Latency Of Somatosensory Evoked Potentials Research Articles

Brainstem Associated Somatosensory Evoked Potentials and Response to Vagus Nerve Stimulation: An Investigation of the Vagus Afferent Network.

Despite decades of clinical usage, selection of patients with drug resistant epilepsy who are most likely to benefit from vagus nerve stimulation (VNS) remains a challenge. The mechanism of action of VNS is dependent upon afferent brainstem circuitry, which comprises a critical component of the Vagus Afferent Network (VagAN). To evaluate the association between brainstem afferent circuitry and seizure response, we retrospectively collected intraoperative data from sub-cortical recordings of somatosensory evoked potentials (SSEP) in 7 children with focal drug resistant epilepsy who had failed epilepsy surgery and subsequently underwent VNS. Using multivariate linear regression, we demonstrate a robust negative association between SSEP amplitude (p < 0.01), and seizure reduction. There was no association between SSEP latency and seizure outcomes. Our findings provide novel insights into the mechanism of VNS and inform our understanding of the importance of brainstem afferent circuitry within the VagAN for seizure responsiveness following VNS.

Dexmedetomidine versus fentanyl in intraoperative neuromuscular monitoring using propofol based total intravenous anesthesia regimen in kyphoscoliosis correction surgery

BackgroundIntraoperative neuromuscular monitoring (IONM) is used to reduce the risk of postoperative neurological deficit in patients undergoing kyphoscoliosis correction surgery. Somatosensory evoked potentials (SSEPs) are among the several techniques developed by neurophysiologists to increase the sensitivity of intraoperative monitoring. We administered total intravenous anesthesia (TIVA) to 20 patients undergoing kyphoscoliosis deformity correction surgeries: group A: propofol and dexmedetomidine and group B: propofol and fentanyl. The primary objective of our study was to compare the effect of dexmedetomidine and fentanyl on intraoperative hemodynamic parameters and their interference with SSEP’s readings. The secondary objective was to assess the total intraoperative requirement of inhalational anesthetic agents, quality of surgical field, and the cost-effectiveness of either regimen.ResultsIntraoperative hemodynamic stability, analgesia, surgical field, and cost-effectiveness (due to reduced requirement of sevoflurane) were better with dexmedetomidine than fentanyl. SSEPs were successfully recorded with both the drugs while the requirement of inhalation anesthetic agents was significantly reduced in the dexmedetomidine group than in the fentanyl group. There were no injuries while recording SSEPs. The latency and amplitude of SSEPs were maintained throughout either group. No intraoperative awakening or awareness was noted (bispectral index was maintained in the range of 40 to 60). No postoperative neurological deficit was noted in any patient.ConclusionsBoth dexmedetomidine and fentanyl can be successfully used in propofol-based TIVA for SSEP monitoring in kyphoscoliosis correction surgeries, but the better analgesic profile, ease of maintaining stable hemodynamics with a significant reduction in inhalational agent requirement, and opioid-sparing effect by dexmedetomidine make it a more desirable agent to be used in propofol-based TIVA.

Effects of desflurane and sevoflurane on somatosensory-evoked and motor-evoked potential monitoring during neurosurgery: a randomized controlled trial

BackgroundBetter protection can be provided during neurosurgery due to the establishment of somatosensory-evoked potential (SEP) and motor-evoked potential (MEP) monitoring technologies. However, some studies have showed that inhaled halogenated anesthetics have a significant impact on neurophysiological monitoring.MethodsA total of 40 consecutive patients undergoing neurosurgery were randomly assigned to two groups receiving inhaled anesthetics, either desflurane or sevoflurane. Multiples levels (concentrations of 0.3, 0.6 and 0.9) of anesthetics were administered at minimum alveolar concentration (MAC), and then the latencies and amplitudes of SEPs and MEPs were recorded.ResultsSEP and MEP signals were well preserved in patients who underwent neurosurgery under general anesthesia supplemented with desflurane or sevoflurane at concentrations of 0.3, 0.6 and 0.9 MAC. In each desflurane or sevoflurane group, the amplitudes of SEPs and MEPs decreased and the latencies of SEPs were prolonged significantly as the MAC increased (P < 0.05). The SEP latencies of both the upper and lower limbs in the desflurane group were significantly longer, and the SEP amplitudes were significantly lower than those in the sevoflurane group (P < 0.05). The MEP amplitudes in the desflurane group were significantly lower than those in the sevoflurane group (P < 0.05), only the amplitudes of the upper limbs at 0.3 MAC did not vary significantly.ConclusionsSEPs and MEPs were inhibited in a dose-dependent manner by both desflurane and sevoflurane. At the same MAC concentration, desflurane appeared to have a stronger inhibitory effect than sevoflurane. All patients studied had normal neurological examination findings, hence, these results may not be applicable to patients with preexisting deficits.Trial registrationThe study registered on the Chinese Clinical Trial Registry (www.chictr.org.cn), Clinical Trials identifier ChiCTR2100045504 (18/04/2021).

