Measurement Of Somatosensory Evoked Potentials Research Articles

Somatosensory-Evoked Potentials and Clinical Assessments of Sensory Function Over Time in Patients With Subacute Stroke.

Objective: To demonstrate the utility of somatosensory evoked potentials (SEPs) following median nerve stimulation for chronological assessment of sensory function in patients with subacute stroke during rehabilitation. Design: Retrospective study. Patients: Forty-seven patients with hemiparesis due to stroke during the subacute phase. Methods: We screened 363 patients who underwent SEP measurements at a rehabilitation hospital. Among them, 47 who underwent SEP measurements within 1 week after admission and at least 2 weeks after the initial assessment were included in this study. Sensorimotor assessments, including the Semmes-Weinstein monofilament test (SWMT), pain sensation, position sensation, two-point discrimination, and Stroke Impairment Assessment Set (SIAS) motor tests simultaneously with SEP measurements were available for 20 of the 47 patients. The relationship between the SEP peak count and each sensorimotor assessment was examined. Results: SEP amplitudes and latencies showed no significant differences between the initial and second assessments (paired t-test, p > 0.05). However, the counts of SEP peaks after NI (N20) increased (Wilcoxon signed-rank test, p < 0.05), indicating changes in the SEP waveform. Furthermore, strong correlations were observed between SEP peak counts, stage, and all functional assessments (counts and SWMT, RS = -0.77, p < 0.001; counts and pain sensation, RS = -0.71, p < 0.001; counts and position sensation, RS = 0.75, p < 0.001; counts and two-point discrimination, RS = -0.74, p < 0.001; stage and SWMT, RS = -0.74, p < 0.001; stage and pain sensation, RS = -0.69, p < 0.001; stage and position sensation, RS = 0.74, p < 0.001; and stage and two-point discrimination, RS = -0.75, p < 0.001; all Spearman's rank correlation coefficients). Conclusion: Despite the limitations of the retrospective study design, our study highlights the utility of SEPs for evaluating sensory function in patients with subacute stroke, setting the foundation for further investigations on the use of SEPs to assess functional changes in patients with subacute stroke undergoing rehabilitation.

Does Forward Head Posture Influence Somatosensory Evoked Potentials and Somatosensory Processing in Asymptomatic Young Adults?

The current investigation used somatosensory evoked potentials (SEPs) to assess differences in sensorimotor integration and somatosensory processing variables between asymptomatic individuals with and without forward head posture (FHP). We assessed different neural regions of the somatosensory pathway, including the amplitudes of the peripheral N9, spinal N13, brainstem P14, peak-to-peak amplitudes of parietal N20 and P27, and frontal N30 potentials. Central conduction time (N13-N20) was measured as the difference in peak latencies of N13 and N20. We measured these variables in 60 participants with FHP defined as a craniovertebral angle (CVA) < 50° and 60 control participants matched for age, gender, and body mass index (BMI) with normal FHP defined as CVA > 55°. Differences in variable measures were examined using the parametric t-test. Pearson's correlation was used to evaluate the relationship between the CVA and sensorimotor integration and SEP measurements. A generalized linear model (GLM) was used to compare the SEP measures between groups, with adjustment for educational level, marital status, BMI, and working hours per week. There were statistically significant differences between the FHP group and control group for all sensorimotor integration and SEP processing variables, including the amplitudes of spinal N13 (p < 0.005), brainstem P14 (p < 0.005), peak-to-peak amplitudes of parietal N20 and P27 (p < 0.005), frontal N30 potentials (p < 0.005), and the conduction time N13-N20 (p = 0.004). The CVA significantly correlated with all measured neurophysiological variables indicating that as FHP increased, sensorimotor integration and SEP processing became less efficient. FHP group correlations were: N9 (r = -0.44, p < 0.001); N13 (r = -0.67, p < 0.001); P14 (r = -0.58, p < 0.001); N20 (r = -0.49, p = 0.001); P27 (r = -0.58, p < 0.001); N30 potentials (r = -0.64, p < 0.001); and N13-N20 (r = -0.61, p < 0.001). GLM identified that increased working hours adversely affected the SEP measures (p < 0.005), while each 1° increase in the CVA was associated with improved SEP amplitudes and more efficient central conduction time (N13-N20; p < 0.005). Less efficient sensorimotor integration and SEP processing may be related to previous scientific reports of altered sensorimotor control and athletic skill measures in populations with FHP. Future investigations should seek to replicate our findings in different spine disorders and symptomatic populations in an effort to understand how improving forward head posture might benefit functional outcomes of patient care.

