Tag: functional magnetic resonance imaging

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Mapping the Functional Boundaries of the Speech Articulation Network Using Positive and Negative Direct Electrical Stimulation With Resting-State Functional MRI

Neurosurgery 98:577–587, 2026

This clinical research integrates positive and negative direct electrical stimulation (DES) with presurgical resting-state fMRI to refine the speech articulation network (SAN) atlas in glioma patients. Analyzing 25 patients, the study maps DES-positive and DES-negative seed-based connectivity, compares anticorrelated networks, and evaluates sensitivity and specificity across group-frequency thresholds.

Key findings show DES-positive sites robustly identify bilateral SAN regions (rolandic operculum, inferior frontal and superior temporal gyri), while DES-negative points delineate functional borders and improve atlas specificity; a 41% SAN-positive threshold yields approximately 80% sensitivity and specificity for clinical use.

Resting-state fMRI and DES: Resting-state functional MRI (rs-fMRI) is a noninvasive tool for mapping brain networks, while direct electrical stimulation (DES) during awake surgery (AwS) is the gold standard for causally identifying functional brain regions, especially for speech articulation mapping in glioma patients.

Inclusion of DES-negative points: Incorporating both DES-positive (eliciting function) and DES-negative (no function elicited) points enables more precise mapping of the speech articulation network (SAN) and its functional borders, improving specificity and sensitivity compared to using only positive points.

Comprehensive SAN atlas: A new SAN atlas was created from 25 glioma patients using 32 DES-positive and 42 DES-negative points, with presurgical rs-fMRI seed-based connectivity analysis, providing a more accurate and clinically relevant definition of the SAN.

Distinct connectivity patterns: DES-positive points consistently mapped the SAN to bilateral rolandic operculum, inferior frontal gyrus, and superior temporal gyrus, while DES-negative points revealed distinct, only partially overlapping connectivity patterns, helping delineate the SAN’s functional borders.

Threshold for clinical use: A 41% frequency threshold for the SAN-positive network achieves approximately 80% sensitivity and specificity, offering a practical balance for clinical application in presurgical planning.

Functional borders and overlap: Minimal overlap between SAN-positive and SAN-negative networks identifies functional borders, especially in the precentral sulcus and inferior frontal gyrus, aiding neurosurgeons in distinguishing critical from non-critical areas during mapping.

Clinical implications: Defining precise SAN borders improves intraoperative decision-making, reduces irrelevant stimulation, shortens mapping time, and enhances safety in both awake and asleep brain surgeries.

Limitations and future directions: The study’s limitations include sample size, heterogeneity, and MRI field strength; future research should use larger, more homogeneous cohorts and higher-resolution imaging to further refine SAN mapping.

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Stratifying trigeminal neuralgia and characterizing an abnormal property of brain functional organization: a resting-state fMRI and machine learning study

J Neurosurg 143:74–82, 2025

Resting-state fMRI and machine learning revealed distinct brain connectivity and activity differences between classical and idiopathic trigeminal neuralgia (TN) and controls. These findings identify potential neuroimaging biomarkers for TN subtypes, aiding diagnosis and understanding of TN pathophysiology.

Primary trigeminal neuralgia (TN) includes classical (CTN) and idiopathic (ITN) types, sharing clinical features but differing in neurovascular compression (NVC) presence.

• Resting-state fMRI and machine learning were used to analyze brain functional connectivity and spontaneous activity in 50 TN patients (28 CTN, 22 ITN) and 43 controls.

• TN patients showed increased connectivity between the medial prefrontal cortex (mPFC) and left planum temporale, and decreased connectivity between mPFC and left superior frontal gyrus.

• CTN patients had further reduced connectivity between the left insula and left occipital pole, and decreased activity in the right temporal pole compared to ITN.

• TN patients exhibited heightened neural activity in frontal regions compared to controls.

• Machine learning (support vector machine) distinguished TN patients from controls with moderate accuracy (AUC 0.80).

• Findings suggest potential fMRI biomarkers for TN subtypes, aiding understanding of pathophysiology and improving diagnosis.

• Study limitations include small sample size and exclusion of bilateral/secondary TN, warranting further research.

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Mapping of cortical language function by functional magnetic resonance imaging and repetitive navigated transcranialmagnetic stimulation in 40 healthy subjects

Mapping of cortical language function by functional magnetic resonance imaging and repetitive navigated transcranial magnetic stimulation in 40 healthy subjects

Acta Neurochir (2016) 158:1303–1316

Functional magnetic resonance imaging (fMRI) is considered to be the standard method regarding noninvasive language mapping. However, repetitive navigated transcranial magnetic stimulation (rTMS) gains increasing importance with respect to that purpose. However, comparisons between both methods are sparse.

