Median Nerve Somatosensory Evoked Potentials Research Articles

A Novel Technique for Intraoperative Mapping of the Somatosensory Cortex

Intraoperative mapping of the nervous system is used to identify "eloquent" cortical areas. In this technical report, we describe a novel way of mapping the somatosensory cortex so that injury to those critical pathways can be avoided. An 8-year-old female with drug resistant epilepsy presented for resection of a right posterior parietal focal cortical dysplasia. Left median nerve stimulation was used to record somatosensory evoked potentials (SEPs) directly from the somatosensory cortex with a strip electrode. A handheld monopolar electrode was also used to record both the median and tibial SEP. Total intravenous anesthesia with propofol and remifentanil was used. SEP recordings were obtained from a 4-contact strip electrode placed across the central sulcus. A phase reversal was identified and the most likely post central gyrus was noted. With the strip electrode left in place, a monopolar handheld electrode was used to record the median nerve SEPs from different locations on the postcentral gyrus. The tibial nerve was also stimulated to record where the highest amplitude tibial nerve SEP was present. This map was used delineate functionally "eloquent" areas to avoid during surgery. During resection, the median nerve SEP was recorded from the strip electrode continuously. No significant change in the SEP was noted, and the patient awoke without any sensory deficits. Sensory mapping of the cortex is possible with a handheld monopolar electrode. This technique is easy to perform and can help reduce neurological morbidity.

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.

Median Nerve Somatosensory Evoked Potentials in Patients with Chiari Malformation

Median Nerve Somatosensory Evoked Potentials in Patients with Chiari Malformation

Somatosensory pathway dysfunction in patients with amyotrophic lateral sclerosis in a completely locked-in state

ObjectiveTo investigate somatosensory pathway function in patients with amyotrophic lateral sclerosis (ALS) dependent on invasive ventilation and in a completely locked-in state (CLIS). MethodsWe examined median nerve somatosensory evoked potentials (SEPs) in 17 ALS patients in a CLIS, including 11 patients with sporadic ALS, one with familial ALS with genes not examined, four with a Cu/Zn superoxide-dismutase-1 (SOD1) gene variant (Val118Leu, Gly93Ser, Cys146Arg), and one with a fused-in-sarcoma gene variant (P525L). We evaluated N9, N13, N20 and P25, and central conduction time (CCT); the data were compared with those of 73 healthy controls. ResultsN20 and N13 were abolished in 12 and 10 patients, and their latencies was prolonged in four and three patients, respectively. The CCT was prolonged in five patients with measurable N13 and N20. Two patients with SOD1 gene mutations had absent or slightly visible N9. Compared to the CCT and latencies and amplitudes of N13 and N20 in the controls, those in the patient cohort were significantly abnormal. ConclusionsThe central somatosensory pathway is severely involved in patients with ALS in a CLIS. SignificanceOur findings suggest that median nerve SEP cannot be utilized for communication in patients with ALS in a CLIS.

Sensory Gating during Voluntary Finger Movement in Amyotrophic Lateral Sclerosis with Sensory Cortex Hyperexcitability.

Cortical responses in somatosensory evoked potentials (SEP) are enhanced in patients with amyotrophic lateral sclerosis (ALS). This study investigated whether sensory gating is involved in the pathophysiology of sensory cortical hyperactivity in ALS patients. The median nerve SEP was recorded at rest and during voluntary finger movements in 14 ALS patients and 13 healthy control subjects. The parietal N20, P25, and frontal N30 were analyzed, and sensory gating was assessed by measuring the amplitude of each component during finger movement. The amplitudes of the N20 onset-peak, N20 peak-P25 peak, and N30 onset-peak were higher in ALS patients than in controls. Nonetheless, there were no significant differences in the amplitude reduction ratio of SEPs between patients and controls. There was a significant correlation between the baseline amplitudes of the N20 onset-peak or N20 peak-P25 peak and their gating ratios in patients with ALS. Our findings indicate that the excitability of the primary sensory cortex and secondary motor cortex is enhanced in ALS, while sensory gating is preserved in the early stages of ALS. This result suggests that enhanced SEP is caused by the hyperexcitability of the primary sensory and secondary motor cortices but not by the dysfunction of inhibitory mechanisms during voluntary movements.

