Intraoperative Stimulation Research Articles

Stereotactic radiofrequency lesioning of caudal zona incerta for parkinsonian tremor.

This video showcases stereotactic radiofrequency lesioning of the caudal zona incerta (CZi) for parkinsonian tremor in a 70-year-old patient. The preoperative evaluation, including imaging and frame placement, is detailed. The surgical procedure involves meticulous targeting and trajectory planning. Intraoperative stimulation is utilized for motor response assessment. Two temporary lesioning phases precede the final procedure at 75°C. The postoperative CT scan highlights the lesion site. Immediate tremor relief is observed postoperatively, with the effect persisting at the 1-month follow-up. Supporting readings underscore the efficacy and safety of CZi for tremor management. The video can be found here: https://stream.cadmore.media/r10.3171/2024.7.FOCVID2462.

Multimodal and Repeated Localization of Primary Hand Motor Function to the Lateral Postcentral Gyrus in a Case of Frontal Motor Area Brain Metastasis

BACKGROUND AND IMPORTANCE: The human motor homunculus is a well-known topographical map of the functional-anatomical relationships of the precentral gyrus. Within this homunculus, the primary hand motor area is considered one of the least plastic functional-anatomical relationships. Only a few cases in the literature describe relocation of functional hand representation away from the classical anatomical location. These cases have been reported in the context of children, primary gliomas, or arteriovenous malformations. CLINICAL PRESENTATION: Here, we describe a unique case where the area of lowest hand motor stimulation threshold (ie, hand motor representation) was found in the postcentral gyrus in an older adult with a metastasis in the premotor area of the brain. This localization was based on intraoperative cortical stimulation–evoked motor potentials and confirmed with electrophysiological phase reversal and MRI-based neuronavigation. This mapping was repeated and consistent 2 months later during a reoperation for recurrence. In addition, the remapped anatomical location was found in an area that was active during finger tapping on preoperative functional MRI. CONCLUSION: These findings suggest that neuroplastic remapping of hand motor cortex to the postcentral gyrus can occur in brain metastases even in adults. This has implications for planning tumor resections and interventional neurorehabilitation strategies, and it suggests that the motor homunculus may have more plastic potential in adulthood than previously recognized.

Effect of Tourniquet-Related Nerve Ischemia on Response to Handheld Nerve Stimulation in Ulnar Nerve Transposition.

Tourniquet-related nerve ischemia has been well studied in several reconstructive procedures, but the time-course of impaired response to intraoperative stimulation is unclear. The present study evaluated ischemic effects on conduction during ulnar nerve transposition and examined the relationship between intra- and pre- operative diagnostics. We hypothesized that intraoperative ischemia would have minimal impact on conduction. Thirty patients scheduled for anterior transposition were enrolled after preoperative examination, electrodiagnostic testing, and ultrasound. Demographic and symptom severity data were recorded. A handheld biphasic nerve stimulator was used intraoperatively to assess minimum amplitude and pulse duration needed for muscle response. Measurements were taken at 15-minute intervals after placement. Changes in threshold amplitude and pulse duration were calculated between each 15-minute interval; no significant difference was found in the change of either value (p = 0.70 and 0.178). A weak negative correlation existed between preoperative CMAP amplitudes and average intraoperative pulse duration, which increased to a moderate correlation when compared to 45-minute pulse duration (r=-0.62, p<0.01). Preoperative ulnar nerve cross-sectional area (CSA) demonstrated no significant correlation with average pulse duration but a moderate correlation with pulse duration at 45 minutes (r=0.63, p=0.01). Tourniquet use did not prevent effective intraoperative stimulation of the ulnar nerve for at least 45 minutes. The window for meaningful stimulation with tourniquet usage appears to be greater than previously thought. Preoperative nerve CMAP amplitude and CSA does appear to influence pulse duration required after 45 minutes of ischemia, suggesting that injured nerves are more susceptible to ischemia. 1.

Comparison of Postoperative Muscle Strength Recovery Between Cisatracurium and Rocuronium.

