Neurophysiology during peripheral nerve surgery.

Electrophysiological monitoring of the peripheral nervous system during a variety of surgeries provides useful information that supplements and complements preoperative assessment. Monitoring improves localization and understanding of the underlying pathophysiology of peripheral nerve lesions leading to more rational treatment decisions and improved outcomes. Monitoring is accomplished by adaptation of routine electrodiagnostic techniques (i.e., nerve conduction studies, evoked potentials, and electromyography) with special attention to technical factors including electrical and movement artifact. These techniques have been successfully applied during surgery for entrapment neuropathies, traumatic nerve injury and repair, peripheral nerve tumors, and adjacent structure procedures that risk peripheral nerve injury. A clear understanding of the anatomy and neurophysiology is necessary, as is understanding and performing the difficult technical aspects of these studies to provide accurate information to enhance patient outcome and recovery. As in any intraoperative neurophysiologic monitoring (IONM) setting, constant and accurate communication between the IONM team, surgeon, and anesthesia team is critically important to meet these goals.

Impact of long-term epidural electrical stimulation enabled task-specific training on secondary conditions of chronic paraplegia in two humans.

Introduction: Spinal cord injury (SCI) often results in chronic secondary health conditions related to autonomic and metabolic dysfunction. Epidural electrical stimulation (EES) combined with task-specific training has been shown to enable motor function in individuals with chronic paralysis. The reported effects of EES on secondary health conditions, such as bladder function and body composition, are limited. We report the impact of EES on SCI-related secondary health changes in bladder function and body composition.Methods: Two participants with motor and sensory complete SCI performed 6 months of rehabilitation without EES followed by 12 months of task-specific training with EES after implantation of a 16-electrode array on the surface of the lumbosacral spinal cord. Participants performed three days of training per week in the laboratory, and additionally performed task-specific activities with EES at home during this time frame. Changes in bladder and body composition were recorded via clinically-available testing of neurogenic bladder functionality and dual-energy X-ray absorptiometry, respectively.Results: In one participant, we observed an increase in episodes of urinary incontinence with worsening bladder compliance and pressures at the end of the study. Bone mineral density changes were insignificant in both participants; however, one participant showed a substantial increase in lean mass (+9.1 kg; 6 months of training) via redistribution of body fat through an android/gynoid ratio reduction (-0.15; 6 months of training).Conclusion: EES optimized for standing and stepping may negatively impact neurogenic bladder functionality. Close monitoring of bladder health is imperative to prevent undesirable bladder compliance, which can lead to upper urinary tract deteriorations. Conversely, EES may serve as an adjunct tool with regular exercise modalities to improve body composition through activation of musculature innervated by spinal segments that are below the SCI.

Correction to: Is the new ASNM intraoperative neuromonitoring supervision "guideline" a trustworthy guideline? A commentary.

The article Is the new ASNM intraoperative neuromonitoring supervision "guideline" a trustworthy guideline? A commentary, written by Stanley A. Skinner, Elif Ilgaz Aydinlar, Lawrence F. Borges, Bob S. Carter, Bradford L. Currier, Vedran Deletis, Charles Dong, John Paul Dormans, Gea Drost, Isabel Fernandez­Conejero, E. Matthew Hoffman, Robert N. Holdefer, Paulo Andre Teixeira Kimaid, Antoun Koht, Karl F. Kothbauer, David B. MacDonald, John J. McAuliffe III, David E. Morledge, Susan H. Morris, Jonathan Norton, Klaus Novak, Kyung Seok Park, Joseph H. Perra, Julian Prell, David M. Rippe, Francesco Sala, Daniel M. Schwartz, Martín J. Segura, Kathleen Seidel, Christoph Seubert, Mirela V. Simon, Francisco Soto, Jeffrey A. Strommen, Andrea Szelenyi, Armando Tello, Sedat Ulkatan, Javier Urriza and Marshall Wilkinson, was originally published electronically on the publisher's internet portal (currently SpringerLink) on 05 January 2019 without open access. With the author(s)' decision to opt for Open Choice the copyright of the article changed on 30 January 2019 to © The Author(s) 2019 and the article is forthwith distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits use, duplication, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license and indicate if changes were made. The original article has been corrected.