Directional recordings of somatosensory evoked potentials from the sensory thalamus in chronic poststroke pain patients

ObjectiveThe aim of this feasibility study was to investigate the properties of median nerve somatosensory evoked potential (SEPs) recorded from segmented Deep Brain Stimulation (DBS) leads in the sensory thalamus (VP) and how they relate to clinical and anatomical findings. MethodsWe analyzed four patients with central post-stroke pain and DBS electrodes placed in the VP. Median nerve SEPs were recorded with referential and bipolar montages. Electrode positions were correlated with thalamus anatomy and tractography-based medial lemniscus. Early postoperative clinical paresthesia mapping was performed by an independent pain nurse. Finally, we performed frequency and time–frequency analyses of the signals. ResultsWe observed differences of SEP amplitudes recorded along different directions in the VP. SEP amplitudes did not clearly correlate to both atlas-based anatomical position and fiber-tracking results of the medial lemniscus. However, the contacts of highest SEP amplitude correlated with the contacts of lowest effect-threshold to induce paraesthesia. ConclusionsSEP recordings from directional DBS leads offer additional information about the neurophysiological (re)organization of the sensory thalamus. SignificanceDirectional recordings of thalamic SEPs bear the potential to assist clinical decision-making in DBS for pain.

Neurodevelopmental and genetic findings in neonates with intracranial arteriovenous shunts: A case series.

Despite the latest advances in prenatal diagnosis and postnatal embolization procedures, intracranial arteriovenous shunts (AVSs) are still associated with high mortality and morbidity rates. Our aim was to evaluate the presentation and clinical course, the neurodevelopmental outcome, and the genetic findings of neonates with AVSs. In this retrospective observational study, medical records of neonates with cerebral AVSs admitted to our hospital from January 2020 to July 2022 were revised. In particular, we evaluated neuroimaging characteristics, endovascular treatment, neurophysiological features, neurodevelopmental outcomes, and genetic findings. We described the characteristics of 11 patients with AVSs. Ten infants (90.9%) required embolization during the first three months of life. In 5/9 infants, pathological electroencephalography findings were observed; of them, two patients presented seizures. Eight patients performed Median Nerve Somatosensory Evoked Potentials (MN-SEPs): of them, six had an impaired response. We found normal responses at Visual Evoked Potentials and Brainstem Auditory Evoked Potentials. Eight patients survived (72.7%) and were enrolled in our multidisciplinary follow-up program. Of them, 7/8 completed the Bayley-III Scales at 6 months of corrected age: none of them had cognitive and language delays; conversely, a patient had a moderate delay on the Motor scale. The remaining survivor patient developed cerebral palsy and could not undergo Bayley-III evaluation because of the severe psychomotor delay. From the genetic point of view, we found a novel pathogenic variant in the NOTCH3 gene and three additional genomic defects of uncertain pathogenicity. We propose SEPs as an ancillary test to discern the most vulnerable infants at the bedside, particularly to identify possible future motor impairment in follow-up. The early identification of a cognitive or motor delay is critical to intervene with personalized rehabilitation treatment and minimize future impairment promptly. Furthermore, the correct interpretation of identified genetic variants could provide useful information, but further studies are needed to investigate the role of these variants in the pathogenesis of AVSs.

Sensorimotor integration and motor learning during a novel force-matching task in young adults with attention-deficit/hyperactivity disorder.

Attention-Deficit/Hyperactivity Disorder (ADHD) is a neurodevelopmental disorder that exhibits unique neurological and behavioral characteristics. Those with ADHD often have noted impairments in motor performance and coordination, including during tasks that require force modulation. The present study provides insight into the role of altered neural processing and SMI in response to a motor learning paradigm requiring force modulation and proprioception, that previous literature has suggested to be altered in those with ADHD, which can also inform our understanding of the neurophysiology underlying sensorimotor integration (SMI) in the general population. Adults with ADHD (n = 15) and neurotypical controls (n = 15) performed a novel force-matching task, where participants used their right-thumb to match a trace template that varied from 2-12% of their Abductor Pollicis Brevis maximum voluntary contraction. This motor task was completed in pre, acquisition, and post blocks. Participants also completed a retention test 24 h later. Median nerve somatosensory-evoked potentials (SEPs) were collected pre and post motor acquisition. SEPs were stimulated at two frequencies, 2.47 Hz and 4.98 Hz, and 1,000 sweeps were recorded using 64-electrode electroencephalography (EEG) at 2,048 Hz. SEP amplitude changes were normalized to each participant's baseline values for that peak. Both groups improved at post measures (ADHD: 0.85 ± 0.09; Controls: 0.85 ± 0.10), with improvements maintained at retention (ADHD: 0.82 ± 0.11; Controls: 0.82 ± 0.11). The ADHD group had a decreased N18 post-acquisition (0.87 ± 0.48), while the control N18 increased (1.91 ± 1.43). The N30 increased in both groups, with a small increase in the ADHD group (1.03 ± 0.21) and a more pronounced increase in controls (1.15 ± 0.27). Unique neural differences between groups were found after the acquisition of a novel force-matching motor paradigm, particularly relating to the N18 peak. The N18 differences suggest that those with ADHD have reduced olivary-cerebellar-M1 inhibition when learning a novel motor task dependent on force-modulation, potentially due to difficulties integrating the afferent feedback necessary to perform the task. The results of this work provide evidence that young adults with ADHD have altered proprioceptive processing when learning a novel motor task when compared to neurotypical controls.

