Somatosensory Evoked Potential Signals Research Articles

Time varying characteristic in somatosensory evoked potentials as a biomarker of spinal cord ischemic-reperfusion injury in rat.

Spinal cord ischemic-reperfusion injury (SCIRI) could occurs during surgical procedures without detection, presenting a complex course and an unfavorable prognosis. This may lead to postoperative sensory or motor dysfunction in areas innervated by the spinal cord, and in some cases, permanent paralysis. Timely detection of SCIRI and immediate waring can help surgeons implement remedial intervention to prevent irreversible spinal cord injury. Therefore, it is crucial to develop a precise and effective method for early detection of SCIRI. This study utilized rat models to simulate intraoperative SCIRI and employed somatosensory evoked potentials (SEP) for continuous monitoring during surgery. In this study, SEP signal changes were examined in six groups with varying severities of SCIRI and one normal control group. SEP signal changes were examined during operations in different groups and correlated with postoperative behavioral and histopathological data. The result demonstrated specific changes in SEP signals during SCIRI, termed as time-varying characteristics, which are associated with the duration of ischemia and subsequent reperfusion. Time-varying characteristics in SEP could potentially serve as a new biomarker for the intraoperative detection of SCIRI. This finding is significant for clinical surgeons to identify and guide early intervention of SCIRI timely. Additionally, this measurement is easily translatable to clinical application.

Hypothermia effects on neuronal plasticity post spinal cord injury.

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. 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. 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). 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. 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. 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.

EEG Investigation on the Tactile Perceptual Performance of a Pneumatic Wearable Display of Softness

Multisensory human–machine interfaces for virtual- or augmented-reality systems are lacking wearable actuated devices that can provide users with tactile feedback on the softness of virtual objects. They are needed for a variety of uses, such as medical simulators, tele-operation systems and tele-presence environments. Such interfaces require actuators that can generate proper tactile feedback, by stimulating the fingertips via quasi-static (non-vibratory) forces, delivered through a deformable surface, so as to control both the contact area and the indentation depth. The actuators should combine a compact and lightweight structure with ease and safety of use, as well as low costs. Among the few actuation technologies that can comply with such requirements, pneumatic driving appears to be one of the most promising. Here, we present an investigation on a new type of pneumatic wearable tactile displays of softness, recently described by our group, which consist of small inflatable chambers arranged at the fingertips. In order to objectively assess the perceptual response that they can elicit, a systematic electroencephalographic study was conducted on ten healthy subjects. Somatosensory evoked potentials (SEPs) were recorded from eight sites above the somatosensory cortex (Fc2, Fc4, C2 and C4, and Fc1, Fc3, C1 and C3), in response to nine conditions of tactile stimulation delivered by the displays: stimulation of either only the thumb, the thumb and index finger simultaneously, or the thumb, index and middle finger simultaneously, each repeated at tactile pressures of 10, 20 and 30 kPa. An analysis of the latency and amplitude of the six components of SEP signals that typically characterise tactile sensing (P50, N100, P200, N300, P300 and N450) showed that this wearable pneumatic device is able to elicit predictable perceptual responses, consistent with the stimulation conditions. This proved that the device is capable of adequate actuation performance, which enables adequate tactile perceptual performance. Moreover, this shows that SEPs may effectively be used with this technology in the future, to assess variable perceptual experiences (especially with combinations of visual and tactile stimuli), in objective terms, complementing subjective information gathered from psychophysical tests.

Lower Extremity Somatosensory Evoked Potentials Predict Functional Outcomes in Complete Traumatic Cervical Spinal Cord Injury

Traumatic cervical spinal cord injury (tCSCI) is often a debilitating injury, making early prognosis important for medical and surgical planning. Currently, the best early predictors of prognosis are physical examination, imaging studies, and patient demographics. Despite these factors, patient outcomes continue to vary significantly. The purpose of this study was to evaluate the prognostic value of somatosensory evoked potentials (SSEPs) with functional outcomes in tCSCI patients. A retrospective study was conducted on prospectively collected data from 2 academic institutions. Patients 18years and older who had tCSCI and underwent posterior cervical decompression and stabilization with intraoperative neuromonitoring were reviewed. The outcomes of interest were the American Spinal Injury Association (ASIA) Impairment Scale (AIS) grade and ASIA motor score at follow-up. Outcomes measures were assessed via student t-tests, chi-squared tests, and multivariable regression analysis. A total of 79 patients were included. In complete injuries, detectable lower extremity SSEPs were associated with higher ASIA motor scores at follow-up (P= 0.002), greater increases in ASIA motor scores at follow-up (P= 0.009), and a greater likelihood of clinically important improvement in ASIA motor score (P= 0.024). Incomplete, AIS grade C injuries has higher rates of grade conversion (P= 0.019) and clinically important improvement in ASIA motor score (P= 0.010), compared to AIS grade A or B injuries. The detection of lower extremity SSEP signals during initial surgical treatment of tCSCI is associated with greater improvement in ASIA motor scores postoperatively. The association is most applicable to patients with complete injury.

