Cortical Somatosensory Evoked Potentials Research Articles

Value of multi-channel somatosensory evoked potentials recording in patients undergoing scoliosis correction surgery.

We aimed to investigate the value of intraoperative multi-channel recording of somatosensory evoked potentials (SSEPs) in patients undergoing posterior instrumentation surgery with fusion. This study included 176 patients with scoliosis who underwent posterior correction surgery from January 2019 to June 2020. Among them, 88 patients underwent routine SSEPs monitoring via single-channel (Cz'-Fpz) cortical recording (control group), while the remaining 88 patients underwent multi-channel (Cz'-Fpz and C3'-C4') SSEPs monitoring in the cortex. Chi-square and Fisher's exact tests were used to analyze the influence of age, spinal deformity classification, and Cobb angle on waveform differentiation and the success rate of SSEPs monitoring. Univariate analysis revealed that age, type of scoliosis, and Cobb angle exerted significant effects on the success rate of intraoperative SSEPs monitoring, and the SSEPs waveform differentiation rate was poorest among patients with congenital scoliosis. Intraoperative monitoring results indicated that the success rate of single-channel SSEPs monitoring was 90.9%, while that of multi-channel monitoring was 98.9% (P < 0.05). Among the intraoperative alarm cases, the incidence of adverse events after single-channel SSEPs monitoring was 66.7%, while the incidence of adverse events after multi-channel SSEPs monitoring was only 28.6%. Multi-channel cortical SSEPs monitoring can effectively and accurately evaluate the function of the posterior column of the spinal cord. Use of multi-channel SSEP monitoring may help to improve the success rate of monitoring and reduce the incidence of postoperative adverse events in patients with congenital scoliosis.

Cortical somatosensory evoked potential amplitudes and clinical outcome after cardiac arrest: a retrospective multicenter study

ObjectiveBilaterally absent cortical somatosensory evoked potentials (SSEPs) reliably predict poor outcome in comatose cardiac arrest (CA) patients. Cortical SSEP amplitudes are a recent prognostic extension; however, amplitude thresholds, inter-recording, and inter-rater agreement remain uncertain.MethodsIn a retrospective multicenter cohort study, we determined cortical SSEP amplitudes of comatose CA patients using a standardized evaluation pathway. We studied inter-recording agreement in repeated SSEPs and inter-rater agreement by four raters independently determining 100 cortical SSEP amplitudes. Primary outcome was assessed using the cerebral performance category (CPC) upon intensive care unit discharge dichotomized into good (CPC 1–3) and poor outcome (CPC 4–5).ResultsOf 706 patients with SSEPs with median 3 days after CA, 277 (39.2%) had good and 429 (60.8%) poor outcome. Of patients with bilaterally absent cortical SSEPs, one (0.8%) survived with CPC 3 and 130 (99.2%) had poor outcome. Otherwise, the lowest cortical SSEP amplitude in good outcome patients was 0.5 µV. 184 (42.9%) of 429 poor outcome patients had lower cortical SSEP amplitudes. In 106 repeated SSEPs, there were 6 (5.7%) with prognostication-relevant changes in SSEP categories. Following a standardized evaluation pathway, inter-rater agreement was almost perfect with a Fleiss’ kappa of 0.88.InterpretationBilaterally absent and cortical SSEP amplitudes below 0.5 µV predicted poor outcome with high specificity. A standardized evaluation pathway provided high inter-rater and inter-recording agreement. Regain of consciousness in patients with bilaterally absent cortical SSEPs rarely occurs. High-amplitude cortical SSEP amplitudes likely indicate the absence of severe brain injury.

Somatosensory Evoked Potentials

The measurement of somatosensory evoked potentials(SEPs)is a basic clinical technique used for functional mapping and monitoring of brain and spinal cord responses during surgery. Since the potential evoked by a single stimulus is smaller compared to the surrounding electrical activity(background brain activity and/or electromagnetic artifacts), the average measurement of responses to multiple controlled stimuli across time-locked trials must be taken to determine the resultant waveform. SEPs can be analyzed in terms of polarity, latency from stimulus onset, or the amplitude from the baseline for each waveform component. The amplitude is used for monitoring purposes, while the polarity is used for mapping purposes. For example, an amplitude 50% lower than that of the control waveform may suggest the presence of significant influence on the sensory pathway, whereas a phase reversal in polarity, established by a cortical SEP distribution, usually indicates localization to the central sulcus.

