Hypothermia effects on neuronal plasticity post spinal cord injury.

BACKGROUND: SCI is a time-sensitive debilitating neurological condition without treatment options. Although the central nervous system is not programmed for effective endogenous repairs or regeneration, neuroplasticity partially compensates for the dysfunction consequences of SCI. OBJECTIVE AND HYPOTHESIS: The purpose of our study is to investigate whether early induction of hypothermia impacts neuronal tissue compensatory mechanisms. Our hypothesis is that although neuroplasticity happens within the neuropathways, both above (forelimbs) and below (hindlimbs) the site of spinal cord injury (SCI), hypothermia further influences the upper limbs' SSEP signals, even when the SCI is mid-thoracic. STUDY DESIGN: A total of 30 male and female adult rats are randomly assigned to four groups (n = 7): sham group, control group undergoing only laminectomy, injury group with normothermia (37°C), and injury group with hypothermia (32°C +/-0.5°C). METHODS: The NYU-Impactor is used to induce mid-thoracic (T8) moderate (12.5 mm) midline contusive injury in rats. Somatosensory evoked potential (SSEP) is an objective and non-invasive procedure to assess the functionality of selective neuropathways. SSEP monitoring of baseline, and on days 4 and 7 post-SCI are performed. RESULTS: Statistical analysis shows that there are significant differences between the SSEP signal amplitudes recorded when stimulating either forelimb in the group of rats with normothermia compared to the rats treated with 2h of hypothermia on day 4 (left forelimb, p = 0.0417 and right forelimb, p = 0.0012) and on day 7 (left forelimb, p = 0.0332 and right forelimb, p = 0.0133) post-SCI. CONCLUSION: Our results show that the forelimbs SSEP signals from the two groups of injuries with and without hypothermia have statistically significant differences on days 4 and 7. This indicates the neuroprotective effect of early hypothermia and its influences on stimulating further the neuroplasticity within the upper limbs neural network post-SCI. Timely detection of neuroplasticity and identifying the endogenous and exogenous factors have clinical applications in planning a more effective rehabilitation and functional electrical stimulation (FES) interventions in SCI patients.

Somatosensory evoked potentials recorded from DBS electrodes: the origin of subcortical N18.

The different peaks of somatosensory-evoked potentials (SEP) originate from a variety of anatomical sites in the central nervous system. The origin of the median nerve subcortical N18 SEP has been studied under various conditions, but the exact site of its generation is still unclear. While it has been claimed to be located in the thalamic region, other studies indicated its possible origin below the pontomedullary junction. Here, we scrutinized and compared SEP recordings from median nerve stimulation through deep brain stimulation (DBS) electrodes implanted in various subcortical targets. We studied 24 patients with dystonia, Parkinson's disease, and chronic pain who underwent quadripolar electrode implantation for chronic DBS and recorded median nerve SEPs from globus pallidus internus (GPi), subthalamic nucleus (STN), thalamic ventral intermediate nucleus (Vim), and ventral posterolateral nucleus (VPL) and the centromedian-parafascicular complex (CM-Pf). The largest amplitude of the triphasic potential of the N18 complex was recorded in Vim. Bipolar recordings confirmed the origin to be close to Vim electrodes (and VPL/CM-Pf) and less close to STN electrodes. GPi recorded only far-field potentials in unipolar derivation. Recordings from DBS electrodes located in different subcortical areas allow determining the origin of certain subcortical SEP waves more precisely. The subcortical N18 of the median nerve SEP-to its largest extent-is generated ventral to the Vim in the region of the prelemniscal radiation/ zona incerta.

Intraoperative Neurophysiological Monitoring in Corrective Surgery of Scoliosis - Experience at a Tertiary Care Hospital.