Diagnostic Accuracy of Somatosensory Evoked Potential monitoring during Scoliosis correction surgery in the pediatric population: A Systematic Review (P7-4.002)

<h3>Objective:</h3> To evaluate the diagnostic accuracy of intraoperative somatosensory evoked potential (SSEP) monitoring in predicting the risk of perioperative neurological outcomes during scoliosis fusion surgery for idiopathic scoliosis (IS) in the pediatric age group (≤ 21 years). <h3>Background:</h3> Scoliosis correction surgery is the most effective treatment for pediatric IS. However, new neurological deficits during the surgery can potentially affect the outcomes of this surgery. Intraoperative neuromonitoring techniques like SSEP provide real-time information about the spinal cord and nerve roots and can be used as a reliable indicator to predict perioperative neurological deficits. <h3>Design/Methods:</h3> A systematic review of various databases to find literature on pediatric IS patients who underwent scoliosis correction with intraoperative neuromonitoring. Data collection included study design, patient demographics, procedure, neuromonitoring modalities, SSEP alarm criteria, SSEP changes (including reversible and irreversible changes), and perioperative neurological deficit. We calculated the sensitivity, specificity, and diagnostic odds ratio (DOR) of SSEP changes (total, transient, and persistent) and SSEP loss for predicting perioperative neurological deficits. <h3>Results:</h3> We included eighteen studies for our final analysis, with a total cohort of 4674 children. The incidence of a significant SSEP change was 3.1% (145/4674), while the incidence of a new neurological deficit was 1.01% (47/4674). The incidence of new neurological deficits in children with an intraoperative SSEP change was 28.28% (41/145), while it was 0.13% (6/4529) in children without an SSEP change. SSEP changes had a sensitivity of 72%, specificity of 97%, and DOR of 98.64, while SSEP loss had a sensitivity of 42%, specificity of 99.3%, and a DOR of 143.76 for predicting new neurologic deficit. Transient and Persistent SSEP changes had sensitivities of 37% and 39%, specificities of 97% and 99.2%, and DORs of 18.09 and 75.43, respectively. <h3>Conclusions:</h3> Intraoperative SSEP monitoring can predict perioperative neurological injury and help improve the surgical outcomes in pediatric scoliosis fusion surgery. <b>Disclosure:</b> Dr. Gorijala has nothing to disclose. Dr. Shaik has nothing to disclose. The institution of Dr. Thirumala has received research support from University of Pittsburgh. Dr. Anetakis has nothing to disclose. Jeffery Balzer has nothing to disclose. Donald Crammond has nothing to disclose. Dr. Shandal has nothing to disclose. Dr. Lee has nothing to disclose. The institution of Dr. Shaw has received research support from LSRS. The institution of Dr. Shaw has received research support from CSRS. The institution of Dr. Shaw has received research support from AO Spine. Dr. Shaw has received intellectual property interests from a discovery or technology relating to health care. Mr. Reddy has nothing to disclose.

Effects of dexmedetomidine on evoked potentials in spinal surgery under combined intravenous inhalation anesthesia: a randomized controlled trial

ObjectiveWe aimed to investigate the effects of different doses of dexmedetomidine (Dex) on evoked potentials in adult patients undergoing spinal surgery under intravenous anesthesia with low-concentration desflurane.MethodsNinety patients were divided into three groups at random. To maintain anesthesia in the control group (group C), desflurane 0.3 MAC (minimal alveolar concentration), propofol, and remifentanil were administered. Dex (0.5 μg·kg−1) was injected for 10 min as a loading dose in the low-dose Dex group (group DL), then adjusted to 0.2 μg·kg−1·h−1 until the operation was completed. Dex (1 μg·kg−1) was injected for 10 min as a loading dose in the high-dose Dex group (group DH), then adjusted to 0.7 μg·kg−1·h−1 until the operation was completed. The additional medications were similar to those given to group C. The perioperative hemodynamics, body temperature, intraoperative drug dosages, fluid volume, urine volume, blood loss, the latency and amplitude of somatosensory evoked potentials (SEPs) at four different time points, the incidence of positive cases of SEPs and transcranial motor evoked potentials (tcMEPs), and perioperative adverse reactions were all recorded.ResultsData from 79 patients were analyzed. The MAP measured at points T2-T4 in group DH was higher than at corresponding points in group C (P < 0.05). The MAP at point T4 in group DL was higher than at corresponding points in group C (P < 0.05). The remifentanil dosage in group DH was significantly lower than in group C (P = 0.015). The fluid volume in group DL was significantly lower than in group C (P = 0.009). There were no significant differences among the three groups in the amplitude and latency of SEP at different time points, nor in the incidence of warning SEP signals. The incidence of positive tcMEP signals did not differ significantly between groups C and DL (P > 0.05), but was significantly higher in group DH than in groups DL (P < 0.05) or C (P < 0.05). The incidence of intraoperative hypertension was significantly higher in group DH than in group C (P = 0.017).ConclusionsLow-dose Dex has no effect on the SEPs and tcMEPs monitoring during spinal surgery. High-dose Dex has no effect on SEPs monitoring, but it may increase the rate of false positive tcMEPs signals and the incidence of intraoperative hypertension.Trial registrationThis study has completed the registration of the Chinese Clinical Trial Center at 11/09/2020 with the registration number ChiCTR2000038154.

