A Comparison of Probabilistic vs Deterministic Fiber Tracking of the Dentato-Rubro-Thalamic Tract

Neurosurgery 90:419–425, 2022

The ventral intermediate (VIM) thalamic nucleus is the main target for the surgical treatment of refractory tremor. Initial targeting traditionally relies on atlas-based stereotactic targeting formulas, which only minimally account for individual anatomy. Al- ternative approaches have been proposed, including direct targeting of the dentato-rubro- thalamic tract (DRTT), which, in clinical settings, is generally reconstructed with deterministic tracking. Whether more advanced probabilistic techniques are feasible on clinical-grade magnetic resonance acquisitions and lead to enhanced reconstructions is poorly understood.

OBJECTIVE: To compare DRTT reconstructed with deterministic vs probabilistic tracking. METHODS: Thisisaretrospectivestudyof19patientswithessentialtremorwhounderwentdeep brain stimulation (DBS) with intraoperative neurophysiology and stimulation testing. We assessed the proximity of the DRTT to the DBS lead and to the active contact chosen based on clinical response.

RESULTS: In the commissural plane, the deterministic DRTT was anterior (P<104)and  < 104) to the DBS lead. By contrast, although the probabilistic DRTT was also anterior to the lead (P < 104), there was no difference in the mediolateral dimension (P = .5). Moreover, the 3- dimensional Euclidean distance from the active contact to the probabilistic DRTT was smaller vs the distance to the deterministic DRTT (3.32 ± 1.70 mm vs 5.01 ± 2.12 mm; P < 104).

CONCLUSION: DRTT reconstructed with probabilistic fiber tracking was superior in spatial proximity to the physiology-guided DBS lead and to the empirically chosen active contact. These data inform strategies for surgical targeting of the VIM.

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Navigated Transcranial Magnetic Stimulation for “Somatotopic” Tractography of the Corticospinal Tract

SOMATOTOPIC RECONSTRUCTION OF CORTICOSPINAL TRACT

Operative Neurosurgery 10:542–554, 2014

Diffusion tensor imaging tractography provides 3-dimensional reconstruction of principal white matter tracts, but its spatial accuracy has been questioned. Navigated transcranial magnetic stimulation (nTMS) enables somatotopic mapping of the motor cortex.

OBJECTIVE: We used motor maps to reconstruct the corticospinal tract (CST) by integrating elements of its somatotopic organization. We analyzed the accuracy of this method compared with a standard technique and verified its reliability with intraoperative subcortical stimulation.

METHODS: We prospectively collected data from patients who underwent surgery between January 2012 and October 2013 for lesions involving the CST. nTMS-based diffusion tensor imaging tractography was compared with a standard technique. The reliability and accuracy between the 2 techniques were analyzed by comparing the number of fibers, the concordance in size, and the location of the cortical end of the CST and the motor area. The accuracy of the technique was assessed by using direct subcortical stimulation.

RESULTS: Twenty patients were enrolled in the study. nTMS-based tractography provided a detailed somatotopic reconstruction of the CST. This nTMS-based reconstruction resulted in a decreased number of fibers (305.16 231.7 vs 10246 193, P , .001) and a significantly greater overlap between the motor cortex and the cortical end-region of the CST compared with the standard technique (90.5 6 8.8% vs 58.3 6 16.6%, P , .001). Direct subcortical stimulation confirmed the CST location and the somatotopic reconstruction in all cases.

CONCLUSION: These results suggest that nTMS-based tractography of the CST is more accurate and less operator dependent than the standard technique and provides a reliable anatomic and functional characterization of the motor pathway.

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Arcuate fasciculus in brain tumor surgery

J Neurosurg 117:839–843, 2012 

Disturbance of the arcuate fasciculus in the dominant hemisphere is thought to be associated with language- processing disorders, including conduction aphasia. Although the arcuate fasciculus can be visualized in vivo with diffusion tensor imaging (DTI) tractography, its involvement in functional processes associated with language has not been shown dynamically using DTI tractography. In the present study, to clarify the participation of the arcuate fasciculus in language functions, postoperative changes in the arcuate fasciculus detected by DTI tractography were evaluated chronologically in relation to postoperative changes in language function after brain tumor surgery.

Methods. Preoperative and postoperative arcuate fasciculus area and language function were examined in 7 right-handed patients with a brain tumor in the left hemisphere located in proximity to part of the arcuate fasciculus. The arcuate fasciculus was depicted, and its area was calculated using DTI tractography. Language functions were measured using the Western Aphasia Battery (WAB).

Results. After tumor resection, visualization of the arcuate fasciculus was increased in 5 of the 7 patients, and the total WAB score improved in 6 of the 7 patients. The relative ratio of postoperative visualized area of the arcuate fasciculus to preoperative visualized area of the arcuate fasciculus was increased in association with an improvement in postoperative language function (p = 0.0039).

Conclusions. The role of the left arcuate fasciculus in language functions can be evaluated chronologically in vivo by DTI tractography after brain tumor surgery. Because increased postoperative visualization of the fasciculus was significantly associated with postoperative improvement in language functions, the arcuate fasciculus may play an important role in language function, as previously thought. In addition, postoperative changes in the arcuate fasciculus detected by DTI tractography could represent a predicting factor for postoperative language-dependent functional outcomes in patients with brain tumor.

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Correlation between language function and the left arcuate fasciculus detected by diffusion tensor imaging tractography after brain tumor surgery

J Neurosurg 117:839–843, 2012

Disturbance of the arcuate fasciculus in the dominant hemisphere is thought to be associated with language-processing disorders, including conduction aphasia. Although the arcuate fasciculus can be visualized in vivo with diffusion tensor imaging (DTI) tractography, its involvement in functional processes associated with language has not been shown dynamically using DTI tractography. In the present study, to clarify the participation of the arcuate fasciculus in language functions, postoperative changes in the arcuate fasciculus detected by DTI tractography were evaluated chronologically in relation to postoperative changes in language function after brain tumor surgery.

Methods. Preoperative and postoperative arcuate fasciculus area and language function were examined in 7 right-handed patients with a brain tumor in the left hemisphere located in proximity to part of the arcuate fasciculus. The arcuate fasciculus was depicted, and its area was calculated using DTI tractography. Language functions were measured using the Western Aphasia Battery (WAB).

Results. After tumor resection, visualization of the arcuate fasciculus was increased in 5 of the 7 patients, and the total WAB score improved in 6 of the 7 patients. The relative ratio of postoperative visualized area of the arcuate fasciculus to preoperative visualized area of the arcuate fasciculus was increased in association with an improvement in postoperative language function (p = 0.0039).

Conclusions. The role of the left arcuate fasciculus in language functions can be evaluated chronologically in vivo by DTI tractography after brain tumor surgery. Because increased postoperative visualization of the fasciculus was significantly associated with postoperative improvement in language functions, the arcuate fasciculus may play an important role in language function, as previously thought. In addition, postoperative changes in the arcuate fasciculus detected by DTI tractography could represent a predicting factor for postoperative language-dependent functional outcomes in patients with brain tumor.

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