Tag: Direct cortical stimulation

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Functional Reorganization of the Mesial Frontal Premotor Cortex in Patients With Supplementary Motor Area Seizures

Neurosurgery 92:186–194, 2023

Direct cortical stimulation of the mesial frontal premotor cortex, including the supplementary motor area (SMA), is challenging in humans. Limited access to these brain regions impedes understanding of human premotor cortex functional organization and somatotopy.

OBJECTIVE: To test whether seizure onset within the SMA was associated with functional remapping of mesial frontal premotor areas in a cohort of patients with epilepsy who underwent awake brain mapping after implantation of interhemispheric subdural electrodes.

METHODS: Stimulation trials from 646 interhemispheric subdural electrodes were analyzed and compared between patients who had seizure onset in the SMA (n = 13) vs patients who had seizure onset outside of the SMA (n = 12). 1:1 matching with replacement between SMA and non-SMA data sets was used to ensure similar spatial distribution of electrodes. Centroids and 95% confidence regions were computed for clustered head, trunk, upper extremity, lower extremity, and vision responses. A generalized linear mixedeffects model was used to test for significant differences in the resulting functional maps. Clinical, radiographic, and histopathologic data were reviewed.

RESULTS: After analyzing direct cortical stimulation trials from interhemispheric electrodes, we found significant displacement of the head and trunk responses in SMA compared with non-SMA patients (P < .01 for both). These differences remained significant after accounting for structural lesions, preexisting motor deficits, and seizure outcome.

CONCLUSION: The somatotopy of the mesial frontal premotor regions is significantly altered in patients who have SMA-onset seizures compared with patients who have seizure onset outside of the SMA, suggesting that functional remapping can occur in these brain regions.

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Clinical Pearls and Methods for Intraoperative Awake Language Mapping

Neurosurgery 89:143–153, 2021

Intraoperative language mapping of tumor and peritumor tissue is a well-established technique for avoiding permanent neurological deficits and maximizing extent of resection.

Although there are several components of language that may be tested intraoperatively (eg, naming, writing, reading, and repetition), there is a lack of consistency in how patients are tested intraoperatively as well as the techniques involved to ensure safety during an awake procedure.

Here, we review appropriate patient selection, neuroanesthetic techniques, cortical and subcortical language mapping stimu- lation paradigms, and selection of intraoperative language tasks used during awake craniotomies.

We also expand on existing language mapping reviews by considering how intensity and timing of electrical stimulation may impact interpretation of mapping results.

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Incidence and linguistic quality of speech errors: a comparison of preoperative transcranial magnetic stimulation and intraoperative direct cortex stimulation

J Neurosurg 134:1409–1418, 2021

Given the interindividual variance of functional language anatomy, risk prediction based merely on anatomical data is insufficient in language area–related brain tumor surgery, suggesting the need for direct cortical and subcortical mapping during awake surgery. Reliable, noninvasive preoperative methods of language localization hold the potential for reducing the necessity for awake procedures and may improve patient counseling and surgical planning. Repetitive navigated transcranial magnetic stimulation (rnTMS) is an evolving tool for localizing language-eloquent areas. The aim of this study was to investigate the reliability of rnTMS in locating cortical language sites.

METHODS Twenty-five patients with brain tumors in speech-related areas were prospectively evaluated with preoperative rnTMS (5 Hz, train of five, average 105% resting motor threshold) and navigated direct cortical stimulation (DCS; bipolar, 50 Hz, 6–8 mA, 200-μsec pulse width) during awake surgeries employing a picture-naming task. Positive and negative stimulation spots within the craniotomy were documented in the same MRI data set. TMS and DCS languagepositive areas were compared with regard to their spatial overlap, their allocation in a cortical parcellation system, and their linguistic qualities.

RESULTS There were over twofold more positive language spots within the exposed area on rnTMS than on DCS. The comparison of positive rnTMS and DCS (ground truth) overlaps revealed low sensitivity (35%) and low positive predictive value (16%) but high specificity (90%) and high negative predictive value (96%). Within the overlaps, there was no correlation in error quality. On DCS, 73% of language-positive spots were located in the pars opercularis and pars triangularis of the frontal operculum and 24% within the supramarginal gyrus and dorsal portion of the superior temporal gyrus, while on rnTMS language positivity was distributed more evenly over a large number of gyri.

CONCLUSIONS The current protocol for rnTMS for language mapping identified language-negative sites with good dependability but was unable to reliably detect language-positive spots. Further refinements of the technique will be needed to establish rnTMS language mapping as a useful clinical tool.