Modulation of the Somatosensory Evoked Potential by Attention and Spinal Cord Stimulation.

Introduction: Spinal Cord Stimulation (SCS) is a last-resort treatment for patients with intractable chronic pain in whom pharmacological and other treatments have failed. Conventional tonic SCS is accompanied by tingling sensations. More recent stimulation protocols like burst SCS are not sensed by the patient while providing similar levels of pain relief. It has been previously reported that conventional tonic SCS can attenuate sensory-discriminative processing in several brain areas, but that burst SCS might have additional effects on the medial, motivational-affective pain system. In this explorative study we assessed the influence of attention on the somatosensory evoked brain responses under conventional tonic SCS as well as burst SCS regime.Methods: Twelve chronic pain patients with an implanted SCS device had 2-weeks evaluation periods with three different SCS settings (conventional tonic SCS, burst SCS, and sham SCS). At the end of each period, an electro-encephalography (EEG) measurement was done, at which patients received transcutaneous electrical pulses at the tibial nerve to induce somatosensory evoked potentials (SEP). SEP data was acquired while patients were attending the applied pulses and while they were mind wandering. The effects of attention as well as SCS regimes on the SEP were analyzed by comparing amplitudes of early and late latencies at the vertex as well as brain activity at full cortical maps.Results: Pain relief obtained by the various SCS settings varied largely among patients. Early SEP responses were not significantly affected by attention nor SCS settings (i.e., burst, tonic, and sham). However, late SEP responses (P300) were reduced with tonic and burst SCS: conventional tonic SCS reduced P300 brain activity in the unattended condition, while burst SCS reduced P300 brain activity in both attended and unattended conditions.Conclusion: Burst spinal cord stimulation for the treatment of chronic pain seems to reduce cortical attention that is or can be directed to somatosensory stimuli to a larger extent than conventional spinal cord stimulation treatment. This is a first step in understanding why in selected chronic pain patients burst SCS is more effective than tonic SCS and how neuroimaging could assist in personalizing SCS treatment.

Heartbeat and somatosensory perception

Our perception of the external world is influenced by internal bodily signals. For example, we recently showed that timing of stimulation along the cardiac cycle and spontaneous fluctuations of heartbeat-evoked potential (HEP) amplitudes influence somatosensory perception and the associated neural processing (Al et al., 2020). While cardiac phase affected detection sensitivity and late components of the somatosensory-evoked potentials (SEPs), HEP amplitudes affected detection criterion and both early and late SEP components. In a new EEG study, we investigate whether these results are replicable in a modified paradigm, which includes two succeeding temporal intervals. In one of the intervals, subjects received a weak electrical finger stimulation and reported first whether they detected any stimulation and then allocated the stimulus to one of the two intervals. Our results confirm the previously reported cardiac cycle and prestimulus HEP effects on somatosensory perception and evoked potentials. In addition, we obtained two new findings. Source analyses in this and our original study show that the increased likelihood of conscious perception goes along with HEP fluctuations in parietal and posterior cingulate regions, known to play important roles in interoceptive processes. Furthermore, HEP amplitudes were shown to decrease when subjects engaged in the somatosensory task compared to a resting state condition. Our findings are consistent with the view that HEP amplitudes are a marker of interoceptive (versus exteroceptive) attention and provide a neural underpinning for this view.