OBJECTIVE: To evaluate the role of intraoperative neurophysiological monitoring (IONM) in reducing the postoperative neurologic deficit following corrective surgery of scoliosis. STUDY DESIGN: Observational Study. Place and Duration of the Study: Spine Surgery Department, Combined Military Hospital, Rawalpindi, from December 2022 to May 2023. METHODOLOGY: The study included 170 cases of scoliosis operated under multimodal IONM. Decreased amplitude of ≥50% in SSEP or 70-80% in MEPs were considered warning signs. Cases were divided into two groups: Group 1 (signal drop) and Group 2 (no signal drop). Group 1 was subdivided into Group 1a (true positive), Group 1b (false positive) and Group 1c (intermediate positive). Group 2 was subdivided into Group 2a (true negative) and Group 2b (false negative). RESULTS: Evoked potential changes were observed in 27 (15.9%) cases. This includes transient drop of signals in 16 (9.4%) and sustained drop of signals in 11 (6.5%) cases. Among sustained signal drop, 9 (5.29%) cases had exhibited postoperative neurological deficit whereas 2 (1.17%) cases did not show postoperative neurological deficit (false positive). Multimodal IONM in the current study shows sensitivity of 100%, specificity of 98.6%, positive predictive value of 92.6%, and negative predictive value of 100%. CONCLUSION: Multimodal IONM reduces the incidence of postoperative neurological deficit in corrective surgery of scoliosis by effectively detecting neurologic injury during surgery. Monitoring events alert surgical team to exercise immediate corrective measures which likely results in recovery of lost signals and predict the favorable outcome. KEY WORDS: Intraoperative monitoring, Motor evoked potentials, Neurological deficit, Scoliosis, Somatosensory evoked potentials.

Intraoperative High-Resolution Color-Coded Ultrasound to Identify the Posterior Median Sulcus for Midline Myelotomy in Intramedullary Spinal Cord Surgery.

A 14-year-old boy presented with a 2-year history of slowly increasing weakness and atrophy in the right forearm and leg. Magnetic resonance imaging (MRI) revealed an intramedullary diffusely infiltrating lateralized tumor at C3-7. An extended biopsy was planned. After laminotomy and durotomy, the swollen spinal cord was noted to be rotated by 45° with the right dorsal root entry zone being in the midline. A 15 MHz linear ultrasound probe was used to identify the midline by visualizing the dorsal median sulcal vein within the midline raphe. A myelotomy was made in that zone without deterioration of somatosensory evoked potentials (SEPs) and an extended biopsy was performed. Histological examination revealed a pilocytic astrocytoma. Modern intraoperative high-resolution color-coded ultrasound enables the identification of the midline in intramedullary spinal cord lesions even when the spinal cord anatomy is distorted.

Intraoperative Neurophysiologic Monitoring and Mapping During Surgery on Intramedullary Spinal Cord Tumors in Children and Adolescents.

SUMMARY: Surgical resection of intramedullary spinal cord tumors carries significant risks of neurologic deficits, especially in cases of infiltrative tumors. In pediatric patients, this type of surgery may be associated with a high risk of poor neurologic outcome. Intraoperative neurophysiologic monitoring has been adopted as part of the clinical routine by many centers as a useful adjunct for intraoperative assessment of neurologic integrity. To what extent intraoperative neurophysiologic mapping strategies may further support intraoperative decision-making is still a matter of debate. Here, we report on a small cohort of five pediatric patients in whom mapping with the double-train paradigm was used to identify the dorsal column and corticospinal tract and to guide the surgical resection. We also discuss the possible benefits and challenges regarding the available literature.

Intraoperative Monitoring of Scoliosis Surgery in Young Patients.

SUMMARY: Intraoperative neurophysiologic monitoring has added substantially to the safety of spinal deformity surgery correction since its introduction over four decades ago. Monitoring routinely includes both somatosensory evoked potentials and motor evoked potentials. Either modality alone will detect almost all instances of spinal cord injury during deformity correction. The combined use of the two modalities provides complementary information, can permit more rapidly identification of problems, and enhances safety though parallel redundancy should one modality fail. Both techniques are well established and continue to be refined. Although there is room for provider preference, proper monitoring requires attention to technical detail, understanding of the underlying physiology, and familiarity with effects of commonly used anesthetic agents.