Electrophysiological Guidance of Epidural Electrode Array Implantation over the Human Lumbosacral Spinal Cord to Enable Motor Function after Chronic Paralysis.

Epidural electrical stimulation (EES) of the spinal cord has been shown to restore function after spinal cord injury (SCI). Characterization of EES-evoked motor responses has provided a basic understanding of spinal sensorimotor network activity related to EES-enabled motor activity of the lower extremities. However, the use of EES-evoked motor responses to guide EES system implantation over the spinal cord and their relation to post-operative EES-enabled function in humans with chronic paralysis attributed to SCI has yet to be described. Herein, we describe the surgical and intraoperative electrophysiological approach used, followed by initial EES-enabled results observed in 2 human subjects with motor complete paralysis who were enrolled in a clinical trial investigating the use of EES to enable motor functions after SCI. The 16-contact electrode array was initially positioned under fluoroscopic guidance. Then, EES-evoked motor responses were recorded from select leg muscles and displayed in real time to determine electrode array proximity to spinal cord regions associated with motor activity of the lower extremities. Acceptable array positioning was determined based on achievement of selective proximal or distal leg muscle activity, as well as bilateral muscle activation. Motor response latencies were not significantly different between intraoperative recordings and post-operative recordings, indicating that array positioning remained stable. Additionally, EES enabled intentional control of step-like activity in both subjects within the first 5 days of testing. These results suggest that the use of EES-evoked motor responses may guide intraoperative positioning of epidural electrodes to target spinal cord circuitry to enable motor functions after SCI.

Publisher Correction: Neuromodulation of lumbosacral spinal networks enables independent stepping after complete paraplegia.

In the version of this article originally published, Dimitry G. Sayenko's affiliations were not correct. The following affiliation for this author was missing: Department of Neurosurgery, Center for Neuroregeneration, Houston Methodist Research Institute, Houston, TX, USA. This affiliation has been added for the author, and the rest of the affiliations have been renumbered accordingly. The error has been corrected in the HTML and PDF versions of this article.

Neuromodulation of lumbosacral spinal networks enables independent stepping after complete paraplegia.

Spinal sensorimotor networks that are functionally disconnected from the brain because of spinal cord injury (SCI) can be facilitated via epidural electrical stimulation (EES) to restore robust, coordinated motor activity in humans with paralysis1-3. Previously, we reported a clinical case of complete sensorimotor paralysis of the lower extremities in which EES restored the ability to stand and the ability to control step-like activity while side-lying or suspended vertically in a body-weight support system (BWS)4. Since then, dynamic task-specific training in the presence of EES, termed multimodal rehabilitation (MMR), was performed for 43 weeks and resulted in bilateral stepping on a treadmill, independent from trainer assistance or BWS. Additionally, MMR enabled independent stepping over ground while using a front-wheeled walker with trainer assistance at the hips to maintain balance. Furthermore, MMR engaged sensorimotor networks to achieve dynamic performance of standing and stepping. To our knowledge, this is the first report of independent stepping enabled by task-specific training in the presence of EES by a human with complete loss of lower extremity sensorimotor function due to SCI.

Enabling Task-Specific Volitional Motor Functions via Spinal Cord Neuromodulation in a Human With Paraplegia.

We report a case of chronic traumatic paraplegia in which epidural electrical stimulation (EES) of the lumbosacral spinal cord enabled (1) volitional control of task-specific muscle activity, (2) volitional control of rhythmic muscle activity to produce steplike movements while side-lying, (3) independent standing, and (4) while in a vertical position with body weight partially supported, voluntary control of steplike movements and rhythmic muscle activity. This is the first time that the application of EES enabled all of these tasks in the same patient within the first 2 weeks (8 stimulation sessions total) of EES therapy.

Motor evoked potential monitoring during cryoablation of musculoskeletal tumors.