Clinical utility of complex assessment with evoked potentials in acute lymphoblastic leukemia survivors: comparison of various treatment protocols

BackgroundOne of the greatest success of pediatric hematology is a prominent improvement of survival in acute lymphoblastic leukemia (ALL). Therefore, special attention needs to be paid to long-term side effects of the treatment such as neurotoxicity. One of the few diagnostic methods that allow an objective assessment of sensory systems are evoked potentials (EP).MethodsThe analyzed group consisted of 167 ALL long-term survivors, aged 4.9–28.4 years, without auditory, visual and sensory deviations. Patients were treated with New York (NY, n = 35), previous modified Berlin-Frankfurt-Münster (pBFM, n = 47) and BFM95 (n = 85) protocols. In order to assess the impact of radiotherapy on recorded EP, a joint analysis of NY and pBFM groups was performed. The control group consisted of 35 patients, aged 6–17 years. The analyzed patients underwent a complex assessment with visual EP (VEP), somatosensory EP (SEP) and brainstem auditory EP (BAEP) in accordance with current standards.ResultsALL treatment contributed to the shortening of wave I latency (1.59 vs 1.90, P = 0.003) and prolongation of I-III (2.23 vs 2.04, P = 0.004) and I-V (4.57 vs 4.24, P = 0.002) interwave latencies of BAEP. A significant effect was also noticed in P100 (106.32 vs 101.57, P < 0.001) and N135 (151.42 vs 138.22, P < 0.001) latencies of VEP and N18 amplitude (3.24 vs 4.70, P = 0.007) and P25 latency (21.32 vs 23.39, P < 0.001) of SEP. The distribution of abnormalities between protocols was similar in BAEP (NY - 68.6%, pBFM - 61.7%, BFM95–69.4%, P = 0.650), VEP (NY - 68.6%, pBFM - 42.5%, BFM95–58.3%, P = 0.053) and significantly different for SEP (NY - 62.9%, pBFM - 36.2%, BFM95–53.0%, P = 0.045). The harmful effect of radiotherapy was most clearly marked in numerous disturbances of SEP parameters.ConclusionsThe presented analysis indicates a high frequency of subclinical abnormalities in EP regardless of the analyzed protocol. To our knowledge current study is the largest and one of the most complex research examining the role of EP in ALL patients. The obtained results indicate the possibility of using a single, objective and non-invasive measurement of EP in ALL survivors in order to stratify the risk of developing sensory abnormalities in adulthood.

Noninvasive measurement of sensory action currents in the cervical cord by magnetospinography

ObjectiveTo obtain magnetic recordings of electrical activities in the cervical cord and visualize sensory action currents of the dorsal column, intervertebral foramen, and dorsal horn. MethodsNeuromagnetic fields were measured at the neck surface upon median nerve stimulation at the wrist using a magnetospinography system with high-sensitivity superconducting quantum interference device sensors. Somatosensory evoked potentials (SEPs) were also recorded. Evoked electrical currents were reconstructed by recursive null-steering beamformer and superimposed on cervical X-ray images. ResultsEstimated electrical currents perpendicular to the cervical cord ascended sequentially. Their peak latency at C5 and N11 peak latency of SEP were well-correlated in all 16 participants (r = 0.94, p < 0.0001). Trailing axonal currents in the intervertebral foramens were estimated in 10 participants. Estimated dorsal–ventral electrical currents were obtained within the spinal canal at C5. Current density peak latency significantly correlated with cervical N13–P13 peak latency of SEPs in 13 participants (r = 0.97, p < 0.0001). ConclusionsMagnetospinography shows excellent spatial and temporal resolution after median nerve stimulation and can identify the spinal root entry level, calculate the dorsal column conduction velocity, and analyze segmental dorsal horn activity. SignificanceThis approach is useful for functional electrophysiological diagnosis of somatosensory pathways.

The effect of movie-watching on electroencephalographic responses to tactile stimulation

Movie-watching is becoming a popular acquisition method to increase compliance and enable neuroimaging data collection in challenging populations such as children, with potential to facilitate studying the somatosensory system. However, relatively little is known about the possible crossmodal (audiovisual) influence of movies on cortical somatosensory processing. In this study, we examined the impact of dynamic audiovisual movies on concurrent cortical somatosensory processing using electroencephalography (EEG). Forty healthy young adults (18–25 years) received passive tactile fingertip stimulation while watching an “entertaining” movie and a novel “low-demand” movie called ‘Inscapes’ compared to eyes-open rest. Watching a movie did not modulate properties of early or late somatosensory-evoked potentials (SEPs). Similarly, no crossmodal influence on somatosensory adaptation, denoted by a reduction in SEP amplitude with repetitive tactile stimulation, was found. The prominent oscillatory responses in the alpha and beta frequency bands following tactile stimulation differed as a function of viewing condition, with stronger alpha/beta event-related desynchronization (ERD) during movie-watching compared to rest. These findings highlight that movie-watching is a valid acquisition method during which SEPs can be measured in basic research and clinical studies, but that the attentional demands of movies need to be taken into account when performing oscillatory analyses.

