Somatosensory Potentials Research Articles

Large Postural Sways Prevent Foot Tactile Information From Fading: Neurophysiological Evidence.

Cutaneous foot receptors are important for balance control, and their activation during quiet standing depends on the speed and the amplitude of postural oscillations. We hypothesized that the transmission of cutaneous input to the cortex is reduced during prolonged small postural sways due to receptor adaptation during continued skin compression. Central mechanisms would trigger large sways to reactivate the receptors. We compared the amplitude of positive and negative post-stimulation peaks (P50N90) somatosensory cortical potentials evoked by the electrical stimulation of the foot sole during small and large sways in 16 young adults standing still with their eyes closed. We observed greater P50N90 amplitudes during large sways compared with small sways consistent with increased cutaneous transmission during large sways. Postural oscillations computed 200 ms before large sways had smaller amplitudes than those before small sways, providing sustained compression within a small foot sole area. Cortical source analyses revealed that during this interval, the activity of the somatosensory areas decreased, whereas the activity of cortical areas engaged in motor planning (supplementary motor area, dorsolateral prefrontal cortex) increased. We concluded that large sways during quiet standing represent self-generated functional behavior aiming at releasing skin compression to reactivate mechanoreceptors. Such balance motor commands create sensory reafference that help control postural sway.

Utility of somatosensory and motor-evoked potentials in reflecting gross and fine motor functions after unilateral cervical spinal cord contusion injury.

Fine motor skills are thought to rely on the integrity of ascending sensory pathways in the spinal dorsal column as well as descending motor pathways that have a neocortical origin. However, the neurophysiological processes underlying communication between the somatosensory and motor pathways that regulate fine motor skills during spontaneous recovery after spinal cord contusion injury remain unclear. Here, we established a rat model of cervical hemicontusive injury using C5 laminectomy followed by contusional displacement of 1.2 mm (mild injury) or 2.0 mm (severe injury) to the C5 spinal cord. Electrophysiological recordings were performed on the brachial muscles up to 12 weeks after injury to investigate the mechanisms by which spinal cord pathways participate in motor function. After spinal cord contusion injury, the amplitudes of somatosensory and motor-evoked potentials were reduced, and the latencies were increased. The forelimb open field locomotion test, grooming test, rearing test and Montoya staircase test revealed improvement in functions. With increasing time after injury, the amplitudes of somatosensory and motor-evoked potentials in rats with mild spinal cord injury increased gradually, and the latencies gradually shortened. In comparison, the recovery times of somatosensory and motor-evoked potential amplitudes and latencies were longer, and the recovery of motor function was delayed in rats with severe spinal cord injury. Correlation analysis revealed that somatosensory-evoked potential and motor-evoked potential parameters were correlated with gross and fine motor function in rats with mild spinal cord contusion injury. In contrast, only somatosensory-evoked potential amplitude was correlated with fine motor skills in rats with severe spinal cord injury. Our results show that changes in both somatosensory and motor-evoked potentials can reflect the changes in gross and fine motor functions after mild spinal cord contusion injury, and that the change in somatosensory-evoked potential amplitude can also reflect the change in fine motor function after severe spinal cord contusion injury. This study was approved by the Animal Ethics Committee of Nanfang Hospital, Southern Medical University, China (approval No. NFYY-2017-67) on June 11, 2017.

Peripheral input and phantom limb pain: A somatosensory event-related potential study.