Background Neuromuscular blocking agents are crucial for anesthesia but can cause reversible paralysis, leading to risks like postoperative residual dysfunction. Undetected paralysis in thepost-anesthesia care unit (PACU) jeopardizes patient safety by impairing airway function and increasing complications. Effective reversal, assessed clinically or via nerve stimulation, is critical to prevent residual postoperative curarization (RPOC), which is linked to significant morbidity and mortality. Evaluating agents like rocuronium and cisatracurium helps optimize anesthesia outcomes and patient recovery. Methodology The study included 100American Society of Anaesthesiologists (ASA) I and II patients approved by the Institutional Review Board of Kasturba Medical College, Mangalore, India. Patients were briefed about the study, provided written informed consent, and underwent pre-anesthetic evaluations, including discussions on anesthetic procedures and associated risks. They were instructed to fast overnight after consenting. Results The study compared 100 ASA I and II patients receiving rocuronium or cisatracurium during anesthesia, analyzing age distribution (p=0.429), gender (p=0.839), ASA status (p=0.228), and physical characteristics (height, weight, BMI, p>0.05). Recovery parameters such as hand grip, sustained head lift, and double burst stimulation (DBS) twitch response showed no significant differences between groups (p=0.538 for hand grip and sustained head lift; p=0.220 for DBS. Late recovery rates at 15 minutes were observed with 16% for hand grip, 14% for sustained head lift, and 26% for DBS in the rocuronium group; compared to 14%, 10%, and 16%, respectively, in the cisatracurium group. Conclusion The study found significant postoperative residual curarization in both groups, emphasizing the need for intraoperative and PACU peripheral nerve stimulation for effective assessment. Further research on intraoperative variables could improve understanding of residual paralysis in PACU, guiding better anesthesia management.

A New Surgical Option For Patients with Unresolved Bell's Palsy.

This paper describes a new surgical procedure with electrical stimulation of the facial nerve for unresolved Bell's palsy and compares the facial nerve recovery with another group who underwent traditional middle cranial fossa decompression. All patients with total unilateral facial paralysis had surgery by the senior author 3months from onset of Bell's Palsy. Surgical decompression was performed in 13 patients between 1992-2012 (Group 1). Surgical exposure with intraoperative electrical stimulation of the facial nerve in the peri-geniculate region was performed in 47 patients between 2012-2022 (Group 2). The facial recovery at 1month and 3month were significantly better in Group 2. The degree of synkinesis was significantly less in Group 2. The trans-mastoid electrical stimulation of the facial nerve is less invasive, requires no hospital stay, and less time off work compared to the middle cranial fossa approach. The earlier facial movement at one month results in less long-term unwanted faulty regeneration or synkinesis.

Human Cervical Epidural Spinal Electrogram Topographically Maps Distinct Volitional Movements.

Little is known about the electrophysiologic activity of the intact human spinal cord during volitional movement. We analyzed epidural spinal recordings from a total of five human subjects of both sexes during a variety of upper extremity movements and found that these spinal epidural electrograms contain spectral information distinguishing periods of movement, rest, and sensation. Cervical epidural electrograms also contained spectral changes time-locked with movement. We found that these changes were primarily associated with increased power in the theta (4-8 Hz) band and feature increased theta phase to gamma amplitude coupling, and this increase in theta power can be used to topographically map distinct upper extremity movements onto the cervical spinal cord in accordance with established myotome maps of the upper extremity. Our findings have implications for the development of neurostimulation protocols and devices focused on motor rehabilitation for the upper extremity, and the approach presented here may facilitate spatiotemporal mapping of naturalistic movements.