A Prediction Model for Normal Variation of Somatosensory Evoked Potential During Scoliosis Surgery

Somatosensory evoked potential (SEP) has been commonly used as intraoperative monitoring to detect the presence of neurological deficits during scoliosis surgery. However, SEP usually presents an enormous variation in response to patient-specific factors such as physiological parameters leading to the false warning. This study proposes a prediction model to quantify SEP amplitude variation due to noninjury-related physiological changes of the patient undergoing scoliosis surgery. Based on a hybrid network of attention-based long-short-term memory (LSTM) and convolutional neural networks (CNNs), we develop a deep learning-based framework for predicting the SEP value in response to variation of physiological variables. The training and selection of model parameters were based on a 5-fold cross-validation scheme using mean square error (MSE) as evaluation metrics. The proposed model obtained MSE of 0.027[Formula: see text][Formula: see text] on left cortical SEP, MSE of 0.024[Formula: see text][Formula: see text] on left subcortical SEP, MSE of 0.031[Formula: see text][Formula: see text] on right cortical SEP, and MSE of 0.025[Formula: see text][Formula: see text] on right subcortical SEP based on the test set. The proposed model could quantify the affection from physiological parameters to the SEP amplitude in response to normal variation of physiology during scoliosis surgery. The prediction of SEP amplitude provides a potential varying reference for intraoperative SEP monitoring.

Clinical Application of Evoked Potentials in the Operation of Cervical Spondylotic Myelopathy with Different Imaging.

Objective To observe the effects of improvement of cervical spondylotic myelopathy with different imaging signals after cortical somatosensory-evoked potentials on the functional recovery of postoperative patients and the effect of surgery. Methods A total of 60 patients with cervical spondylotic myelopathy who were hospitalized in our hospital from January 2020 to December 2020 were selected and divided into a case group (30 cases) with MRI-indicated changes in intramedullary signals and a control group (30 cases) with MRI-indicated spinal cord changes. Intragroup and intergroup control studies were conducted through general observation indexes, neurological evaluation indexes, imaging, and evoked potential observation indexes. Somatosensory-evoked potentials were performed before operation, 1 week after operation, and 24 weeks after operation, and the JOA score of each patient was obtained before operation, 1 week after operation, and 24 weeks after operation. Results The JOA score of 1 week after operation of the case group is (16.25 ± 1.54) and the control group is (11.89 ± 1.63), and there is a statistically significant difference (P < 0.05). The JOA score of the case group 24 weeks after operation is (25.27 ± 1.03) and the control group is (13.28 ± 1.03), and the difference is statistically significant (P < 0.05). The improvement rate of 1 week after operation and 24 weeks after operation was statistically significant between the two groups (P < 0.05). The case group improvement rate is (70.5 ± 8.72)% and the control group is (40.5 ± 9.81)%, and the difference is statistically significant between the two groups (P < 0.05). Conclusion The preoperative intramedullary signal changes can be used as an effective index for patients with cervical spondylotic myelopathy to use somatosensory-evoked potentials to assess the prognosis of patients after surgery.

Misconceptions in IONM Part II: Does Anodal Blocking Occur and Is Bipolar Stimulation Necessary with Intraoperative Somatosensory Evoked Potentials?

