Intraoperative Stimulation Research Articles

S122. Intraoperative electrical stimulation to identify the corticospinal tract and dorsal column during spinal cord tumor surgery

Introduction Anatomical identification of the corticospinal tract (CT) and the dorsal column (DC) of the exposed spinal cord is difficult when anatomical landmarks are distorted by tumour growth. Intraoperative neurophysiological identification is complicated by the fact that direct stimulation of the DC may result in muscle motor responses due to the centrally activated H-reflex. This study aimed to provide a technique for intraoperative neurophysiological differentiation between CT and DC in the surgical exposed spinal cord. Methods Recordings were obtained from 32 consecutive patients undergoing intramedullary or intradural-extramedullary spinal cord tumour surgery from 07/2015 to 03/2017. A double train stimulation paradigm with an intertrain interval of 60 ms was devised by a hand held probe with simultaneous recording of responses from limb muscles. Results In non spastic patients (55% of cohort) an identical second response was noted following the first response after CT stimulation, but the second response was absent after DC stimulation. In patients with preexisting spasticity (45%), CT stimulation again resulted in two identical responses, whereas DC stimulation generated a second response that differed substantially from the first one. The recovery times of interneurons in the spinal cord grey matter for the CT were much shorter than those for the DC. Therefore, when a second stimulus train was applied 60 ms after the first, the CT-fibre interneurons had already recovered ready to generate a second response, whereas the DC interneurons were still in the refractory period. Conclusion Intraoperative mapping of the surgical exposed spinal cord using double-train stimulation paradigm allows neurophysiological distinction of CT from DC pathways during spinal cord surgery in patients with and without preexisting spasticity.

A new method for monitoring abnormal muscle response in hemifacial spasm: A prospective study

ObjectiveTo examine a new abnormal muscle response (AMR) monitoring method during microvascular decompression (MVD) for hemifacial spasm. Methods486 patients with hemifacial spasm were monitored for an AMR during MVD with a new method involving preoperative mapping and intraoperative centrifugal stimulation of the facial nerve. For the last 62 patients, we performed the AMR monitoring using both, the new and conventional methods simultaneously. ResultsPreoperative facial nerve mapping showed that the maximal AMR was detected most frequently (66.9%) at the “F” location (the direction towards the frontalis muscle). An intraoperative AMR was observed in 86.2% of the patients, which disappeared after MVD in 96.4% of the patients. A comparison of the new and conventional methods respectively showed that AMR disappearance after MVD was observed in 98.2% and 61.8% of the patients, no AMR in 0% and 9.1%, and persistent AMR after MVD in 1.8% and 29.1%. ConclusionsThe new AMR monitoring method demonstrated greater AMR monitoring efficacy and supports the finding that disappearance of an AMR is a good indicator of effective decompression during MVD surgery. SignificancePreoperative mapping and intraoperative centrifugal stimulation of the facial nerve during MVD surgery in HFS patients showed greater efficacy of AMR monitoring.

Intraoperative Monitoring with Cortical Estimulation

Introduction: Resection of gliomas in eloquent areas such as motor and supplementary motor areas has always been a main challenge for the surgeon due to the risk of severe neurological sequelae. An important tool used during the procedure to avoid postoperative deficits is the intraoperative cortical stimulation of eloquent areas as a safe option of functional area mapping. Methods: In this study, authors examined 50 patients with gliomas located in the motor and supplementary motor area that have undergone surgery with cortical stimulation, using clinical assessment of muscle strength in the pre- and immediate postoperative assessments and three months after surgery as parameters. Results: There was significant difference (p<0.001) between the preoperative and immediate postoperative assessments regarding the occurrence of severe neurological deficit, demonstrating a worsening of the neurological status after surgery. Concerning the comparison between the immediate postoperative period and the assessment performed three months after surgery, it was observed that all the patients who had severe deficit (11 cases) improved (p<0.001). No statistical difference was found between the malignancy grade and the evolution of the neurological deficit in the assessments performed in the three evaluated periods. Conclusion: In the immediate postoperative period following surgical resection of glial tumors in the motor and supplementary motor areas with intraoperative cortical monitoring, most patients have significant alterations in their muscle strength. However, three months after surgery there was significant improvement of these neurological deficits and no patient had severe sequelae.