Following amputation, nearly all amputees report nonpainful phantom phenomena and many of them suffer from chronic phantom limb pain (PLP) and residual limb pain (RLP). The aetiology of PLP remains elusive and there is an ongoing debate on the role of peripheral and central mechanisms. Few studies have examined the entire somatosensory pathway from the truncated nerves to the cortex in amputees with PLP compared to those without PLP. The relationship among afferent input, somatosensory responses and the change in PLP remains unclear. Transcutaneous electrical nerve stimulation was applied on the truncated median nerve, the skin of the residual limb and the contralateral homologous nerve in 22 traumatic upper-limb amputees (12 with and 10 without PLP). Using somatosensory event-related potentials, the ascending volley was monitored from the brachial plexus, the spinal cord, the brainstem and the thalamus to the primary somatosensory cortex. Peripheral input could evoke PLP in amputees with chronic PLP (7/12), but not in amputees without a history of PLP (0/10). The amplitudes of the somatosensory components were comparable between amputees with and without PLP. In addition, evoked potentials from the periphery through the spinal, subcortical and cortical segments were not significantly associated with PLP. Peripheral input can modulate PLP but seems insufficient to cause PLP. These findings suggest the multifactorial complexity of PLP and different mechanisms for PLP and RLP. Peripheral afferent input plays a role in PLP and has been assumed to be sufficient to generate PLP. In this study we found no significant differences in the electrical potentials generated by peripheral stimulation from the truncated nerve and the skin of the residual limb in amputees with and without PLP. Peripheral input could enhance existing PLP but could not cause it. These findings indicate the multifactorial complexity of PLP and an important role of central processes in PLP.

Changes of orofacial somatosensory attenuation during speech production

Modulation of auditory activity occurs before and during voluntary speech movement. However, it is unknown whether orofacial somatosensory input is modulated in the same manner. The current study examined whether or not the somatosensory event-related potentials (ERPs) in response to facial skin stretch are changed during speech and nonspeech production tasks. Specifically, we compared ERP changes to somatosensory stimulation for different orofacial postures and speech utterances. Participants produced three different vowel sounds (voicing) or non-speech oral tasks in which participants maintained a similar posture without voicing. ERP’s were recorded from 64 scalp sites in response to the somatosensory stimulation under six task conditions (three vowels × voicing/posture) and compared to a resting baseline condition. The first negative peak for the vowel /u/ was reliably reduced from the baseline in both the voicing and posturing tasks, but the other conditions did not differ. The second positive peak was reduced for all voicing tasks compared to the posturing tasks. The results suggest that the sensitivity of somatosensory ERP to facial skin deformation is modulated by the task and that somatosensory processing during speaking may be modulated differently relative to phonetic identity.

Maintaining the permanence principle for death during in situ normothermic regional perfusion for donation after circulatory death organ recovery: A United Kingdom and Canadian proposal.

There is international variability in the determination of death. Death in donation after circulatory death (DCD) can be defined by the permanent cessation of brain circulation. Post‐mortem interventions that restore brain perfusion should be prohibited as they invalidate the diagnosis of death. Retrieval teams should develop protocols that ensure the continued absence of brain perfusion during DCD organ recovery. In situ normothermic regional perfusion (NRP) or restarting the heart in the donor's body may interrupt the permanent cessation of brain perfusion because, theoretically, collateral circulations may restore it. We propose refinements to current protocols to monitor and exclude brain reperfusion during in situ NRP. In abdominal NRP, complete occlusion of the descending aorta prevents brain perfusion in most cases. Inserting a cannula in the ascending aorta identifies inadequate occlusion of the descending aorta or any collateral flow and diverts flow away from the brain. In thoracoabdominal NRP opening the aortic arch vessels to atmosphere allows collateral flow to be diverted away from the brain, maintaining the permanence standard for death and respecting the dead donor rule. We propose that these hypotheses are correct when using techniques that simultaneously occlude the descending aorta and open the aortic arch vessels to atmosphere.

Neurophysiological parameters of sensory perception and cognition among different modalities of learners.

