Provocative changes in nerve conductions: Fact or fiction?

At times electrodiagnostic medical consultants (EMCs) are asked to perform studies in both a neutral position, and then again after the patient is in a provocative position that exacerbates symptoms, to assess for measurable electrophysiologic changes. While this approach might seem initially appealing, particularly when standard studies are not effective at diagnosis, empiric studies in several conditions have been unimpressive. Studies in median neuropathy at the wrist, thoracic outlet syndrome, piriformis syndrome, and radial tunnel syndrome have failed to demonstrate reproducible changes in nerve conduction studies in positions that exacerbate symptoms. Furthermore, there is lack of a plausible pathophysiologic mechanism for producing both measurable and rapidly reversible electrophysiologic changes after just a few minutes, or less, of compression. Axon loss and demyelination would not be rapidly reversible, and positional changes of 2 min or less (the durations generally studied) would be insufficient to produce measurable nerve ischemia. Last, we have gained a greater appreciation for how much nerves move within limbs with changes in joint position; this movement can lead to misleading changes in nerve conduction studies. It is thus appropriate to conclude that testing nerve conduction in provocative or symptomatic positions adds no value to electrodiagnostic testing.

Training factors that influence electrodiagnostic medicine knowledge.

INTRODUCTION/AIMS: Self-assessment examinations (SAEs) help trainees assess their progress in education. SAEs also provide feedback to training programs as to how factors in training influence examination performance. This study's goal was to examine the relationship between the number of months of training in electrodiagnostic (EDx) medicine, the number of EDx studies during training, and scores on the American Association of Neuromuscular and Electrodiagnostic Medicine SAE. METHODS: This was a retrospective study of the 2023 AANEM-SAE results. In addition to the examination score, participants were asked approximately how many EDx studies they performed in training and how many months of training they had completed. Analysis included correlation of the examination scores with months of training as well as number of EDx studies. In addition, a multivariate linear regression model was developed. RESULTS: A total of 756 participants completed the proctored examination in May 2023. Examination score was moderately and positively correlated with the number of months of training (Pearson r = .5; p < .001) as well as the number of EDx studies during training (Pearson r = .55; p < .001). Scores steadily improved with additional months of training, but leveled off after 300-400 EDx studies. Regression analysis indicated that higher numbers of EDx studies were correlated with a higher examination score even after accounting for the number of months of study. DISCUSSION: We believe that a greater number of months of training is associated with better performance on the AANEM-SAE and that greatest improvement in examination performance occurs during the first 300-400 EDx studies.

Comparison of electrodiagnostic findings in acute traumatic versus chronic non-traumatic ulnar neuropathy at the elbow.

INTRODUCTION/AIMS: A common concept is that traumatic nerve injuries are more likely axonal, and that compressive neuropathies are more likely demyelinating. The purpose of this study was to compare traumatic versus non-traumatic ulnar neuropathy at the elbow (UNE) to look for electrodiagnostic differences between the two groups. METHODS: A retrospective 3 year review of UNE patients at two academic health science centers was conducted. Patients were grouped into acute traumatic UNE versus chronic non-traumatic UNE based on clinical history. Electrodiagnostic measurements were compared between the two groups. RESULTS: There were 50 subjects with acute traumatic UNE and 41 with chronic non-traumatic UNE. Mean age and sex distribution were similar but those with traumatic UNE had a 7 month duration of symptoms, while those with chronic UNE had 29 month duration (p < .001). All electrodiagnostic measurements were similar between the two groups including compound muscle action potential amplitudes, motor conduction velocities, frequency of conduction block, sensory nerve studies, and needle electromyography. DISCUSSION: We did not find a difference between the two groups. One should not make inferences regarding acuity or etiology based on electrodiagnostic features alone.

Electrodiagnostic reporting preferences of referring physicians: An exploratory survey.

INTRODUCTION/AIMS: Electrodiagnostic (EDX) studies play a crucial role in the evaluation of patients with peripheral nervous system disorders. Accurate and succinct communication of test results is critical to patient safety and clinical decision-making. The objective of this study was to explore EDX reporting preferences of referring physicians to improve quality of communication and patient care. METHODS: An online survey was developed, and a purposive sampling strategy was used to recruit physicians in the authors' professional networks. Quantitative and qualitative survey data underwent frequency and thematic analyses, respectively. RESULTS: There were 40 respondents, including: 21 non-surgical specialists, 12 surgical specialists, and 7 family physicians. Sections rated as most critical were diagnostic impression (97%) and summary/interpretation (72%). Only 18% reported numeric data as critical to their needs, preferring this data to be formatted as bullet points or tables without nerve conduction study waveforms. Regarding the format of the data summary and diagnostic impression sections, the majority of respondents preferred bullet points rather than paragraphs. DISCUSSION: The results of this exploratory survey suggest that physicians who refer patients for EDX studies prefer reports that emphasize the interpretation of EDX data and a clear diagnostic impression, particularly in bullet point format. This project highlights important preferences and how they compare to recommended reporting guidelines, which may help improve communication and ultimately patient care. Future efforts should explore larger sample sizes with all key stakeholders in the EDX process to better understand reporting styles and preferences with greater nuance and context.

Motor Unit Number Index of the Upper Trapezius: A Meta-Analysis and Cross-sectional Study of Its Reliability.

Motor unit number index of the upper trapezius (MUNIX-Trapezius) is a candidate biomarker for bulbar lower motor neuron function; however, reliability data is incomplete. To assess MUNIX-Trapezius reliability in controls, we conducted a systematic review, a cross-sectional study (n = 20), and a meta-analysis. We demonstrated a high inter- and intra-rater intraclass correlation (0.86 and 0.94, respectively), indicating that MUNIX-Trapezius is reliable with between-study variability moderated by age and MUNIX technique. With further validation, this measure can serve as a disease monitoring and response biomarker of bulbar function in the therapeutic development for amyotrophic lateral sclerosis.