A Randomized Sham-Controlled Cross-Over Study on the Short-Term Effect of Non-Invasive Cervical Vagus Nerve Stimulation on Spinal and Supraspinal Nociception in Healthy Subjects.

The aim of the present study was to test the effects of vagus nerve stimulation (VNS) on the descending pain inhibition, quantified by the nociceptive flexor (RIII) reflex and the conditioned pain modulation (CPM) paradigm, and on supraspinal nociceptive responses, assessed by pain intensity and unpleasantness ratings and late somatosensory evoked potentials (SEPs), in healthy subjects. Non-invasive vagus nerve stimulation (nVNS) showed promising effects on headache and pain treatment. Underlying mechanisms are only incompletely understood but may include the activation of the descending pain inhibitory system and/or the modification of emotional responses to pain. Twenty-seven adult, healthy, and pain-free subjects participated in this double-blind cross-over study conducted at a university research center. They received 4minutes of cervical nVNS or sham stimulation in randomized order. RIII reflexes, pain ratings, and SEPs were assessed before, during, and 5, 15, 30, and 60minutes after nVNS/sham stimulation, followed by CPM testing. The primary outcome was the nVNS effect on the RIII reflex size. Three subjects were excluded after the preparatory session (before randomization), 1 subject was excluded after outlier analysis, leaving 23 for analysis. RIII reflex areas were 917.1±563.8µV×ms (mean±SD) before, 952.4±467.4µV×ms during and 929.2±484.0µV×ms immediately after nVNS and 858.4±489.2µV×ms before, 913.9±539.7µV×ms during and 862.4±476.0µV×ms after sham stimulation, revealing no differences between the immediate effects of nVNS and sham stimulation (F [3,66] =0.67, P=.574). There also were no effects of nVNS over sham on RIII reflex areas up to 60minutes after nVNS (F [1.7,37.4] =1.29, P=.283). Similarly, there was no statistically significant effect of nVNS on pain intensity ratings and thresholds, RIII reflex thresholds, late SEP amplitudes, and the CPM effect, compared to sham. Pain unpleasantness ratings statistically significantly decreased from 4.4±2.4 (NRS 0-10) to 4.1±2.5 during nVNS compared to sham stimulation (F [1,22] =8.74, P=.007), but there were no longer lasting effects (5-60minutes after stimulation). The present study does not support an acute effect of nVNS on descending pain inhibition, pain intensity perception or supraspinal nociception in healthy adults. However, there was a small effect on pain unpleasantness during nVNS, suggesting that nVNS may preferentially act on affective, not somatosensory pain components.

Sacral Reflex Characteristics of Patients with Multiple System Atrophy.

Objectives To observe and analyze the parameters of the sacral reflex and pudendal nerve somatosensory evoked potential (SSEP) in patients with multiple system atrophy (MSA) with respect to factors such as age, disease course, and subtype and provide evidence for the clinical diagnosis of MSA. Materials and Methods A total of 51 MSA patients and 30 healthy controls were selected from the First Affiliated Hospital of Wenzhou Medical University from May 2013 to November 2015. Electrophysiological sacral reflex detection and SSEP detection were performed using the Keypoint EMG/EP system. The extraction rate, latency, and amplitude of the sacral reflex and SSEP in the MSA group and control group were compared. Results The sacral reflex latency and amplitude in patients with MSA were statistically different from those of the healthy controls. The latency of sacral reflex increases with the prolongation of the disease course, and the amplitude and initiation rate decrease with the prolongation of the disease course. There was no significant difference in sacral reflex latency and amplitude between MSA patients of different ages and subtypes. There was no significant difference in the latency or amplitude of SSEP between the MSA group and healthy control group. Conclusions The latency of sacral reflex increases with the prolongation of the disease course, and the amplitude and extraction rate decrease with the prolongation of the disease course. There was no significant difference in the parameters of sacral reflex between young MSA patients and elderly patients. And there was no statistically significant difference between MSA-P subtypes and MSA-C subtypes. This trial is registered with ISRCTNCR2009041.