INTRODUCTION:Different types of learners based on sensory modalities are observed. Cognition or physiological alterations in the sensory pathways might play its role in different modalities of visual, auditory, read and write, and kinesthetic learners which are based on different sensory modalities of perceptionOBJECTIVE:The objective of this study is to ascertain an objective parameter (neurophysiological parameters) for the classification of learners based on their preferred sensory modalityMATERIALS AND METHODS:An experimental cross-sectional study was conducted among 100 medical students. Learners were classified into visual, auditory, read-write, and kinesthetic learners based on the interpretation drawn on the basis of the VARK questionnaire. Sensory-evoked potentials (SEPs), including pattern shift visual (PSVEPs), brain stem auditory (BAEPs), short-latency somatosensory (SSEP), and event-related potentials (P300) were measured. SEPs measured in microvolts were recorded from the scalp with the help of active and reference electrodes. Multiple responses to sensory stimuli (using NIHON KOHDEN Corporation Neuropack X1, Tokyo, Japan) were recored and averaged using the computerized signal averging technique.RESULTS:No statistically significant difference was observed in conduction velocities (in terms of latency and amplitude) of SEP among different type of learners, except latency N145 wave form in VEP (P < 0.05). A characteristic pattern of minimal comparative latency was observed among the majority of visual learners. Similary, P300 has shown a characteristic pattern of decreased comparative latency among majority of read and write learners.CONCLUSION:Study findings suggested that among existing teaching and learning modalities, visual modalities were observed faster but to retain it in memory and for abstract thinking, students should utilize read and writing skills which are lacking in the era of digitalization and overuse of electronic devices.

Large body sways help maintaining balance by increasing the transmission of cutaneous input following prolonged periods of reduced body oscillations: EEG, microneurography and behavioral evidence

Introduction Important for balance control, the activation of the cutaneous foot receptors largely depends on the speed and amplitude of the body oscillations during standing. Material and methods Here, we tested the hypothesis that the transmission of cutaneous inputs to the cortex is reduced during prolonged intervals of small body sways due to continued local skin compression and that under such circumstances, central mechanisms trigger large sways to reactivate the cutaneous receptors. We compared the amplitude of the somatosensory cortical potentials (P50-N90) evoked by electric stimulations of the foot sole during either small or large sways in 16 adults that were standing still with the eyes closed. Results We found greater P50-N90 amplitude when the stimulation occurred during large body sways, consistent with an increased sensory transmission. Importantly, body oscillations computed 200 ms prior to large sways had smaller amplitude than intervals that were not followed by large sways. Discussion The hypothesis of a depressed sensory transmission during continued skin compression was supported by our microneurographic recordings showing adaptation/suppression of tactile fibres discharge during continuous pressure applied to the mechanoreceptors. Finally, the hypothesis that large sways during standing correspond to a self-generated functional behaviour to release skin compression is supported by cortical source and EMG analyses showing respectively that large sways were preceded by activation of cortical areas known to be engaged in motor planning (supplementary motor area and dorsolateral prefrontal cortex) and by ankle muscle activations. Together, the present findings provide evidence for an important sensory function of large body sways for balance control.

Characterization of multi-channel intraneural stimulation in transradial amputees

Although peripheral nerve stimulation using intraneural electrodes has been shown to be an effective and reliable solution to restore sensory feedback after hand loss, there have been no reports on the characterization of multi-channel stimulation. A deeper understanding of how the simultaneous stimulation of multiple electrode channels affects the evoked sensations should help in improving the definition of encoding strategies for bidirectional prostheses. We characterized the sensations evoked by simultaneous stimulation of median and ulnar nerves (multi-channel configuration) in four transradial amputees who had been implanted with four TIMEs (Transverse Intrafascicular Multichannel Electrodes). The results were compared with the characterization of single-channel stimulation. The sensations were characterized in terms of location, extent, type, and intensity. Combining two or more single-channel configurations caused a linear combination of the sensation locations and types perceived with such single-channel stimulations. Interestingly, this was also true when two active sites from the same nerve were stimulated. When stimulating in multi-channel configuration, the charge needed from each electrode channel to evoke a sensation was significantly lower than the one needed in single-channel configuration (sensory facilitation). This result was also supported by electroencephalography (EEG) recordings during nerve stimulation. Somatosensory potentials evoked by multi-channel stimulation confirmed that sensations in the amputated hand were perceived by the subjects and that a perceptual sensory facilitation occurred. Our results should help the future development of more efficient bidirectional prostheses by providing guidelines for the development of more complex stimulation approaches to effectively restore multiple sensations at the same time.