ABSTRACT Current intraoperative somatosensory evoked potential (SSEP) guidelines recommend bipolar stimulation with the anode at or near the crease of the wrist and the cathode 2–4 cm proximal to the anode for median nerve SSEPs. The rationale for this cathode proximal bipolar configuration appears to be the avoidance of anodal blocking; however, there is a paucity of experimental support for the existence of anodal blocking. Evidence that bipolar stimulation preferentially drives stimulation from the cathode better than monopolar cathodal or monopolar anodal in peripheral nerves in human neurophysiology is also lacking. This study compared anode proximal to anode distal bipolar stimulation of median nerve SSEPs and the efficacy of monopolar cathode to monopolar anode stimulation in generating median, ulnar, and tibial nerve SSEPs. No difference in median nerve cortical SSEP amplitude was observed between anode proximal and anode distal bipolar stimulation at supramaximal stimulation suggesting cathode proximal bipolar is equal to anode proximal bipolar stimulation at supramaximal intensity. This data suggests that anodal blocking does not occur inintraoperative SSEPs. Furthermore, no differences were observed in ulnar, median, and tibial nerve SSEP cortical or subcortical amplitudes and latencies between monopolar cathodal or monopolar anodal stimulation suggesting monopolar cathode and anode stimulation are equally effective at evincing intraoperative SSEPs at supramaximal intensity.

SY2.3. Evaluation of dystonia

Dystonia is a syndrome characterized by sustained or intermittent muscle contractions causing abnormal, often repetitive, movements, postures, or both. It can be primary or secondary and the patient can present with pure dystonia or dystonia along with other movement disorders such as tremor, myoclonus, parkinsonism, etc. Evaluation of a patient presenting primarily with dystonia includes detailed clinical evaluation, haematologic and neurometabolic work up, imaging and neurophysiological/ electrophysiological studies. This presentation will focus on the electrophysiological evaluation of dystonia, which helps in understanding the pathophysiology and better characterization of the abnormal movement. Compared to tremor and myoclonus, electrophysiological evaluation of muscle spasms and dystonia is difficult. The first step is recording surface EMG from the involved muscles for prolonged periods during abnormal movements (dystonia), rest, and with voluntary contraction. The agonists and antagonists should be included to detect co-contraction, and the unaffected muscles of the same or opposite limbs should also be studied to document overflow dystonia if present. During EMG evaluation, patients are also asked to perform various tasks which can induce dystonia, such as mental arithmetic, finger tapping and opening and closing fist of the unaffected hand, writing (in patients with writer’s cramp). EMG is analyzed to determine: (i) the pattern of EMG activity in agonists and antagonists during dystonia (spasm) (ii) duration of each EMG burst (iii) the regularity of occurrence of EMG bursts, (iv) presence of overflow activity in remote muscles while performing discrete voluntary acts, and (v) the difference in the degree of EMG activity (area of rectified EMG) between epochs with and without muscle spasms. Other investigations which are often useful to characterize dystonia or a dystonic syndrome include: (i) H-reflex recovery curve (ii) mechanically and electrically induced long-latency muscle stretch reflex (iii) reciprocal inhibition between antagonistic muscles (iv) brainstem reflexes such as blink reflex (v) cortical SEP (vi) Bereitschaftpotential (BP) and Contingent negative variation (CNV) and (viii) transcranial magnetic stimulation (TMS). TMS specifically helps to study the excitatory and inhibitory changes in the brain in patients with dystonia and may also be a useful tool to monitor therapeutic interventions.

Intraoperative Monitoring (IOM) P-IM002. Somatosensory evoked potentials in cervical and cerebellopontine angle Neurosurgical procedures: Experience from a tertiary care center in india

Introduction . The role of Intraoperative neuromonitoring (IONM) as a guiding technique in neurosurgical procedures is well established. Somato-Sensory Evoked Potentials (SSEPs) are an important modality in IONM. We report our experience with SSEPs in surgeries of Cervical Spine, Cranio-Vertebral junctions and Cerebellopontine angle at our centre. Methods . Sixty two patients underwent surgery in the cervical region and cerebellopontine angle under IONM guidance at the Department of Neurosurgery from May 2018 and September 2018. Out of which SSEPs were not performed in 22 patients and SSEPs could not be recorded in 20 patients due to technical reasons, therefore 20 patients were included in the study. SSEPs were recorded during the surgical procedures to provide information about neural integrity. Median nerves in both the limbs were stimulated at the level of the wrist using sterile transdermal needle electrodes. SSEP recordings were obtained using corkscrew needle electrodes placed at the scalp in Cp3, Cp4 and Fz, according to the 10-20 recording system. Signals were acquired using Medtronics NimEclipse© and Natus Protektor© system. The cortical recordings were taken from Cp3-Fz and Cp3-Cp4 montage for right sided SSEP and Cp4-Fz and Cp4-Cp3 montage for left sided SSEP. Results . The stimulation intensity was decided on a case-to-case basis. Range of stimulation varied from 10 - 23 mA with frequency of 4.70 Hz and stimulation duration of 0.2 ms. Real time averaging of 1000 waveforms was done. N20 and P22 latencies were checked pre-operatively just after induction, intra-operatively and post-operatively just before closure. In all the 20 patients, intra-operative period was uneventful. All cases showed normal recovery in the post- operative period. Conclusion . SSEP monitoring is a very useful tool for intraoperative sensory tract monitoring in the patients undergoing Cervical and Cerebellopontine region surgery. Change in the latency or amplitude in the cortical SSEP recordings can predict injury to the vital structures which can be reversed by surgeons if early warning is raised by Neurophysiologists.

