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Varina L. Boerwinkle, Lucia Mirea, William D. Gaillard, Bethany L. Sussman, Diana Larocque, Alexandra Bonnell, Jennifer S. Ronecker, Matthew M. Troester, John F. Kerrigan, Stephen T. Foldes, Brian Appavu, Randa Jarrar, Korwyn Williams, Angus A. Wilfong and P. David Adelson

patients undergo surgery. 7 The primary determinant of surgical candidacy and postoperative seizure frequency is accurate localization of the seizure onset zone (SOZ), which, when excised or disconnected, should lead to cure. 25 Recently, several studies have indicated that resting-state functional MRI (rs-fMRI) localizes where seizures originate in the brain, 2–4 and its implementation improves surgical outcome. 5 Agreement of rs-fMRI SOZ and intracranial electroencephalography (EEG) SOZ localization is 90%. 4 Quantification of resection with respect to preoperative

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Dhananjaya I. Bhat, B. Indira Devi, Komal Bharti and Rajanikant Panda

OBJECTIVE

The authors aimed to understand the alterations of brain resting-state networks (RSNs) in patients with pan–brachial plexus injury (BPI) before and after surgery, which might provide insight into cortical plasticity after peripheral nerve injury and regeneration.

METHODS

Thirty-five patients with left pan-BPI before surgery, 30 patients after surgery, and 25 healthy controls underwent resting-state functional MRI (rs-fMRI). The 30 postoperative patients were subdivided into 2 groups: 14 patients with improvement in muscle power and 16 patients with no improvement in muscle power after surgery. RSNs were extracted using independent component analysis to evaluate connectivity at a significance level of p < 0.05 (familywise error corrected).

RESULTS

The patients with BPI had lower connectivity in their sensorimotor network (SMN) and salience network (SN) and greater connectivity in their default mode network (DMN) before surgery than the controls. Connectivity of the left supplementary motor cortex in the SMN and medial frontal gyrus and in the anterior cingulate cortex in the SN increased in patients whose muscle power had improved after surgery, whereas no significant changes were noted in the unimproved patients. There was a trend toward reduction in DMN connectivity in all the patients after surgery compared with that in the preoperative patients; however, this result was not statistically significant.

CONCLUSIONS

The results of this study highlight the fact that peripheral nerve injury, its management, and successful treatment cause dynamic changes within the brain's RSNs, which includes not only the obvious SMN but also the higher cognitive networks such as the SN and DMN, which indicates brain plasticity and compensatory mechanisms at work.

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Constantin Tuleasca, Jean Régis, Elena Najdenovska, Tatiana Witjas, Nadine Girard, Jean-Philippe Thiran, Meritxell Bach Cuadra, Marc Levivier and Dimitri Van De Ville

TO THE EDITOR: We read with great interest the recent article by Lehner et al. 5 ( Lehner KR, Yeagle EM, Argyelan M, et al: Validation of corpus callosotomy after laser interstitial thermal therapy: a multimodal approach. J Neurosurg [epub ahead of print November 16, 2018. DOI: 10.3171/2018.4.JNS172588 ]), discussing corpus callosotomy performed by laser interstitial thermal therapy (LITT) in a small cohort of 5 patients in the context of a multimodal approach. The authors additionally used resting-state functional MRI (rs-fMRI) to assess the outcome of this

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Domenico Zacà, Jorge Jovicich, Francesco Corsini, Umberto Rozzanigo, Franco Chioffi and Silvio Sarubbo

, Tartaro A , Caulo M : Modifications of default-mode network connectivity in patients with cerebral glioma . PLoS One 7 : e40231 , 2012 13 Freyschlag CF , Duffau H : Awake brain mapping of cortex and subcortical pathways in brain tumor surgery . J Neurosurg Sci 58 : 199 – 213 , 2014 14 Huang H , Ding Z , Mao D , Yuan J , Zhu F , Chen S , : PreSurgMapp: a MATLAB toolbox for presurgical mapping of eloquent functional areas based on task-related and resting-state functional MRI . Neuroinformatics 14 : 421 – 438 , 2016 15 Jezzard

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Constantin Roder, Edyta Charyasz-Leks, Martin Breitkopf, Karlheinz Decker, Ulrike Ernemann, Uwe Klose, Marcos Tatagiba and Sotirios Bisdas

OBJECTIVE

The authors' aim in this paper is to prove the feasibility of resting-state (RS) functional MRI (fMRI) in an intraoperative setting (iRS-fMRI) and to correlate findings with the clinical condition of patients pre- and postoperatively.

METHODS

Twelve patients underwent intraoperative MRI-guided resection of lesions in or directly adjacent to the central region and/or pyramidal tract. Intraoperative RS (iRS)–fMRI was performed pre- and intraoperatively and was correlated with patients' postoperative clinical condition, as well as with intraoperative monitoring results. Independent component analysis (ICA) was used to postprocess the RS-fMRI data concerning the sensorimotor networks, and the mean z-scores were statistically analyzed.

RESULTS

iRS-fMRI in anesthetized patients proved to be feasible and analysis revealed no significant differences in preoperative z-scores between the sensorimotor areas ipsi- and contralateral to the tumor. A significant decrease in z-score (p < 0.01) was seen in patients with new neurological deficits postoperatively. The intraoperative z-score in the hemisphere ipsilateral to the tumor had a significant negative correlation with the degree of paresis immediately after the operation (r = −0.67, p < 0.001) and on the day of discharge from the hospital (r = −0.65, p < 0.001). Receiver operating characteristic curve analysis demonstrated moderate prognostic value of the intraoperative z-score (area under the curve 0.84) for the paresis score at patient discharge.