Central Neuropathic Pain and Complex Regional Pain Syndrome Following Brachial Plexus Injury Treated Successfully With Dorsal Root Entry Zone Lesioning

Abstract INTRODUCTION Central neuropathic pain (CNP) and complex regional pain syndrome (CRPS) present as chronic, unrelenting, and disabling pain resulting from central and peripheral nervous system injuries. For patients who have failed conservative management, dorsal root entry zone (DREZ) lesioning may serve as an alternative for the management of intractable pain. METHODS A 36-yr-old male presented with complete right brachial plexus injury and avulsion of nerve roots following a motorcycle accident. He developed disabling type I CRPS of the right upper extremity. After failing medical therapy, he underwent a trial of conventional SCS using 2 percutaneous leads in the upper cervical spine but did not get topographical coverage. He underwent a second SCS trial with the placement of a paddle lead using burst therapy, but his initial partial pain relief subsided after 3 d. Subsequently, he underwent SCS removal, C2 to T1 right DREZ lesioning, and C4 to T1 laminoplasty. The patient gained a significant pain relief and became more functional. Five months postoperatively, he experienced an improvement in his pain and narcotic consumption. RESULTS Using an insulated neurotomy electrode, 2-mm-deep lesions were made at 75°C for 15 s. A total of 83 lesions were made from T2 to C3. Each lesion was spaced 1 mm apart. The impedance was less than 1000 ohms, which was consistent within an area of injury. Somatosensory and motor-evoked potentials were at baseline during the case without significant changes. CONCLUSION When SCS fails, lesioning of the dorsal root entry zone is a useful tool in the armamentarium for the management of refractory brachial plexus neuropathic pain.

Dunn’s Model of Sensory Processing: An Investigation of the Axes of the Four-Quadrant Model in Healthy Adults

Abstract Date Presented 04/05/19 We examined the constructs of behavioral response and threshold of Dunn’s four-quadrant model of sensory processing. We tested if these axes, as measured by the Adult and Adolescent Sensory Profile, are ordinal ranges and if variation is consistent with external measures of characteristics that may also reflect sensory processing, Eysenck's personality model, and somatosensory event-related potentials and sensory gating. Primary Author and Speaker: Alexia Metz Contributing Authors: Daniella Boling, Ashley DeVore, Holly Holladay, Karen Karmol, Jo Fu Liao

P14-S Latency of Mismatch Negativity as a predictor of outcome in critically patients with subarachnoid haemorrhage

Background Multimodal neurophysiological markers support clinical assessments in individuals with disorders of consciousness (DoC). Few studies focused on subarachnoid haemorrhage (SAH) related coma. Furthermore, these patients often need sedation during the acute phase, making behavioral and neurophysiological monitoring challenging. We investigated which neurophysiological marker could better predict outcome in acute DoC related to SAH. Methods We studied 14 SAH patients admitted in the Sainte Anne hospital neurological ICU, between Oct 2017 and June 2018. All patients underwent within the first 72 h: clinical evaluation, EEG and multimodal evoked potentials (somatosensory potentials, brainstem auditory evoked potentials (BAEPs), late latency event-related potentials, N100 and mismatch negativity (MMN)). Quantitative EEG analysis using spectral and connectivity analysis was performed. According to the Glascow Outcome scale (GOS), we defined two clinical outcome groups: favorable (F) and unfavorable (UF). Results Clinical examination, EEG visual and quantitative analysis, presence of N20, BAEP, N100 and MMN were not significantly different in the two groups. However, mean latencies of N100 (F = 80 ms; UF = 106 ms;) and of MMN (F = 139 ms; UF = 197msec) were significantly different in the two groups (Mann Whitney test, respectively p = 0.017 and p = 0.035). Conclusions This study suggests that during the acute phase, in sedated patients with DoC related to SAH, latencies of N100 and latencies of MMN could be more discriminatory than the “classical” interpretation of these markers (present/absent) and the EEG analysis, in term of prognosis. These results need to be confirmed in a larger study.

Fast Intracortical Sensory-Motor Integration: A Window Into the Pathophysiology of Parkinson's Disease.