Evaluation of long-term results of single intraoperative electrical neurostimulation after autologous plastic surgery of a resection defect of the tibial portion of the sciatic nerve in adult rats

Introduction World literature data indicate the effectiveness of single intraoperative electrical stimulation (IES) of the proximal segment of the damaged nerve to stimulate its regeneration, but there is no data on its effect on the long-term results of autoplasty of resection defects.The purpose of the work was to evaluate the long-term results of a single IES after autologous plastic surgery of the tibial portion of the sciatic nerve in rats.Materials and methods Thirty rats after autologous repair of the resection defect of the tibial portion of the sciatic nerve were divided into series 1 (unstimulated control, n = 16) and series 2 (single IES for 40 minutes, n = 14). At 4 and 6 months after surgery, the static sciatic functional index (SFI) and morphometry of epoxy transverse semithin sections of the tibial nerve at the level of the middle third of the leg were assessed. For comparison with the normal values, the corresponding data from 7 intact rats were used.Results The number of animals with excellent results of SFI restoration was 12.5 % in series 1 and 50 % in series 2 (p = 0.05). The numerical density of regenerated myelinated fibers (MF) exceeded the norm: in series 1 — by 63 % (p &lt; 0.01) and 34 % (p &lt; 0.01), in series 2 — by 58 % (p &lt; 0.01) and 47 % (p &lt; 0.01), respectively. In series 2, there were greater values in comparison with series 1: the median diameters of MFs were by 11.7 % and 15.7 %, the median diameters of their axons were by 5.4 % and 11.9 %, the median thickness of the myelin sheath was by 17.0 % and 24.1 %, respectively (p &lt; 0.05 4 months and p &lt; 0.01 6 months after surgery). Four months after surgery in series 1 and 2, the numerical densities of endoneurial vessels exceeded the intact control by 134 % (p &lt; 0.05) and 156 % ( 0.05), their average diameters by 18 % and 16 % (p &lt; 0.01) respectively, and lumen diameters increased only in series 2 by 8 % (p = 0.07). After 6 months of the experiment in series 1 and 2, the numerical densities of microvessels decreased, but significantly exceeded the control by 66 % (p &lt; 0.05) and 83 % (p &lt; 0.05), the average diameters — by 14 % and 36 % (p &lt; 0.05), lumen diameters — by 26 % (p &lt; 0.05) and 50 % (p &lt; 0.01), respectively.Discussion The difference between stimulated and unstimulated animals in all MF size parameters 6 months after surgery was greater than after 4 months, indicating a persistent neuroregenerative effect.Conclusions A significant increase in the diameters of regenerating nerve fibers in the tibial nerve, as well as the diameters of their axons and the thickness of the myelinated sheaths 4 and 6 months after autoplasty of the tibial portion of the sciatic nerve in the group of animals with a single 40-minute IES of the proximal portion of the sciatic nerve indicates the promoting effect of the applied additive effect on regenerative axono- and myelinogenesis. Increase in the lumens and improvement of blood flow of the endoneurial vessels of the tibial nerve in the series with IES ensured the stability of the neuroregenerative effect. The functional significance of the effects of a single IES is confirmed by a significantly higher percentage of animals with excellent results in restoring the static functional index.

Resting State Functional Networks in Gliomas: Validation With Direct Electric Stimulation of a New Tool for Planning Brain Resections.

Precise mapping of functional networks in patients with brain tumor is essential for tailoring personalized treatment strategies. Resting-state functional MRI (rs-fMRI) offers an alternative to task-based fMRI, capable of capturing multiple networks within a single acquisition, without necessitating task engagement. This study demonstrates a strong concordance between preoperative rs-fMRI maps and the gold standard intraoperative direct electric stimulation (DES) mapping during awake surgery. We conducted an analysis involving 28 patients with glioma who underwent awake surgery with DES mapping. A total of 100 DES recordings were collected to map sensorimotor (SMN), language (LANG), visual (VIS), and speech articulation cognitive domains. Preoperative rs-fMRI maps were generated using an updated version of the ReStNeuMap software, specifically designed for rs-fMRI data preprocessing and automatic detection of 7 resting-state networks (SMN, LANG, VIS, speech articulation, default mode, frontoparietal, and visuospatial). To evaluate the agreement between these networks and those mapped with invasive cortical mapping, we computed patient-specific distances between them and intraoperative DES recordings. Automatically detected preoperative functional networks exhibited excellent agreement with intraoperative DES recordings. When we spatially compared DES points with their corresponding networks, we found that SMN, VIS, and speech articulatory DES points fell within the corresponding network (median distance = 0 mm), whereas for LANG a median distance of 1.6 mm was reported. Our findings show the remarkable consistency between key functional networks mapped noninvasively using presurgical rs-fMRI and invasive cortical mapping. This evidence highlights the utility of rs-fMRI for personalized presurgical planning, particularly in scenarios where awake surgery with DES is not feasible to protect eloquent areas during tumor resection. We have made the updated tool for automated functional network estimation publicly available, facilitating broader utilization of rs-fMRI mapping in various clinical contexts, including presurgical planning, functional reorganization over follow-up periods, and informing future treatments such as radiotherapy.

