Tag: DTI tractography

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Navigated Transcranial Magnetic Stimulation and Diffusion Tensor Imaging Tractography in Insular Glioma Surgery

Operative Neurosurgery 29:62–70, 2025

Navigated transcranial magnetic stimulation (nTMS) and DTI tractography enable precise preoperative risk stratification in insular glioma surgery, identifying patients at higher risk for postoperative motor deficits by assessing resting motor threshold, tumor proximity to the corticospinal tract, and fiber tract integrity, thus improving surgical planning and outcomes.

• Navigated transcranial magnetic stimulation (nTMS) and nTMS-based DTI tractography were evaluated for preoperative risk stratification in insular glioma surgery.

• Thirty-two patients with insular gliomas underwent preoperative nTMS mapping and DTI tractography to assess motor cortex and corticospinal tract (CST) involvement.

• Higher resting motor threshold (RMT) ratios, CST-tumor distances <3 mm, and decreased peritumoral fractional anisotropy (pFA) ratios were significantly associated with new postoperative motor deficits.

• All patients with new postoperative motor deficits had a CST-tumor distance below 3 mm; lower pFA ratios also correlated with deficits.

• One-third of patients with intraoperative ischemic events developed permanent motor deficits, suggesting additional mediating factors such as CST integrity and cortical excitability.

• A risk model combining RMT ratio, CST distance <3 mm, and low pFA ratio predicted an 82% risk for new motor deficits.

• Preoperative nTMS-based DTI tractography may improve individual risk stratification and surgical planning for insular glioma patients.

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Minimally Invasive Surgery of Deep-Seated Brain Lesions Using Tubular Retractors and Navigated Transcranial Magnetic Stimulation-Based Diffusion Tensor Imaging Tractography Guidance: The Minefield Paradigm

Operative Neurosurgery 24:656–664, 2023

Surgical treatment of deep-seated brain lesions is a major challenge for neurosurgeons. Recently, tubular retractors have been used to help neurosurgeons in achieving the targeting and resection of deep lesions.

OBJECTIVE: To describe a novel surgical approach based on the combination of tubular retractors and preoperative mapping by navigated transcranial magnetic stimulation (nTMS) and nTMS-based diffusion tensor imaging (DTI) tractography for the safe resection of deep-seated lesions.

METHODS: Ten consecutive patients affected by deep-seated brain lesions close to eloquent motor/language/visual pathways underwent preoperative nTMS mapping of motor/language cortical areas and nTMS-based DTI tractography of adjacent eloquent white matter tracts, including optic radiations. The nTMS-based information was used to plan the optimal surgical trajectory and to guide the insertion of tubular retractors within the brain parenchyma without causing injury to the eloquent cortical and subcortical structures. After surgery, all patients underwent a new nTMS-based DTI tractography of fascicles close to the tumor to verify their structural integrity.

RESULTS: Gross total resection was achieved in 8 cases, subtotal resection in 1 case, and a biopsy in 1 case. No new postoperative deficits were observed, except in 1 case where a visual field defect due to injury to the optic radiations occurred. Postoperative nTMS-based DTI tractography showed the integrity of the subcortical fascicles crossed by tubular retractors trajectory in 9 cases.

CONCLUSION: The novel strategy combining tubular retractors with functional nTMS-based preoperative mapping enables a safe microsurgical resection of deep-seated lesions through the preservation of eloquent cortical areas and subcortical fascicles, thus reducing the risk of new permanent deficits.

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The Impact of Diffusion Tensor Imaging Fiber Tracking of the Corticospinal Tract Based on Navigated Transcranial Magnetic Stimulation on Surgery of Motor-Eloquent Brain Lesions

Neurosurgery 83:768–782, 2018

Navigated transcranialmagnetic stimulation (nTMS) enables preoperative mapping of the motor cortex (M1). The combination of nTMSwith diffusion tensor imaging fiber tracking (DTI-FT) of the corticospinal tract (CST) has been described; however, its impact on surgery of motor-eloquent lesions has not been addressed.

OBJECTIVE: To analyze the impact of nTMS-basedmapping on surgery ofmotor-eloquent lesions.

METHODS: In this retrospective case-control study, we reviewed the data of patients operated for suspected motor-eloquent lesions between 2012 and 2015. The patients underwent nTMS mapping of M1 and, from 2014, nTMS-based DTI-FT of the CST. The impact on the preoperative risk/benefit analysis, surgical strategy, craniotomy size, extent of resection (EOR), and outcome were compared with a control group.

RESULTS: We included 35 patients who underwent nTMS mapping of M1 (group A), 35 patients who also underwent nTMS-based DTI-FT of the CST (group B), and a control group composed of 35 patients treated without nTMS (group C). The patients in groups A and B received smaller craniotomies (P = .01; P = .001), had less postoperative seizures (P = .02), and a better postoperativemotor performance (P=.04) and Karnofsky Performance Status (P=.009) than the controls. Group B exhibited an improved risk/benefit analysis (P=.006), an increased EOR of nTMS-negative lesions in absence of preoperative motor deficits (P = .01), and less motor and Karnofsky Performance Status worsening in case of preoperative motor deficits (P = .02, P = .03) than group A.

CONCLUSION: nTMS-based mapping enables a tailored surgical approach for motor eloquent lesions. It may improve the risk/benefit analysis, EOR and outcome, particularly when nTMS-based DTI-FT is performed.

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Subcortical anatomy as an anatomical and functional landmark in insulo-opercular gliomas

Subcortical anatomy as an anatomical and functional landmark in insulo-opercular gliomas

J Neurosurg 123:1081–1092, 2015

Little attention has been given to the functional challenges of the insular approach to the resection of gliomas, despite the potential damage of essential neural networks that underlie the insula. The object of this study is to analyze the subcortical anatomy of the insular region when infiltrated by gliomas, and compare it with the normal anatomy in nontumoral hemispheres.

Methods Ten postmortem human hemispheres were dissected, with isolation of the inferior fronto-occipital fasciculus (IFOF) and the uncinate fasciculus. Probabilistic diffusion tensor imaging (DTI) tractography was used to analyze the subcortical anatomy of the insular region in 10 healthy volunteers and in 22 patients with insular Grade II and Grade III gliomas. The subcortical anatomy of the insular region in these 22 insular gliomas was compared with the normal anatomy in 20 nontumoral hemispheres.

Results In tumoral hemispheres, the distances between the peri-insular sulci and the lateral surface of the IFOF and uncinate fasciculus were enlarged (p < 0.05). Also in tumoral hemispheres, the IFOF was identified in 10 (90.9%) of 11 patients with an extent of resection less than 80%, and in 4 (36.4%) of 11 patients with an extent of resection equal to or greater than 80% (multivariate analysis: p = 0.03).

Conclusions Insular gliomas grow in the space between the lateral surface of the IFOF and uncinate fasciculus and the insular surface, displacing and compressing the tracts medially. Moreover, these tracts may be completely infiltrated by the tumor, with a total disruption of the bundles. In the current study, the identification of the IFOF with DTI tractography was significantly associated with the extent of tumor resection. If the IFOF is not identified preoperatively, there is a high probability of achieving a resection greater than 80%.

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