Peripheral Nerve Injury in Thoracic Surgery Detected by Automated Somatosensory Evoked Potential Monitoring.

Study Objective. Our objectives were to estimate the incidence of symptoms of peripheral nerve injury (sPNI) in thoracic surgical patients undergoing video-assisted thoracic surgery or open thoracotomy and to determine whether intraoperative somatosensory evoked potentials (SSEPs) waveform changes correlate with postoperative peripheral neuropathic symptoms. Methods. We conducted a prospective observational study in the operating room of a tertiary hospital. We measured SSEPs intraoperatively and assessed patients for sPNI postoperatively. Results. Forty-four patients consented. Six were excluded from analysis. We found that 42% (95% confidence interval [CI] = 26% to 57%) of patients undergoing thoracic surgery had significant changes in SSEP amplitude and latency. Furthermore, 16% (95% CI = 4% to 28%) of patients had new postoperative symptoms of sensory or motor deficits in an upper extremity. We calculated a sensitivity of 66.7% (95% CI = 29.0% to 100%) and a specificity of 50% (95% CI = 33% to 67.3%) for the identification of sPNI based on automated intraoperative SSEP changes. Conclusions. We identified the incidence of SSEP changes in thoracic surgery (42%) and the incidence of postoperative sPNI after thoracic surgery (16%). We identified a positive correlation between intraoperative SSEP changes and postoperative sPNI, which after multivariate analysis was not significant given the small sample size of the study. By the time sensory and/or motor changes are detected postoperatively, it may be too late to reverse the nerve damage. Future versions of the EPAD device could provide anesthesiologists a way to monitor for the development of sPNI, and make changes before a potential injury becomes permanent.

Heart–brain interactions shape somatosensory perception and evoked potentials

Even though humans are mostly not aware of their heartbeats, several heartbeat-related effects have been reported to influence conscious perception. It is not clear whether these effects are distinct or related phenomena, or whether they are early sensory effects or late decisional processes. Combining electroencephalography and electrocardiography, along with signal detection theory analyses, we identify two distinct heartbeat-related influences on conscious perception differentially related to early vs. late somatosensory processing. First, an effect on early sensory processing was found for the heartbeat-evoked potential (HEP), a marker of cardiac interoception. The amplitude of the prestimulus HEP negatively correlated with localization and detection of somatosensory stimuli, reflecting a more conservative detection bias (criterion). Importantly, higher HEP amplitudes were followed by decreases in early (P50) as well as late (N140, P300) somatosensory-evoked potential (SEP) amplitudes. Second, stimulus timing along the cardiac cycle also affected perception. During systole, stimuli were detected and correctly localized less frequently, relating to a shift in perceptual sensitivity. This perceptual attenuation was accompanied by the suppression of only late SEP components (P300) and was stronger for individuals with a more stable heart rate. Both heart-related effects were independent of alpha oscillations' influence on somatosensory processing. We explain cardiac cycle timing effects in a predictive coding account and suggest that HEP-related effects might reflect spontaneous shifts between interoception and exteroception or modulations of general attentional resources. Thus, our results provide a general conceptual framework to explain how internal signals can be integrated into our conscious perception of the world.

Critical Limit of Lower-Extremity Lengthening in Total Hip Arthroplasty: An Intraoperative Neuromonitorization Study.