PURPOSE: To describe the use of intraprocedural motor evoked potential (MEP) monitoring to minimize risk of neural injury during percutaneous cryoablation of perineural musculoskeletal tumors. MATERIALS AND METHODS: A single-institution retrospective review of cryoablation procedures performed to treat perineural musculoskeletal tumors with the use of MEP monitoring between May 2011 and March 2013 yielded 59 procedures to treat 64 tumors in 52 patients (26 male). Median age was 61 years (range, 4-82 y). Tumors were located in the spine (n = 27), sacrum (n = 3), retroperitoneum (n = 4), pelvis (n = 22), and extremities (n = 8), and 21 different tumor histologies were represented. Median tumor size was 4.0 cm (range, 0.8-15.0 cm). Total intravenous general anesthesia, computed tomographic guidance, and transcranial MEP monitoring were employed. Patient demographics, tumor characteristics, MEP findings, and clinical outcomes were assessed. RESULTS: Nineteen of 59 procedures (32%) resulted in decreases in intraprocedural MEPs, including 15 (25%) with transient decreases and four (7%) with persistent decreases. Two of the four patients with persistent MEP decreases (50%) had motor deficits following ablation. No functional motor deficit developed in a patient with transient MEP decreases or no MEP change. The risk of major motor injury with persistent MEP changes was significantly increased versus transient or no MEP change (P = .0045; relative risk, 69.8; 95% confidence interval, 5.9 to > 100). MEP decreases were 100% sensitive and 70% specific for the detection of motor deficits. CONCLUSIONS: Persistent MEP decreases correlate with postprocedural sustained motor deficits. Intraprocedural MEP monitoring helps predict neural injury and may improve patient safety during cryoablation of perineural musculoskeletal tumors.

Sensitivity and specificity of diagnostic ultrasound in the diagnosis of phrenic neuropathy.

OBJECTIVES: To determine the sensitivity and specificity of B-mode ultrasound in the diagnosis of neuromuscular diaphragmatic dysfunction, including phrenic neuropathy. METHODS: A prospective study of patients with dyspnea referred to the EMG laboratory over a 2-year time frame for evaluation of neuromuscular respiratory failure who were recruited consecutively and examined with ultrasound for possible diaphragm dysfunction. Sonographic outcome measures were absolute thickness of the diaphragm and degree of increased thickness with maximal inspiration. The comparison standard for diagnosis of diaphragm dysfunction was the final clinical diagnosis of clinicians blinded to the diaphragm ultrasound results, but taking into account other diagnostic workup, including chest radiographs, fluoroscopy, phrenic nerve conduction studies, diaphragm EMG, and/or pulmonary function tests. RESULTS: Of 82 patients recruited over a 2-year period, 66 were enrolled in the study. Sixteen patients were excluded because of inconclusive or insufficient reference testing. One hemidiaphragm could not be adequately visualized; therefore, hemidiaphragm assessment was conducted in a total of 131 hemidiaphragms in 66 patients. Of the 82 abnormal hemidiaphragms, 76 had abnormal sonographic findings (atrophy or decreased contractility). Of the 49 normal hemidiaphragms, none had a false-positive ultrasound. Diaphragmatic ultrasound was 93% sensitive and 100% specific for the diagnosis of neuromuscular diaphragmatic dysfunction. CONCLUSION: B-mode ultrasound imaging of the diaphragm is a highly sensitive and specific tool for diagnosis of neuromuscular diaphragm dysfunction. CLASSIFICATION OF EVIDENCE: This study provides Class II evidence that diaphragmatic ultrasound performed by well-trained individuals accurately identifies patients with neuromuscular diaphragmatic respiratory failure (sensitivity 93%; specificity 100%).

B-mode ultrasound assessment of diaphragm structure and function in patients with COPD.

BACKGROUND: Electromyographic evaluation of diaphragmatic neuromuscular disease in patients with COPD is technically difficult and potentially high risk. Defining standard values for diaphragm thickness and thickening ratio using B-mode ultrasound may provide a simpler, safer means of evaluating these patients. METHODS: Fifty patients with a diagnosis of COPD and FEV1 < 70% underwent B-mode ultrasound. Three images were captured both at end expiration (Tmin) and at maximal inspiration (Tmax). The thickening ratio was calculated as (Tmax/Tmin), and each set of values was averaged. Findings were compared with a database of 150 healthy control subjects. RESULTS: There was no significant difference in diaphragm thickness or thickening ratio between sides within groups (control subjects or patients with COPD) or between groups, with the exception of the subgroup with severe air trapping (residual volume > 200%), in which the only difference was that the thickening ratio was higher on the left (P = .0045). CONCLUSIONS: In patients with COPD presenting for evaluation of coexisting neuromuscular respiratory weakness, the same values established for healthy control subjects serve as the baseline for comparison. This knowledge expands the role of ultrasound in evaluating neuromuscular disease in patients with COPD.