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.

Abstract WMP93: Somatosensory Evoked Potentials Monitoring In Acute Ischemic Stroke (Promise) Study: A Biomarker Of Functional Recovery Prior To Mechanical Thrombectomy (clinicaltrials.gov: NCT04099615)

Hypothesis: Somatosensory evoked potentials (SEPs), as surrogate of cerebral blood flow, may give substantial additional predictive value to that provided by clinical and imaging factors and optimize the selection of patients benefiting from mechanical thrombectomy (MT) Methods: Bilateral median nerve SEPs were recorded before and continuously during MT in consecutive patients with AIS and anterior LVO. N20 response ipsilateral to the ischemic hemisphere was measured. The adjusted predictive value of the N20 on functional Independence (modified Rankin Scale score ≤2) after MT was analyzed by binary logistic regression and its predictive value on the full range of disability by ordinal logistic regression. We constructed different regression models with other clinical and imaging predictors at the pre- and in- hospital setting to determine the independent predictive power of N20 for a potential treatment decision-making Results: A total of 223 patients were recruited. A blinded reading of SEPs recordings identified presence of N20 in 110 (49.3%), absence in 58 (26%) and not assessable in 55 patients due to radiofrequency interferences. Prior to MT, N20 had positive predictive value (PPV) of 93% (95%CI, 0.8 to 0.98) and increased 10 fold the likelihood of good functional outcome at 7 days (adjusted OR, 9.9; 95%CI, 3.1-44.6). Receiver operating curves showed that N20 had a higher capacity to predict good functional outcome (AUC 0.82) than models constructed with pre-hospital (age, sex, serum glucose, median blood pressure, NIHSS; AUC 0.75) or in-hospital (NIHSS, ASPECTS; AUC 0.72) factors. During MT, N20 had PPV of 100% (95% CI, 0.85-1) and was the unique independent factor associated with functional independence (adjusted OR, 2.74; 95%CI, 1.90-4.29). Perfusion CT or MR was available in a subgroup of 116 patients. Baseline N20 showed a higher capacity to predict good functional outcome (n=168, AUC 0.71) compared with ischemic core (n=127, AUC 0.66), ischemic penumbra (Tmax>6) (n=116, AUC 0.54) and collateral status (n=191, AUC 0.61) Conclusions: SEPs monitoring is a fast and bedside technique that could complement current clinical factors in terms of increasing the eligibility of AIS patients for MT and improving prognosis.

Reconstructing subcortical and cortical somatosensory activity via the RAMUS inverse source analysis technique using median nerve SEP data

This study concerns reconstructing brain activity at various depths based on non-invasive EEG (electroencephalography) scalp measurements. We aimed at demonstrating the potential of the RAMUS (randomized multiresolution scanning) technique in localizing weakly distinguishable far-field sources in combination with coinciding cortical activity. As we have shown earlier theoretically and through simulations, RAMUS is a novel mathematical method that by employing the multigrid concept, allows marginalizing noise and depth bias effects and thus enables the recovery of both cortical and subcortical brain activity. To show this capability with experimental data, we examined the 14–30 ms post-stimulus somatosensory evoked potential (SEP) responses of human median nerve stimulation in three healthy adult subjects. We aim at reconstructing the different response components by evaluating a RAMUS-based estimate for the primary current density in the nervous tissue. We present source reconstructions obtained with RAMUS and compare them with the literature knowledge of the SEP components and the outcome of the unit-noise gain beamformer (UGNB) and standardized low-resolution brain electromagnetic tomography (sLORETA). We also analyzed the effect of the iterative alternating sequential technique, the optimization technique of RAMUS, compared to the classical minimum norm estimation (MNE) technique. Matching with our previous numerical studies, the current results suggest that RAMUS could have the potential to enhance the detection of simultaneous deep and cortical components and the distinction between the evoked sulcal and gyral activity.