The effect of limb lengthening on neural structures was assessed with use of intraoperative neuromonitoring (IONM) during primary total hip arthroplasty (THA). The relationship between the critical limit of lengthening and anthropometric measurements was evaluated. Motor evoked potentials (MEPs) from the deep peroneal nerve (tibialis anterior muscle), tibial nerve (gastrocnemius muscle), and femoral nerve (quadriceps muscle), as well as somatosensory evoked potentials (SEPs) from the posterior tibial nerve, were recorded in 16 patients undergoing THA. Height, weight, the distance between the anterior superior iliac spine and the medial malleolus (ASIS-MM distance), and the total femoral length were measured preoperatively. Lower-extremity traction was performed after resection of the femoral head, and the amount of extremity lengthening was measured with use of an image intensifier. A maximum of 50% reduction in any one of the SEP or MEP amplitudes or a 10% increase in the SEP latency were considered to be indicative of the critical limit of lengthening. Initial IONM changes (indicating the safe limit of lengthening) and maximum allowed IONM changes (indicating the critical limit of lengthening) were reached in the deep peroneal nerve in all cases. The mean safe limit of lengthening (and standard deviation) was 14.9 ± 6.2 mm (3% relative to femoral length and 1.7% relative to ASIS-MM distance), whereas the critical limit of lengthening was exceeded at a mean of 22.4 ± 5.6 mm (5% relative to femoral length and 2.6% relative to ASIS-MM distance). When the critical limit was reached in the deep peroneal nerve, the mean decrease in MEP amplitudes was 27% (95% confidence interval [CI], 22.1% to 32.7%) for the tibial nerve and 12% (95% CI, 6.9% to 18.1%) for the femoral nerve. There was a positive correlation between critical lengthening and femoral length (r = 0.782; p < 0.001), ASIS-MM distance (r = 0.811; p < 0.001), and height (r = 0.835; p = 0.001). No correlation existed between the critical lengthening amount and the decrease in amplitude in the tibial and femoral nerves. The critical limit of nerve lengthening was directly correlated with anthropometric measurements. Nerve lengthening of 5% relative to femoral length and of 2.6% relative to ASIS-MM distance was found to be critical; however, these limits depended on the predetermined threshold values for IONM. Prognostic Level IV. See Instructions for Authors for a complete description of levels of evidence.

Somatosensory and motor evoked potentials during correction surgery of scoliosis in neurologically asymptomatic Chiari malformation-associated scoliosis: A comparison with idiopathic scoliosis

ObjectivesTo analyze the somatosensory evoked potentials (SEPs) and motor evoked potentials (MEPs) in neurologically asymptomatic Chiari malformation-associated scoliosis (CMS) patients with and without syringomyelia as compared with those in idiopathic scoliosis (IS) ones, and to identify whether the deformities have impacts on the neurophysiological monitoring. Patients and methodsThis study included neurologically asymptomatic CMS patients undergoing posterior correction surgery between January 2010 and January 2016. IS patients were involved as control group and a subgroup of age- and height-matched IS patients were selected. The age, standing height and Cobb angles of main curve were measured. The SEPs latency and amplitude, MEPs amplitude, and the rate of abnormal SEPs pathologic change were compared between CMS and IS patients using independent-sample t-test and Chi-square test. ResultsSixty CMS patients and 210 IS patients were included. There was no difference between CMS patients and IS or matched IS patients in SEPs latency and amplitude, MEPs amplitude or rate of abnormal SEPs (p > 0.05). Forty-eight CMS patients concurrent with syringomyelia were associated with higher Cobb angle of main curve and lower SEPs amplitude than those without syringomyelia (p < 0.05). No significant difference was found between CMS patients with and without syringomyelia in age, height, SEPs latency, MEPs amplitude or rate of abnormal SEPs (p > 0.05). ConclusionNeurologically asymptomatic CMS patients showed similar absolute values of neurophysiological monitoring with IS patients. The syringomyelia in CMS indicated more severe curvature and lower SEPs amplitude even after posterior fossa decompression.

Intraoperative neurophysiological monitoring in paediatric Chiari surgery-help or hindrance?