Role of Intraoperative Neurophysiological Monitoring in Preventing Stroke After Cardiac Surgery

BackgroundPerioperative stroke after cardiac surgical procedures carries significant morbidity. Dual intraoperative neurophysiological monitoring with electroencephalography (EEG) and somatosensory-evoked potentials detects cerebral hypoperfusion and predicts postoperative stroke in noncardiac procedures. We further evaluated preoperative risk factors and intraoperative neuromonitoring ability to predict postoperative stroke after cardiac operations. MethodsAll patients who underwent cardiac operations with intraoperative neurophysiological monitoring from 2009 to 2020 at a single academic medical center were retrospectively analyzed. Patients with circulatory arrest were excluded. Risks factors analyzed were sex, age, tobacco use, hypertension, diabetes mellitus, dyslipidemia, atrial fibrillation, prior cerebrovascular accident, cerebrovascular disease, antiplatelet/anticoagulant use, abnormal somatosensory-evoked potentials and EEG baselines, and significant somatosensory-evoked potentials and EEG change as well as their permanence. Patients were divided into 2 groups by 30-day postoperative stroke occurrence. Univariate and multivariate logistical regressions were used for postoperative stroke significant predictors, and Kaplan-Meier curves estimated survival. ResultsThe study included 620 patients (67.6% men), mean age 65.1 ± 14.1 years, with stroke in 5.32%. In univariate analysis, diabetes (odds ratio [OR], 2.62) and permanence of EEG change (OR, 5.35) were each associated with increased postoperative stroke odds. In multivariate analysis, diabetes (OR, 2.64) and permanent EEG change (OR, 4.22) were independently significantly associated with postoperative stroke. Overall survival was significantly better for patients with no intraoperative neurophysiological monitoring changes (P < .005). ConclusionsPermanent EEG change and diabetes were significant postoperative stroke predictors in cardiac operations. Furthermore, overall survival out to 10 years postoperatively was significantly higher in the group without intraoperative neurophysiological monitoring changes, emphasizing its important predictive role.

Intraoperative Sensory Signals Predict Prognosis for Patients with Traumatic Cervical Spinal Cord Injury

In patients with traumatic cervical spinal cord injury (tCSCI), the potential role of intraoperative neuromonitoring as a prognostic tool has been insufficiently studied. This study aimed to determine if detectable signals during intraoperative neuromonitoring portend a greater likelihood of recovery for patients with tCSCI. Patients who underwent decompression and surgical fixation following tCSCI were retrospectively reviewed through previously prospectively collected data from the Surgical Timing in Acute Spinal Cord Injury Study. Improvement in American Spinal Injury Association (ASIA) motor score and ASIA Impairment Scale grade conversion rates at final follow-up were compared between patients with detectable intraoperative neuromonitoring somatosensory evoked potential (SSEP) signals and those without detectable signals. Forty-nine patients had intraoperative neuromonitoring. Patients with incomplete tCSCI had detectable lower extremity SSEPs more often than patients with complete tCSCI (56.3% vs. 23.5%, P= 0.028). There was no difference in detectable upper extremity SSEPs between complete and incomplete tCSCI (65.6% vs. 58.8%, P= 0.638). Of the 17 patients with complete tCSCI, patients with detectable lower extremity SSEPs had ASIA motor scores similar to the nondetectable cohort on admission (21.5 vs. 16.2, P= 0.609) but higher ASIA motor scores at final follow-up (57.5 vs. 27.1, P= 0.041). Of the 32 patients with incomplete spinal cord injury, there was no difference in grade conversion or motor scores between detectable and nondetectable SSEP cohorts. The presence of upper extremity SSEP signals in patients who present with complete tCSCI portends greater improvement in ASIA motor scores and likelihood of American Spinal Injury Association Impairment Scale grade conversion at final follow-up.

P115. Intraoperative sensory signals predict prognosis for patients with traumatic cervical spinal cord injury