Methods We performed fMRI and rTMS language mapping of the left hemisphere in 40 healthy, right-handed subjects in combination with the tasks that are most commonly used in the neurosurgical context (fMRI: word-generation=WGEN task; rTMS: object-naming=ON task). Different rTMS error rate thresholds (ERTs) were calculated, and Cohen’s kappa coefficient and the cortical parcellation system (CPS) were used for systematic comparison of the two techniques.

Results Overall, mean kappa coefficients were low, revealing no distinct agreement. We found the highest agreement for both techniques when using the 2-out-of-3 rule (CPS region defined as language positive in terms of rTMS if at least 2 out of 3 stimulations led to a naming error). However, kappa for this threshold was only 0.24 (kappa of <0, 0.01–0.20, 0.21– 0.40, 0.41–0.60, 0.61–0.80 and 0.81–0.99 indicate less than chance, slight, fair, moderate, substantial and almost perfect agreement, respectively).

Conclusions Because of the inherent differences in the underlying physiology of fMRI and rTMS, the different tasks used and the impossibility of verifying the results via direct cortical stimulation (DCS) in the population of healthy volunteers, one must exercise caution in drawing conclusions about the relative usefulness of each technique for language mapping. Nevertheless, this study yields valuable insights into these two mapping techniques for the most common language tasks currently used in neurosurgical practice.

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Combined noninvasive language mapping by navigated transcranial magnetic stimulation and functional MRI and its comparison with direct cortical stimulation

Combined noninvasive language mapping by navigated transcranial magnetic stimulation and functional MRI and its comparison with direct cortical stimulation

 

J Neurosurg 123:212–225, 2015

Repetitive navigated transcranial magnetic stimulation (rTMS) is now increasingly used for preoperative language mapping in patients with lesions in language-related areas of the brain. Yet its correlation with intraoperative direct cortical stimulation (DCS) has to be improved. To increase rTMS’s specificity and positive predictive value, the authors aim to provide thresholds for rTMS’s positive language areas. Moreover, they propose a protocol for combining rTMS with functional MRI (fMRI) to combine the strength of both methods.

Methods The authors performed multimodal language mapping in 35 patients with left-sided perisylvian lesions by using rTMS, fMRI, and DCS. The rTMS mappings were conducted with a picture-to-trigger interval (PTI, time between stimulus presentation and stimulation onset) of either 0 or 300 msec. The error rates (ERs; that is, the number of errors per number of stimulations) were calculated for each region of the cortical parcellation system (CPS). Subsequently, the rTMS mappings were analyzed through different error rate thresholds (ERT; that is, the ER at which a CPS region was defined as language positive in terms of rTMS), and the 2-out-of-3 rule (a stimulation site was defined as language positive in terms of rTMS if at least 2 out of 3 stimulations caused an error). As a second step, the authors combined the results of fMRI and rTMS in a predefined protocol of combined noninvasive mapping. To validate this noninvasive protocol, they correlated its results to DCS during awake surgery.

Results The analysis by different rTMS ERTs obtained the highest correlation regarding sensitivity and a low rate of false positives for the ERTs of 15%, 20%, 25%, and the 2-out-of-3 rule. However, when comparing the combined fMRI and rTMS results with DCS, the authors observed an overall specificity of 83%, a positive predictive value of 51%, a sensitivity of 98%, and a negative predictive value of 95%.

Conclusions In comparison with fMRI, rTMS is a more sensitive but less specific tool for preoperative language mapping than DCS. Moreover, rTMS is most reliable when using ERTs of 15%, 20%, 25%, or the 2-out-of-3 rule and a PTI of 0 msec. Furthermore, the combination of fMRI and rTMS leads to a higher correlation to DCS than both techniques alone, and the presented protocols for combined noninvasive language mapping might play a supportive role in the language-mapping assessment prior to the gold-standard intraoperative DCS.

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Real-Time Atlas-Based Stereotactic Neuronavigation

Real-Time Atlas-Based Stereotactic Neuronavigation

Neurosurgery 74:128–134, 2014

Surgery for tumors in eloquent brain faces immense challenges when attempting to maximize resection and avoid neurological deficits.

OBJECTIVE: In order to give the surgeon real-time atlas-based anatomic information linked to the patient’s anatomy, we developed a software-based interface between deformable anatomic templates (DATs) and an intraoperative navigation system.