The role of intraoperative neurophysiological monitoring (IONM) during surgery for Chiari I malformation has not been fully elucidated. Questions remain regarding its utility as an adjunct to foramen magnum decompression surgery, specifically, does IONM improve the safety profile of foramen magnum decompression surgery and can IONM parameters help in intraoperative surgical decision-making. This study aimed to describe a single institution experience of IOM during paediatric Chiari I surgery. The methodology comprised a retrospective review of prospectively collected electronic neurosurgical departmental operative database. Inclusion criteria were children under 16years of age who had undergone foramen magnum decompression for Chiari I malformation with IONM. In addition to basic demographic data, details pertaining to presenting features and post-operative outcomes were obtained. These included primary symptoms of Chiari I malformation and indications for surgery. MRI findings, including the presence of syringomyelia on pre-and post-operative imaging, were reviewed. Details of the surgical technique for each patient were recorded. Only patients with either serial brainstem auditory evoked potential (BAEP) and/or upper limb somatosensory evoked potential (SSEP) recordings were included. Two time points were used for the purposes of analysing IONM data; initial baseline before skin incision and final at the time of skin closure. Thirty-seven children underwent foramen magnum decompression (FMD) with IONM. Mean age was 10.5years (range 1-16years) with a male:female ratio 13:24. The commonest clinical features on presentation included headaches (15) and scoliosis (13). Twenty-four patients had evidence of associated syringomyelia (24/37 = 64.9%). A reduction in the SSEP latency was observed in all patients. SSEP amplitude was more variable, with a decrease seen in 18 patients and an increase observed in 12 patients. BAEP recordings decreased in 13 patients and increased in 4 patients. There were no adverse neurological events following surgery; the primary symptom was resolved or improved in all patients at 3-month follow-up. Resolution or improvement in syringomyelia was observed in 19/24 cases. Our data shows that FMD for Chiari malformation (CM) is associated with changes in SSEPs and BAEPs. However, we did not identify a definite link between clinical outcomes and IONM, nor did syrinx outcome correlate with IONM. There may be a role for IONM in CM surgery but more robust data with better-defined parameters are required to further understand the impact of IONM in CM surgery.

Utility of Trial-to-Trial Latency Variability of Somatosensory Evoked Potentials for Diagnosis of Spinal Cord Demyelination.

Traditional measurement of somatosensory evoked potentials (SEPs) depends on averaging of many recordings, which introduces loss of dynamic variability. Single trial extraction provides a new measurement of SEP latency variability for evaluation of the neurodynamic status of the somatosensory pathway. The aim of this study was to apply a single trial SEP to diagnose the severity of demyelination in a chronical spinal cord injury model. The severity of demyelination was measured by myelin area and staining intensity at the ventral column (VC), lateral column (LC), and dorsal column (DC) by histological examination with Luxol fast blue staining. Results showed that there was a strong negative correlation of the latency variability of trial-to-trial SEP with the myelin area in three columns (DC: r=-0.90, p<0.05; VC: r=-0.91, p<0.05; LC: r=-0.89, p<0.05), and the staining intensity in three columns (DC: r=-0.95, p<0.05; VC: r=-0.94, p<0.05; LC: r=-0.93, p<0.05). These data suggest that single trial SEP can provide a dynamic indicator of spinal cord demyelination.

Effects of Athermal Shortwave Diathermy Treatment on Somatosensory Evoked Potentials and Motor Evoked Potentials in Rats With Spinal Cord Injury.

A study on shortwave diathermy (SWD) versus no treatment following induced spinal cord injury (SCI) in rats. To investigate the effects of athermal SWD treatment on somatosensory evoked potentials (SEPs) and motor evoked potentials (MEPs) and hindlimb movements in rats with SCI. SWD has been proven to improve vascular circulation and reduce inflammation. However, there have been few studies on neuroprotective effect of SWD on SCI. Twenty-four female Sprague-Dawley (SD) rats were randomly divided into four groups: sham, SCI, SWD, and intact groups. The SCI model was established using the modified Allen weight-drop method. The SWD group received 15 sessions of athermal SWD treatment over a 3-week period of time at 24 hours after SCI. While the sham group and SCI group received no treatment after surgery. Hindlimb movements were evaluated by the Basso, Beattie, and Bresnahan (BBB) scale before surgery, and on days 1, 7, 14, and 21 after the surgery, respectively. The SEP and MEP measurements were simultaneously performed to detect the responses of neural conduction. The week-by-week BBB scores showed a gradual improvement in the rats of both SCI and SWD groups from the first week to the end of the study; however, the BBB scores of the SWD group were higher than those of the SCI group over the course of 3 weeks. Data from the SEP and MEP measurements showed a significant improvement in the SWD group compared with the SCI group at each time point of observation, with a more prominent increase of amplitude and a more evident reduction of latency. There was a linear correlation between the BBB scores and the latency and amplitude of SEPs or MEPs. Athermal SWD treatment might facilitate the recovery of locomotor function and exert neuroprotective effect on the SCI. N/A.