<h3>BACKGROUND CONTEXT</h3> Traumatic cervical spinal cord injury (tCSCI) is a devasting life-altering event. Prognosis is largely determined by the formal neurological assessment known as International Standards for Neurological Classification of Spinal Cord Injury (ISNCSCI), which is graded using the American Spinal Injury Association Impairment Scale grade (AIS grade). AIS grade A is designated as a loss of sacral motor and sensory functions and is associated with the worst prognosis. Many studies have shown that AIS grades are a predictor for neurologic recovery and functional status postinjury. However, the timing of the ISNCSCI exam and AIS grade can greatly influence the reliability of the prognosis. Intraoperative neuromonitoring is routinely used during spine surgery to detect injuries to the spinal cord or nerve roots by measuring signal transmission. However, in patients with SCI, the role of intraoperative neuromonitoring as a potential prognostic tool has not been studied. <h3>PURPOSE</h3> The purpose of this study was to assess if detected signals during intraoperative neuromonitoring portends a greater likelihood of recovery for patients with tCSCI. <h3>STUDY DESIGN/SETTING</h3> Retrospective cohort study at a high-volume, academic level I trauma center. <h3>PATIENT SAMPLE</h3> A total of 49 patients undergoing decompression and surgical fixation of following tCSCI. <h3>OUTCOME MEASURES</h3> Improvement in ASIA motor score and AIS grade conversion rate. <h3>METHODS</h3> Patients undergoing decompression and surgical fixation following tCSCI were retrospectively reviewed at a single high-volume, academic level I trauma center. Improvement in ASIA motor score and AIS grade conversion rates at final followup were compared between patients with detectable intraoperative neuromonitoring upper extremity somatosensory evoked potential (SSEP) signals and those without detectable signals. Motor evoked potentials (MEP) were not routinely performed. <h3>RESULTS</h3> A total of 49 patients with tCSCI underwent decompression and surgical fixation with intraoperative neuromonitoring. Seventeen patients with complete SCI and 32 patients with AIS grades B or C on admission were included in the study with a mean followup of 14.3 months. Patients with incomplete SCI had detectable lower extremity SSEPs more often compared to patients with complete SCI (56.3% vs 23.5%, p = 0.028). However, there was no difference in detectable upper extremity SSEPs between complete and incomplete SCI (65.6% vs 58.8%, p=0.638). Of the 17 patients with complete SCI, patients with detectable upper extremity SSEPs cohort had a higher rate of AIS grade conversion compared to the nondetectable cohort (80.0% vs 28.6%, p = 0.034). Furthermore, the detectable upper extremity SSEPs cohort had greater ASIA motor scores on admission (25.9 vs 5.4, p=0.002), at final follow-up (54.0 vs 8.9, and with overall improvement (26.1 vs 3.4, p=0.021) compared to the non-detectable cohort. Patients with detectable lower extremity SSEPs had similar ASIA motor scores on admission (21.5 vs 16.2, 0.609) but higher ASIA motor scores at final followup (57.5 vs 27.1, p=0.041) compared to the nondetectable cohort. Of the 32 patients with incomplete SCI, there was no difference in AIS grade conversion or ASIA motor scores between the detectable and non-detectable SSEP cohorts. <h3>CONCLUSIONS</h3> The presence of upper extremity SSEP signals in patients who present with complete tCSCI portended a better prognosis with greater likelihood of conversion to an incomplete AIS grade and greater motor score at final followup. These results demonstrate an objective and measurable marker of prognosis that can be used for clinical decision making and patient counseling regarding neurologic recovery. <h3>FDA DEVICE/DRUG STATUS</h3> This abstract does not discuss or include any applicable devices or drugs.

Long-term Neurologic Outcome After Spinal Ependymoma Resection With Multimodal Intraoperative Electrophysiological Recording: Cohort Study and Review of the Literature.

ObjectiveTo evaluate how multimodal intraoperative neuromonitoring (IONM) changes during spinal ependymoma (SE) resection correlate with long-term neuro-functional outcomes. MethodsA retrospective analysis of patients aged 18 years or older who underwent surgical resection for SE over a 10-year period was conducted. IONM changes were defined as sustained transcranial motor evoked potential (TcMEP) and/or somatosensory evoked potential (SSEP) signal decrease of 50% or greater from baseline. Primary endpoints were postoperative modified McCormick Neurologic Scale (MNS) scores at postoperative day (POD) < 2, 6 weeks, 1 year, and 2 years. Univariate and multivariate analyses were performed.ResultsTwenty-nine patients were identified. Average age was 44.2±15.4 years. Sixteen (55.2%) were male and 13 (44.8%) were female. Tumor location was 10 cervical-predominant (34.5%), 13 thoracic-predominant (44.8%), and 6 lumbar/conus-predominant (20.7%). A majority (69.0%) were World Health Organization grade 2 tumors. Twentyfour patients (82.8%) achieved gross total resection. Thirteen patients (44.8%) had a sustained documented IONM signal change and 10 (34.5%) had a TcMEP change with or without derangement in SSEP. At POD < 2, 6 weeks, 1 year, and 2 years, MNS was significantly higher for those when analyzing subgroups with either any sustained IONM or TcMEP±SSEP signal attenuation > 50% below baseline (all p<0.05). ConclusionSustained IONM derangements > 50% below baseline, particularly for TcMEP, are significantly associated with higher MNS postoperatively out to 2 years. Intraoperative and postoperative management of these patients warrant special consideration to limit neurologic morbidity.