Evaluation, treatment, and outcomes of suprascapular neuropathy: a 5-year review.

OBJECTIVE: To report our diagnostic and treatment experiences, and patient outcomes, in patients with suprascapular neuropathy (SSN). DESIGN: Retrospective cohort study. SETTING: A tertiary medical center. PATIENTS: 65 patients with electromyographically (EMG)-confirmed SSN. METHODS: A 5-year retrospective chart review of patients with EMG-confirmed SSN. MAIN OUTCOME MEASURES: Descriptive statistics were used to summarize demographics, risk factors, causes, EMG findings, diagnostic evaluation, treatments, and self-reported outcomes. Exact Mantel-Haenszel χ(2) tests and Fisher exact tests were used to assess correlation between these measures. RESULTS: The 3 most common causes of SSN were trauma (32 patients), an inflammatory process (ie, brachial neuritis) (14), and the presence of a cyst (13). Remaining cases were related to a rotator cuff tear or were due to overuse. No cases were attributed to notch abnormalities. At the time of follow-up (a mean of 50 months [range, 15-84 months] after EMG), 50% of subjects returned to activity with no restrictions (excellent outcome) and 40% returned to activity with restrictions (good outcome), regardless of cause and treatment. EMG findings, specifically the presence/absence of fibrillation potentials, did not predict recovery. CONCLUSIONS: SSN should be considered in patients with shoulder pain and weakness. Magnetic resonance imaging and ultrasound help to exclude a structural process. Identifying a structural cause, specifically a cyst or rotator cuff tear, is important because it appears that these patients have improved recovery with return to normal activities when treated surgically. Although EMG data did not have prognostic value in this study, the data were limited and further study is warranted. Regardless of cause or treatment, most patients with SSN returned to activities in some capacity.

Diaphragm depth in normal subjects.

INTRODUCTION: Needle electromyography (EMG) of the diaphragm carries the potential risk of pneumothorax. Knowing the approximate depth of the diaphragm should increase the test's safety and accuracy. METHODS: Distances from the skin to the diaphragm and from the outer surface of the rib to the diaphragm were measured using B mode ultrasound in 150 normal subjects. RESULTS: When measured at the lower intercostal spaces, diaphragm depth varied between 0.78 and 4.91 cm beneath the skin surface and between 0.25 and 1.48 cm below the outer surface of the rib. Using linear regression modeling, body mass index (BMI) could be used to predict diaphragm depth from the skin to within an average of 1.15 mm. CONCLUSIONS: Diaphragm depth from the skin can vary by more than 4 cm. When image guidance is not available to enhance accuracy and safety of diaphragm EMG, it is possible to reliably predict the depth of the diaphragm based on BMI.

Variability in diaphragm motion during normal breathing, assessed with B-mode ultrasound.

STUDY DESIGN: Clinical measurement, cross-sectional. OBJECTIVES: To establish a set of normal values for diaphragm thickening with tidal breathing in healthy subjects. BACKGROUND: Normal values for diaphragm contractility, as imaged sonographically, have not been described, despite the known role of the diaphragm in contributing to spinal stability. If the normal range of diaphragm contractility can be defined in a reliable manner, ultrasound has the potential to be used clinically and in research as a biofeedback tool to enhance diaphragm activation/contractility. METHODS: B-mode ultrasound was performed on 150 healthy subjects to visualize and measure hemi-diaphragm thickness on each side at resting inspiration and expiration. Primary outcome measures were hemi-diaphragm thickness and thickening ratio, stratified for age, gender, and body mass index. Interrater and intrarater reliability were also measured. RESULTS: Normal thickness of the diaphragm at rest ranged from 0.12 to 1.18 cm, with slightly greater thickness in men but no effect of age. Average ± SD change in thickness from resting expiration to resting inspiration was 20.0% ± 15.5% on the right and 23.5% ± 24.4% on the left; however, almost one third of healthy subjects had no to minimal diaphragm thickening with tidal breathing. CONCLUSION: There is wide variability in the degree of diaphragm contractility during quiet breathing. B-mode ultrasound appears to be a reliable means of determining the contractility of the diaphragm, an important muscle in spinal stability. Further studies are needed to validate this imaging modality as a clinical tool in the neuromuscular re-education of the diaphragm to improve spinal stability in both healthy subjects and in patients with low back pain.