Probabilistic stimulation mapping from intra-operative thalamic deep brain stimulation data in essential tremor

Deep brain stimulation (DBS) is a therapy for Parkinson’s disease (PD) and essential tremor (ET). The mechanism of action of DBS is still incompletely understood. Retrospective group analysis of intra-operative data recorded from ET patients implanted in the ventral intermediate nucleus of the thalamus (Vim) is rare. Intra-operative stimulation tests generate rich data and their use in group analysis has not yet been explored. Objective. To implement, evaluate, and apply a group analysis workflow to generate probabilistic stimulation maps (PSMs) using intra-operative stimulation data from ET patients implanted in Vim. Approach. A group-specific anatomical template was constructed based on the magnetic resonance imaging scans of 6 ET patients and 13 PD patients. Intra-operative test data (total: n = 1821) from the 6 ET patients was analyzed: patient-specific electric field simulations together with tremor assessments obtained by a wrist-based acceleration sensor were transferred to this template. Occurrence and weighted mean maps were generated. Voxels associated with symptomatic response were identified through a linear mixed model approach to form a PSM. Improvements predicted by the PSM were compared to those clinically assessed. Finally, the PSM clusters were compared to those obtained in a multicenter study using data from chronic stimulation effects in ET. Main results. Regions responsible for improvement identified on the PSM were in the posterior sub-thalamic area (PSA) and at the border between the Vim and ventro-oral nucleus of the thalamus (VO). The comparison with literature revealed a center-to-center distance of less than 5 mm and an overlap score (Dice) of 0.4 between the significant clusters. Our workflow and intra-operative test data from 6 ET-Vim patients identified effective stimulation areas in PSA and around Vim and VO, affirming existing medical literature. Significance. This study supports the potential of probabilistic analysis of intra-operative stimulation test data to reveal DBS’s action mechanisms and to assist surgical planning.

Systematic Review Between Resting-State fMRI and Task fMRI in Planning for Brain Tumour Surgery.

As an alternative to task-based functional magnetic resonance imaging (T-fMRI), resting-state functional magnetic resonance imaging (Rs-fMRI) is suggested for preoperative mapping of patients with brain tumours, with an emphasis on treatment guidance and neurodegeneration prediction. A systematic review was conducted of 18 recent studies involving 1035 patients with brain tumours and Rs-fMRI protocols. This was accomplished by searching the electronic databases PubMed, Scopus, and Web of Science. For clinical benefit, we compared Rs-fMRI to standard T-fMRI and intraoperative direct cortical stimulation (DCS). The results of Rs-fMRI and T-fMRI were compared and their correlation with intraoperative DCS results was examined through a systematic review. Our exhaustive investigation demonstrated that Rs-fMRI is a dependable and sensitive preoperative mapping technique that detects neural networks in the brain with precision and identifies crucial functional regions in agreement with intraoperative DCS. Rs-fMRI comes in handy, especially in situations where T-fMRI proves to be difficult because of patient-specific factors. Additionally, our exhaustive investigation demonstrated that Rs-fMRI is a valuable tool in the preoperative screening and evaluation of brain tumours. Furthermore, its capability to assess brain function, forecast surgical results, and enhance decision-making may render it applicable in the clinical management of brain tumours.