Multimodal evoked potentials are useful for the diagnosis of pediatric acute disseminated encephalomyelitis.

BACKGROUND: The application of evoked potentials (EPs) to the diagnosis of acute disseminated encephalomyelitis (ADEM ) has not been investigated in detail. The aim of this study, therefore, was to analyze the value of multimodal EPs in the early diagnosis of pediatric ADEM. METHODS: This was a retrospective study in which we enrolled pediatric ADEM patients and controls (Cs) from neurology units between 2017 and 2021. We measured indices in patients using brainstem auditory evoked potentials (BAEPs), visual evoked potentials (VEPs) and somatosensory evoked potentials (SEPs), and then we analyzed their early diagnostic value in ADEM patients. RESULTS: The mean age of the ADEM group was 6.15 ± 3.28 years (range,1-12 years) and the male/female ratio was 2.1:1 The mean age of the Cs was 5.97 ± 3.40 years (range,1-12 years) and the male/female ratio was 1.3:1. As we used magnetic resonance imaging (MRI) as the diagnostic criterion, the sensitivity, specificity, and accuracy (κ was 0.88) of multimodal EPs were highly consistent with those of MRI; and the validity could be ranked in the following order with respect to the diagnosis of ADEM: multimodal Eps > single SEP > single VEP > single BAEP. Of 34 patients with ADEM, abnormalities in multimodal EPs were 94.12%, while abnormalities in single VEPs, BAEPs and SEPs were 70.59%,64.71%and 85.3%, respectively. We noted significant differences between single VEP/BAEPs and multimodal EPs (χ2 = 6.476/8.995,P = 0.011/0.003). CONCLUSIONS: The combined application of multimodal EPs was superior to BAEPs, VEPs, or SEPs alone in detecting the existence of central nerve demyelination, and we hypothesize that these modalities will be applicable in the early diagnosis of ADEM.

Diagnostic utility of different types of somatosensory evoked potential changes in pediatric idiopathic scoliosis correction surgery.

PURPOSE: To evaluate the diagnostic accuracy of intraoperative somatosensory evoked potential (SSEP) monitoring and types of SSEP changes in predicting the risk of postoperative neurological outcomes during correction surgery for idiopathic scoliosis (IS) in the pediatric age group (≤ 21 years). METHODS: Database review was performed to identify literature on pediatric patients with IS who underwent correction with intraoperative neuromonitoring. The sensitivity, specificity, and diagnostic odds ratio (DOR) of transient and persistent SSEP changes and complete SSEP loss in predicting postoperative neurological deficits were calculated. RESULTS: Final analysis included 3778 patients. SSEP changes had a sensitivity of 72.9%, specificity of 96.8%, and DOR of 102.3, while SSEP loss had a sensitivity of 41.8%, specificity of 99.3%, and DOR of 133.2 for predicting new neurologic deficits. Transient and persistent SSEP changes had specificities of 96.8% and 99.1%, and DORs of 16.6 and 59, respectively. CONCLUSION: Intraoperative SSEP monitoring can predict perioperative neurological injury and improve surgical outcomes in pediatric scoliosis fusion surgery. LEVEL OF EVIDENCE: Level 2. This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .

Subclinical Neck Pain Leads to Differential Changes in Early Somatosensory Evoked Potentials in Response to a Novel Force Matching Tracking Task.