Parkinson’s Disease (PD) is a prototypical basal ganglia disorder. Nigrostriatal dopaminergic denervation leads to progressive dysfunction of the cortico-basal ganglia-thalamo-cortical sensorimotor loops, causing the classical motor symptoms. Although the basal ganglia do not receive direct sensory input, they are important for sensorimotor integration. Therefore, the basal ganglia dysfunction in PD may profoundly affect sensory-motor interaction in the cortex. Cortical sensorimotor integration can be probed with transcranial magnetic stimulation (TMS) using a well-established conditioning-test paradigm, called short-latency afferent inhibition (SAI). SAI probes the fast-inhibitory effect of a conditioning peripheral electrical stimulus on the motor response evoked by a TMS test pulse given to the contralateral primary motor cortex (M1). Since SAI occurs at latencies that match the peaks of early cortical somatosensory potentials, the cortical circuitry generating SAI may play an important role in rapid online adjustments of cortical motor output to changes in somatosensory inputs. Here we review the existing studies that have used SAI to examine how PD affects fast cortical sensory-motor integration. Studies of SAI in PD have yielded variable results, showing reduced, normal or even enhanced levels of SAI. This variability may be attributed to the fact that the strength of SAI is influenced by several factors, such as differences in dopaminergic treatment or the clinical phenotype of PD. Inter-individual differences in the expression of SAI has been shown to scale with individual motor impairment as revealed by UPDRS motor score and thus, may reflect the magnitude of dopaminergic neurodegeneration. The magnitude of SAI has also been linked to cognitive dysfunction, and it has been suggested that SAI also reflects cholinergic denervation at the cortical level. Together, the results indicate that SAI is a useful marker of disease-related alterations in fast cortical sensory-motor integration driven by subcortical changes in the dopaminergic and cholinergic system. Since a multitude of neurobiological factors contribute to the magnitude of inhibition, any mechanistic interpretation of SAI changes in PD needs to consider the group characteristics in terms of phenotypical spectrum, disease stage, and medication.

Dunn's Model of Sensory Processing: An Investigation of the Axes of the Four-Quadrant Model in Healthy Adults.

We examined the behavioral response (BR) and threshold (T) axes of Dunn’s four-quadrant model of sensory processing (1997). We assessed whether they are ordinal ranges and if variation is associated with other similarly described characteristics: Introversion/Extraversion (I/E) of Eysenck’s personality model (Sato, 2005), and somatosensory event related potentials (SERP) and their gating (Davies & Gavin, 2007). From healthy adults (n = 139), we obtained: Adult/Adolescent Profile (A/ASP, Brown & Dunn, 2002) and Eysenck’s Personality Questionnaire, Brief Version (Sato, 2005) scores and peak amplitude and gating factor of SERP P50. We found that BR scores did not differ across normative categories of the A/ASP, but T scores significantly increased along the axis. I/E scores did not vary with BR scores. There were no differences or correlations in P50 amplitudes and gating with T scores. The findings suggest that the BR axis may not reflect a construct with ordinal range, but the T axis may. Dunn’s concept of BR appears to be distinct from Eysenck’s concept of I/E. SERP and its gating may not be directly reflective of sensory processing thresholds in healthy adults. Conclusions are limited by having few participants with passive behavior regulation or low threshold patterns of processing.

Friction in Passive Tactile Perception Induces Phase Coherency in Late Somatosensory Single Trial Sequences.

Event related potentials represent a noninvasive means for studying sensory and cognitive processes that occur in response to particular stimuli. Here, we report on a phase measure for estimating single trial interaction of late somatosensory potentials (LSPs) following a tribological well defined mechanical stimulation of the human fingertip. Stimuli are presented via a programmable Braille-display with actively switchable pins which was slid along the apex of the passive fingertip, i.e., the fingertip rested stationarily in a finger holding system with circular opening at the bottom. The event was the raising and the lowering of either one, three, or five lines of pins. Differences were identified by measures based on instantaneous phase synchronization to the stimuli across trials, in particular the wavelet phase synchronization stability (WPSS) measure for single trial sequences of LSPs. In particular, we show that the higher the friction the stronger and more localized the induced phase coherency is. We concluded that the WPSS analysis of single sequences of LSPs represents a reliable method which allows for the quantification of brain responses upon distinct tactile stimuli.