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The Cost of Brain Surgery: Awake vs Asleep Craniotomy for Perirolandic Region Tumors

Neurosurgery 81:307–314, 2017

Cost effectiveness has become an important factor in the health care system, requiring surgeons to improve efficacy of procedures while reducing costs. An awake craniotomy (AC) with direct cortical stimulation (DCS) presents one method to resect eloquent region tumors; however, some authors assert that this procedure is an expensive alternative to surgery under general anesthesia (GA) with neuromonitoring.

OBJECTIVE: To evaluate the cost effectiveness and clinical outcomes between AC and GA patients.

METHODS: Retrospective analysis of a cohort of 17 patients with perirolandic gliomas who underwent an AC with DCS were case-control matched with 23 patients with perirolandic gliomas who underwent surgery under GA with neuromonitoring (ie, motor-evoked potentials, somatosensory-evoked potentials, phase reversal). Inpatient costs, qualityadjusted life years (QALY), extent of resection, and neurological outcome were compared between the groups.

RESULTS: Total inpatient expense per patient was $34 804 in the AC group and $46 798 in the GA group (P = .046). QALY score for the AC group was 0.97 and 0.47 for the GA group (P = .041). The incremental cost per QALY for the AC group was $82 720 less than the GA group. Postoperative Karnofsky performance status was 91.8 in the AC group and 81.3 in the GA group (P=.047). Length of hospitalization was 4.12 days in the AC group and 7.61 days in the GA group (P = .049).

CONCLUSION: The total inpatient costs for awake craniotomies were lower than surgery under GA. This study suggests better cost effectiveness and neurological outcome with awake craniotomies for perirolandic gliomas.

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Brain surface reformatted imaging (BSRI) for intraoperative neuronavigation in brain tumor surgery

Brain surface reformatted imaging (BSRI) for intraoperative neuronavigation in brain tumor surgery

Acta Neurochir (2015) 157:265–274

For safe resection of lesions situated in or near eloquent brain regions, determination of their spatial and functional relationship is crucial. Since functional magnetic resonance imaging and intraoperative neurophysiological mapping are not available in all neurosurgical departments, we aimed to evaluate brain surface reformatted imaging (BSRI) as an additional display mode for neuronavigation.

Methods Eight patients suffering from perirolandic tumors were preoperatively studied withMRI and navigated transcranial magnetic stimulation (nTMS). Afterwards, the MRI was automatically transformed into BSR images in neuronavigation software (Brainlab, Brainlab AG, Feldkirchen, Germany). One experienced neuroradiologist, one experienced neurosurgeon, and two residents determined hand representation areas ipsilateral to each tumor on two-dimensional (2D) MR images and on BSR images. All results were compared to results from intraoperative direct cortical mapping of the hand motor cortex and to preoperative nTMS results.

Results Findings from nTMS and intraoperative direct cortical mapping of the hand motor cortex were congruent in all cases. Hand representation areas were correctly determined on BSR images in 81.3%and on 2D-MR images in 93.75%(p= 0.26). In a subgroup analysis, experienced observers showed more familiarity with BSRI than residents (96.9 vs. 84.4 % correct results, p=0.19), with an equal error rate for 2D-MRI. The time required to define hand representation areas was significantly shorter using BSRI than using standard MRI (mean 27.4 vs. 40.4 s, p=0.04).

Conclusions With BSRI, a new method for neuronavigation is now available, allowing fast and easy intraoperative localization of distinct brain regions.

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Localizing hand motor area using resting-state fMRI: validated with direct cortical stimulation

resting

Acta Neurochir (2014) 156:2295–2302

Resting-state functional magnetic resonance imaging (R-fMRI) is a promising tool in clinical application, especially in presurgicalmapping for neurosurgery. This study aimed to investigate the sensitivity and specificity of R-fMRI in the localization of hand motor area in patients with brain tumors validated by direct cortical stimulation (DCS).We also compared this technique to task-based blood oxygenation level-dependent (BOLD) fMRI (T-fMRI).

Methods R-fMRI and T-fMRI were acquired from 17 patients with brain tumors. The cortex sites of the hand motor area were recorded by DCS. Site-by-site comparisons between R-fMRI/TfMRI andDCS were performed to calculate R-fMRI and T-fMRI sensitivity and specificity using DCS as a “gold standard”. RfMRI and T-fMRI performances were compared statistically

Results A total of 609 cortex sites were tested with DCS and compared with R-fMRI findings in 17 patients. For hand motor area localization, R-fMRI sensitivity and specificity were 90.91 and 89.41%, respectively. Given that two subjects could not comply with T-fMRI, 520 DCS sites were compared with T-fMRI findings in 15 patients. The sensitivity and specificity of T-fMRI were 78.57 and 84.76 %, respectively. In the 15 patients who successfully underwent both R-fMRI and T-fMRI, there was no statistical difference in sensitivity or specificity between the two methods (p=0.3198 and p= 0.1431, respectively)

Conclusions R-fMRI sensitivity and specificity are high for localizing hand motor area and even equivalent or slightly higher compared with T-fMRI. Given its convenience for patients, R-fMRI is a promising substitute for T-fMRI for pre-surgical mapping.