Contralateral and Ipsilateral Interactions in the Somatosensory Pathway in Healthy Humans.

Hyper-adaptability, the ability to adapt to changes in the internal environment caused by neurological disorders, is necessary to recover from various disabilities, such as motor paralysis and sensory impairment. In the recovery from motor paralysis, the pre-existing neural pathway of the ipsilateral descending pathway, which is normally suppressed and preserved in the course of development, is activated to contribute to the motor control of the paretic limb. Conversely, in sensory pathways, it remains unclear whether there are compensatory pathways which are beneficial for the recovery of sensory impairment due to damaged unilateral somatosensory pathways, such as thalamic hemorrhage. Here, we investigated the interaction between the left and right somatosensory pathways in healthy humans using paired median nerve somatosensory evoked potentials (SEPs). Paired median nerve SEPs were recorded at CP3 and CP4 with a reference of Fz in the International 10–20 System. The paired median nerve stimulation with different interstimulus intervals (ISIs; 1, 2, 3, 5, 10, 20, 40, 60, and 100 ms) was performed to test the influence of the first stimulus (to the right median nerve) on the P14, P14/N20, and N20/P25 components induced by the second stimulus (left side). Results showed that the first stimulation had no effect on SEP amplitudes (P14, P14/N20, and N20/P25) evoked by the second stimulation in all ISI conditions, suggesting that there might not be a neural connectivity formed by a small number of synapses in the left–right interaction of the somatosensory pathway. Additionally, the somatosensory pathway may be less diverse in healthy participants.

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.

Enlarged high frequency oscillations of the median nerve somatosensory evoked potential and survival in amyotrophic lateral sclerosis

ObjectiveA large N20 and P25 of the median nerve somatosensory evoked potential (SEP) predicts short survival in amyotrophic lateral sclerosis (ALS). We investigated whether high frequency oscillations (HFOs) over N20 are enlarged and associated with survival in ALS. MethodsA total of 145 patients with ALS and 57 healthy subjects were studied. We recorded the median nerve SEP and measured the onset-to-peak amplitude of N20 (N20o-p), and peak-to-peak amplitude between N20 and P25 (N20p-P25p). We obtained early and late HFO potentials by filtering SEP between 500 and 1 kHz, and measured the peak-to-peak amplitude. We followed up patients until endpoints (death or tracheostomy) and analyzed the relationship between SEP or HFO amplitudes and survival using a Cox analysis. ResultsPatients showed larger N20o-p, N20p-P25p, and early and late HFO amplitudes than the control values. N20p-P25p was associated with survival periods (p = 0.0004), while early and late HFO amplitudes showed no significant association with survival (p = 0.4307, and p = 0.6858, respectively). ConclusionsThe HFO amplitude in ALS is increased, but does not predict survival. SignificanceThe enlarged HFOs in ALS might be a compensatory phenomenon to the hyperexcitability of the sensory cortex pyramidal neurons.

Median somatosensory evoked potential as a predictor of clinical outcome after urgent surgical extracranial internal carotid artery recanalization

ObjectiveChanges in the N20/P25 amplitude of somatosensory evoked potentials (SEP) of the median nerve have been found to correlate with those in cortical regional cerebral blood flow (rCBF). Our study presents the use of median nerve SEP amplitude in predicting the clinical outcome of urgent surgical internal carotid artery (ICA) recanalization. MethodsA total of 27 patients suffering an acute ischemic stroke (AIS) with extracranial ICA occlusion within 24 h were prospectively recruited. The primary preoperative endpoints included the SEP amplitude absolute value (SEP-amp) and the SEP amplitude side-to-side ratio (SEP-ratio).Clinical outcome at 3 months postoperatively was assessed using the modified Rankin scale (mRS-3M). ResultsThe positive predictive values (PPVs) for SEP-amp and SEP-ratio were 95.5% and 100%, respectively, with the negative predictive values (NPVs) being 60.0% and 100%, respectively. The SEP-ratio correlated fully with mRS-3M. ConclusionThe median SEP side-to-side N20/P25 amplitude ratio seems to be a very strong positive and negative predictor of the clinical outcome of urgent recanalization of an extracranial ICA occlusion. SignificanceThe results suggest that cortical evoked activity may help in selection patient for surgical recanalization and predict clinical recovery after an acute ischemic stroke.