Cortical somatosensory processing after botulinum toxin therapy in post-stroke spasticity.

In dystonic and spastic movement disorders, abnormalities of motor control and somatosensory processing as well as cortical modulations associated with clinical improvement after botulinum toxin A (BoNT-A) treatment have been reported, but electrophysiological evidence remains controversial. In the present observational study, we aimed to uncover central correlates of post-stroke spasticity (PSS) and BoNT-A-related changes in the sensorimotor cortex by investigating the cortical components of somatosensory evoked potentials (SEPs). Thirty-one chronic stroke patients with PSS of the upper limb were treated with BoNT-A application into the affected muscles and physiotherapy. Clinical and electrophysiological evaluations were performed just before BoNT-A application (W0), then 4 weeks (W4) and 11 weeks (W11) later. PSS was evaluated with the modified Ashworth scale (MAS). Median nerve SEPs were examined in both upper limbs with subsequent statistical analysis of the peak-to-peak amplitudes of precentral P22/N30 and postcentral N20/P23 components. At baseline (W0), postcentral SEPs were significantly lower over the affected cortex. At follow up, cortical SEPs did not show any significant changes attributable to BoNT-A and/or physiotherapy, despite clear clinical improvement. Our results imply that conventional SEPs are of limited value in evaluating cortical changes after BoNT-A treatment and further studies are needed to elucidate its central actions.

Intraoperative thalamocortical tract monitoring via direct cortical recordings during craniotomy

ObjectiveNeuromonitoring of primary motor regions allows preservation of motor strength and is frequently employed during cranial procedures. Less is known about protection of sensory function and ability to modulate movements, both of which rely on integrity of thalamocortical afferents (TCA) to fronto-parietal regions. We describe our experience with TCA monitoring and their cortical relays during brain tumor surgery. MethodologyTo study its feasibility and usefulness, continuous somatosensory evoked potentials (SSEP) recording via a subdural electrode was attempted in 32 consecutive patients. ResultsMedian and posterior tibial SSEP were successfully monitored in 31 and 17 patients respectively. SSEP improved lesion localization and prevented unnecessary cortical stimulation in 9 and 16 cases respectively. A threshold of ≥30% SSEP amplitude decrease influenced management in 10 patients while a decrement of ≥50 % had a sensitivity of 0.89 and specificity of 1 in detecting worsening of sensory function. Simultaneous motor evoked potentials (MEP) and SSEP monitoring were performed in 10 cases, 9 of which showed short-lived fluctuations of the former. ConclusionDirect cortical SSEP monitoring is feasible, informs management and predicts outcome. SignificanceEarly intervention prevents sensory deficit. Concomitant MEP fluctuations may reflect modulation of motor activity by TCA.