BACKGROUND: Neural adaptions in response to sensorimotor tasks are impaired in those with untreated, recurrent mild-to-moderate neck pain (subclinical neck pain (SCNP)), due to disordered central processing of afferent information (e.g., proprioception). Neural adaption to force modulation, a sensorimotor skill reliant on accurate proprioception, is likely to be impaired in those with SCNP. This study examined changes in somatosensory evoked potential (SEP) peak amplitudes following the acquisition of a novel force matching tracking task (FMTT) in those with SCNP compared to non-SCNP. METHODS: 40 (20 female (F) & 20 male (M); average age (standard deviation, SD): 21.6 (3.01)) right-handed participants received controlled electrical stimulation at 2.47 Hz and 4.98 Hz (averaged 1000 sweeps/frequency) over the right-median nerve, to elicit SEPs before and after FMTT acquisition. Participants used their right thumb to match a series of force profiles that were calibrated to their right thumb (abductor pollicis brevis muscle) strength. To determine if motor learning was impacted, retention was assessed 24 to 48 hours later. Outliers were removed before running independent t-tests on normalized SEP peak amplitudes, and repeated measures analysis of variance (ANOVA) with planned contrasts on absolute and normalized motor performance accuracy. Benjamini-hochberg test was used to correct for multiple independent SEP comparisons. RESULTS: SEP peaks: N18 (t(29.058) = 2.031, p = 0.026), N20 (t(35) = -5.460, p < 0.001), and P25 (t(33) = -2.857, p = 0.004) had group differences. Motor performance: Absolute error (n = 38) had a main effect of time, and significant pre-and post-acquisition contrast for time (both p < 0.001). CONCLUSIONS: Group differences in the olivary-cerebellar pathway (N18), and cortical processing at the somatosensory cortex (N20 and P25), suggests that SCNP alters cortical and cerebellar processing compared to non-SCNP in response to FMTT acquisition. The sensory-motor integration differences in the SCNP group suggests that those with SCNP may rely more on feedback loops for discrete sensorimotor tasks dependent on proprioception. Early SEP changes may be used as a marker for altered neuroplasticity in the context of motor skill acquisition of a novel discrete FMTT in those with SCNP.

Cost-benefit analysis of intraoperative neuromonitoring for cardiac surgery.

BACKGROUND: Intraoperative neuromonitoring (IONM) can detect large vessel occlusion (LVO) in real-time during surgery. The aim of this study was to conduct a cost-benefit analysis of utilizing IONM among patients undergoing cardiac surgery. METHODS: A decision-analysis tree with terminal Markov nodes was constructed to model functional outcome, as measured via the modified Rankin Scale (mRS), among 65-year-old patients undergoing cardiac surgery. Our cost-benefit analysis compares the use of IONM (electroencephalography and somatosensory evoked potential) against no IONM in preventing neurological complications from perioperative LVO during cardiac surgery. The study was performed over a lifetime horizon from a societal perspective in the United States. Base case and one-way probabilistic sensitivity analyses were performed. RESULTS: At a baseline LVO rate of 0.31%, the mean attributable lifetime expenditure for IONM-monitored cardiac surgeries relative to unmonitored cardiac surgeries was $1047.41 (95% CI, $742.12 - $1445.10). At a critical LVO rate of approximately 3.67%, the costs of both monitored and unmonitored cardiac surgeries were the same. Above this critical rate, implementing IONM became cost-saving. On one-way sensitivity analysis, variation in LVO rate from 0% - 10% caused lifetime costs attributable to receiving IONM to range from $1150.47 - $29404.61; variations in IONM cost, percentage of intervenable LVOs, IONM sensitivity, and mechanical thrombectomy cost exerted comparably minimal influence over lifetime costs. DISCUSSION: We find considerable cost savings favoring the use of IONM under certain parameters corresponding to high-risk patients. This study will provide financial perspective to policymakers, clinicians, and patients alike on the appropriate use of IONM during cardiac surgery.

A Novel Approach to Screen for Somatosensory Evoked Potentials in Critical Care.