Prognostic value Analysis of Intraoperative Transcranial Electrical Stimulation motor evoked Potential Monitoring in Postoperative limb Function changes of Neurosurgical Patient

Objective: To explore the predictive value of intraoperative transcranial electrical stimulation motor evoked potential (TES-MEP) monitoring for postoperative muscle strength change in patients undergoing craniocerebral surgery. Methods: In this study, 166 patients who underwent intraoperative motor evoked potential (MEP) monitoring were retrospectively analyzed. Univariate analysis and binary Logistic regression were used to analyze the influencing factors of postoperative muscle strength changes. Receiver operating characteristic (ROC) curve analysis was performed to evaluate the predictive value of abnormal changes of MEP amplitude in postoperative muscle strength changes. Results: Binary Logistic regression analysis showed that the abnormal amplitude of MEP during operation was an independent risk factor for short-term and long-term muscle strength decline after operation (P &lt; 0.05). ROC curve analysis showed that the area under the curve (AUC) for abnormal changes of MEP amplitude to predict short-term postoperative muscle strength decline was 0.754, with a sensitivity of 0.516, with a specificity of 0.993, and the AUC for long-term postoperative was 0.782, with a sensitivity of 0.591 and specificity of 0.972. Conclusions: The decrease of MEP amplitude more than 50% as a warning standard has a good predictive value for the change of limb function after operation, and the abnormal changes of MEP amplitude indicate that the muscle strength of patients after operation may be lower than that before operation.

Intraoperative transcutaneous electroacupoint stimulation on early postoperative fatigue in patients with Parkinson's disease undergoing deep brain stimulation surgery

BackgroundIn this clinical trial, we evaluated the effects of transcutaneous electroacupoint stimulation (TEAS) on postoperative fatigue (POF) in Parkinson disease (PD) patients undergoing deep brain stimulation (DBS) surgery. MethodsA total 60 PD patients undergoing DBS surgery were enrolled. They were randomized to receive either electrical stimulation [alternative frequency 2/10 Hz, dense and disperse, intensity adjusted to the maximum tolerated by the participants (6–15 mAmp)] via surface electrodes (TEAS group) or surface electrodes only without electrical stimulation (Con group) at bilateral Zusanli and Sanyinjiao acupuncture points. All participants received their assigned intervention (TEAS or Con) during the 1st stage of surgery [(except during microelectrode recording (MER)] and the entire 2nd stage of surgery. Intraoperative anesthetic requirements were adjusted based on bispectral index (BIS) monitor. POF was assessed by Christensen fatigue scales (ChrFS), along with Quality of Recovery-15 (QoR-15) and mini-mental state examination (MMSE) postoperatively over a 7-day-period. We recorded the usage of rescue analgesics and anti-emetics. ResultsFifty-nine patients’ datasets were included for final analyses. Fewer patients in TEAS experienced severe POF (defined as ChrFS ≥6) at T3 than those in the Con group (TEAS vs. Con: 7 vs. 22, p < 0.001). During the 1st stage of surgery, more patients in Con group required dexmedetomidine infusion (TEAS vs. Con: 2 vs. 6; P < 0.01). Total dosages of propofol and remifanil during the 2nd stage of surgery were TEAS vs. Con: 374.7 ± 61.2 vs 421.5 ± 81.9; p < 0.001 and 572.3 ± 82.0 vs. 662 ± 148.2; P < 0.001, respectively. Postoperative rescue analgesics (TEAS vs. Con: 2 vs. 6; P < 0.001) were used less in the TEAS group. TEAS patients reported better POF, MMSE and QoR15 scores than those in the Con group during most of the assessment period. ConclusionsIntraoperative TEAS decreased the severity of POF, reduced intraoperative anesthetic requirements and facilitated post-DBS recovery in this group of PD patients.

Comparative validation of automated presurgical tractography based on constrained spherical deconvolution and diffusion tensor imaging with direct electrical stimulation.