SSEP amplitudes add information for prognostication in postanoxic coma

ObjectiveTo investigate whether somatosensory evoked potential (SSEP) amplitude adds information for prediction of poor outcome in postanoxic coma. MethodsIn this retrospective cohort study we included adult patients admitted after cardiac arrest between January 2010 and June 2018 who remained in coma and had SSEP recorded for prognostication. Outcome was dichotomized in poor (Cerebral Performance Category (CPC) 4–5) and good (CPC 1–3) at ICU discharge. Sensitivity of bilaterally absent N20 potential was calculated. In case the N20 potential was not bilaterally absent, the amplitude contralateral to stimulation side (baseline-N20, N20-P25, and maximum) was determined. At a specificity of 100%, SEPP amplitude sensitivities were determined for poor outcome. ResultsSSEP recordings were performed in 197 patients of whom 57 had bilaterally absent N20 potentials. From 140 patients, 16 (11%) had a good outcome. The sensitivity for poor outcome of bilaterally absent N20 was 31%. At a specificity of 100%, contralateral amplitude thresholds were 0.34 μV (baseline-N20), 0.99 μV (N20-P25) and 1.0 μV (maximum), corresponding to a sensitivity for poor outcome of 38%, 44% and 40%. Combination of bilaterally absent N20 and a N20-P25 threshold below 0.99 μV yielded a sensitivity of 62%. ConclusionsOur results confirm that very low cortical SSEP amplitudes are highly predictive of poor outcome in patients with postanoxic coma. Adding ‘N20-P25 threshold amplitude’ to the ‘bilaterally absent N20′ criterion, increased sensitivity substantially.

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.

Opposite modulations of corticospinal excitability by intermittent and continuous peripheral electrical stimulation in healthy subjects

Peripheral electrical stimulation (PES) modulates the excitability of the corticospinal tract (CST). This modulation of CST excitability depends on the PES intensity, defined by the amplitude and the width of each pulse, the total pulse number, the stimulation frequency, and the intervention duration. Another key PES parameter is the stimulation pattern; little is known about how PES pattern affects CST excitability, as previous studies did not control other PES parameters. Here, we investigated the effect of the net difference in PES pattern on CST excitability. We use three controlled PESs, intermittent PES (30 Hz) (stimulation trains at 30 Hz with pauses), continuous PES (12 Hz) (constant stimulation at 12 Hz without pauses), and continuous PES (30 Hz) with the same stimulation frequency as the intermittent PES (30 Hz), to compare the effect of the stimulation frequency. The motor evoked potentials (MEPs) and somatosensory evoked potentials (SEPs) of healthy subjects were recorded before and after these three types of PESs in separate sessions. We found that intermittent PES (30 Hz) increased MEP amplitudes, whereas continuous PES (12 and 30 Hz) decreased amplitudes. A significant change in subcortical SEP component occurred during continuous PES (12 and 30 Hz), but not intermittent PES (30 Hz), whereas cortical SEP components showed similar behavior in three types of PESs. We conclude that (1) opposing modulations of CST excitability were induced by the differences in the PES pattern, and (2) these modulations appear to be mediated through different processes in the sensorimotor system. Our findings suggest the possibility that it may be preferable to select the PES pattern in therapeutic interventions based on the putative desired effect and the neural structure being targeted.

Hypoxic-Ischemic Encephalopathy Evaluated by Brain Autopsy and Neuroprognostication After Cardiac Arrest

Neuroprognostication studies are potentially susceptible to a self-fulfilling prophecy as investigated prognostic parameters may affect withdrawal of life-sustaining therapy. To compare the results of prognostic parameters after cardiac arrest (CA) with the histopathologically determined severity of hypoxic-ischemic encephalopathy (HIE) obtained from autopsy results. In a retrospective, 3-center cohort study of all patients who died following cardiac arrest during their intensive care unit stay and underwent autopsy between 2003 and 2015, postmortem brain histopathologic findings were compared with post-CA brain computed tomographic imaging, electroencephalographic (EEG) findings, somatosensory-evoked potentials, and serum neuron-specific enolase levels obtained during the intensive care unit stay. Data analysis was conducted from 2015 to 2020. The severity of HIE was evaluated according to the selective eosinophilic neuronal death (SEND) classification and patients were dichotomized into categories of histopathologically severe and no/mild HIE. Of 187 included patients, 117 were men (63%) and median age was 65 (interquartile range, 58-74) years. Severe HIE was found in 114 patients (61%) and no/mild HIE was identified in 73 patients (39%). Severe HIE was found in all 21 patients with bilaterally absent somatosensory-evoked potentials, all 15 patients with gray-white matter ratio less than 1.10 on brain computed tomographic imaging, all 9 patients with suppressed EEG, 15 of 16 patients with burst-suppression EEG, and all 29 patients with neuron-specific enolase levels greater than 67 μg/L more than 48 hours after CA without confounders. Three of 7 patients with generalized periodic discharges on suppressed background and 1 patient with burst-suppression EEG had a SEND 1 score (<30% dead neurons) in the cerebral cortex, but higher SEND scores (>30% dead neurons) in other oxygen-sensitive brain regions. In this study, histopathologic findings suggested severe HIE after cardiac arrest in patients with bilaterally absent cortical somatosensory-evoked potentials, gray-white matter ratio less than 1.10, highly malignant EEG, and serum neuron-specific enolase concentration greater than 67 μg/L.