CONCLUSIONS

The use of iRS-fMRI with ICA-based postprocessing and functional activity mapping is feasible and the results may correlate with clinical parameters, demonstrating a significant negative correlation between the intensity of the iRS-fMRI signal and the postoperative neurological changes.

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Constantin Tuleasca, Thomas A. W. Bolton, Jean Régis, Elena Najdenovska, Tatiana Witjas, Nadine Girard, Francois Delaire, Marion Vincent, Mohamed Faouzi, Jean-Philippe Thiran, Meritxell Bach Cuadra, Marc Levivier and Dimitri Van De Ville

OBJECTIVE

The tremor circuitry has commonly been hypothesized to be driven by one or multiple pacemakers within the cerebello-thalamo-cortical pathway, including the cerebellum, contralateral motor thalamus, and primary motor cortex. However, previous studies, using multiple methodologies, have advocated that tremor could be influenced by changes within the right extrastriate cortex, at both the structural and functional level. The purpose of this work was to evaluate the role of the extrastriate cortex in tremor generation and further arrest after left unilateral stereotactic radiosurgery thalamotomy (SRS-T).

METHODS

The authors considered 12 healthy controls (HCs, group 1); 15 patients with essential tremor (ET, right-sided, drug-resistant; group 2) before left unilateral SRS-T; and the same 15 patients (group 3) 1 year after the intervention, to account for delayed effects. Blood oxygenation level–dependent functional MRI during resting state was used to characterize the dynamic interactions of the right extrastriate cortex, comparing HC subjects against patients with ET before and 1 year after SRS-T. In particular, the authors applied coactivation pattern analysis to extract recurring whole-brain spatial patterns of brain activity over time.

RESULTS

The authors found 3 different sets of coactivating regions within the right extrastriate cortex in HCs and patients with pretherapeutic ET, reminiscent of the “cerebello-visuo-motor,” “thalamo-visuo-motor” (including the targeted thalamus), and “basal ganglia and extrastriate” networks. The occurrence of the first pattern was decreased in pretherapeutic ET compared to HCs, whereas the other two patterns showed increased occurrences. This suggests a misbalance between the more prominent cerebellar circuitry and the thalamo-visuo-motor and basal ganglia networks. Multiple regression analysis showed that pretherapeutic standard tremor scores negatively correlated with the increased occurrence of the thalamo-visuo-motor network, suggesting a compensatory pathophysiological trait. Clinical improvement after SRS-T was related to changes in occurrences of the basal ganglia and extrastriate cortex circuitry, which returned to HC values after the intervention, suggesting that the dynamics of the extrastriate cortex had a role in tremor generation and further arrest after the intervention.

CONCLUSIONS

The data in this study point to a broader implication of the visual system in tremor generation, and not only through visual feedback, given its connections to the dorsal visual stream pathway and the cerebello-thalamo-cortical circuitry, with which its dynamic balance seems to be a crucial feature for reduced tremor. Furthermore, SRS-T seems to bring abnormal pretherapeutic connectivity of the extrastriate cortex to levels comparable to those of HC subjects.

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Hui Ming Khoo, Haruhiko Kishima, Naoki Tani, Satoru Oshino, Tomoyuki Maruo, Koichi Hosomi, Takufumi Yanagisawa, Hiroaki Kazui, Yoshiyuki Watanabe, Toshio Shimokawa, Toshihiko Aso, Atsushi Kawaguchi, Fumio Yamashita, Youichi Saitoh and Toshiki Yoshimine

known, the neural networks and underlying pathophysiological mechanisms of this neurological disorder remain unclear. In recent years, spontaneous brain activity and its relation to cognition and behavior have been studied extensively. 20 Resting-state functional MRI (rs-fMRI) studies have shown alterations in connectivity within the default mode network (DMN) to be associated with cognitive impairments in several disorders, e.g., Alzheimer’s disease (AD), multiple sclerosis, traumatic brain injury, and attention deficit hyperactivity disorder. 4 , 5 , 10 , 12 , 27

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Michael G. Hart, Rolf J. F. Ypma, Rafael Romero-Garcia, Stephen J. Price and John Suckling

J : The brainweb: phase synchronization and large-scale integration . Nat Rev Neurosci 2 : 229 – 239 , 2001 101 Vértes PE , Alexander-Bloch A , Bullmore ET : Generative models of rich clubs in Hebbian neuronal networks and large-scale human brain networks . Philos Trans R Soc Lond B Biol Sci 369 : 20130531 , 2014 102 Wang J , Zuo X , He Y : Graph-based network analysis of resting-state functional MRI . Front Syst Neurosci 4 : 16 , 2010 103 Watts DJ , Strogatz SH : Collective dynamics of “small-world” networks . Nature

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Michael P. Catalino, Shun Yao, Deborah L. Green, Edward R. Laws Jr., Alexandra J. Golby and Yanmei Tie

F unctional brain mapping was traditionally studied for epilepsy and tumor surgery by intraoperative direct electrical stimulation (DES) pioneered by Penfield, Ojemann, Berger, and Duffau. 2 , 14 , 43 , 46 Motor and language mapping has been well studied and broadly adopted, but cognition and emotion mapping is rare. 28 , 60 In the last decade, our anatomical understanding of brain function has evolved from a purely localizationist perspective to a network-based approach. 13 Indirect functional network mapping with resting-state functional MRI (rs-fMRI) has