BACKGROUND: Somatosensory evoked potentials (SSEPs) help prognostication, particularly in patients with diffuse brain injury. However, use of SSEP is limited in critical care. We propose a novel, low-cost approach allowing acquisition of screening SSEP using widely available intensive care unit (ICU) equipment, specifically a peripheral "train-of-four" stimulator and standard electroencephalograph. METHODS: The median nerve was stimulated using a train-of-four stimulator, and a standard 21-channel electroencephalograph was recorded to generate the screening SSEP. Generation of the SSEP was supported by visual inspection, univariate event-related potentials statistics, and a multivariate support vector machine (SVM) decoding algorithm. This approach was validated in 15 healthy volunteers and validated against standard SSEPs in 10 ICU patients. The ability of this approach to predict poor neurological outcome, defined as death, vegetative state, or severe disability at 6 months, was tested in an additional set of 39 ICU patients. RESULTS: In each of the healthy volunteers, both the univariate and the SVM methods reliably detected SSEP responses. In patients, when compared against the standard SSEP method, the univariate event-related potentials method matched in nine of ten patients (sensitivity = 94%, specificity = 100%), and the SVM had 100% sensitivity and specificity when compared with the standard method. For the 49 ICU patients, we performed both the univariate and the SVM methods: a bilateral absence of short latency responses (n = 8) predicted poor neurological outcome with 0% FPR (sensitivity = 21%, specificity = 100%). CONCLUSIONS: Somatosensory evoked potentials can reliably be recorded using the proposed approach. Given the very good but slightly lower sensitivity of absent SSEPs in the proposed screening approach, confirmation of absent SSEP responses using standard SSEP recordings is advised.

Intraoperative Neurophysiological Monitoring During Lead Placement for Dorsal Root Ganglion Stimulation: A Literature Review and Case Series.

INTRODUCTION: Dorsal root ganglion stimulation (DRG-S) is a viable interventional option for intractable pain management. Although systematic data are lacking regarding the immediate neurologic complications of this procedure, intraoperative neurophysiological monitoring (IONM) can be a valuable tool to detect real-time neurologic changes and prompt intervention(s) during DRG-S performed under general anesthesia and deep sedation. MATERIALS AND METHODS: In our single-center case series, we performed multimodal IONM, including peripheral nerve somatosensory evoked potentials (pnSSEPs) and dermatomal somatosensory evoked potentials (dSSEPs), spontaneous electromyography (EMG), transcranial motor evoked potentials (MEPs), and electroencephalogram (EEG) for some trials and all permanent DRG-S lead placement per surgeon preference. Alert criteria for each IONM modality were established before data acquisition and collection. An IONM alert was used to implement an immediate repositioning of the lead to reduce any possible postoperative neurologic deficits. We reviewed the literature and summarized the current IONM modalities commonly applied during DRG-S, including somatosensory evoked potentials and EMG. Because DRG-S targets the dorsal roots, we hypothesized that including dSSEP would allow more sensitivity as a proxy for potential sensory changes under generalized anesthesia than would including standard pnSSEPs. RESULTS: From our case series of 22 consecutive procedures with 45 lead placements, one case had an alert immediately after DRG-S lead positioning. In this case, dSSEP attenuation was seen, indicating changes in the S1 dermatome, which occurred despite ipsilateral pnSSEP from the posterior tibial nerve remaining at baselines. The dSSEP alert prompted the surgeon to reposition the S1 lead, resulting in immediate recovery of the dSSEP to baseline status. The rate of IONM alerts reported intraoperatively was 4.55% per procedure and 2.22% per lead (n = 1). No neurologic deficits were reported after the procedure, resulting in no postoperative neurologic complications or deficits. No other IONM changes or alerts were observed from pnSSEP, spontaneous EMG, MEPs, or EEG modalities. Reviewing the literature, we noted challenges and potential deficiencies when using current IONM modalities for DRG-S procedures. CONCLUSIONS: Our case series suggests dSSEPs offer greater reliability than do pnSSEPs in quickly detecting neurologic changes, and subsequent neural injury, during DRG-S cases. We encourage future studies to focus on adding dSSEP to standard pnSSEP to provide a comprehensive, real-time neurophysiological assessment during lead placement for DRG-S. More investigation, collaboration, and evidence are required to evaluate, compare, and standardize comprehensive IONM protocols for DRG-S.

Effectiveness of MEP and SSEP Monitoring in the Diagnosis of Neurological Dysfunction Immediately After Craniotomy Aneurysm Clipping.