Efficacy of functional electrical stimulation in rehabilitating patients with foot drop symptoms after stroke and its correlation with somatosensory evoked potentials—a crossover randomised controlled trial

ObjectiveThe connectivity between somatosensory evoked potentials (SEPs) and cortical plasticity remains elusive due to a lack of supporting data. This study investigates changes in pathological latencies and amplitudes of SEPs caused by an acute stroke after 2 weeks of rehabilitation with functional electrical stimulation (FES). Furthermore, changes in SEPs and the efficacy of FES against foot drop (FD) stroke symptoms were correlated using the 10-m walk test and foot–ankle strength.MethodsA randomised controlled two-period crossover design plus a control group (group C) was designed. Group A (n = 16) was directly treated with FES, while group B (n = 16) was treated after 2 weeks. The untreated control group of 20 healthy adults underwent repeated SEP measurements for evaluation only.ResultsThe repeated-measures ANOVA showed a decrease in tibial nerve (TN) P40 and N50 latencies in group A after the intervention, followed by a decline in non-paretic TN SEP in latency N50 (p < 0.05). Moreover, compared to groups B and C from baseline to 4 weeks, group A showed a decrease in paretic TN latency P40 and N50 (p < 0.05). An increase in FD strength and a reduction in step cadence in group B (p < 0.05) and a positive tendency in FD strength (p = 0.12) and step cadence (p = 0.08) in group A were observed after the treatment time. The data showed a moderate (r = 0.50–0.70) correlation between non-paretic TN latency N50 and step cadence in groups A and B after the intervention time.ConclusionThe FES intervention modified the pathological gait in association with improved SEP afferent feedback.Registered on 25 February 2021 on ClinicalTrials.gov under identifier number: NCT04767360.

Prediction of Single Trial Somatosensory Evoked Potentials From Mechanical Stimulation Intensity.

Somatosensory evoked potentials (SSEPs) are important for both scientific research and the evaluation of treatment efficacy in neurorehabilitation. SSEPs measure the response in the sensorimotor cortex to a peripheral stimulation. Individual responses are often noisy, so SSEPs have typically required hundreds of stimulation-response trials to produce a single measurement. This work presents a method to estimate single trial SSEPs from tendon hammer accelerations. While predictions from the input side can not completely replace actual measurements of SSEPs, the results produced may help to provide clinicians insight where full scale SSEP measurement is not practical.

Feasibility of non-invasive recording of somatosensory evoked potential in pigs

BackgroundNon-invasive measurement of somatosensory-evoked potentials (SEP) in a large animal model is important to translational cognitive research. We sought to develop a methodology for neurophysiological recording via a transcranial electroencephalography (EEG) cap under an effective sedative regimen with dexmedetomidine, midazolam, and butorphanol that will produce sedation instead of anesthesia while not compromising data quality.ResultsPigs received intramuscular dexmedetomidine, midazolam, and butorphanol for SEP assessment with peroneal nerve stimulation. Semi-quantitative sedation assessment was performed after the animal was sufficiently sedated and 30 min later, during the transcranial SEP recording. SEP data were analyzed with commercial software. Binary qualitative analysis of the recording was categorized by an experienced neurophysiologist. All four animals had adequate surface SEP recordings. Animals received 43 [21–47] mcg/kg of dexmedetomidine, 0.3 [0.2–0.3] mg/kg of midazolam, and 0.3 [0.3–0.3] mg/kg of butorphanol IM. All treatments resulted in moderate to deep sedation (Baseline median sedation score 11.5 [11–12]; median score at 30 min: 11.5 [10.5–12]). Heart rate (median [range]) (55 [49–71] beats per minute), respiratory rate (24 [21–30] breaths per minute), and hemoglobin oxygen saturation (99 [98–100]%) and body temperature (37.7 [37.4–37.9] °C) remained within clinically acceptable ranges. There were no undesirable recovery incidents.ConclusionsIn this pilot study, we demonstrate the feasibility of SEP recording via a transcranial EEG cap under an effective sedative regimen in pigs. Our approach will expand the use of a large animal model in neurotranslational research.