Maximizing surgical resection in revision surgery for an intramedullary spinal cord tumour using DTI/tractography and direct spinal cord stimulation: A technical note

BackgroundIntramedullary spinal cord tumours are formidable lesions in spine surgery due to the high risk of postoperative deficits associated with surgical resection. Traditional MRI imaging fails to provide a 3-D rendering of the relationship between the tumour and spinal cord sensory and motor pathways; in contrast, DTI/tractography can show this relationship with the potential to reduce surgery-related morbidity. The use of intraoperative somatosensory evoked potentials (SSEP) and transcranial motor evoked potentials (MEP) have also been considered a standard of care to minimize neurologic complications of surgery. However, in situations where both baseline SSEPs and MEPs are unobtainable, D-wave and direct cord stimulation can become invaluable intra-operative tools. MethodsA 6 year old child presented with new growth from an incompletely resected thoracic intramedullary dermoid tumour. Pre-operative DTI/tractography images were obtained. During tumour resection, SSEP and MEP signals were unable to be obtained, however intraoperative monitoring of the spinal cord was undertaken with D-wave monitoring and direct cord stimulation. ResultsThis multimodal monitoring technique allowed identification of the corticospinal tracts intra-operatively and allowed safe tumour resection. Post-operative MRI revealed gross total resection and the patient returned to her pre-operative neurological baseline without incurring any further deficits. ConclusionsWe have presented a technical description of the clinical utility of DTI/tractography in surgical planning, and D-wave monitoring with direct cord stimulation as adjuncts in the resection of an intramedullary cord tumour. This is particularly useful in the scenario where TcMEP/SSEP signals cannot be obtained and in revision surgery for intramedullary spinal cord tumours.

240. Utility of intraoperative neuromonitoring alerts relating to adverse outcomes in spine surgery: a study of 289 patients

<h3>BACKGROUND CONTEXT</h3> Although rare, one of the most problematic complications during spine surgery is neurologic injury with subsequent deficit. The use of multimodal intraoperative neuromonitoring (MIOM) during spine surgery provides the surgical team with real-time assessment of the neurological physiology and function. MIOM is thought to be sensitive and specific for identifying perioperative neurological injury in spinal surgery especially deformity surgery. However, results from recent studies have cast doubt on the effectiveness of certain MIOM techniques in detecting neurological injury in spine surgery patients. <h3>PURPOSE</h3> The purpose of this study was to improve spine surgery patient safety and outcomes by minimizing the incidence of postoperative new neurological deficits correlated to intraoperative neuromonitoring alerts from two neuromonitoring signals: motor evoked potentials (MEPs) and somatosensory evoked potentials (SSEPs). <h3>STUDY DESIGN/SETTING</h3> A multicenter, multisurgeon prospective quality improvement initiative that was performed in conjunction with neuro alert (NA) monitoring services. All data was retrospectively analyzed. <h3>PATIENT SAMPLE</h3> A total of 289 patients who (1) received nondeformity lumbar (45%), cervical (45%) or thoracic (10%) surgery between July 2018 and July 2019 and (2) underwent SSEP and MEP monitoring throughout the entire surgery. <h3>OUTCOME MEASURES</h3> This study investigated the incidence of immediate postoperative (≤ 48 hours) new neurological deficits. sensitivty, specificity, postive predictive value (PPV), and negative predictive value (NPV) was calculated for the SSEP and MEP signals. <h3>METHODS</h3> This study was a multicenter, multisurgeon prospective quality improvement initiative that was performed in conjunction with neuro alert (NA) monitoring services. All neuromonitoring was carried out in accordance with the guidelines set forth by the American Academy of Neurology and the American Board for Neurophysiological Monitoring Programs. Two commonly used MIOM signals were tracked: somatosensory evoked potentials (SSEPs) and motor evoked potentials (MEPs). Intraoperative data were recorded using a paper data collection tool. SSEP and MEP signal changes were classified as alerts based on the following best practices guidelines outlined in the literature: 50% or greater decrease in signal amplitude and/or a 10% or greater increase in signal latency with no signal recovery. Immediate postoperative (≤ 48 hours) new neurological deficit status was assessed for all patients. Neurological deficit information was recorded via paper during a postoperative physical exam that all physicians conducted on the patient within 48 hours after surgery. The sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) for the SSEP and MEP signals were calculated. <h3>RESULTS</h3> SSEP and MEP neuromonitoring data was analyzed for 289 patients who (1) received non-deformity lumbar (45%), cervical (45%) or thoracic (10%) surgery between July 2018 and July 2019 and (2) underwent SSEP and MEP monitoring throughout the entire surgery. A total of 22 MEP and 16 SSEP alerts were triggered. Ninety percent (20) of MEP alerts occurred during anterior cervical discectomy and fusion (ACDF) procedures; one MEP alert was triggered during a posterior cervical fusion and one MEP alert was triggered during a lumbar laminectomy. 56% (9) of SSEP alerts occurred during transforaminal lumbar interbody fusion procedures while 25% (4) occurred during ACDFs and 19% (3) occurred during lumbar laminectomy surgeries. MEP and SSEP alerts were most frequently triggered during the decompression surgical step (45% and 25%, respectively). There were 6 instances (n = 6) of new neurological deficits that occurred within 48 hours postsurgery. These deficits were as follows: foot drop (n = 1), leg weakness (n = 1), arm weakness (n = 2), bilateral paraparesis (n = 1) and unilateral paraparesis (n = 1). The patient who developed unilateral paraparesis was myelopathic. All other patients with new neurological deficits did not have a history of myelopathy. The MEP alert should have been triggered for all 6 patients, however the signal was only alerted in the patient who developed bilateral paraparesis and in one patient who developed arm weakness. In 4/6 patients, MEP alerts were not triggered but a new neurological deficit occurred, resulting in a false negative rate of 67% and a sensitivity of 33%. In addition, MEPs had a specificity of 92.4%, PPV of 11% and NPV of 98.5%. The SSEP signal showed 100% sensitivity and displayed a specificity, PPV and NPV of 95.2%, 12.5% and 100%, respectively. <h3>CONCLUSIONS</h3> The MEP signal had a low sensitivity of 33%, which differed greatly from that of the SSEP signal (100%). The specificity, PPV and NPV were comparable between the SSEPs and MEPs. The PPV was low for both signals. Results indicate that the accuracy of SSEP and MEP alerts in detecting new neurological deficits in spine surgery patients immediately postsurgery is questionable. The effectiveness of these two intraoperative neuromonitoring techniques in identifying neurological injury seems uncertain and needs to be explored further. <h3>FDA DEVICE/DRUG STATUS</h3> This abstract does not discuss or include any applicable devices or drugs