Multimodal Approach for Radical Excision of Focal Cortical Dysplasia by Combining Advanced Magnetic Resonance Imaging Data to Intraoperative Ultrasound, Electrocorticography, and Cortical Stimulation: A Preliminary Experience.

Type II focal cortical dysplasia is the most common malformation of cortical development associated with drug resistant epilepsy and susceptible to surgical resection. Although, at present, advanced imaging modalities are capable of detecting most cortical disorders, it is still a challenge for the surgeon to visualize them intraoperatively. The lack of direct identification between normal brain and subtle dysplastic tissue may explain the poor results in terms of being seizure-free versus other forms of epilepsy. The aim of this study is to compare magnetic resonance imaging (MRI) and intraoperative ultrasound-guided neuronavigation, along with cortical stimulation and acute electrocorticography, as a multimodal surgical approach to cortical dysplasia's tailored resection. Six consecutive patients with type II cortical dysplasia underwent epilepsy surgery by means of MRI/intraoperative ultrasound-guided neuronavigation. Intraoperative cortical stimulation of sensory/motor cortex was performed to localize cortical eloquent areas. Acute electrocorticography was used to identify epileptogenic tissue. These findings were correlated to real-time ultrasound imaging to establish the extent of the resection. Intraoperative ultrasound depicted cortical dysplasias at a higher resolution and accuracy than MRI. Therefore it maximized the extent of the resection. Both postoperative MRIs and pathology documented the extent of the resection in all patients. Seizure-freedom was achieved in 5 cases (Engel class IA), and in 1 patient it was classified as Engel class IB. No postoperative neurological deficits were observed. These results strongly suggest feasibility of ultrasound-guided resection of focal cortical dysplasia. Providing high resolution and accuracy, it allows an easy, real-time discrimination between normal and dysplastic brain.

Electric Field Comparison between Microelectrode Recording and Deep Brain Stimulation Systems-A Simulation Study.

The success of deep brain stimulation (DBS) relies primarily on the localization of the implanted electrode. Its final position can be chosen based on the results of intraoperative microelectrode recording (MER) and stimulation tests. The optimal position often differs from the final one selected for chronic stimulation with the DBS electrode. The aim of the study was to investigate, using finite element method (FEM) modeling and simulations, whether lead design, electrical setup, and operating modes induce differences in electric field (EF) distribution and in consequence, the clinical outcome. Finite element models of a MER system and a chronic DBS lead were developed. Simulations of the EF were performed for homogenous and patient-specific brain models to evaluate the influence of grounding (guide tube vs. stimulator case), parallel MER leads, and non-active DBS contacts. Results showed that the EF is deformed depending on the distance between the guide tube and stimulating contact. Several parallel MER leads and the presence of the non-active DBS contacts influence the EF distribution. The DBS EF volume can cover the intraoperatively produced EF, but can also extend to other anatomical areas. In conclusion, EF deformations between stimulation tests and DBS should be taken into consideration as they can alter the clinical outcome.

Linking late cognitive outcome with glioma surgery location using resection cavity maps.

Patients with a diffuse glioma may experience cognitive decline or improvement upon resective surgery. To examine the impact of glioma location, cognitive alteration after glioma surgery was quantified and related to voxel‐based resection probability maps. A total of 59 consecutive patients (range 18–67 years of age) who had resective surgery between 2006 and 2011 for a supratentorial nonenhancing diffuse glioma (grade I–III, WHO 2007) were included in this observational cohort study. Standardized neuropsychological examination and MRI were obtained before and after surgery. Intraoperative stimulation mapping guided resections towards neurological functions (language, sensorimotor function, and visual fields). Maps of resected regions were constructed in standard space. These resection cavity maps were compared between patients with and without new cognitive deficits (z‐score difference >1.5 SD between baseline and one year after resection), using a voxel‐wise randomization test and calculation of false discovery rates. Brain regions significantly associated with cognitive decline were classified in standard cortical and subcortical anatomy. Cognitive improvement in any domain occurred in 10 (17%) patients, cognitive decline in any domain in 25 (42%), and decline in more than one domain in 10 (17%). The most frequently affected subdomains were attention in 10 (17%) patients and information processing speed in 9 (15%). Resection regions associated with decline in more than one domain were predominantly located in the right hemisphere. For attention decline, no specific region could be identified. For decline in information speed, several regions were found, including the frontal pole and the corpus callosum. Cognitive decline after resective surgery of diffuse glioma is prevalent, in particular, in patients with a tumor located in the right hemisphere without cognitive function mapping.