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.

The Effect of Xenon-Based Anesthesia on Somatosensory-Evoked Potentials in Patients Undergoing Carotid Endarterectomy

The aim of this study was to investigate the influence of xenon-based anesthesia on somatosensory-evoked potentials. Observational cohort study. University hospital. Twenty subsequent adult patients undergoing elective carotid endarterectomy. Xenon-based anesthesia. Cortical-evoked responses to median nerve stimulation were quantified by measurement of the amplitude and latency of the N20 wave, which are typically assessed during carotid surgery to detect intraoperative cerebral hypoperfusion and ischemia. Primary (N20 amplitude and latency) and secondary (mean arterial pressure, norepinephrine requirements and depth of anesthesia) were assessed during (1) propofol/remifentanil and (2) subsequent xenon/remifentanil anesthesia. Xenon at an inspiratory fraction of 62.5 ± 7% decreased norepinephrine requirement (0.067 ± 0.04 v 0.028 ± 0.02 µg/kg/min, p < 0.001), and mean arterial pressure was unchanged (90.6 ± 15.0 v 93.1 ± 9.6 mmHg, p = 0.40). Somatosensory-evoked potentials were available in all patients during xenon/remifentanil. Despite similar depth of anesthesia (Narcotrend index 38.4 ± 6.2 v 38.5 ± 5.8) during propofol and xenon, N20 amplitude was reduced after xenon wash-in from 3.7 ± 1.7 to 1.4 ± 2.8 µV, p < 0.001 on the surgical and 3.6 ± 1.6 to 1.4 ± 0.6 µV, p < 0.001 on the contralateral side. N20 latency remained unchanged during xenon (22.9 ± 2.1 v 22.5 ± 2.8 ms, p = 0.34 and 22.9 ± 2.0 v 22.9 ± 3.0, p = 0.97). Xenon influences somatosensory-evoked potentials measurement by reducing N20 wave amplitude but not latency. When xenon is considered as an anesthetic for carotid endarterectomy, wash-in needs to be completed before carotid surgery is commenced to provide stable baseline somatosensory-evoked potential measurement.

Automated Variable Stimulus Tendon Tapping Modulates Somatosensory Evoked Potentials.

Somatosensory Evoked Potentials (SSEPs) are an important tool for both basic neuroscience research and evaluation of therapeutic techniques. While a large body of work exists in the study of electrically induced SSEPs both as a metric for therapeutic performance and tool for physiological research, comparatively little work has explored stretch response SSEPs evoked via tendon tapping. The measurement of SSEPs necessitates both timing and stimulation intensity consistency. This work presents an evaluation of a simple tapping device for automating this procedure and a comparison to manual tendon tapping demonstrating significantly reduced variability in both timing and intensity. The variable intensity nature of automated tapping is then used to measure SSEPs in a single subject, with apparent modulation of peak-peak amplitude by stimulation intensity.