METHODS: Magnetic resonance imaging (MRI), diffusion tensor imaging, and/or functional MRI were performed on 3 patients preoperatively for the purposes of tumor resection by the use of neuronavigation. The DAT was registered to the patients’ navigation coordinate system and utilized coordinates from the navigation system during surgery. This provided the surgeon with a list of proximal anatomic and functional structures and a real-time image of the atlas at that location fused to the patient’s MRI. The clinical feasibility of this approach was evaluated during the resection of 3 eloquent tumors (right postcentral gyrus, left inferior frontal gyrus, and left occipital cuneus gyrus).

RESULTS: Tumor resection was performed successfully in all 3 patients. With the use of the coordinates from the navigation system, anatomic and functional structures and their distances were visualized interactively during tumor resection by using the DAT.

CONCLUSION: This is a proof of concept that an interactive atlas-based navigation can provide detailed anatomic and functional information that supplements MRI, diffusion tensor imaging, and functional MRI. The atlas-based navigation generated distances to important anatomic structures from the navigation probe tip. It can be used to guide direct electrical stimulation and highlight areas to avoid during tumor resection.

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Deformable Anatomic Templates Improve Analysis of Gliomas With Minimal Mass Effect in Eloquent Areas

Deformable Anatomic Templates Improve Analysis of Gliomas With Minimal Mass Effect in Eloquent Areas

Neurosurgery 73:534–542, 2013

Despite improvements in advanced magnetic resonance imaging and intraoperative mapping, cases remain in which it is difficult to determine whether viable eloquent structures are involved by a glioma. A novel software program, deformable anatomic templates (DAT), rapidly embeds the normal location of eloquent cortex and functional tracts in the magnetic resonance images of glioma-bearing brain.

OBJECTIVE: To investigate the feasibility of the DAT technique in patients with gliomas related to eloquent brain.

METHODS: Forty cases of gliomas (grade II-IV) with minimal mass effect were referred for a prospective preoperative and postoperative DAT analysis. The DAT results were compared with the patient’s functional magnetic resonance imaging, diffusion tensor imaging, operative stimulation, and new postoperative clinical deficits.

RESULTS: Fifteen of the 40 glioma patients had overlap between tumor and eloquent structures. Immediate postoperative neurological deficits were seen in 9 cases in which the DAT showed the eloquent area both within the tumor and within or at the edge of the resection cavity. In 6 cases with no deficits, DAT placed the eloquent area in the tumor but outside the resection cavity.

CONCLUSION: This is proof of concept that DAT can improve the analysis of diffuse gliomas of any grade by efficiently alerting the surgeon to the possibility of eloquent area invasion. The technique is especially helpful in diffuse glioma because these tumors tend to infiltrate rather than displace eloquent structures. DAT is limited by tract displacement in gliomas that produces moderate to severe mass effect.

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A systematic review of functional magnetic resonance imaging and diffusion tensor imaging modalities used in presurgical planning of brain tumour resection

fMRI and DTI

Neurosurg Rev (2013) 36:205–214

Historically, brain tumour resection has relied upon standardised anatomical atlases and classical mapping techniques for successful resection. While these have provided adequate results in the past, the emergence of new technologies has heralded a wave of less invasive, patient-specific techniques for the mapping of brain function.

Functional magnetic resonance imaging (fMRI) and, more recently, diffusion tensor imaging (DTI) are two such techniques. While fMRI is able to highlight localisation of function within the cortex, DTI represents the only technique able to elucidate white matter structures in vivo. Used in conjunction, both of these techniques provide important presurgical information for thorough preoperative planning, as well as intraoperatively via integration into frameless stereotactic neuronavigational systems.

Together, these techniques show great promise for improved neurosurgical outcomes. While further research is required for more widespread clinical validity and acceptance, results from the literature provide a clear road map for future research and development to cement these techniques into the clinical setup of neurosurgical departments globally.

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Navigated Transcranial Magnetic Stimulation and Functional Magnetic Resonance Imaging: Advanced Adjuncts in Preoperative Planning for Central Region Tumors

Neurosurgery 68:1317–1325, 2011 DOI: 10.1227/NEU.0b013e31820b528c

Tumor resection in the vicinity of the motor cortex poses a challenge to all neurosurgeons. For preoperative assessment of eloquent cortical areas, functional magnetic resonance imaging (fMRI) is used, whereas intraoperatively, direct cortical stimulation (DCS) is performed. Navigated transcranial magnetic stimulation (nTMS) is comparable to DCS in activating cortical pyramidal neurons.