Role of High Frequency Oscillations of Somatosensory Evoked Potentials in Deciphering Pathophysiology of Migraine.

Background Habituation deficit is considered as a neurophysiological abnormality among migraineurs in the interictal period. For clear comprehension and clarity about the mechanism underlying habituation in migraine, a sophisticated method, i.e., high frequency oscillations (HFOs) evoked potentials, have been utilized. However, studies pertaining to this in the Indian context are rare. Objective The aim of the study is to determine the utility of HFO of somatosensory evoked potential (SSEP) in deciphering the pathophysiology of migraine. Materials and Methods Sixty subjects including 30 migraineurs in the interictal period and 30 healthy controls were considered for the study. Median nerve SSEP was recorded in patients and controls by standard protocols. HFO was extracted offline using the Digital zero-phase shift band-pass filtering at 450 and 750 Hz. The early and late HFOs were determined with respect to the N20 peak and were compared between the groups. Results Of total 30 migraineurs, 18 had hemicranial headache and 12 had holocranial headache. N20 latency, P25 latency, N20 onset to peak amplitude, and N20 onset to P25 amplitude were comparable in migraineurs and controls. The intraburst frequency of early HFOs in migraineurs was significantly higher ( p = 0.04), whereas the peak-to-peak amplitude was significantly lower ( p = 0.001). Conclusion Early HFOs on SSEP represent the thalamocortical excitatory drive in migraineurs. Overall, the study reports that reduced amplitude of early HFOs in the interictal period suggest reduced thalamocortical drive in migraineurs.

Proximal Upper Limb Sensorimotor Integration in Response to Novel Motor Skill Acquisition.

Previous studies have shown significant changes in cortical and subcortical evoked potential activity levels in response to motor training with the distal upper-limb muscles. However, no studies to date have assessed the neurological processing changes in somatosensory evoked potentials (SEPs) associated with motor training whole-arm movements utilizing proximal upper-limb muscles. The proximal upper-limb muscles are a common source of work-related injuries, due to repetitive glenohumeral movements. Measuring neurophysiological changes following performance of a proximal motor task provide insight into potential neurophysiological changes associated with occupational postures and movements involving proximal upper limb muscles. This study sought to assess the impact of a novel motor skill acquisition task on neural processing of the proximal upper-limb muscle groups, through the measurement of short-latency median nerve SEPs. One group of 12 participants completed a novel motor training task, consisting of tracing a sinusoidal waveform varying in amplitude and frequency. Baseline SEP measurements were recorded from each participant, followed by a mental recitation control task. Pre-test SEP measurements were then recorded, followed by the motor training task, and post-test SEP recordings. The participants completed the tracing with their right thumb, using glenohumeral rotation only to move their hand. Significant improvements in task accuracy were demonstrated, indicating that motor acquisition had occurred. Significant changes were also seen in the N11, N13, N20, N24, P25, and the N30 SEP peaks were seen following the motor training task. Conclusion: Early SEPs appear to be a sensitive measure of changes in sensorimotor integration in response to novel motor skill acquisition within the proximal upper-limb muscles.

Is there inter-observer variation in the interpretation of SSEPs in comatose cardiac arrest survivors? Further considerations following the Italian multicenter ProNeCa study

BackgroundBilateral absence of N20 peak in median nerve Somatosensory Evoked Potentials (SSEPs) is considered the most valid predictor of poor outcome in comatose survivors after cardiopulmonary resuscitation. We investigated the consistency in interpreting SSEP recordings in a multicentre study. Methods44 SSEP recordings randomly extracted from 600 recordings of 392 patients included in the “Prognostication of Neurological outcome after Cardiac Arrest (ProNeCa) study” were blindly read by three expert neurophysiologists. Agreement between raters, and individual agreement of each rater vs. reference standard (RS), were calculated using Kappa Coefficients. Inter-rater reliability was calculated with Intra-class Correlation Coefficient (ICC). ResultsWhen raters had to evaluate the presence of N20 with normal amplitude, the inter-rater agreement was very high (Kappa = 0.84). In the case of N20 absence the agreement was good (Kappa = 0.66), but when N20 amplitude was low, the agreement decreased to moderate (Kappa = 0.579) becoming even weaker when it was “Non Assessable” (Kappa = 0.107). The agreement of each rater with the RS had a range from moderate to very good; rater1 Kappa = 0.589 (95%CI 0.397–0.781; p < 0.001), rater2 Kappa = 0.644 (95%CI 0.460–0.828; p < 0.001), rater3 Kappa = 0.859 (95%CI 0.698–1.000; p < 0.001). The ICC was barely good, 0.682 (95%CI 0.539−0.798; p = 0.0075). ConclusionDifferent health professionals, using different equipment in a multicentre study, had very good inter-rater agreement in interpreting SSEP records. The interpretation of “Non Assessable” SEPPs, mainly in relation to noise level, is still a crucial issue because it increases rater uncertainty. For this reason, it is important to focus on improving recording quality and interpretation of records.