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

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

T88. Optimizing lower limb Somatosensory Evoked Potentials (SEPs) with additional derivations

SEPs recorded over the scalp serve as surrogate markers of dorsal column proprioceptive pathway integrity during surgery. Changes in SEP amplitude and/or latency meeting “alarm criteria” can indicate neural injury and prompt the surgical team to take action. Alarm criteria (e.g. 50% drop in amplitude) lose specificity when SEP measurement variability is high (e.g. ⩾25%). Lower limb scalp SEPs has vary dipole vectors between individuals. Standard recording electrode derivations of SEPs have been shown to be suboptimal when compared to a derivation individually optimized for each patient. Scalp lower limb SEPs were monitored from a consecutive sample of 51 patients during non-emergent procedures at Mayo Clinic Rochester. Two additional scalp electrodes at Cz and Pz were setup beside the standard scalp electrodes (CPz, Fz, CPi and CPc). Two standard derivations (CPz-Fz and CPi-CPc) and five expanded derivations (CPz-CPc, Cz-CPc, Pz-CPc, CPz-CPi and Pz-Fz) were recorded. P38 amplitudes were measured for all derivations; the derivation with the lowest coefficient of variation (CV) and highest amplitude from each group (standard vs. expanded montage) were determined. The P38 with highest amplitude and lowest CV were found in the expanded montage in 78 (76%) and 71 (70%) out of 102 limbs from 51 patients. The expanded montage significantly lowered the minimum CV by 1.75% (P < 0.0001, linear regression) and increased the maximal amplitude by 0.13 μV (P < 0.0001, linear regression) as compared to the standard montage. The CPz-CPc was the most frequent derivation with lowest CV and highest amplitude among all seven derivations. The effort to implement an expanded scalp montage should be balanced with the potential improvements, which by our data, are only incremental. An expanded scalp montage may be highest yield in patients where recordings from a conventional montage are of poor quality.

Somatosensory evoked potentials after decompressive craniectomy for traumatic brain injury.

Somatosensory evoked potentials (SSEPs) are used for neuroprognosis after severe traumatic brain injury (TBI). However decompressive craniectomy (DC), involving removal of a portion of the skull to alleviate elevated intracranial pressure, is associated with an increase in SSEP amplitude. Accordingly, SSEPs are not available for neuroprognosis over the hemisphere with DC. We aim to determine the degree to which SSEP amplitudes are increased in the absence of cranial bone. This will serve as a precursor for translation to clinically prognostic ranges. Intra-operative SSEPs were performed before and after bone flap replacement in 22 patients with severe TBI. SSEP measurements were also performed in a comparison non-traumatic group undergoing craniotomy for tumor resection. N20/P25 amplitudes and central conduction time were measured with the bone flap in (BI) and out (BO). Linear regressions, adjusting for skull thickness and study arm, were performed to evaluate the contribution of bone presence to SSEP amplitudes. Latencies were not different between BO or BI trials in either group. Mean N20/P25 amplitudes recorded with BO were statistically different (p = 0.0001) from BI in both cohorts, showing an approximate doubling in BO amplitudes. For contralateral-ipsilateral montages r2 was 0.28 and for frontal pole montages r2 was 0.62. Cortical SSEP amplitudes are influenced by the presence of cortical bone as is particularly evident in frontal pole montages. Larger, longitudinal trials to assess feasibility of neuroprognosis over the hemisphere with DC in severe TBI patients are warranted.

Somatosensory evoked potentials in patients with high-grade aneurysmal subarachnoid hemorrhage.