A high-resolution computational localization method for transcranial magnetic stimulation mapping

BackgroundTranscranial magnetic stimulation (TMS) is used for the mapping of brain motor functions. The complexity of the brain deters determining the exact localization of the stimulation site using simplified methods (e.g., the region below the center of the TMS coil) or conventional computational approaches. ObjectiveThis study aimed to present a high-precision localization method for a specific motor area by synthesizing computed non-uniform current distributions in the brain for multiple sessions of TMS. MethodsPeritumoral mapping by TMS was conducted on patients who had intra-axial brain neoplasms located within or close to the motor speech area. The electric field induced by TMS was computed using realistic head models constructed from magnetic resonance images of patients. A post-processing method was implemented to determine a TMS hotspot by combining the computed electric fields for the coil orientations and positions that delivered high motor-evoked potentials during peritumoral mapping. The method was compared to the stimulation site localized via intraoperative direct brain stimulation and navigated TMS. ResultsFour main results were obtained: 1) the dependence of the computed hotspot area on the number of peritumoral measurements was evaluated; 2) the estimated localization of the hand motor area in eight non-affected hemispheres was in good agreement with the position of a so-called “hand-knob”; 3) the estimated hotspot areas were not sensitive to variations in tissue conductivity; and 4) the hand motor areas estimated by this proposal and direct electric stimulation (DES) were in good agreement in the ipsilateral hemisphere of four glioma patients. Conclusion(s)The TMS localization method was validated by well-known positions of the “hand-knob” in brains for the non-affected hemisphere, and by a hotspot localized via DES during awake craniotomy for the tumor-containing hemisphere.

Awake versus Asleep Deep Brain Stimulation Surgery: Technical Considerations and Critical Review of the Literature.

Advancements in neuroimaging have led to a trend toward direct, image-based targeting under general anesthesia without the use of microelectrode recording (MER) or intraoperative test stimulation, also referred to as “asleep” deep brain stimulation (DBS) surgery. Asleep DBS, utilizing imaging in the form of intraoperative computed tomography (iCT) or magnetic resonance imaging (iMRI), has demonstrated reliable targeting accuracy of DBS leads implanted within the globus pallidus and subthalamic nucleus while also improving clinical outcomes in patients with Parkinson’s disease. In lieu, of randomized control trials, retrospective comparisons between asleep and awake DBS with MER have shown similar short-term efficacy with the potential for decreased complications in asleep cohorts. In lieu of long-term outcome data, awake DBS using MER must demonstrate more durable outcomes with fewer stimulation-induced side effects and lead revisions in order for its use to remain justifiable; although patient-specific factors may also be used to guide the decision regarding which technique may be most appropriate and tolerable to the patient.

Intraoperative Identification and Preservation of Verbal Memory in Diffuse Gliomas: A Matched-Pair Cohort Study.

Recent glioma surgery series with intraoperative electrical stimulation (IES) language mapping have demonstrated high rates of postoperative memory impairment, raising a question regarding the efficacy of this approach to preserve memory. To evaluate if intraoperative identification and preservation of verbal memory sites with IES mapping in diffuse gliomas in eloquent areas consistently protect patients from long-term postoperative decline in short-term memory. A cohort of 16 subjects with diffuse low-grade or anaplastic gliomas that were operated with IES and intraoperative evaluation of language and verbal memory (cohort A) was matched by tumor side, pathology, and radiotherapy with a cohort of 16 subjects that were operated with IES and evaluation of language (cohort B). Detailed neuropsychological assessment was performed before and 6 mo after surgery. Intraoperative memory mapping was a strong predictor of verbal memory prognosis. In cohort A, 4 patients (26.7%) had a decline of at least one of the 4 short-term memory tests evaluated. In cohort B, 11 patients (73.3%) had a decline of at least one of the 4 tests. This difference was statistically significant in multivariate analysis (P=.022; odds ratio=9.88; 95% confidence interval=1.39-70.42). Verbal memory areas identified intraoperatively with the current paradigm are critically involved in verbal memory, as memory impairment can be significantly reduced by adapting the resection to avoid those memory areas. Incorporation of verbal memory evaluation in stimulation mapping protocols might assist in reducing postoperative sequelae and preserving the patient's quality of life.