Effect of thoracic spinal cord injury on forelimb somatosensory evoked potential

In this paper, we investigate the forelimbs somatosensory evoked potential (SSEP) signals, which are representative of the integrity of ascending sensory pathways and their stability as well as function, recorded from corresponding cortices, post thoracic spinal cord injury (SCI). We designed a series of distinctive transection SCI to investigate whether forelimbs SSEPs change after right T10 hemi-transection, T8 and T10 double hemi-transection and T8 complete transection in rat model of SCI. We used electrical stimuli to stimulate median nerves and recorded SSEPs from left and right somatosensory areas of both cortices. We monitored pre-injury baseline and verified changes in forelimbs SSEP signals on Days 4, 7, 14, and 21 post-injury. We previously characterized hindlimb SSEP changes for the abovementioned transection injuries. The focus of this article is to investigate the quality and quantity of changes that may occur in the forelimb somatosensory pathways post-thoracic transection SCI. It is important to test the stability of forelimb SSEPs following thoracic SCI because of their potential utility as a proxy baseline for the traumatic SCIs in clinical cases wherein there is no opportunity to gather baseline of the lower extremities. We observed that the forelimb SSEP amplitudes increased following thoracic SCI but gradually returned to the baseline. Despite changes found in the raw signals, statistical analysis found forelimb SSEP signals become stable relatively soon. In summary, though there are changes in value (with p > 0.05), they are not statistically significant. Therefore, the null hypothesis that the mean of the forelimb SSEP signals are the same across multiple days after injury onset cannot be rejected during the acute phase.

A novel approach of using brachial plexus blockade as an experimental model for diagnosis of intraoperative nerve dysfunction with somatosensory evoked potentials: a blinded proof-of-concept study.

Intraoperative nerve dysfunction has been difficult to investigate because of its rarity and unpredictable occurrence. The diagnostic test attributes of nerve function monitors have not been clearly defined. This proof-of-concept study aimed to assess the feasibility of using brachial plexus blockade (BPB) in awake patients as an experimental model for nerve dysfunction to characterize the diagnostic test attributes of somatosensory evoked potentials (SSEPs). We obtained baseline SSEPs and neurologic function in patients and subsequently placed BPBs (experimental model) to generate progressive states of nerve dysfunction. We monitored SSEP changes (index test) and neurologic symptoms (reference standard) simultaneously during the onset of BPB to determine the temporal relationships and diagnostic test attributes of SSEPs. Brachial plexus blockade produced differential motor and sensory dysfunction that allowed simultaneous clinical and neurophysiologic assessment. One hundred and fifty-seven pairs of multiple data points from 14 patients were included for final analysis. The onset of abnormal SSEP signals almost always preceded the onset of neurologic symptoms. The sensitivities and specificities of SSEP to detect the impairment of power (motor rating score ≤ 4/5), cold sensation, and two-point discrimination were 100% and 67%, 99% and 55%, and 100% and 46%, respectively. This study found that BPB can produce sufficient differential nerve dysfunction to allow adequate evaluation of the diagnostic test attributes of SSEPs as a nerve monitor. The results of this study may stimulate further work on refining intraoperative nerve dysfunction models and diagnostic nerve function monitors. www.clinicaltrials.gov (NCT03409536); registered 24 January 2018.