Added value of somato-sensory evoked potentials amplitude for prognostication after cardiac arrest

AimsBilateral absence of cortical somato-sensory evoked potentials (SSEPs) robustly predicts poor outcome after cardiac arrest (CA), but it is uncertain if SSEP amplitudes provide additional information. Here, we examined the prognostic value of cortical SSEP amplitude in comparison with other known outcome predictors. MethodsWe retrospectively determined SSEP amplitudes in a prospective CA registry, identified an amplitude cut-off for worst Cerebral Performance Category (CPC) within three months, and examined correlations of SSEP amplitude with pupillary light reflex (PLR), myoclonus, peak serum neuron specific enolase (NSE), and 24–36 h and 36–72 h EEG (reactivity, epileptiform features). ResultsAmong 158 patients, 54% awoke. Amplitudes correlated with EEG findings, present PLR, myoclonus, NSE. A cut-off for cortical SSEP ≤ 0.41 μV was 100% specific for poor outcome (95% CI: 96–100%); sensitivity increased marginally vs. SSEPs absence [47% (35–59%) vs 46% (34–58%)] for CPC 4–5. Adding SSEPs ≤0.41 μV to a multimodal prognostic model including EEG, clinical features, and NSE improved prediction for mortality, but not for CPC 3–5 at three months. No statistical correlation between amplitudes and good outcome was observed. SSEP amplitudes correlated inversely with CPC at three months in the overall cohort (r = −0.332; p < 0.0001) but not in the subgroup with present SSEPs (r = −0.102; p = 0.256). ConclusionDecreased SSEPs amplitudes are associated with poor outcome after cardiac arrest; however, adding this to a multimodal prognostic approach including EEG, clinical and blood biomarkers, improves slightly prediction of mortality, but not of poor or good outcome.

Neurophysiology for predicting good and poor neurological outcome at 12 and 72 h after cardiac arrest: The ProNeCA multicentre prospective study

AimsTo assess the accuracy of electroencephalogram (EEG) and somatosensory evoked potentials (SEPs) recorded at 12 and 72 h from resuscitation for predicting six-months neurological outcome in patients who are comatose after cardiac arrest. MethodsProspective multicentre prognostication study. EEG was classified according to the American Clinical Neurophysiology Society terminology. SEPs were graded according to the presence and amplitude of their cortical responses. Neurological outcome was defined as good (cerebral performance categories [CPC] 1–3) vs. poor (CPC 4–5). None of the patients underwent withdrawal of life-sustaining treatment. ResultsA total of 351 patients were included, of whom 134 (38%) had good neurological outcome. At 12 h, a continuous, nearly continuous and low-voltage EEG pattern predicted good neurological outcome with 71[61–80]% sensitivity, while an isoelectric EEG and a bilaterally absent/absent-pathological amplitude (AA/AP) cortical SEP pattern predicted poor neurological outcome with 14[8–21]% and 59[50–68]% sensitivity, respectively. Specificity was 100[97–100]% for all predictors. At 72 h, both an isoelectric, suppression or burst-suppression pattern on EEG and an AA/AP SEP pattern predicted poor outcome with 100[97–100]% specificity. Their sensitivities were 63[55–70]% and 66[58–74]%, respectively. When EEG and SEPs were combined, sensitivity for poor outcome prediction increased to 79%. ConclusionsIn comatose resuscitated patients, EEG and SEPs predicted good and poor neurological outcome respectively, with 100% specificity as early as 12 h after cardiac arrest. At 72 h after arrest, unfavourable EEG and SEP patterns predicted poor neurological outcome with 100% specificity and high sensitivity, which further increased after their combination.