Accurate presurgical brain mapping enables preoperative risk assessment and intraoperative guidance. This cross-sectional study investigated whether constrained spherical deconvolution (CSD) methods were more accurate than diffusion tensor imaging (DTI)-based methods for presurgical white matter mapping using intraoperative direct electrical stimulation (DES) as the ground truth. Five different tractography methods were compared (three DTI-based and two CSD-based) in 22 preoperative neurosurgical patients undergoing surgery with DES mapping. The corticospinal tract (CST, N = 20) and arcuate fasciculus (AF, N = 7) bundles were reconstructed, then minimum distances between tractograms and DES coordinates were compared between tractography methods. Receiver-operating characteristic (ROC) curves were used for both bundles. For the CST, binary agreement, linear modeling, and posthoc testing were used to compare tractography methods while correcting for relative lesion and bundle volumes. Distance measures between 154 positive (functional response, pDES) and negative (no response, nDES) coordinates, and 134 tractograms resulted in 860 data points. Higher agreement was found between pDES coordinates and CSD-based compared to DTI-based tractograms. ROC curves showed overall higher sensitivity at shorter distance cutoffs for CSD (8.5 mm) compared to DTI (14.5 mm). CSD-based CST tractograms showed significantly higher agreement with pDES, which was confirmed by linear modeling and posthoc tests (PFWE < .05). CSD-based CST tractograms were more accurate than DTI-based ones when validated using DES-based assessment of motor and sensory function. This demonstrates the potential benefits of structural mapping using CSD in clinical practice.

Motor or non-motor speech interference? A multimodal fMRI and direct cortical stimulation mapping study

We retrospectively analyzed data from 15 patients, with a normal pre-operative cognitive performance, undergoing awake surgery for left fronto-temporal low-grade glioma. We combined a pre-surgical measure (fMRI maps of motor- and language-related centers) with intra-surgical measures (MNI-registered cortical sites data obtained during intra-operative direct electrical stimulation, DES, while they performed the two most common language tasks: number counting and picture naming).Selective DES effects along the precentral gyrus/inferior frontal gyrus (and/or the connected speech articulation network) were obtained. DES of the precentral gyrus evoked the motor speech arrest, i.e., anarthria (with apparent mentalis muscle movements). We calculated the number of shared voxels between the lip-tongue and overt counting related- and silent naming-related fMRI maps and the Volumes of Interest (VOIs) obtained by merging together the MNI sites at which a given speech disturbance was observed, normalized on their mean the values (i.e., Z score). Both tongue- and lips-related movements fMRI maps maximally overlapped (Z = 1.05 and Z = 0.94 for lips and tongue vs. 0.16 and −1.003 for counting and naming) with the motor speech arrest seed. DES of the inferior frontal gyrus, pars opercularis and the rolandic operculum induced speech arrest proper (without apparent mentalis muscle movements). This area maximally overlapped with overt counting-related fMRI map (Z = −0.11 and Z = 0.09 for lips and tongue vs. 0.9 and 0.0006 for counting and naming). Interestingly, our fMRI maps indicated reduced Broca's area activity during silent speech compared to overt speech. Lastly, DES of the inferior frontal gyrus, pars opercularis and triangularis evoked variations of the output, i.e., dysarthria, a motor speech disorder occurring when patients cannot control the muscles used to produce articulated sounds (phonemes). Silent object naming-related fMRI map maximally overlapped (Z = −0.93 and Z = −1.04 for lips and tongue vs. −1.07 and 0.99 for counting and naming) with this seed.Speech disturbances evoked by DES may be thought of as selective interferences with specific recruitment of left inferior frontal gyrus and precentral cortex which are differentiable in terms of the specific interference induced.

Analyzing the Effect of Intraoperative Stimulation Voltage on Facial Numbness Following Radiofrequency Thermocoagulation in the Treatment of Idiopathic Trigeminal Neuralgia.