Effects of white noise duration on somatosensory event-related potentials.

Exposure to auditory white noise has been shown to facilitate cognitive function. This phenomenon is called stochastic resonance. The present study examined the effects of white noise duration on behavioral data [reaction time (RT), the SD of RT, and error rates] and the N140 and P300 components of event-related potentials in somatosensory Go/No-go paradigms. A Go or No-go stimulus was presented to the second or fifth digit of the left hand, respectively, at the same probability. Before recording event-related potentials, participants heard three different white noise durations (1, 3, and 5-min conditions), and performed somatosensory Go/No-go paradigms while listening to white noise. RT was significantly shorter under the 5 and 3-min conditions than under the 1-min condition, whereas SD of RT and error rates remained unchanged. The peak latency of Go-P300 was the shortest under the 5-min condition. White noise did not affect the peak latency of N140 or the peak amplitude of N140 or P300. Our results suggest that 5-min white noise exposure accelerated RT and the latency of Go-P300, reflecting changes in the neural activation of response execution processing.

The influence of the dynamics and the level of maturity of the cortical functions as a prerequisite for the development of speech in children

Introduction/Objective. The development of speech is the result of interaction of different systems of the cortex, which gradually acquires the ability of phonological presentation and motor control, in the presence of a series of physical and physiological changes in the morphology of the articulation system. The objective of the study was to examine the impact of laterality and cortical responses on the development of speech in children. Methods. Research is a quasi-experimental design with two groups. The sample covered 60 children from Belgrade, of both sexes, ages 5.5?7 years, divided into two groups, experimental (30) and control (30). We used the following instruments: test for assessing laterality and ascertaining evoked potentials. Results. On the visual lateralization subtest there was a statistically significant difference (?2 = 7.56, p &lt; 0.05) between the observed groups. The visual evoked potentials on all measured parameters gave a statistically significant difference between the groups: waveform cortical responses ? left (?2 = 30.00, df = 1, p &lt; 0.05); cortical responses ? right (?2 = 6.667, df = 1 , p &lt; 0.05); waveform amplitude ? left (?2 = 13.469, df = 1, p &lt; 0.05); amplitude ? right (?2 = 40.00, df = 1, p &lt; 0.05), somatosensory potentials (?2 = 18.261, df = 1, p &lt;0.05); waveform amplitude (?2 = 12.000, df = 1, p &lt; 0.05); waveform latency (?2 = 5.455, df = 1, p &lt; 0.05). Conclusion. Visual laterality, as well as visual and somatosensory cortical responses to stimuli is better in children without the present articulation disorder, which could be used for timely prevention planning.

Cord Splitting Access to Ventral Intradural Cysts of Cervicothoracic Junction and Thoracic Spine

Surgical treatment of ventrally located intradural cysts is difficult and controversial. Laminectomy with division of the denticulate ligaments and gentle cord mobilization remains the standard approach but risks further neurologic deterioration secondary to cord manipulation. Our purpose is to evaluate the safety and effectiveness of a midline cord-splitting approach as an alternative for treating ventral thoracic intradural cysts. We describe 2 patients who were treated for ventral intradural cysts causing progressive and severe myelopathy. Under general anesthesia and continuous neurophysiologic monitoring, laminectomy, durotomy, and cord splitting through a midline approach gave direct access to both lesions. Cyst drainage was supplemented by a cystopleural shunt in 1 case. Cyst collapse and cord reexpansion were documented in both patients with a magnetic resonance imaging scan 1 week after surgery. In both cases there was a significant neurologic improvement, which was maintained 2 years postoperatively. Intraoperative monitoring recorded no loss of somatosensory or motor potentials during surgery. Follow-up magnetic resonance imaging scans 2 years postoperatively showed no evidence of cyst recurrence, and both patients remained neurologically improved and stable. We have been able to drain 2 ventral intradural cysts using a cord-splitting technique. This has allowed safe access to purely ventrally located lesions, which were inaccessible dorsally or dorsolaterally. By using this method we have been able to avoid a more invasive ventral transthoracic approach necessitating vertebrectomy and reconstruction and risking serious complications.

