Lower Extremity Somatosensory Evoked Potentials Research Articles

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

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

The efficacy of somatosensory evoked potentials in evaluating new neurological deficits after spinal thoracic fusion and decompression.

Posterior thoracic fusion (PTF) is used as a surgical treatment for a wide range of pathologies. The monitoring of somatosensory evoked potentials (SSEPs) is used to detect and prevent injury during many neurological surgeries. The authors conducted a study to evaluate the efficacy of SSEPs in predicting perioperative lower-extremity (LE) neurological deficits during spinal thoracic fusion surgery. The authors included patients who underwent PTF with SSEP monitoring performed throughout the entire surgery from 2010 to 2015 at the University of Pittsburgh Medical Center (UPMC). The sensitivity, specificity, odds ratio, and receiver operating characteristic curve were calculated to evaluate the diagnostic accuracy of SSEP changes in predicting postoperative deficits. Univariate analysis was completed to determine the impact of age exceeding 65 years, sex, obesity, abnormal baseline testing, surgery type, and neurological deficits on the development of intraoperative changes. From 2010 to 2015, 771 eligible patients underwent SSEP monitoring during PTF at UPMC. Univariate and linear regression analyses showed that LE SSEP changes significantly predicted LE neurological deficits. Significant changes in LE SSEPs had a sensitivity and specificity of 19% and 96%, respectively, in predicting LE neurological deficits. The diagnostic odds ratio for patients with new LE neurological deficits who had significant changes in LE SSEPs was 5.86 (95% CI 2.74-12.5). However, the results showed that a loss of LE waveforms had a poor predictive value for perioperative LE deficits (diagnostic OR 1.58 [95% CI 0.19-12.83]). Patients with new postoperative LE neurological deficits are 5.9 times more likely to have significant changes in LE SSEPs during PTF. Surgeon awareness of an LE SSEP loss may alter surgical strategy and positively impact rates of postoperative LE neurological deficit status. The relatively poor sensitivity of LE SSEP monitoring may indicate a need for multimodal neurophysiological monitoring, including motor evoked potentials, in thoracic fusion surgery.

The diagnostic accuracy of somatosensory evoked potentials in evaluating neurological deficits during 1057 lumbar interbody fusions

BackgroundLumbar interbody spinal fusion (LIF) surgeries are performed to treat or prevent back pain in patients with degenerated intervertebral discs and a variety of spinal diseases. However, post-operative neurological complications may ensue. Intraoperative monitoring techniques have been used to predict and potentially reduce the risk of complications. MethodsThis study examined the diagnostic accuracy of significant changes of somatosensory evoked potentials (SSEPs) to evaluate and predict post-operative neurological deficits after LIF. All patients underwent LIF at UPMC from 2010 to 2012. One thousand fifty-seven patients had pre-operative baseline and continuous intraoperative SSEP monitoring. Statistical analysis was completed using SPSS version 22. No relevant disclosure. ResultsPatient outcomes were not significantly affected by age over 65, gender, obesity, and abnormal baselines. Lower extremity (LE) significant changes in SSEPs and LE loss of responses resulted in a sensitivity/specificity of 0.03/0.99 and 0.03/0.99; they had an AUC of 0.54/0.73 with a 95% confidence interval (CI) of [0.34, 0.74]/[0.29, 1.00]. ConclusionsSignificant SSEP changes during LIF are a very specific but poorly sensitive indicator of perioperative neurological deficits. The odds ratio for LE loss of responses was 29.14 with a 95% CI of 1.79-475.5, so LE SSEP loss of responses can serve as a biomarker of perioperative neurological deficits after LIF.

Factors Associated With Inadequate Intraoperative Baseline Lower Extremity Somatosensory Evoked Potentials.

Intraoperative neurophysiologic monitoring involves the use of various modalities, including somatosensory evoked potentials (SEP), to assess the integrity of the at-risk nervous system during surgeries. Reliable baseline tracings are important because they are data against which future tracings are compared to detect potential injury. In some cases, adequate baselines may be difficult to achieve. Therefore, we analyzed several patient-specific factors to determine which variables are associated with inadequate intraoperative SEP baseline signals. This is a single-center, retrospective chart review of 631 consecutive patients who underwent spine or cranial surgeries between 2010 and 2011. Variables analyzed included age, glucose levels, diabetes mellitus type 2, hypertension, hyperlipidemia, height, weight, sex, smoking, preexisting neurologic conditions, surgical history, lower extremity edema, and neurologic examination findings. Association between these patient factors and baseline lower extremity SEP signals were analyzed. Height, weight, neurologic deficits, lower extremity edema, and history of neurologic disease are each associated with inadequate baseline lower extremity SEPs after controlling for confounding variables. Baseline signals were able to be acquired in 94.1% of patients. Adequate baselines are paramount for successful intraoperative neurophysiologic monitoring. However, certain patient-specific factors are associated with inadequate baseline SEP signals. Physical examination findings and a detailed chart review can be done to identify these factors and guide expectations during monitoring. Further research related to patient-specific factors amenable to modification can further improve our capacity to protect the nervous system during surgery.