OBJECTIVE: To evaluate the reliability of nTMS compared with fMRI and DCS for preoperative resection planning of centrally located tumors.

METHODS: In a prospective series, 11 patients (ages, 20-63 years; mean, 41.9 ± 14.9 years, 2 women) with tumors located in or adjacent to the motor cortex were evaluated for surgery. fMRI and nTMS were applied for preoperative assessment of the extent of tumor resection. A 3-dimensional anatomic data set with superimposed fMRI data was integrated in the eXimia Navigated Brain Stimulation station for ensuing motor cortex mapping by nTMS. Responses from nTMS were evaluated by electromyographic response. During surgery, the coordinates of each DCS site were unambiguously defined and integrated into neuronavigation. A post hoc comparison of the coordinates of nTMS, fMRI, and DCS was performed.

RESULTS: Distances from nTMS to DCS (10.5 ± 5.67 mm) were significantly smaller than those from fMRI to DCS (15.0 ± 7.6 mm).

CONCLUSION: nTMS anticipates information usually only enabled by DCS and therefore allows surgical planning in eloquent cortex surgery.

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Functional Magnetic Resonance Imaging and Diffusion Tensor Tractography Incorporated Into an Intraoperative 3-Dimensional Ultrasound-Based Neuronavigation System: Impact on Therapeutic Strategies, Extent of Resection, and Clinical Outcome

Neurosurgery 67:251-264, 2010 DOI: 10.1227/01.NEU.0000371731.20246.AC

Functional neuronavigation with intraoperative 3-dimensional (3D) ultrasound may facilitate safer brain lesion resections than conventional neuronavigation.

OBJECTIVE: In this study, functional magnetic resonance imaging (fMRI) and diffusion tensor tractography (DTT) were used to map eloquent areas. We assessed the use of fMRI and DTT for preoperative assessments and determined whether using these data together with 3D ultrasound during surgery enabled safer lesion resection.

METHODS:We reviewed 51 consecutive patients with intracranial lesions in whom fMRI with or without DTT was used to map eloquent areas. To assess a possible impact of fMRI/DTT, we reviewed and analyzed the quality of the fMRI/DTT data, any change in therapeutic strategies, lesion to eloquent area distance (LEAD), extent of resection, and clinical outcome.

RESULTS: As a result of the fMRI/DTT mapping, the therapeutic strategies were changed in 4 patients. The median tumor residue for glioma patients was 11% (n = 33) and 0% for nonglioma lesions (n = 12). For gliomas, there was a significant correlation between decreasing LEAD and increasing tumor residue. Of the glioma patients, 42% underwent gross total resection (≥ 95%) and 12% suffered neurological worsening after surgery as a result of complications. Of glioma patients with an LEAD of ≤ 5 mm, 24% underwent gross total resection and 10% experienced neurological deterioration.

CONCLUSION: This study demonstrates that preoperative fMRI and DTT had direct consequences for therapeutic strategies and indicates their impact on intraoperative strategies to spare eloquent cortex and tracts. Functional neuronavigation combined with intraoperative 3D ultrasound can, in most patients, enable resection of brain lesions with general anesthesia without jeopardizing neurological function.

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Agraphia after awake surgery for brain tumor: new insights into the anatomo-functional network of writing

Surgical Neurology. Volume 72, Issue 3, Pages 223-241 (September 2009)

Background

Controversy still exists about neural basis underlying writing and its relation with the sites subserving oral language. Our objective is to study functional areas involved in writing network, based on the observations of different postoperative writing disorders in a population of patients without preoperative agraphia.

Methods

We analyzed the postoperative agraphia profiles in 15 patients who underwent surgery for cerebral LGGs in functional language areas, using electrical mapping under local anesthesia. These profiles were then correlated to the sites of the lesions, shown by preoperative cerebral imaging.

Results

Our findings showed that (1) spoken language and writing functions could be dissociated, and that (2) writing is subserved, at least partially, by a network of 5 areas located in the dominant hemisphere for language: the superior parietal region, the supramarginalis gyrus, the second and third frontal convolutions, the supplementary motor area, and the insula. Each of these areas seems to have a different role in writing, which will be detailed in this article. However, among the patients, only those with lesions of the supplementary motor area did not recover from agraphia in the postoperative period (in 50% of cases).

Conclusions

On the basis of these results, and in the light of the recent literature, we discuss the relevance of each area in this anatomo-functional network as well as the clinical implications of such better knowledge of the neural basis of writing, especially for brain surgery and functional rehabilitation.

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