Two-dimensional ultrasound imaging of the diaphragm: quantitative values in normal subjects.

INTRODUCTION: Real time ultrasound imaging of the diaphragm is an under-used tool in the evaluation of patients with unexplained dyspnea or respiratory failure. METHODS: We measured diaphragm thickness and the change in thickness that occurs with maximal inspiration in 150 normal subjects, with results stratified for age, gender, body mass index, and smoking history. RESULTS: The lower limit of normal diaphragm thickness at end expiration or functional residual capacity is 0.15 cm, and an increase of at least 20% in diaphragm thickness from functional residual capacity to total lung capacity is normal. A side to side difference in thickness at end expiration of > 0.33 cm is abnormal. Diaphragm thickness and contractility are minimally affected by age, gender, body habitus, or smoking history. CONCLUSIONS: This study confirms previous findings in much smaller groups of normal controls for quantitative ultrasound of the diaphragm and provides data that can be applied widely to the general population.

Management of spasticity from spinal cord dysfunction.

Spasticity is a common component of those with spinal cord dysfunction. Spasticity can lead not only to pain and potential secondary complications such as contracture and pressure sores but also to significant functional impairment. The clinician must identify specific goals of spasticity treatment and assess the potential benefit of spasticity, particularly as it pertains to transfers and ambulation. Conservative treatment measures that include avoidance and identification of potential noxious stimuli and a daily stretching program that can be performed by the patient or caregivers are initiated in all patients.

Hematoma risk after needle electromyography.

INTRODUCTION: Although needle electromyography (EMG) appears to be a relatively safe procedure based primarily on clinical experience, no evidence-based guidelines exist for EMG procedures in patients taking anticoagulant or antiplatelet medications. We sought to determine whether there is an increased risk of hematoma formation after EMG of potentially high-risk muscles in patients taking anticoagulant or antiplatelet agents. METHODS: After undergoing routine EMG, if any of seven predetermined high-risk muscles were tested, study subjects then underwent ultrasound to evaluate for hematoma formation. RESULTS: Patients were divided into three groups based on medication (warfarin, aspirin/clopidogrel, no blood-thinning medication), with at least 100 muscles examined per group. Two small, subclinical hematomas were seen on ultrasound; there was no difference in hematoma risk between groups (P = 0.43). CONCLUSIONS: Our findings suggest that hematoma formation from standard needle EMG is rare even in high-risk muscles, which have been avoided historically in anticoagulated patients.

Accuracy of diagnoses delivered by an automated hand-held nerve conduction device in comparison to standard electrophysiological testing in patients with unilateral leg symptoms.

INTRODUCTION: Automated hand-held nerve conduction study (NCS) devices are being marketed for use in the diagnosis of lumbosacral radiculopathy (LSR). In this study we compared the specificity and sensitivity of a hand-held NCS device for the detection of LSR with standard electrodiagnostic study (EDX). METHODS: Fifty patients referred to a tertiary referral electromyography (EMG) laboratory for testing of predominantly unilateral leg symptoms (weakness, sensory complaints, and/or pain) were included in the investigation. Twenty-five normal "control" subjects were later recruited to calculate the specificity of the automated protocol. All patients underwent standard EDX and automated testing. RESULTS: Raw NCS data were comparable for both techniques; however, computer-generated interpretations delivered by the automated device showed high sensitivity with low specificity (i.e., many false positives) in both symptomatic patients and normal controls. CONCLUSIONS: The automated device accurately recorded raw data, but the interpretations provided were overly sensitive and lacked the specificity necessary for a screening or diagnostic examination.

Peripheral nerve stimulation and monitoring during operative procedures.

Monitoring of peripheral nerve function is important during the surgical treatment of peripheral nerve and plexus lesions, allowing for rapid assessment of the integrity of the roots, plexus, and nerves. The results of this monitoring assist the surgeon in the overall approach to treatment of these lesions. There are, however, many technical challenges to providing this neurophysiological information in an accurate and rapid fashion. This study assesses the equipment and techniques involved in intraoperative peripheral nerve monitoring and describes its use in the more common clinical scenarios.