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Localizing hand motor area using resting-state fMRI

Localizing hand motor area using resting-state fMRI

Acta Neurochir (2014) 156:2295–2302

Resting-state functional magnetic resonance imaging (R-fMRI) is a promising tool in clinical application, especially in presurgicalmapping for neurosurgery. This study aimed to investigate the sensitivity and specificity of R-fMRI in the localization of hand motor area in patients with brain tumors validated by direct cortical stimulation (DCS).We also compared this technique to task-based blood oxygenation level-dependent (BOLD) fMRI (T-fMRI).

Methods R-fMRI and T-fMRI were acquired from 17 patients with brain tumors. The cortex sites of the hand motor area were recorded by DCS. Site-by-site comparisons between R-fMRI/TfMRI andDCS were performed to calculate R-fMRI and T-fMRI sensitivity and specificity using DCS as a “gold standard”. RfMRI and T-fMRI performances were compared statistically

Results A total of 609 cortex sites were tested with DCS and compared with R-fMRI findings in 17 patients. For hand motor area localization, R-fMRI sensitivity and specificity were 90.91 and 89.41%, respectively. Given that two subjects could not comply with T-fMRI, 520 DCS sites were compared with T-fMRI findings in 15 patients. The sensitivity and specificity of T-fMRI were 78.57 and 84.76 %, respectively. In the 15 patients who successfully underwent both R-fMRI and T-fMRI, there was no statistical difference in sensitivity or specificity between the two methods (p=0.3198 and p= 0.1431, respectively)

Conclusions R-fMRI sensitivity and specificity are high for localizing hand motor area and even equivalent or slightly higher compared with T-fMRI. Given its convenience for patients, R-fMRI is a promising substitute for T-fMRI for pre surgical mapping.

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Role of intraoperative neurophysiological monitoring during fluorescence-guided resection surgery

Role of intraoperative neurophysiological monitoring during fluorescence-guided resection surgery

Acta Neurochir (2013) 155:2201–2213

Fluorescence-guided resection (FGR) using 5- aminolevulinic acid (5-ALA) exhibits a potential risk of permanent neurological deficits that can be minimized using intraoperative neurophysiological monitoring (IONM). We assessed the role of IONM in FGR surgery in patients harboring tumors in or near eloquent areas.

Methods IONM and FGR surgeries were performed on 34 patients (49.8±2.4 years) harbored malignant primary gliomas near eloquent cortical areas or semioval center. Different combinations of neurophysiological techniques were used depending on each patient.

Results Gross total resection (GTR) was achieved in 66.7 % of the patients, mean 90.4±3.7 % without neurological deficits. Resection in four patients was stopped by the occurrence of severe warning criteria despite the presence of fluorescence. Hemispheric transcranial electrical stimulation was safe and confident even in cortical surgery. Notably, a significant percentage of patients exhibited clinical improvement after the surgery. One week after surgery, only one patient worsened, and seven patients improved. At 3 months, 27.8 % of the patients improved, and the other patients maintained a similar status to their pre-surgery condition.Warning common criteria (amplitude reduction and/or latency increase) appeared in 68.2 and 50.0 % of patients during cortical or semioval surgery, respectively, with neither a false-negative nor a false-positive clinical outcome. Although 5-ALA exhibits phototoxicity, VEP did not induce any secondary effects in the visual system, including eyelids.

Conclusions IONM can be helpful during surgery to maximize the tumor resection, meanwhile help to avoid neurological deficits and, therefore, to improve the quality of life of these patients.

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Subcortical Injury Is an Independent Predictor of Worsening Neurological Deficits Following Awake Craniotomy Procedures

Subcortical_Injury_Is_an_Independent_Predictor_of

Neurosurgery 72:160–169, 2013

Tailored craniotomies for awake procedures limit cortical exposure. Recently we demonstrated that the identification of eloquent areas increased the risk of postoperative deficits. However, it was not clear whether the observed neurological deficits were caused by proximity of functional cortex to the tumor [cortical injury] or subcortical injury.

OBJECTIVE: We hypothesize that subcortical injury during tumor resection is an important predictor of postoperative neurological deficits compared to cortical injury.