Psychopathology and patterns of sensory processing in nonsuicidal self-injured adolescents

Nonsuicidal self-injury (NSSI) is a multifaceted and growing phenomenon among adolescents. This study aimed at analyzing some of the psychobehavioral correlates of NSSI compare to features of long latency Somatosensory Evoked Potentials (LL-SSEP). We studied 12 adolescents (mean age 14 ys ± 1 ys), presenting NSSI referred to the Infantile Neuropsychiatry Unit of Gaslini Children’s Hospital of Genoa. We divided the sample in two groups (frequent NSSI - fNSSI and occasional NSSI - oNSSI) based on the Risk-Taking and Self-Harm Inventory for Adolescents (RITSHIA) for evaluated presence and severity of NSSI (cut off at Self-Harm subscale 16). We evaluated: the Theory of Mind subtest of NEPSY-II battery (TOM) for mentalizing ability, temporal features and topographical distribution bilaterally across the cortex of the LL-SSEP following physiological sequence N60-N70-N140. fNSSI presented lower mentalization ability in 5/6 patients compared to oNSSI (normal TOM score in 6/6 patients). Analyzing LL-SSEP we recorded not significant differences in latency of N60 and N70 and amplitude of N140, but fNSSI presented less representation and distribution with less amplitude of N60-N70 and increase latency of N140. Features of LL-SSEP correlate with the ability of mentalization and the intensity of NSSI behavior.

The reversible effect of neck flexion on the somatosensory evoked potentials in patients with Hirayama disease: a preliminary study.

The aim of this study was to examine and characterize the reversibility of the cervical somatosensory electrophysiological pathways during neutral and flexed neck positions. The parameters of somatosensory evoked potentials (SEPs) during neutral and flexed neck positions (N9, N13, and N20 SEP latencies; N9-N13 and N13-N20 inter-peak latencies; and the changes in N9-N13 and N13-N20 inter-peak latency during neutral and flexed neck positions) were measured in the patients with Hirayama disease (HD) and also in the healthy controls. In patients with HD, there was a significant difference in the mean value of N13-N20 inter-peak latency during the flexed neck position compared to that of the healthy controls (p < 0.05). In a multivariate logistic regression analysis, N13-N20 inter-peak latency during the flexed neck position significantly correlated with the presence of HD (p < 0.05). Collectively, in this cohort of patients with HD, the neck flexion of patients with HD showed a reversible effect on the SEP parameter, especially in N13-N20 inter-peak latency. Conventional diagnosis of HD is based on nerve conduction studies and electromyography along with a cervical flexion MRI, and our study suggests the possibility of an additional and cost-effective electrophysiological marker that may be helpful in the diagnosis of HD.

Evidence for a Supraspinal Contribution to the Human Crossed Reflex Response During Human Walking.

In humans, an ipsilateral tibial nerve (iTN) stimulation elicits short-latency-crossed-responses (SLCR) comprised of two bursts in the contralateral gastrocnemius lateralis (cGL) muscle. The average onset latency has been reported to be 57–69 ms with a duration of 30.4 ± 6.6 ms. The aim of this study was to elucidate if a transcortical pathway contributes to the SLCR. In Experiment 1 (n = 9), single pulse supra-threshold transcranial magnetic stimulation (supraTMS) was applied alone or in combination with iTN stimulation (85% of the maximum M-wave) while participants walked on a treadmill (delay between the SLCR and the motor evoked potentials (MEP) varied between −30 and 200 ms). In Experiment 2 (n = 6), single pulse sub-threshold TMS (subTMS) was performed and the interstimulus interval (ISI) varied between 0–30 ms. In Experiment 3, somatosensory evoked potentials (SEPs) were recorded during the iTN stimulation to quantify the latency of the resulting afferent volley at the cortical level. SLCRs and MEPs in cGL occurred at 63 ± 6 ms and 29 ± 2 ms, respectively. The mean SEP latency was 30 ± 3 ms. Thus, a transcortical pathway could contribute no earlier than 62–69 ms (SEP+MEP+central-processing-delay) after iTN stimulation. Combined iTN stimulation and supraTMS resulted in a significant MEP extra-facilitation when supraTMS was timed so that the MEP would coincide with the late component of the SLCR, while subTMS significantly depressed this component. This is the first study that demonstrates the existence of a strong cortical control on spinal pathways mediating the SLCR. This likely serves to enhance flexibility, ensuring that the appropriate output is produced in accord with the functional demand.