Intraoperative Brief Electrical Stimulation of the Spinal Accessory Nerve (BEST SPIN) for prevention of shoulder dysfunction after oncologic neck dissection: a double-blinded, randomized controlled trial

BackgroundShoulder dysfunction is common after neck dissection for head and neck cancer (HNC). Brief electrical stimulation (BES) is a novel technique that has been shown to enhance neuronal regeneration after nerve injury by modulating the brain-derived neurotrophic growth factor (BDNF) pathways. The objective of this study was to evaluate the effect of BES on postoperative shoulder function following oncologic neck dissection.MethodsAdult participants with a new diagnosis of HNC undergoing Level IIb +/− V neck dissection were recruited. Those in the treatment group received intraoperative BES applied to the spinal accessory nerve (SAN) after completion of neck dissection for 60 min of continuous 20 Hz stimulation at 3-5 V of 0.1 msec balanced biphasic pulses, while those in the control group received no stimulation (NS). The primary outcome measured was the Constant-Murley Shoulder (CMS) Score, comparing changes from baseline to 12 months post-neck dissection. Secondary outcomes included the change in the Neck Dissection Impairment Index (ΔNDII) score and the change in compound muscle action potential amplitude (ΔCMAP) over the same period.ResultsFifty-four patients were randomized to the treatment or control group with a 1:1 allocation scheme. No differences in demographics, tumor characteristics, or neck dissection types were found between groups. Significantly lower ΔCMS scores were observed in the BES group at 12 months, indicating better preservation of shoulder function (p = 0.007). Only four in the BES group compared to 17 patients in the NS groups saw decreases greater than the minimally important clinical difference (MICD) of the CMS (p = 0.023). However, NDII scores (p = 0.089) and CMAP amplitudes (p = 0.067) between the groups did not reach statistical significance at 12 months. BES participants with Level IIb + V neck dissections had significantly better ΔCMS and ΔCMAP scores at 12 months (p = 0.048 and p = 0.025, respectively).ConclusionsApplication of BES to the SAN may help reduce impaired shoulder function in patients undergoing oncologic neck dissection, and may be considered a viable adjunct to functional rehabilitation therapies.Trial registrationClinicaltrials.gov (NCT02268344, October 17, 2014).

The Results of Intraoperative Direct Electrical Stimulation of Roots and Placode During Myelomeningocele Repair

The Results of Intraoperative Direct Electrical Stimulation of Roots and Placode During Myelomeningocele Repair

ИНТРАОПЕРАЦИОННАЯ СТИМУЛЯЦИЯ СРЕДИННОГО НЕРВА СНИЖАЕТ РИСК ПОСЛЕОПЕРАЦИОННОЙ ТОШНОТЫ И РВОТЫ ПОСЛЕ УДАЛЕНИЯ ОПУХОЛИ ЗАДНЕЙ ЧЕРЕПНОЙ ЯМКИ

The article presents the results of a prospective randomized double-blind study which was investigating the efficacy of intra-operative transcutaneous stimulation of median nerve on the wrist aimed to prevent post-operative nausea and vomiting after planned resection of brain tumors located in posterior fossa. Methods. 40 patients were included into the study: 20 patients were enrolled into the stimulation group and 20 of them were enrolled into the control group, where the prevention of emetogenic reactions was limited by the use of dexamethasone and ondansetron. Results. The demographic and clinical parameters were compatible in the both groups. During the first 12 hours after recovery, the risk to develop symptoms was significantly lower in the stimulation group (p <0.05): 7 cases versus 14 ones in the control group (RR =0.5; 95% CI 0.26−0.97) and 4 versus 10 cases of vomiting in the control group (RR =0.4; 95% CI 0.15−1.07). No side effects were observed. Conclusion. It was confirmed that this method was effective to prevent postoperative nausea and vomiting in the patients who underwent infratentorial craniotomy.