Somatosensory Cross-Modal Reorganization in Children With Cochlear Implants

Deprived of sensory input, as in deafness, the brain tends to reorganize. Cross-modal reorganization occurs when cortices associated with deficient sensory modalities are recruited by other, intact senses for processing of the latter’s sensory input. Studies have shown that this type of reorganization may affect outcomes when sensory stimulation is later introduced via intervention devices. One such device is the cochlear implant (CI). Hundreds of thousands of CIs have been fitted on people with hearing impairment worldwide, many of them children. Factors such as age of implantation have proven useful in predicting speech perception outcome with these devices in children. However, a portion of the variance in speech understanding ability remains unexplained. It is possible that the degree of cross-modal reorganization may explain additional variability in listening outcomes. Thus, the current study aimed to examine possible somatosensory cross-modal reorganization of the auditory cortices. To this end we used high density EEG to record cortical responses to vibrotactile stimuli in children with normal hearing (NH) and those with CIs. We first investigated cortical somatosensory evoked potentials (CSEP) in NH children, in order to establish normal patterns of CSEP waveform morphology and sources of cortical activity. We then compared CSEP waveforms and estimations of cortical sources between NH children and those with CIs to assess the degree of somatosensory cross-modal reorganization. Results showed that NH children showed expected patterns of CSEP and current density reconstructions, such that postcentral cortices were activated contralaterally to the side of stimulation. Participants with CIs also showed this pattern of activity. However, in addition, they showed activation of auditory cortical areas in response to somatosensory stimulation. Additionally, certain CSEP waveform components were significantly earlier in the CI group than the children with NH. These results are taken as evidence of cross-modal reorganization by the somatosensory modality in children with CIs. Speech perception in noise scores were negatively associated with CSEP waveform components latencies in the CI group, suggesting that the degree of cross-modal reorganization is related to speech perception outcomes. These findings may have implications for clinical rehabilitation in children with cochlear implants.

Beyond dichotomy: patterns and amplitudes of SSEPs and neurological outcomes after cardiac arrest

BackgroundWe hypothesized that the absence of P25 and the N20–P25 amplitude in somatosensory evoked potentials (SSEPs) have higher sensitivity than the absence of N20 for poor neurological outcomes, and we evaluated the ability of SSEPs to predict long-term outcomes using pattern and amplitude analyses.MethodsUsing prospectively collected therapeutic hypothermia registry data, we evaluated whether cortical SSEPs contained a negative or positive short-latency wave (N20 or P25). The N20–P25 amplitude was defined as the largest difference in amplitude between the N20 and P25 peaks. A good or poor outcome was defined as a Glasgow-Pittsburgh Cerebral Performance Category (CPC) score of 1–2 or 3–5, respectively, 6 months after cardiac arrest.ResultsA total of 192 SSEP recordings were included. In all patients with a good outcome (n = 51), both N20 and P25 were present. Compared to the absence of N20, the absence of N20–P25 component improved the sensitivity for predicting a poor outcome from 30.5% (95% confidence interval [CI], 23.0–38.8%) to 71.6% (95% CI, 63.4–78.9%), while maintaining a specificity of 100% (93.0–100.0%). Using an amplitude < 0.64 μV, i.e., the lowest N20–P25 amplitude in the good outcome group, as the threshold, the sensitivity for predicting a poor neurological outcome was 74.5% (95% CI, 66.5–81.4%). Using the highest N20–P25 amplitude in the CPC 4 group (2.31 μV) as the threshold for predicting a good outcome, the sensitivity and specificity were 52.9% (95% CI, 38.5–67.1%) and 96.5% (95% CI, 91.9–98.8%), respectively. The predictive performance of the N20–P25 amplitude was good, with an area under the receiver operating characteristic curve (AUC) of 0.94 (95% CI, 0.90–0.97). The absence of N20 was statistically inferior regarding outcome prediction (p < 0.05), and amplitude analysis yielded significantly higher AUC values than did the pattern analysis (p < 0.05).ConclusionsThe simple pattern analysis of whether the N20–P25 component was present had a sensitivity comparable to that of the N20–P25 amplitude for predicting a poor outcome. Amplitude analysis was also capable of predicting a good outcome.