OBJECTIVE The aim of this prospective study was to investigate the value of somatosensory evoked potentials (SEPs) in predicting outcome in patients with high-grade aneurysmal subarachnoid hemorrhage (SAH). METHODS Between January 2013 and January 2015, 48 patients with high-grade SAH (Hunt and Hess Grade III, IV, or V) who were admitted within 3 days after hemorrhage were enrolled in the study. Right and left median and tibial nerve SEPs were recorded on Day 3 after hemorrhage and recorded again 2 weeks later. Glasgow Outcome Scale (GOS) scores were determined 6 months after hemorrhage and dichotomized as poor (Scores 1-3) or good (Scores 4-5). Results of SEP measurements were dichotomized (present or missing cortical responses or normal or prolonged latencies) for each nerve and side. These variables were summed and tested using logistic regression and a receiver operating characteristic curve to assess the value of SEPs in predicting long-term outcome. RESULTS At the 6-month follow-up visit, 29 (60.4%) patients had a good outcome, and 19 (39.6%) had a poor outcome. The first SEP measurement did not correlate with clinical outcome (area under the curve [AUC] 0.69, p = 0.52). At the second measurement of median nerve SEPs, all patients with a good outcome had cortical responses present bilaterally, and none of them had bilateral prolonged latencies (p = 0.014 and 0.003, respectively). In tibial nerve SEPs, 7.7% of the patients with a good GOS score had one or more missing cortical responses, and bilateral prolonged latencies were found in 23% (p = 0.001 and 0.034, respectively). The second measurement correlated with the outcome regarding each of the median and tibial nerve SEPs and the combination of both (AUC 0.75 [p = 0.010], 0.793 [p = 0.003], and 0.81 [p = 0.001], respectively). CONCLUSIONS Early SEP measurement after SAH did not correlate with clinical outcome, but measurement of median and tibial nerve SEPs 2 weeks after a hemorrhage did predict long-term outcome in patients with high-grade SAH.

Effects of different exercise modalities on ataxia in multiple sclerosis patients: a randomized controlled study

Purpose: To investigate the effects of different exercise protocols on ataxia in patients with multiple sclerosis (MS).Method: A total of 42 MS patients, 17 male and 25 female (Expanded Disability Status Scale (EDSS): 3–5), were enrolled in this randomized controlled study. The patients were divided into three groups: a balance training (BT) group, a lumbar stabilization (LS) group and a task-oriented training (TT) group. All groups received balance training; additionally, the LS group received lumbar stabilization exercises, and the TT group received task-oriented training. The Berg Balance Scale (BBS), International Cooperative Ataxia Rating Scale (ICARS), Functional Reach Test (FRT), 2-Minute Walk Test (2MWT), Sensory Organization Test (SOT), and measurement of Somatosensory Evoked Potentials (SSEPs) were performed before and at the end of the 18 training sessions.Results: The BBS, ICARS, FRT, 2MWT, and composite balance score of the SOT were improved in all groups. The ICARS kinetic function sub-score and the left limb cortical onset amplitudes of SSEPs were increased significantly in both the TT and the LS groups. The ICARS total score, composite balance score, and 2MWT were different between groups (p < 0.05). According to multiple comparison analyses of the ICARS total score and the composite balance score, the LS, and the TT group were different from the BT group (p < 0.005), while the LS and the TT groups improved similarly (p > 0.005). The 2MWT results were better for the LS group than the BT group, while the BT and the TT groups improved similarly.Conclusion: Balance training alone is not sufficient for rehabilitation of ataxic MS patients. A combination of lumbar stabilization exercises or task-oriented training increases the success of balance rehabilitation.Implications for rehabilitationMultiple sclerosis is a chronic inflammatory and autoimmune disease of central nervous system and ataxia is one of the most challenging symptoms of this disease.Different exercise modalities are commonly employed to control ataxic symptoms in MS patients.Lumbar stabilization exercises or task-oriented training should be considered as complementary approach to improve balance and coordination in ataxic multiple sclerosis patients.

The effect of anaesthesia on somatosensory evoked potential measurement in a rat model

Somatosensory evoked potentials (SEPs) are widely used to study the functional integrity of ascending sensory pathways. For animal studies, SEPs provide a convenient method to quantitatively assess the functionality of the nervous system with low invasiveness. Even though they are frequently used in animal models, little attention is paid to the fact that SEPs are vulnerable to contamination from experimental factors such as anaesthetic delivery. In this study, the effect of isoflurane on SEP measurement was investigated in a rat model. The aim was to find out the adjustments for anaesthetic delivery optimizing the quality of the recordings. Two aspects were studied: the effect of isoflurane dosage on the SEP parameters and on the repeatability of the measurements. The SEP quality was found to be best when 1.5% isoflurane concentration was used. This dosage resulted in the best signal-to-noise ratio and equal repeatability of the measurements compared with the others. Our findings can help in refining the anaesthetic protocols related to SEP recordings in a rat model and, by improving the quality of the measurements, potentially reducing the number of subjects needed to carry out studies.