Effect of intraoperative electromyogram stimulation on surgical effectiveness of cubital tunnel syndrome

Objective To observe the effect of intraoperative electromyogram (EMG) stimulation on surgical effectiveness of cubital tunnel syndrome. Methods A total of 288 patients with cubital tunnel syndrome and confirmed as invalid conservative treatment cases were divided into intraoperative EMG stimulation treatment group (experimental group) and control group, 144 cases in each. All cases were monitored by intraoperative electrophysiological examination 1 time before operation, and by recording the latency and amplitude of compound muscle action potential (CMAP) in the abductor muscle of the little finger. After release again the same intraoperative electrophysiological monitoring was done. In the experimental group after the release of nerve compression at the most serious site, electrical stimulation was done, and the stimulation parameters were as follows: 100 mA, 2 Hz, 10 min. The latency and amplitude of CMAP before and after the intraoperative release were compared. The patients were followed up every 2 months, and all cases were followed up for at least 8 months. The number of cases with different evaluation criteria was evaluated at each follow-up visit. The chi square test was used for the comparative analysis. Results The amplitude difference was (3.4±0.4) mV, and the latency difference was (10.1±0.2) ms in the control group, and those were (2.5±0.4) mV and (14.4±0.6) ms in the experimental group, with the difference being statistically significant (P=0.007 and P=0.001). At 2nd month after operation, the number of cases obtaining recovery and improvement in the experimental group was significantly greater than in the control group (P=0.000), more significant at 4th month after operation. At 6th month after operation, the recovery rate and improvement in experimental group and control group showed no significant difference (P=0.054). At 8th month after operation, the number of ineffective cases in experimental group was significantly less than in the control group (P=0.000). Conclusion Intraoperative EMG stimulation after surgical release of cubital tunnel syndrome can quickly improve the CMAP amplitude and latency of abductor muscle of the little finger. Key words: Intraoperative electromyogram stimulation; Cubital tunnel syndrome

Resection of primary motor cortex tumors: feasibility and surgical outcomes

Brain tumors involving the primary motor cortex are often deemed unresectable due to the potential neurological consequences that result from injury to this region. Nevertheless, we have challenged this dogma for many years and used asleep, as well as awake, intraoperative stimulation mapping to maximize extent of resection. It remains unclear whether these tumors can be resected with acceptable morbidity, whether performing the surgery with the patient awake or asleep impacts extent of resection, and how stimulation mapping influences outcomes. A retrospective chart review was performed on the senior author's cohort to identify patients treated between 1998 and 2016 who underwent resection of tumors that were located within the primary motor cortex. Clinical notes, operative reports, and radiographic images were reviewed to identify intraoperative stimulation mapping findings and functional outcomes following tumor resection. Extent of resection was quantified volumetrically. Characteristics of patients were analyzed to identify factors associated with postoperative motor deficits. Forty-nine patients underwent 53 resections of tumors located primarily within the motor cortex. Stimulation mapping was performed in all cases. Positive cortical sites for motor response were identified in 91% of cases, and subcortical sites in 74%. Awake craniotomy was performed in 65% of cases, while 35% were done under general anesthesia. The mean extent of resection was 91%. There was no statistically significant difference in extent of resection in cases done awake compared with those done under general anesthesia. New or worsened postoperative motor deficits occurred in 32 patients (60%), and 20 patients (38%) had a permanent deficit. Of the permanent deficits, 14 were mild, 4 were moderate, and 2 were severe (3.8% of cases). Decreased intraoperative motor response and diffusion restriction on postoperative MRI were associated with permanent deficit. Awake motor mapping surgery was associated with increased diffusion signal on postoperative MRI. Resection of tumors from the primary motor cortex is associated with an increased risk of motor deficit, but most of these deficits are transient or mild and have little functional impact. Excellent extent of resection can be achieved with intraoperative stimulation mapping, suggesting that these tumors are indeed amenable to resection and should not be labeled unresectable. Injury to small perforating or en passage blood vessels was the most common cause of infarction that led to moderate or severe deficits. Awake motor mapping was not superior to mapping done under general anesthesia with regard to long-term functional outcome.

Continuous intraoperative recurrent laryngeal nerve monitoring during thyroid surgery. The Greek experience

Introduction: Recurrent laryngeal nerve injury is a serious complication of thyroid surgery. The anatomic dissection and visual identification of the inferior laryngeal nerve is the standard of care to avoid this complication. The intermittent intraoperative nerve stimulation technique has failed to improve nerve safety. The continuous recurrent laryngeal nerve monitoring is a promising new technique, currently under study to evaluate its feasibility and safety outcomes. We present our experience of applying this method in a private thyroid surgery clinic in Greece

Resection of gliomas deemed inoperable by neurosurgeons based on preoperative imaging studies.