Multimodal Intraoperative Spinal Cord Monitoring during Spinal Deformity Surgery: Efficacy, Diagnostic Characteristics, and Algorithm Development

Objective: This study aims to present the diagnostic characteristics of multimodal intraoperative monitoring (IOM) in spinal deformity surgery and to define and categorise the neuromonitoring events, as well as propose an algorithm of action. Materials and Methods: We reviewed 1,155 consecutive patients (807 female, 348 male) who underwent deformity correction using standardised perioperative care, cortical/cervical somatosensory evoked potentials (SSEPs), and upper/lower limb transcranial electrical motor evoked potential (MEPs) by a single surgeon. The mean age at surgery was 13.8 years (range 10–23.3). We categorised IOM events as true, transient true, and false positive or negative. Diagnostic performance criteria were calculated. Results: The most common diagnosis was adolescent idiopathic scoliosis in 717 (62%) patients. We identified 3 true positive monitoring events occurring in 2 patients (0.17%), 8 transient true positive (0.69%), and 8 transient false positive events (0.69%). There were no false negative events and no patient had postoperative neurological complications. The multimodal IOM technique had a sensitivity of 100%, specificity of 99.3%, positive predictive value of 55.6%, and negative predictive value of 100%. Sensitivity was 100% for MEPs and multimodal monitoring compared to 20% for cortical or cervical SSEPs. The frequency of true or transient true positive events was higher (p = 0.07) in Scheuermann’s kyphosis (3/91 patients, 3.3%) compared to adolescent idiopathic scoliosis (6/717 patients, 0.84%). Conclusion: Multimodal IOM is highly sensitive and specific for spinal cord injury. This technique is reliable for the assessment of the condition of the spinal cord during major deformity surgery. We propose an algorithm of intraoperative action to allow close cooperation between the surgical, anaesthetic, and neurophysiology teams and to prevent neurological deficits.

Abdominal Aortic Transplantation of Bone Marrow Mesenchymal Stem Cells Regulates the Expression of Ciliary Neurotrophic Factor and Inflammatory Cytokines in a Rat Model of Spinal Cord Ischemia-Reperfusion Injury.

BackgroundThis study aimed to investigate the effects of abdominal aortic transplantation of bone marrow mesenchymal stem cells (BMMSCs) on the expression of inflammatory cytokines in a rat model of spinal cord ischemia-reperfusion injury.Material/MethodsAdult female Sprague-Dawley rats (N=160) were divided into five groups: the sham operation group (N-32); the control group (N=32); the BMMSC transplanted group (N=32); the anti-ciliary neurotrophic factor (CNTF)-treated BMMSC transplanted group (N=32); and the CNTF small interfering RNA (siRNA)-treated BMMSC transplanted group (N=32). Motor behavior was assessed using the Basso, Beattie, and Bresnahan (BBB) locomotor scale. Motor evoked potentials (MEPs) and cortical somatosensory evoked potentials (CSEPs) were measured. Immunohistochemistry, quantitative real-time polymerase chain reaction (qRT-PCR), and Western blot analysis evaluated the expression of spinal inflammatory cytokines.ResultsFollowing surgery, compared with the control group the findings in the BMMSC transplant groups included significantly increased BBB scores; the latency and the amplitude of MEP and CSEP were reduced and increased, respectively; spinal neuronal necrosis was reduced; the number of normal neurons increased; CNTF mRNA and protein expression levels increased; expression levels of interleukin-6 (IL-6) were reduced and IL-10 levels were significantly increased (P<0.05). The effects of abdominal aortic BMMSC transplantation were at least partially reversed by both anti-CNTF and CNTF siRNA treatment.ConclusionsIn a rat model of spinal cord ischemia-reperfusion injury, abdominal aortic transplantation of BMMSCs increased the expression of CNTF, which improved hindlimb locomotor recovery by regulating the expression of IL-6 and IL-10 to reduce inflammation of the spinal cord.