OBJECTIVE: To explore the diagnostic accuracy of motor-evoked potential (MEP) and somatosensory-evoked potential (SSEP) monitoring in predicting immediate neurological dysfunction after craniotomy aneurysm clipping. METHODS: A total of 184 patients with neurosurgery aneurysms in the Affiliated Hospital of Qingdao University from April 2019 to December 2021 were retrospectively included. All patients underwent craniotomy aneurysm clipping, and MEP and SSEP were used to monitor during the operation. Receiver operating characteristic (ROC) curve analysis was used to determine the optimal cutoff value for early warning of MEP and SSEP amplitude decline and to evaluate the effectiveness of MEP and SSEP changes in predicting immediate postoperative neurological dysfunction. RESULTS: Among the 184 patients with intracranial aneurysms, the incidences of immediate postoperative neurological dysfunction were 44.4% (12/27) and 3.2% (5/157) in patients with intraoperative MEP changes and without changes, respectively. For SSEP, The incidence rates were 52.6% (10/19) and 4.2% (7/165), respectively, and the differences were statistically significant ( P <0.001). Significant changes in intraoperative MEP and SSEP were significantly associated with the development of immediate postoperative neurological deficits ( P <0.05). The critical values for early warning of MEP and SSEP amplitude decrease were: 61.6% ( P < 0.001, area under the curve 0.803) for MEP amplitude decrease and 54.6% ( P <0.001, area under the curve 0.770) for SSEP amplitude decrease. The sensitivity and specificity of MEP amplitude change in predicting immediate postoperative neurological dysfunction were 70.6% and 91.0%, respectively. For SSEP amplitude changes, the sensitivity and specificity were 58.8% and 95.8%, respectively. CONCLUSIONS: Motor-evoked potential and SSEP monitoring have moderate sensitivity and high specificity for immediate postoperative neurological dysfunction after craniotomy aneurysm clipping. Motor-evoked potential is more accurate than SSEP. Patients with changes in MEP and SSEP are at greatly increased risk of immediate postoperative neurologic deficits.

The effects of dexmedetomidine on intraoperative neurophysiologic monitoring modalities during corrective scoliosis surgery in pediatric patients: A systematic review.

BACKGROUND: During scoliosis surgery, motor evoked potentials (MEP), and somatosensory evoked potentials (SSEP) have been reported to be affected by the use of higher doses of anesthetic agents. Dexmedetomidine, a sympatholytic agent, an alpha-2 receptor agonist, has been used as an adjunctive agent to lower anesthetic dose. However, there is conflicting evidence regarding the effects of dexmedetomidine on the intraoperative neurophysiological monitoring of MEP and SSEP during surgery, particularly among pediatric patients. OBJECTIVES: This systematic review aimed to determine whether, during spinal fusion surgery in pediatric patients with scoliosis, dexmedetomidine alters MEP amplitude or SSEP latency and amplitude and, if so, whether different doses of dexmedetomidine display different effects (PROSPERO registration number CRD42022300562). METHODS: We searched PubMed, Scopus, and Cochrane Library on January 1, 2022 and included randomized controlled trials, observational cohort and case-control studies and case series investigating dexmedetomidine in the population of interest and comparing against a standardized anesthesia regimen without dexmedetomidine or comparing multiple doses of dexmedetomidine. Animal and in vitro studies and conference abstracts were excluded. RESULTS: We found substantial heterogeneity in the risk of bias (per Cochrane-preferred tools) of the included articles (n = 5); results are summarized without meta-analysis. Articles with the lowest risk of bias indicated that dexmedetomidine was associated with MEP loss and that higher doses of dexmedetomidine increased risk. In contrast, articles reporting no association between dexmedetomidine and MEP loss suffered from higher risk of bias, including suspected or confirmed problems with confounding, outcome measurement, participant selection, results reporting, and lack of statistical transparency and power. CONCLUSION: Given the limitations of the studies available in the literature, it would be advisable to conduct rigorous randomized controlled trials with larger sample sizes to assess the effects of dexmedetomidine use of in scoliosis surgery in pediatric patients.