Radiofrequency thermocoagulation (RFT) effectively alleviates idiopathic trigeminal neuralgia (ITN); however, postoperative facial numbness poses a significant challenge. This issue arises due to the close proximity of high-temperature thermocoagulation, which not only ablates pain-related nociceptive fibers but also affects tactile fibers. Intraoperative sensory stimulation voltage (SV), which reflects the distance between the RFT cannula and the target nerve, potentially possesses the ability to prevent tactile fiber injury. This study aimed to investigate the influence of SV on postoperative facial numbness and provide valuable insights to mitigate its occurrence. A retrospective analysis was performed on 72 ITN patients with maxillary division (V2) pain who underwent RFT between 2020 and 2022. Among them, 13 patients with SV ≤ 0.2V constituted the low SV group. Subsequently, a matched-cohort analysis was conducted on the remaining 59 patients. The patients paired with the low SV patients were subsequently enrolled in the high SV group, adhering to a 1:1 match ratio. The primary outcome was the facial numbness scale assessment at 3days, 3months and 6months post-surgery. The pain intensity and medication burden served as the secondary outcomes. We successfully matched a cohort consisting of 12 patients in the low SV group and 12 patients in the high SV group. Each patient experienced various degrees of facial numbness at 3days post-RFT. Notably, the low SV group exhibited a higher incidence of moderate numbness (66.7% vs. 16.67%, P = 0.036), whereas the high SV group had more cases of mild numbness at the 6-month follow-up (25% vs. 83.3%, P = 0.012). Both groups demonstrated significant decreases in pain intensity and medication burden compared to before the operation. SV proved to be a reliable parameter for mitigating the degree of postoperative facial numbness in RFT treatment for ITN. A relatively high sensory SV ranging from 0.3 to 0.6V during the RFT procedure results in less facial numbness in the treatment of ITN.

Intraoperative Isoflurane End-Tidal Concentration during Infusion of Fentanyl, Tramadol, or Fentanyl-Tramadol Combination in Cats.

The aim of this study was to evaluate the end-tidal concentration of isoflurane required, clinical parameters, intraoperative antinociceptive effect, and postoperative analgesia in cats undergoing ovariohysterectomy, receiving fentanyl, tramadol, or fentanyl/tramadol. Sixty-six cats in three groups, were premedicated with dexmedetomidine and infused with one of the following treatments: fentanyl, tramadol, or fentanyl/tramadol combination. Anesthesia was induced with alfaxolone and maintained with isoflurane, titrated to keep heart rate, respiratory rate and systolic arterial pressure within target values recorded at endotracheal intubation. An intraoperative cumulative scale was performed. Postoperatively, a short form of the Glasgow Composite Measure Pain Scale Feline was used at 2, 12, and 24 h. The groups were similar for age, weight, dose of dexmedetomidine, and alfaxalone administered. A greater reduction in the end-tidal isoflurane fraction was observed with the combined fentanyl/tramadol infusion than with either fentanyl or tramadol alone. No differences in the end-tidal isoflurane fraction were found between fentanyl or tramadol alone. Hemodynamic stability associated with minimal cardiopulmonary changes, low response to noxious intraoperative stimulation, and low postoperative pain scores were also observed with the fentanyl/tramadol combination. The fentanyl/tramadol combination provided a reduction in the end-tidal isoflurane fraction compared with fentanyl or tramadol alone.

Three Useful Tips and Tricks for Intraoperative Nerve Stimulation.

Disposable handheld nerve stimulators are widely used in peripheral nerve surgery. Such devices stimulate a motor nerve or the motor component of a mixed nerve by applying electrical current to the proximal region, targeting the main nerve trunk. This stimulation then travels along the motor nerve, reaching the distal end to control the corresponding muscle(s). In this study, the authors demonstrate three useful tips and tricks for handheld nerve stimulation during targeted muscle reinnervation and peripheral nerve surgery. The three tips are (1) identification of proximal muscle contraction by retrograde electrical stimulation of a distal sensory nerve; (2) graded stimulation for identifying motor nerves within fibrotic scarred tissue beds or parallel to the major motor/mixed nerve of interest; and (3) proximal stimulation for validation of adequate post-targeted muscle reinnervation coaptation(s).