OBJECTIVE Maximal safe resection is a primary objective in the management of gliomas. Despite this objective, surgeons and referring physicians may, on the basis of radiological studies alone, assume a glioma to be unresectable. Because imaging studies, including functional MRI, may not localize brain functions (such as language) with high fidelity, this simplistic approach may exclude some patients from what could be a safe resection. Intraoperative direct electrical stimulation (DES) allows for the accurate localization of functional areas, thereby enabling maximal resection of tumors, including those that may appear inoperable based solely on radiological studies. In this paper the authors describe the extent of resection (EOR) and functional outcomes following resections of tumors deemed inoperable by referring physicians and neurosurgeons. METHODS The authors retrospectively examined the cases of 58 adult patients who underwent glioma resection within 6 months of undergoing a brain biopsy of the same lesion at an outside hospital. All patients exhibited unifocal supratentorial disease and preoperative Karnofsky Performance Scale scores ≥ 70. The EOR and 6-month functional outcomes for this population were characterized. RESULTS Intraoperative DES mapping was performed on 96.6% (56 of 58) of patients. Nearly half of the patients (46.6%, 27 of 58) underwent an awake surgical procedure with DES. Overall, the mean EOR was 87.6% ± 13.6% (range 39.0%-100%). Gross-total resection (resection of more than 99% of the preoperative tumor volume) was achieved in 29.3% (17 of 58) of patients. Subtotal resection (95%-99% resection) and partial resection (PR; < 95% resection) were achieved in 12.1% (7 of 58) and 58.6% (34 of 58) of patients, respectively. Of the cases that involved PR, the mean EOR was 79.4% ± 12.2%. Six months after surgery, no patient was found to have a new postoperative neurological deficit. The majority of patients (89.7%, 52 of 58) were free of neurological deficits both pre- and postoperatively. The remainder of patients exhibited either residual but stable deficits (5.2%, 3 of 58) or complete correction of preoperative deficits (5.2%, 3 of 58). CONCLUSIONS The use of DES enabled maximal safe resections of gliomas deemed inoperable by referring neurosurgeons. With rare exceptions, tumor resectability cannot be determined solely by radiological studies.

Involvement of the middle frontal gyrus in language switching as revealed by electrical stimulation mapping and functional magnetic resonance imaging in bilingual brain tumor patients

Neural basis of language switching and the cognitive models of bilingualism remain controversial. We explored the functional neuroanatomy of language switching implementing a new multimodal protocol assessing neuropsychological, functional magnetic resonance and intraoperative electrical stimulation mapping results.A prospective series of 9 Spanish–Catalan bilingual candidates for awake brain surgery underwent a specific language switching paradigm implemented both before and after surgery, throughout the electrical stimulation procedure and during functional magnetic resonance both pre- and postoperatively. All patients were harboring left-hemispheric intrinsic brain lesions and were presenting functional language-related activations within the affected hemisphere.Language functional maps were reconstructed on the basis of the intraoperative electrical stimulation results and compared to the functional magnetic resonance findings. Single language-naming sites (Spanish and Catalan), as well as language switching naming sites were detected by electrical stimulation mapping in 8 patients (in one patient only Spanish related sites were detected). Single naming points outnumbered the switching points and did not overlap with each other. Within the frontal lobe, the single language naming sites were found significantly more frequently within the inferior frontal gyrus as compared to the middle frontal gyrus [X2 (1) = 20.3, p < .001]. Contrarily, switching naming sites were distributed across the middle frontal gyrus significantly more often than within the inferior frontal gyrus [X2 (1) = 4.1, p = .043]. Notably, there was not always an overlap between functional magnetic resonance and electrical stimulation mapping findings. After surgery, patients did not report involuntary language switching and their neuropsychological scores did not differ significantly from the pre-surgical examinations. Our results suggest a functional division of the frontal cortex between naming and language switching functions, supporting that non-language specific cognitive control prefrontal regions (middle frontal gyrus) are essential to maintain an effective communication together with the classical language-related sites (inferior frontal gyrus).