Changes in motor evoked potentials after erector spinae block in scoliosis surgery-when to take pre-incision baseline recordings?

Multimodal intraoperative neurophysiological monitoring (IONM) is highly valuable in scoliosis surgeries for monitoring spinal cord function, particularly during instrumentation. Accurate timing of baseline recordings of TcMEP and SSEP is crucial, as any changes observed during surgery and instrumentation are compared to these baseline recordings. However, the impact of ultrasound-guided erector spinae block (USG-ESPB) on SSEP and TcMEP is not well-studied in scoliosis surgery. In this report, we present two cases of scoliosis surgery where bilateral two-level USG-ESPB using different concentrations of ropivacaine (0.375% and 0.2%) resulted in a transient and significant deterioration of TcMEP, occurring 3 minutes after the block and lasting for 20 minutes. Remarkably, SSEPs remained unchanged during this period. These findings suggest that USG-ESPB may produce TcMEP changes, highlighting the importance of carefully considering the timing of baseline TcMEP acquisition in scoliosis surgery.

Role of Intraoperative Neuromonitoring to Predict Postoperative Delirium in Cardiovascular Surgery.

OBJECTIVE: Postoperative delirium (POD) can occur in up to 50% of older patients undergoing cardiovascular surgery, resulting in hospitalization and significant morbidity and mortality. This study aimed to determine whether intraoperative neurophysiologic monitoring (IONM) modalities can be used to predict delirium in patients undergoing cardiovascular surgery. DESIGN: Adult patients undergoing cardiovascular surgery with IONM between 2019 and 2021 were reviewed retrospectively. Delirium was assessed multiple times using the Intensive Care Delirium Screening Checklist (ICDSC). Patients with an ICDSC score ≥4 were considered to have POD. Significant IONM changes were evaluated based on a visual review of electroencephalography (EEG) and somatosensory evoked potentials data and documentation of significant changes during surgery. SETTING: University of Pittsburgh Medical Center hospitals. PARTICIPANTS: Patients 18 years old and older undergoing cardiovascular surgery with IONM monitoring. MEASUREMENTS AND MAIN RESULTS: Of the 578 patients undergoing cardiovascular surgery with IONM, 126 had POD (21.8%). Significant IONM changes were noted in 134 patients, of whom 49 patients had delirium (36.6%). In contrast, 444 patients had no IONM changes during surgery, of whom 77 (17.3%) patients had POD. Upon multivariate analysis, IONM changes were associated with POD (odds ratio 2.12; 95% CI 1.31-3.44; p < 0.001). Additionally, baseline EEG abnormalities were associated with POD (p = 0.002). CONCLUSION: Significant IONM changes are associated with an increased risk of POD in patients undergoing cardiovascular surgery. These findings offer a basis for future research and analysis of EEG and somatosensory evoked potential monitoring to predict, detect, and prevent POD.

Modulation of attention to pain by goal-directed action: a somatosensory evoked potentials approach.

Background: Attentional processes are modulated by current goal pursuit. While pursuing salient cognitive goals, individuals prioritize goal-related information and suppress goal-irrelevant ones. This occurs in the context of pain too, where nonpain cognitive goal pursuit was found to have inhibitory effects on pain-related attention. Crucially, how pursuing nonpain motor goals affects pain-related somatosensory attention is still unknown. The aim of this study was to investigate whether nonpain motor goal pursuit would attenuate pain-related somatosensory attention. Methods: Healthy volunteers (N = 45) performed a robotic arm conditioning task where movements were paired with conflicting (pain and reward), threatening (only pain) or neutral (no pain and no reward) outcomes. To increase the motivational value of pursuing the nonpain motor goal, in the conflicting condition participants could receive a reward for a good motor performance. To examine somatosensory attention during movement, somatosensory evoked potentials (SEPs; N120 and P200) were obtained in response to innocuous tactile stimuli administered on a pain-relevant or pain-irrelevant body location. We expected that the threat of pain would enhance somatosensory attention. Furthermore, we expected that the possibility of getting a reward would inhibit this effect, due to pain-reward interactions. Results: Against our predictions, the amplitude of the N120 did not differ across movement types and locations. Furthermore, the P200 component showed significantly larger SEPs for conflicting and threat movements compared to neutral, suggesting that the threat of pain increased somatosensory attention. However, this effect was not modulated by nonpain motor goal pursuit, as reflected by the lack of modulation of the N120 and P200 in the conflicting condition as compared to the threat condition. This study corroborates the idea that pain-related somatosensory attention is enhanced by threat of pain, even when participants were motivated to move to obtain a reward.