Active recharge biphasic stimulation for the intraoperative monopolar review in deep brain stimulation.

Charge balancing is used in deep brain stimulation (DBS) to avoid net charge accumulation at the tissue-electrode interface that can result in neural damage. Charge balancing paradigms include passive recharge and active recharge. In passive recharge, each cathodic pulse is accompanied by a waiting period before the next stimulation, whereas active recharge uses energy to deliver symmetric anodic and cathodic stimulation pulses sequentially, producing a net zero charge. We sought to determine differences in stimulation induced side effect thresholds between active vs. passive recharge during the intraoperative monopolar review. Sixty-five consecutive patients undergoing DBS from 2021 to 2022 were retrospectively reviewed. Intraoperative monopolar review was performed with both active recharge and passive recharge for all included patients to determine side effect stimulation thresholds. Sixteen patients with 64 total DBS contacts met inclusion criteria for further analysis. Intraoperative monopolar review results were compared with the monopolar review from the first DBS programming visit. The mean intraoperative active recharge stimulation threshold was 4.1 mA, while the mean intraoperative passive recharge stimulation threshold was 3.9 mA, though this difference was not statistically significant on t-test (p = 0.442). Mean stimulation threshold at clinic follow-up was 3.2 mA. In Pearson correlation, intraoperative passive recharge thresholds had stronger correlation with follow-up stimulation thresholds (Pearson r = 0.5281, p < 0.001) than intraoperative active recharge (Pearson r = 0.340, p = 0.018), however the difference between these correlations was not statistically significant on Fisher Z correlation test (p = 0.294). The mean difference between intraoperative passive recharge stimulation threshold and follow-up stimulation threshold was 0.8 mA, while the mean difference between intraoperative active recharge threshold and follow-up threshold was 1.2 mA. This difference was not statistically significant on a t-test (p = 0.134). Both intraoperative active recharge and passive recharge stimulation were well-correlated with the monopolar review at the first programming visit. No statistically significant differences were observed suggesting that either passive or active recharge may be utilized intraoperatively.

Adult traumatic brachial plexus injuries: advances and current updates.

Nerve grafting, tendon transfer and joint fusion are routinely used to improve the upper limb function in patients with brachial plexus palsies. Newer techniques have been developed that provide additional options for reconstruction. Nerve transfer is a tool for restoring upper limb function in total root avulsions where nerve grafting is not possible. In partial brachial plexus injuries, nerve transfers can greatly improve shoulder, elbow, wrist and hand function. Intraoperative electrical stimulation can be used to diagnose precisely which nerve is injured and to choose which nerve fascicles should be transferred. Finally, measuring the postoperative outcome can improve the evaluation of our techniques. The aim of this article was to present the current techniques used to treat patients with brachial plexus injury.

Bifurcation of the Radial Nerve in the Arm as a Cause of Traumatic Partial Nerve Palsy: A Case Report

Purpose: To describe the case of a traumatic partial nerve palsy following an open crushing arm injury. The partial palsy was due to the presence of radial nerve bifurcation in the proximal arm. Methods: A 23-year-old male was involved in a motor vehicle accident, where his motorbike crushed against a steel road divider sustaining multiple injuries in the spine, thorax, and right arm. On clinical examination, the patient presented a deep, blunt trauma on the posterior aspect of the proximal arm and partial radial nerve palsy was diagnosed with preservation of the brachioradialis and the extensor radialis longus muscle function. Surgical exploration was carried out. Results: An extensible posterior approach to the arm was performed and two main radial nerve branches were found. The lateral, more sizeable nerve, had an epineural hematoma without any distal response during intraoperative stimulation. The medial, thinner nerve trunk was preserved and, when stimulated, elicited response from the brachioradialis. Conclusion: We describe an uncommon variation of the radial nerve which was associated with partial palsy following blunt force trauma. This anatomical variation should be kept in mind in cases like the one described.