The capacity of neurological pupil index to predict absence of somatosensory evoked potentials after cardiac arrest—A study protocol

Anoxic-ischemic brain injury is the most common cause of death after cardiac arrest (CA). Robust methods to detect severe injury with a low false positive rate (FPR) for poor neurological outcome include the pupillary light reflex (PLR) and somatosensory evoked potentials (SSEP). The PLR can be assessed manually or with automated pupillometry which provides the neurological pupil index (NPi). We aim to describe the interrelation between NPi values and the absence of SSEP cortical response and to evaluate the capacity of NPi to predict the absence of cortical SSEP response in comatose patients after CA. A total of 50 patients will be included in an explorative, prospective, observational study of adult (>18years) comatose survivors of CA admitted to intensive care in a university hospital. NPi assessed with a hand-held pupillometer will be compared to SSEP signals recorded >48hours after CA. Primary outcomes are sensitivity, specificity, and odds ratio for NPi to predict bilateral absence of the SSEP N20 signal, with NPi values corresponding to <5% FPRs of SSEP absence. Secondary outcomes are the PLR and SSEP sensitivity, specificity, and odds ratio for poor neurological outcome at hospital discharge and death at 30days. The PLR and SSEP may have a systematic interrelation, and a certain NPi threshold could potentially predict the absence of cortical SSEP response. If this can be concluded from the present study, SSEP testing could be excluded in certain patients to save resources in the multimodal prognostication after CA. Editorial comment The interrelation between loss of the pupillary light reflex (PLR) and the loss of cortical response to a somatosensory evoked potential (SSEP) in comatose cardiac arrest patients is not known. This exploratory prospective study is designed to evaluate whether a specific degree of attenuated PLR, as measured by semiautomated pupillometry, can predict the bilateral loss of cortical SSEP response in severe anoxic/ischemic brain injury. Such an interrelation between the two methods would enable the use of pupillometry rather than the more resource demanding SSEP for neurologic prognostication in post cardiac arrest patients. ClinicalTrials.gov, NCT04720482, Registered 21 January 2021, retrospectively registered.

A translational study of somatosensory evoked potential time-frequency components in rats, goats, and humans.

Somatosensory evoked potentials (SEPs) have been widely used to assess neurological function in clinical practice. A good understanding of the association between SEP signals and neurological function is helpful for precise diagnosis of impairment location. Previous studies on SEPs have been reported in animal models. However, few studies have reported the relationships between SEP waveforms in animals and those in humans. In this study, we collected normal SEP waveforms and decomposed them into specific time-frequency components (TFCs). Our results showed three stable TFC distribution regions in intact goats and rats and in humans. After we induced spinal cord injury in the animal models, a greater number of small TFC distribution regions were observed in the injured goat and rat groups than in the normal group. Moreover, there were significant correlations (P < 0.05) and linear relationships between the main SEP TFCs of the human group and those of the goat and rat groups. A stable TFC distribution of SEP components was observed in the human, goat and rat groups, and the TFC distribution modes were similar between the three groups. Results in various animal models in this study could be translated to future clinical studies based on SEP TFC analysis. Human studies were approved by the Institutional Review Board of the University of Hong Kong/Hospital Authority Hong Kong West Cluster (approval No. UM 05-312 T/975) on December 5, 2005. Rat experiments were approved by the Committee on the Use of Live Animals in Teaching and Research of Li Ka Shing Faculty of Medicine of the University of Hong Kong (approval No. CULART 2912-12) on January 28, 2013. Goat experiments were approved by the Animal Ethics Committee of Affiliated Hospital of Guangdong Medical University (approval No. GDY2002132) on March 5, 2018.

Role of Intraoperative Neurophysiologic Monitoring in Internal Carotid Artery Injury During Endoscopic Endonasal Skull Base Surgery

In the present study, we investigated the role of intraoperative neuromonitoring (IONM) in internal carotid artery (ICA) injury during endoscopic endonasal skull base surgery (EESBS). The study group included all 13 patients who had experienced an ICA injury during EESBS with IONM from 2004 to 2017. The medical records were reviewed for the perioperative data. The IONM reports were reviewed to evaluate the baseline somatosensory evoked potentials (SSEP), electroencephalography (EEG), and brainstem auditory evoked potentials (BAEP) and their significant changes related to ICA injury and/or the subsequent surgical/endovascular interventions. All 13 patients had undergone SSEP and 7 patients had BAEP monitoring during surgery. EEG was added during emergent angiography following the surgery for 5 patients. Two patients showed significant SSEP changes, and one showed significant SSEP and EEG changes, indicating cerebral hypoperfusion. Of these 3 patients, patient 1 had experienced irreversible SSEP loss with postoperative stroke. Patients 2 and 3 had SSEP and/or EEG changes that had recovered to baseline after interventions without postoperative deficits. Despite ICA injury, 10 patients showed no significant SSEP and/or EEG changes, and all 7 patients with BAEP monitoring showed no significant BAEP changes, indicating adequate cerebral and brainstem perfusion, respectively. The injured ICA was sacrificed in 4 patients, of whom 3 showed stable SSEP and 1 had experienced irreversible SSEP loss. IONM correlated with the postoperative neurologic examination findings in all cases, adequately predicting the neurologic outcomes after ICA injury. SSEP and EEG monitoring can accurately detect cerebral hypoperfusion and provide real-time feedback during surgery. SSEP and EEG changes predicted forneurologic outcomes and guide surgical decisions regarding the preservation or sacrifice of the ICA. Comprehensive multimodality monitoring according to the surgical risks can serve to detect and guide the management of ICA injury in EESBS.