Rethinking the neurophysiological concept of cortical myoclonus.

Cortical myoclonus is thought to result from abnormal electrical discharges arising in the sensorimotor cortex. Given the ease of recording of cortical discharges, electrophysiological features of cortical myoclonus have been better characterized than those of subcortical forms, and electrophysiological criteria for cortical myoclonus have been proposed. These include the presence of giant somatosensory evoked potentials, enhanced long-latency reflexes, electroencephalographic discharges time-locked to individual myoclonic jerks and significant cortico-muscular connectivity. Other features that are assumed to support the cortical origin of myoclonus are short-duration electromyographic bursts, the presence of both positive and negative myoclonus and cranial-caudal progression of the jerks. While these criteria are widely used in clinical practice and research settings, their application can be difficult in practice and, as a result, they are fulfilled only by a minority of patients. In this review we reappraise the evidence that led to the definition of the electrophysiological criteria of cortical myoclonus, highlighting possible methodological incongruencies and misconceptions. We believe that, at present, the diagnostic accuracy of cortical myoclonus can be increased only by combining observations from multiple tests, according to their pathophysiological rationale; nevertheless, larger studies are needed to standardise the methods, to resolve methodological issues, to establish the diagnostic criteria sensitivity and specificity and to develop further methods that might be useful to clarify the pathophysiology of myoclonus.

Pain-Related Vertex Evoked Potentials. Comparison of Surface Electrical to Heat Stimulation.

INTRODUCTION: Demonstration of nociceptive fiber abnormality is important for diagnosing neuropathic pain and small fiber neuropathies. This is usually assessed by brief heat pulses using lasers, contact heat, or special electrodes. We hypothesized that pain-related evoked potentials to conventional surface electrical stimulation (PREPse) can index Aδ afferences despite tactile Aß fibers coactivation. PREPse may be more readily used clinically than contact heat evoked potentials (CHEPS). METHODS: Twenty-eight healthy subjects. Vertex (Cz-A1/A2) recordings. Electrical stimulation of middle finger and second toe with conventional ring, and forearm/leg skin with cup, electrodes. Contact heat stimulation to forearm and leg. Compression ischemic nerve blockade. RESULTS: PREPse peripheral velocities were within the midrange of Aδ fibers. N1-P1 amplitude increased with pain numerical rating scale graded (0-10) electrical stimulation (n = 25) and decreased with increasing stimulation frequency. Amplitudes were unchanged by different presentation orders of four stimulation intensities. PREPse N1 (∼130 milliseconds) and N2 (∼345 milliseconds) peaks were approximately 40 milliseconds earlier than that with CHEPS. PREPse and CHEPS N1-N2 interpeak latency (∼207 milliseconds) were similar. PREPse became unrecordable with nerve blockade of Aδ fibers. CONCLUSIONS: PREPse earlier N1 and N2 peaks, and similar interpeak N1-N2 latencies and central conduction velocities, or synaptic delays, to CHEPS are consistent with direct stimulation of Aδ fibers. The relation of vertex PREPse amplitude and pain, or the differential effects of frequency stimulation, is similar to pain-related evoked potential to laser, special electrodes, or contact heat stimulation. The relationship to Aδ was validated by conduction velocity and nerve block. Clinical utility of PREPse compared with CHEPS needs validation in somatosensory pathways lesions.