A Comparison of Interside Asymmetries of Lower Extremity Somatosensory Evoked Potentials in Anesthetized Patients with Unilateral Lumbosacral Radiculopathy.

Study DesignProspective cohort study.PurposeThis study was to investigate interside asymmetries of three lower extremity somatosensory evoked potentials (SSEPs) in anesthetized patients with unilateral lumbosacral radiculopathy.Overview of LiteratureAlthough interside asymmetry is an established criterion of abnormal SSEP, little is known which of the lower SSEPs is more sensitive in detecting interside asymmetry in anesthetized patients.MethodsSuperficial peroneal nerve SSEP (SPN-SSEP), posterior tibial nerve SSEP (PTN-SSEP), and sural nerve SSEP were obtained in 31 lumbosacral surgery patients with unilateral lumbosacral radiculopathy, and compared with a group of 22 control subjects.ResultsThe lumbosacral group showed significant larger interside asymmetry ratios of P37 latencies in SPN-SSEP and PTN-SSEP, and significant larger interside asymmetry ratio of P37-N45 amplitude in SPN-SSEP, when comparing with the control group. Within the lumbosacral group but not the control group, SPN-SSEP displayed significant larger interside asymmetry ratio in P37 latency. When referencing to the control group, more patients in the lumbosacral group displayed abnormal interside SPN-SSEP latency asymmetries which corroborated the symptom laterality.ConclusionsThe data suggested that SPN-SSEP was more sensitive in detecting interside latency asymmetry in anesthetized patients.

Loss of Lower Extremity Somatosensory Evoked Potentials During Lumbar Laminectomy and Instrumented Fusion: A Case Report

The utilization of lower extremity somatosensory evoked potentials SSEP for monitoring of lumbar spine procedures remains controversial The fact that multiple lumbar spinal nerve roots contribute to the SSEP prior to its transition into the posterior columns of the spinal cord may lead to reduced sensitivity in monitoring these potentials We present a case of a patient undergoing a posterior open approach lumbar laminectomy and instrumented fusion The patient experienced an acute loss of both cortical and subcortical posterior tibial nerve PTN SSEPs during lumbar laminectomy Figure Continuous testing documented a full amplitude recovery of the attenuated evoked potentials forty minutes after loss of signal and completion of the decompression Figure An analysis of the literature case review and discussion on the merits of SSEP monitoring in below the conus medularis procedures is presented nbsp

Neurophysiologic Intraoperative Monitoring During Percutaneous Thoracolumbar Kyphoplasty: A Multimodality Approach

ABSTRACT.We report techniques to monitor the functional integrity of the spinal cord and physiologic status of the spinal nerve roots during percutaneous throracolumbar kyphoplasty for treatment of vertebral compression fractures. Monitoring of the functional integrity of the anterior and posterior spinal cord can be accomplished with the use of electric trcinscranial motor evoked potentials (tceMEPs) and somatosensory evoked potentials (SSEPs), respectively. The physiologic status of the spinal nerve roots can be monitored continuously with spontaneous electromyography (EMG) monitoring. Lower extremity SSEPs are obtained using stimulation of the posterior tibial nerve (PTN) at the ankle; upper extremity SSEPs are obtained using stimulation of the median nerve or ulnar nerve. TceMEPs are obtained with stimulation of the motor cortex (precentral gyrus) at the scalp and recording compound muscle action potentials (CMAPs) in the hands and legs. Intramuscular electromyographic activity is referentially recorded in all extremities and specific muscle groups innervated by spinal nerves at the level of the procedure. SSEPs, tceMEPs, and EMG can be effectively obtained and monitored during percutaneous thoracolumbar kyphoplasty. This technique of multimodality neurophysiologic monitoring provides invaluable intraoperative data for the surgeon regarding the functional integrity of the patient's spinal cord and physiologic status of the spinal nerve roots, thereby decreasing the likelihood iatrogenic neurologic injury and post-operative neurologic deficits.