Trading baseline with forelimbs somatosensory evoked potential for longitudinal analysis in thoracic transection spinal cord injury

Patients who suffered from spinal cord injury (SCI) that come to healthcare professionals for diagnosis and treatment do not have electrophysiology baseline of somatosensory evoked potential (SSEP). The SSEP has always been used in research for data comparison to detect onset and severity of the SCI as well as for assessing its progress, endogenous and therapeutic recovery. This unmet need has motivated us to develop a new tool to substitute the baseline data with forelimb SSEP data of the same day. In this study, we report the development and investigation of three distinctive thoracic transections (right T10 hemi-transection (Rxl), left T8 and right T10 double hemi-transection (Dxl) and T8 complete transection (Cxl)) spinal cord injuries in an adult rat model. We used our well-established monitoring methods to obtain SSEP baselines as well as post-injury signals from days 4, 7, 14 and 21. We observed that spectral coherences obtained from non-injured spinal cord pathways are always above 0.8. The spectral coherence is dimensionless measure with values between 0 and 1 and measures the correlation between two time signals in the frequency domain. Analysis of variance (ANOVA) results also showed that there is a significant difference between the spectral coherence componanet means before and after injury with reaching p = 0.05 for Rxl, p = 0.02 for DxI, and p = 0.00 for CxI. Our signal processing enables us to replicate comparable detection of the natural history of injuries longitudinally without the implication of baseline SSEP signals, highlighting the potential of this analysis method for clinical studies.

Somatosensory Evoked Potentials and Neuroprognostication After Cardiac Arrest.

Improved understanding of post-cardiac arrest syndrome and clinical practices such as targeted temperature management have led to improved mortality in this cohort. Attention has now been placed on development of tools to aid in predicting functional outcome in comatose cardiac arrest survivors. Current practice uses a multimodal approach including physical examination, neuroimaging, and electrophysiologic data, with a primary utility in predicting poor functional outcome. These modalities remain confounded by self-fulfilling prophecy and the withdrawal of life-sustaining therapies. To date, a reliable measure to predict good functional outcome has not been established or validated, but the use of quantitative somatosensory evoked potential (SSEP) shows potential for this use. MEDLINE and EMBASE search using words "Cardiac Arrest" and "SSEP," "Somato sensory evoked potentials," "qSSEP," "quantitative SSEP," "targeted temperature management in cardiac arrest" was conducted. Relevant recent studies on targeted temperature management in cardiac arrest, plus studies on SSEP in cardiac arrest in the setting of hypothermia and without hypothermia, were included. In addition, animal studies evaluating the role of different components of SSEP in cardiac arrest were reviewed. SSEP is a specific indicator of poor outcomes in post-cardiac arrest patients but lacks sensitivity and has not clinically been established to foresee good outcomes. Novel methods of analyzing quantitative SSEP (qSSEP) signals have shown potential to predict good outcomes in animal and human studies. In addition, qSSEP has potential to track cerebral recovery and guide treatment strategy in post-cardiac arrest patients. Lying beyond the current clinical practice of dichotomized absent/present N20 peaks, qSSEP has the potential to emerge as one of the earliest predictors of good outcome in comatose post-cardiac arrest patients. Validation of qSSEP markers in prospective studies to predict good and poor outcomes in the cardiac arrest population in the setting of hypothermia could advance care in cardiac arrest. It has the prospect to guide allocation of health care resources and reduce self-fulfilling prophecy.

Fully Passive Flexible Wireless Neural Recorder for the Acquisition of Neuropotentials from a Rat Model.

Wireless implantable neural interfaces can record high-resolution neuropotentials without constraining patient movement. Existing wireless systems often require intracranial wires to connect implanted electrodes to an external head stage or/and deploy an application-specific integrated circuit (ASIC), which is battery-powered or externally power-transferred, raising safety concerns such as infection, electronics failure, or heat-induced tissue damage. This work presents a biocompatible, flexible, implantable neural recorder capable of wireless acquisition of neuropotentials without wires, batteries, energy harvesting units, or active electronics. The recorder, fabricated on a thin polyimide substrate, features a small footprint of 9 mm × 8 mm × 0.3 mm and is composed of passive electronic components. The absence of active electronics on the device leads to near zero power consumption, inherently avoiding the catastrophic failure of active electronics. We performed both in vitro validation in a tissue-simulating phantom and in vivo validation in an epileptic rat. The fully passive wireless recorder was implanted under rat scalp to measure neuropotentials from its contact electrodes. The implanted wireless recorder demonstrated its capability to capture low voltage neuropotentials, including somatosensory evoked potentials (SSEPs), and interictal epileptiform discharges (IEDs). Wirelessly recorded SSEP and IED signals were directly compared to those from wired electrodes to demonstrate the efficacy of the wireless data. In addition, a convoluted neural network-based machine learning algorithm successfully achieved IED signal recognition accuracy as high as 100 and 91% in wired and wireless IED data, respectively. These results strongly support the fully passive wireless neural recorder's capability to measure neuropotentials as low as tens of microvolts. With further improvement, the recorder system presented in this work may find wide applications in future brain machine interface systems.