Modification of Electrode in Dermatosensory Evoked Potential

Somatosensory evoked potential (SSEP) usually done using bipolar surface stimulator of peripheral nerve and recorded by cortical surface or subdermal needle electrodes, in this study we modify an adhesive large surface area, surface stimulator using the same montage and method then compare the result between them. We took nineteen patients of median nerve SSEP, locate and identify the shape of dermatom assigned according to text using large square adhesive surface electrode. The same as the shape of dermatom, this is the cathode electrode, for the anode, a strip has the same length of the cathode with a width of two centimetres placed beneath the cathode, the circular ground band between stimulated and recording electrode. The subjects In this study prepared for routine SSEP study the result obtained of both study compared using statistical method and we found there was a significant different between two method and the modified as higher amplitude using lesser stimulated threshold but not significant different between latency. That’s happened because we increased the surface area of stimulation which means more the motor nerve was stimulated.

Carbon Monoxide Exerts Functional Neuroprotection After Cardiac Arrest Using Extracorporeal Resuscitation in Pigs.

Neurologic damage following cardiac arrest remains a major burden for modern resuscitation medicine. Cardiopulmonary resuscitation with extracorporeal circulatory support holds the potential to reduce morbidity and mortality. Furthermore, the endogenous gasotransmitter carbon monoxide attracts attention in reducing cerebral injury. We hypothesize that extracorporeal resuscitation with additional carbon monoxide application reduces neurologic damage. Randomized, controlled animal study. University research laboratory. Landrace-hybrid pigs. In a porcine model, carbon monoxide was added using a novel extracorporeal releasing system after resuscitation from cardiac arrest. As markers of cerebral function, neuromonitoring modalities (somatosensory-evoked potentials, cerebral oximetry, and transcranial Doppler ultrasound) were used. Histopathologic damage and molecular markers (caspase-3 activity and heme oxygenase-1 expression) were analyzed. Cerebral oximetry showed fast rise in regional oxygen saturation after carbon monoxide treatment at 0.5 hours compared with extracorporeal resuscitation alone (regional cerebral oxygen saturation, 73% ± 3% vs 52% ± 8%; p < 0.05). Median nerve somatosensory-evoked potentials showed improved activity upon carbon monoxide treatment, whereas post-cardiac arrest cerebral perfusion differences were diminished. Histopathologic damage scores were reduced compared with customary resuscitation strategies (hippocampus: sham, 0.4 ± 0.2; cardiopulmonary resuscitation, 1.7 ± 0.4; extracorporeal cardiopulmonary resuscitation, 2.3 ± 0.2; extracorporeal cardiopulmonary resuscitation with carbon monoxide application [CO-E-CPR], 0.9 ± 0.3; p < 0.05). Furthermore, ionized calcium-binding adaptor molecule 1 staining revealed reduced damage patterns upon carbon monoxide treatment. Caspase-3 activity (cardiopulmonary resuscitation, 426 ± 169 pg/mL; extracorporeal cardiopulmonary resuscitation, 240 ± 61 pg/mL; CO-E-CPR, 89 ± 26 pg/mL; p < 0.05) and heme oxygenase-1 (sham, 1 ± 0.1; cardiopulmonary resuscitation, 2.5 ± 0.4; extracorporeal cardiopulmonary resuscitation, 2.4 ± 0.2; CO-E-CPR, 1.4 ± 0.2; p < 0.05) expression were reduced after carbon monoxide exposure. Carbon monoxide application during extracorporeal resuscitation reduces injury patterns in neuromonitoring and decreases histopathologic cerebral damage by reducing apoptosis. This may lay the basis for further clinical translation of this highly salutary substance.