Effect of isoflurane on somatosensory evoked potentials in a rat model.

Somatosensory evoked potentials (SEPs) are widely used in the clinic as well as research to study the functional integrity of the different parts of sensory pathways. However, most general anesthetics, such as isoflurane, are known to suppress SEPs, which might affect the interpretation of the signals. In animal studies, the usage of anesthetics during SEP measurements is inevitable due to which detailed effect of these drugs on the recordings should be known. In this paper, the effect of isoflurane on SEPs was studied in a rat model. Both time and frequency properties of the cortical recordings generated by stimulating the tibial nerve of rat's hindlimb were investigated at three different isoflurane levels. While the anesthetic agent is shown to generally suppress the amplitude of the SEP, the effect was found to be nonlinear influencing more substantially the latter part of waveform. This finding will potentially help us in future work aiming at separating the effects of anesthetics on SEP from those due to injury in the ascending neural pathways.

Towards treating spinal cord injury in 'patients': one step at a time

For many years, there has been an expectation that developments in neurobiology and work on regeneration of the CNS will have early applications in the area of spinal cord injury. Now, a study by Granger et al . (2012) published in this issue of Brain reports a clinical trial in adult dogs with chronic spinal cord injury caused by an acute event, such as disk herniation. These injuries are common in veterinary practice, and studying therapeutics in this clinical population is sensible. The experimental therapeutic intervention was intraspinal transplantation of cultured autologous cells derived from the olfactory mucosa of the frontal sinus, whereas the control group received injections of cell culture medium only. The data analysis indicated a significant difference between the transplanted and control groups in forelimb–hindlimb coordination measured using kinematic analysis of locomotion on a treadmill during partial weight support. No difference in long tract functional recovery was detected between the groups using motor- and somatosensory-evoked potentials. This veterinary study has relevance to human clinical trial designs in several ways. For example, as the authors point out, the external validity is higher with this heterogeneous dog population than with a genetically homogeneous laboratory animal study. In addition, the cell therapy study had a relevant control group that was injected with cell culture medium and was blinded. Careful reading of the study discloses several interesting points for consideration. It is not clear from the inclusion and exclusion criteria whether the enrolled dogs had undergone decompressive surgery at the time of their index paraplegia. Lack of surgical decompression might mitigate against recovery independent of a transplant effect. At study entry, there was a clinical examination, MRI, measurement of somatosensory-evoked potentials and motor-evoked potentials and urodynamic evaluation. The results of the MRI are not described. Motor-evoked potentials were recorded from one lower …

Correlation of current perception threshold and somatosensory evoked potential in diabetes

To study the relationship between current perception threshold (CPT) and somatosensory evoked potential (SEP) in diabetes. Both CPT and SEP were recorded in 66 diabetic patients. Both the CPT scores (measured at 2000 Hz, 250 Hz, and 5 Hz stimulations) and SEP (peak latency at ERB's point [Lat (ERB)] and popliteal fossa [Lat (PF)]; interpeak latency of "ERB to 7th cervical vertebra" [Δlat (ERB-C7)] and "popliteal fossa to lumbar vertebra" [Δlat (PF-FO)]) were recorded in both upper and both lower limbs, separately. t-tests and correlation analyses were performed to assess relationships between CPT and SEP tests. After adjustment for height and/or age, CPT scores at 2000 Hz were significantly correlated with Lat (ERB) (left: ρ=0.408, P<0.05; right: ρ=0.297, P<0.05), Δlat (ERB-C7) (left: ρ=0.238, P<0.05; right: ρ=0.385, P<0.05), and Lat (PF) (ρ=0.216, P<0.05), and those at 250 Hz were moderately correlated with Lat (ERB) (left: ρ=0.234, P<0.05; right: ρ=0.306, P<0.05). CPT scores at 5 Hz were not significantly correlated with any SEP measurements (P>0.05). Both CPT scores at 2000 Hz and SEP may reliably determine large-fiber function in diabetic neuropathy.