METHODS: A retrospective review of 214 patients undergoing awake craniotomy was carried out in whom preoperative functional magnetic resonance imaging (fMRI) and cortical mapping (CM) were performed. A radiologist blinded to the clinical data reviewed and graded the postoperative changes on diffusion-weighted MR-imaging (DWI).

RESULTS: Of the 40 cases who developed new intraoperative neurological deficit, 36 (90%) occurred during subcortical dissection, 3 (7.5%) during both subcortical and cortical dissection, and 1 (2.5%) during cortical dissection. Neurological dysfunction acquired during subcortical dissection was an independent predictor of postoperative deficits both in the immediate postoperative period (P< .001) and at the 3-month follow-up (P < .001). Significant DWI restriction in the subcortical white matter was predictive of neurological deficits both immediately and at 3 months, P = .011 and P < .001, respectively. New or worsening deficits were seen in 38% of patients; however, at 3 months 13% had a mild persistent neurological deficit.

CONCLUSION: Subcortical injury with significant DWI changes result in postoperative neurological decline despite our efforts to preserve cortical areas of function. This underscores the importance of preserving subcortical fiber tracts during awake craniotomy procedures.

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Preoperative multimodal motor mapping: a comparison of magnetoencephalography imaging, navigated transcranial magnetic stimulation, and direct cortical stimulation

J Neurosurg 117:354–362, 2012

Direct cortical stimulation (DCS) is the gold-standard technique for motor mapping during craniotomy. However, preoperative noninvasive motor mapping is becoming increasingly accurate. Two such noninvasive modalities are navigated transcranial magnetic stimulation (TMS) and magnetoencephalography (MEG) imaging. While MEG imaging has already been extensively validated as an accurate modality of noninvasive motor mapping, TMS is less well studied. In this study, the authors compared the accuracy of TMS to both DCS and MEG imaging.

Methods. Patients with tumors in proximity to primary motor cortex underwent preoperative TMS and MEG imaging for motor mapping. The patients subsequently underwent motor mapping via intraoperative DCS. The loci of maximal response were recorded from each modality and compared. Motor strength was assessed at 3 months postoperatively.

Results. Transcranial magnetic stimulation and MEG imaging were performed on 24 patients. Intraoperative DCS yielded 8 positive motor sites in 5 patients. The median distance ± SEM between TMS and DCS motor sites was 2.13 ± 0.29 mm, and between TMS and MEG imaging motor sites was 4.71 ± 1.08 mm. In no patients did DCS motor mapping reveal a motor site that was unrecognized by TMS. Three of 24 patients developed new, early neurological deficit in the form of upper-extremity paresis. At the 3-month follow-up evaluation, 2 of these patients were significantly improved, experiencing difficulty only with fine motor tasks; the remaining patient had improvement to 4/5 strength. There were no deaths over the course of the study.

Conclusions. Maps of the motor system generated with TMS correlate well with those generated by both MEG imaging and DCS. Negative TMS mapping also correlates with negative DCS mapping. Navigated TMS is an accurate modality for noninvasively generating preoperative motor maps.

 

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Preoperative Functional Mapping for Rolandic Brain Tumor Surgery: Comparison of Navigated Transcranial Magnetic Stimulation to Direct Cortical Stimulation

Neurosurgery 69:581–589, 2011 DOI: 10.1227/NEU.0b013e3182181b89

Transcranial magnetic stimulation (TMS) is the only noninvasive method for presurgical stimulation mapping of cortical function. Recent technical advancements have significantly increased the focality and usability of the method.

OBJECTIVE: To compare the accuracy of a 3-dimensional magnetic resonance imaging– navigated TMS system (nTMS) with the gold standard of direct cortical stimulation (DCS).

METHODS: The primary motor areas of 20 patients with rolandic tumors were mapped preoperatively with nTMS at 110% of the individual resting motor threshold. Intraoperative DCS was available from 17 patients. The stimulus locations eliciting the largest electromyographic response in the target muscles (‘‘hotspots’’) were determined for both methods.

RESULTS: The nTMS and DCS hotspots were located on the same gyrus in all cases. The mean 6 SEM distance between the nTMS and DCS hotspots was 7.83 6 1.18 mm for the abductor pollicis brevis (APB) muscle (n = 15) and 7.07 6 0.88 mm for the tibialis anterior muscle (n = 8). When a low number of DCS stimulations was performed, the distance between the nTMS and DCS hotspots increased substantially (r = 20.86 for APB). After the exclusion of the cases with , 15 DCS APB responses, the mean 6 SEM distance between the hotspots was only 4.70 6 1.09 mm for APB (n = 8).

CONCLUSION: Peritumoral mapping of the motor cortex by nTMS agreed well with the gold standard of DCS. Thus, nTMS is a reliable tool for preoperative mapping of motor function.

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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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