An automated method for identifying an independent component analysis-based language-related resting-state network in brain tumor subjects for surgical planning

As a noninvasive and “task-free” technique, resting-state functional magnetic resonance imaging (rs-fMRI) has been gradually applied to pre-surgical functional mapping. Independent component analysis (ICA)-based mapping has shown advantage, as no a priori information is required. We developed an automated method for identifying language network in brain tumor subjects using ICA on rs-fMRI. In addition to standard processing strategies, we applied a discriminability-index-based component identification algorithm to identify language networks in three different groups. The results from the training group were validated in an independent group of healthy human subjects. For the testing group, ICA and seed-based correlation were separately computed and the detected language networks were assessed by intra-operative stimulation mapping to verify reliability of application in the clinical setting. Individualized language network mapping could be automatically achieved for all subjects from the two healthy groups except one (19/20, success rate = 95.0%). In the testing group (brain tumor patients), the sensitivity of the language mapping result was 60.9%, which increased to 87.0% (superior to that of conventional seed-based correlation [47.8%]) after extending to a radius of 1 cm. We established an automatic and practical component identification method for rs-fMRI-based pre-surgical mapping and successfully applied it to brain tumor patients.

Super-selective cervical nerve root stimulation in contralateral C7 transfer: An intraoperative study

ObjectiveWe designed this study using super-selective intraoperative cervical nerve root stimulation aiming to support decision making about complete or partial contralateral C7 (cC7) nerve root transfer in patients with multiple cervical root avulsion injury. MethodsSuper-selective intraoperative stimulations of anterior, lateral, medial and posterior aspect of C5–C8 nerve roots were performed. Compound muscle action potentials (CMAP) were recorded in the lateral part of the deltoid (DM), long head of biceps brachii (BCM), brachioradial (BRM), long head of triceps brachii (TCM), and extensor digitorum communis (EDC) muscle. Muscle strength was documented immediately after cC7 transfer procedures and on scheduled follow-up visits according to the Medical Research Council (MRC) scale. ResultsIn the DM, stimulation of the posterior aspect of C5 resulted in the largest CMAP amplitudes (2.0 mV ± 1.9; 80% ± 28.3). The BCM CMAPs induced by the different aspects of C6 all revealed homogenous stimulation results. Stimulation of the lateral aspect of C7 induced the largest amplitude of TCM CMAPs (1.3 mV ± 1.0; 67.1% ± 43.3). CMAP amplitudes of individual muscles and individual contributions of cervical nerve roots to the TCM varied between subjects. Overall donor side morbidity was low, no permanent motor deficit occurred. ConclusionA super-selective intraoperative cervical nerve root stimulation may help minimize donor side morbidity in transfer procedures. Individual differences of cervical nerve root innervation pattern need to be addressed in future electrophysiological studies. SignificanceOur study outlines individual differences of cervical nerve root innervation pattern.

Surgical and Clinical Decision Making in Isolated Long Thoracic Nerve Palsy.

Isolated long thoracic nerve palsy results in scapular winging and destabilization. In this study, we review the surgical management of isolated long thoracic nerve palsy and suggest a surgical technique and treatment algorithm to simplify management. In total, 19 patients who required surgery for an isolated long thoracic nerve palsy were reviewed retrospectively. Preoperative demographics, electromyography (EMG), and physical examinations were reviewed. Intraoperative nerve stimulation, surgical decision making, and postoperative outcomes were reviewed. In total, 19 patients with an average age of 32 were included in the study. All patients had an isolated long thoracic nerve palsy caused by either an injury (58%), Parsonage-Turner syndrome (32%), or shoulder surgery (10%); 18 patients (95%) underwent preoperative EMG; 10 with evidence of denervation (56%); and 13 patients had motor unit potentials in the serratus anterior (72%). The preoperative EMG did not correlate with intraoperative nerve stimulation in 13 patients (72%) and did correlate in 5 patients (28%); 3 patients had a nerve transfer (3 thoracodorsal to long thoracic at lateral chest, 1 pec to long thoracic at supraclavicular incision). In the 3 patients who had a nerve transfer, there was return of full forward flexion of the shoulder at an average of 2.5 months. A treatment algorithm based on intraoperative nerve stimulation will help guide surgeons in their clinical decision making in patients with isolated long thoracic nerve palsy. Intraoperative nerve stimulation is the gold standard in the management of isolated long thoracic nerve palsy.