*Poster 47: Correlations Between Recovery of Ambulatory Capacity and Lower-Limb Somatosensory Evoked Potentials in Incomplete Spinal Cord Injury

Objective: To study relationships between posterior tibial (PT) nerve somatosensory evoked potentials (SEP) and recovery of ambulatory capacity in patients with incomplete spinal cord injury (SCI) participating in Lokomat training. Design: Correlation study of functional clinical outcome with quantitative electrophysiological measures of sensory processing. Setting: Queen Elizabeth National Spinal Injuries Unit, Scotland. Participants: 13 acute and 5 chronic incomplete SCI patients. Intervention: 30 hours Lokomat Training over a 6-week period.

Effects of Remote Ischemic Preconditioning on Biochemical Markers and Neurologic Outcomes in Patients Undergoing Elective Cervical Decompression Surgery

Remote ischemic preconditioning (RIPC) may protect the spinal cord from ischemic injury. This randomized clinical trial was designed to assess whether a large clinical trial testing the effect of RIPC on neurologic outcome in patients undergoing spine surgery is warranted. This trial was registered with ClinicalTrials.gov, number NCT00778323. Forty adult cervical spondylotic myelopathy patients undergoing elective decompression surgery were randomly assigned to either the RIPC group (n=20) or the control group (n=20). Limb RIPC consisted of three 5-minutes cycles of upper right limb ischemia with intervening 5-minute periods of reperfusion. Neuron-specific enolase and S-100B levels were measured in serum at set time points. Median nerve somatosensory-evoked potentials (SEPs) were also recorded. Neurologic recovery rate was evaluated using a Japanese Orthopaedic Association scale. RIPC significantly reduced serum S-100B release at 6 hours and 1 day after surgery, and reduced neuron-specific enolase release at 6 hours, and then at 1, 3, and 5 days after surgery. No differences were observed in SEP measurements or the incidence of SEP changes during surgery between the control and RIPC groups. Recovery rate at 7 days, and at 1 and 3 months after surgery was higher in the RIPC group than in the control group (P<0.05). Our results for markers of neuronal ischemic injury and rate of recovery suggest that a clinical trial with sufficient statistical power to detect an effect of RIPC on the incidence of neurologic complications (paresis, palsy, etc) due to spinal cord ischemia-reperfusion injury after spine surgery is warranted [corrected].

Heat shock proteins HSP70 and HSP27 in the cerebral spinal fluid of patients undergoing thoracic aneurysm repair correlate with the probability of postoperative paralysis

An understanding of the time course and correlation with injury of heat shock proteins (HSPs) released during brain and/or spinal cord cellular stress (ischemia) is critical in understanding the role of the HSPs in cellular survival, and may provide a clinically useful biomarker of severe cellular stress. We have analyzed the levels of HSPs in the cerebrospinal fluid (CSF) from patients who are undergoing thoracic aneurysm repair. Blood and CSF samples were collected at regular intervals, and CSF was analyzed by enzyme-linked immunosorbent assay for HSP70 and HSP27. These results were correlated with intraoperative somatosensory-evoked potentials measurements and postoperative paralysis. We find that the levels of these proteins in many patients are elevated and that the degree of elevation correlates with the risk of permanent paralysis. We hypothesize that sequential measurement intraoperatively of the levels of the heat shock proteins HSP70 and HSP27 in the CSF can predict those patients who are at greatest risk for paralysis during thoracic aneurysm surgery and will allow us to develop means of preventing or attenuating this severe and often fatal complication.