Habituation of Somatosensory Event-Related Potentials in Subthreshold Rhythmic (1 Hz) Electrocutaneous Stimulation of the Arm during the Slow-Wave Stage of Daytime Sleep

Previous studies have shown that low-frequency subthreshold electrocutaneous stimulation of the arm during deep slow-wave sleep in humans improves sleep quality. The main cognitive processes are known to operate during sleep, and use of event-related potentials is the main method for analysis of these processes. The aims of the present work were to study the characteristics of somatosensory event-related potentials (sERP) on rhythmic (1 Hz) subthreshold electrocutaneous volley stimulation of the arm during the slow-wave stage of daytime sleep and to evaluate the potential for habituation of sERP to rhythmic stimulation during sleep. Subthreshold stimulation during sleep produced somatosensory event-related potentials (ERP) (group mean, n = 16) in which three long-latency components could be identifi ed, which were more marked in the frontal lead of the contralateral hemisphere. Comparison of sERP averaged from the beginning and end of the volley of stimuli (30 stimuli) demonstrated signifi cant decreases in the amplitudes of all sERP components by the end of the volley. It is suggested that the decrease in sERP amplitude in slow-wave sleep is due to the simplest form of stimulus-dependent nonassociative learning - habituation.

Anesthetic considerations during intraoperative neurophysiological monitoring in spine surgery

Objective We conducted an overview of the intraoperative neurophysiological monitoring (IONM) modalities in spine surgeries and effects of anesthesia and physiological factors on these modalities. Background The development of IONM minimizes iatrogenic neurological complications. All anesthetic agents impact on the modalities of IONM. Materials and methods Medline, articles in Medscape, ScienceDirect, and PubMed were searched. The search was performed in January 2016 and included all articles with no language restriction. The initial search presented 50 articles. The articles studied the types of IONM modalities and effects of anesthesia on these modalities. Data from each study were independently abstracted to capture information on study characteristics, interventions, and quantitative results reported for each outcome of interest. Significant data were collected and thus a structured review was performed. Results A close working relationship of the monitoring team, the anesthesiologist, and the surgeon is a key to the successful conduct and interpretation of IONM, prevention of complications of spinal surgeries, and early detection of these complications. On the basis of the monitoring modalities involved, the basic anesthetic constraints can be identified. Conclusion Using IONM such as somatosensory and motor-evoked potentials has become common to minimize neural risk and to improve intraoperative decision making for any spine surgery. IONM is affected by the choice of the different anesthetic agents and skeletal muscle relaxants, because anesthetic agents have effects on neural synaptic and skeletal muscle relaxants have effects on neuromuscular junctions.

Cooperative hand movements in tetraplegic spinal cord injury patients: Preserved neural coupling

ObjectivesTo evaluate whether the task-specific neural coupling mechanism during the performance of cooperative hand movements is preserved in tetraplegic subjects. MethodsRecordings of ipsilateral and contralateral electromyographic reflex responses in activated forearm muscles and bilateral somatosensory potentials (SSEP) to unilateral ulnar nerve stimulations during rest, cooperative and non-cooperative hand movements. ResultsContralateral reflex responses were present in almost all patients during cooperative hand movements but small in amplitude when hand function was severely impaired. Ipsilateral SSEP potentials were enhanced during both cooperative and, in contrast to healthy subjects, also non-cooperative bimanual movements. ConclusionsBoth results indicate a strong involvement of ipsilateral non-damaged cervical tracts and hemispheres in the control of bimanual hand movements in tetraplegic subjects. SignificanceThis study on the neural control of bimanual movements in patients suffering a cervical injury allows designing therapeutic approaches for the improvement of hand function that are based on physiological insights.