Traumatic injury to peripheral nerves.

This article reviews the epidemiology, classification, localization, prognosis, and mechanisms of recovery of traumatic peripheral nerve injuries (PNIs). Electrodiagnostic (EDx) assessments are critical components of treating patients with PNIs. In particular, motor and sensory nerve conduction studies, needle electromyography, and other electrophysiological methods are useful for localizing peripheral nerve injuries, detecting and quantifying the degree of axon loss, and contributing toward treatment decisions as well as prognostication. It is critical that EDx medical consultants are aware of the timing of these changes as well as limitations in interpretations. Mechanisms of recovery may include recovery from conduction block, muscle fiber hypertrophy, distal axonal sprouting, and axon regrowth from the site of injury. Motor recovery generally reaches a plateau at 18 to 24 months postinjury. When patients have complete or severe nerve injuries they should be referred to surgical colleagues early after injury, as outcomes are best when nerve transfers are performed within the first 3 to 6 months after onset.

Role of electrodiagnosis in nerve transfers for focal neuropathies and brachial plexopathies.

Over the past 2 decades, the surgical treatment of brachial plexus and peripheral nerve injuries has advanced considerably. Nerve transfers have become an important surgical tool in addition to nerve repair and grafting. Electrodiagnosis has traditionally played a role in the diagnosis and localization of peripheral nervous system injuries, but a different approach is needed for surgical decision-making and monitoring recovery. When patients have complete or severe injuries they should be referred to surgical colleagues early after injury, as outcomes are best when nerve transfers are performed within the first 3 to 6 mo after onset. Patients with minimal recovery of voluntary activity are particularly challenging, and the presence of a few motor unit action potentials in these individuals should be interpreted on the basis of timing and evidence of ongoing reinnervation. Evaluation of potential recipient and donor muscles, as well as redundant muscles, for nerve transfers requires an individualized approach to optimize the chances of a successful surgical intervention. Anomalous innervation takes on new importance in these patients. Communication between surgeons and electrodiagnostic medicine specialists (EMSs) is best facilitated by a joint collaborative clinic. Ongoing monitoring of recovery post-operatively is critical to allow for decision making for continued surgical and rehabilitation treatments. Different electrodiagnostic findings are expected with resolution of neurapraxia, distal axon sprouting, and axonal regrowth. As new surgical techniques become available, EMSs will play an important role in the assessment and treatment of these patients with severe nerve injuries.

Radial motor nerve conduction studies recorded from triceps brachii and extensor carpi radialis longus: Techniques and reference values.

INTRODUCTION/AIMS: Optimal timing of nerve transfer surgery in cervical spinal cord injury (SCI) depends upon the integrity of lower motor neurons (LMNs) in recipient nerves, which is best predicted by compound muscle action potential (CMAP) amplitude. There are no established techniques for obtaining the CMAP in two recipient muscles: triceps brachii and extensor carpi radialis longus (ECRL). This study aimed to develop recording techniques for radial motor studies to triceps and ECRL, and to determine reference values for CMAP amplitudes in healthy volunteers. METHODS: This was a prospective observational study of healthy adults aged 18 years and older. Motor nerve conduction studies were performed, stimulating the radial nerve in the axilla, over the axillary pulse at the pectoralis major insertion. Recording was from triceps (long head) and ECRL. CMAP amplitude, area, latency, and stimulus intensity were recorded. Reference values (RV) were calculated for CMAP amplitudes using a value 2 standard deviations below the mean. Cube root or logarithmic transformations were used to correct for non-normal distributions. RESULTS: Twenty-five healthy subjects participated. Triceps mean CMAP amplitude was 15.5 mV (SD 4.19), with an RV of 8.1 mV. ECRL mean CMAP amplitude was 11.5 mV (SD 3.54), with an RV of 6.2 mV. CMAP amplitude at ECRL was 75% (95% confidence interval 50%-100%) of that at triceps. DISCUSSION: We describe a technique for recording radial motor NCS from triceps and ECRL. Knowledge of normal CMAP amplitudes will help identify LMN injury in patients with cervical SCI being considered for nerve transfers.

Infection prevention and control across the continuum of COVID-19 care: A qualitative study of patients', caregivers' and providers' experiences.

INTRODUCTION: Healthcare facilities adopted restrictive visitor policies as a result of the COVID-19 (COVID) pandemic. Though these measures were necessary to promote the safety of patients, families and healthcare providers, it led to isolation and loneliness amongst acute care inpatients that can undermine patient rehabilitation and recovery. The study objectives were to (1) explore how infection prevention and control (IP&C) measures impacted stakeholders' perceptions of care quality and interactions with others and (2) investigate how these experiences and perceptions varied across stakeholder groups and care settings. METHODS: A qualitative descriptive study was conducted. Patients and their families from an inpatient COVID rehabilitation hospital and healthcare providers from an acute or rehabilitation COVID hospital were interviewed between August 2020 and February 2021. RESULTS: A total of 10 patients, 5 family members and 12 healthcare providers were interviewed. Four major themes were identified: (1) IP&C measures challenged the psychosocial health of all stakeholders across care settings; (2): IP&C measures precipitated a need for greater relational care from HCPs; (3) infection prevention tenets perpetuated COVID-related stigma that stakeholders experienced across care settings; and (4) technology was used to facilitate human connection when IP&C limited physical presence. CONCLUSION: IP&C measures challenged psychosocial health and maintenance of vital human connections. Loneliness and isolation were felt by all stakeholders due to physical distancing and COVID-related stigma. Some isolation was mitigated by the relational care provided by HCPs and technological innovations used. The findings of the study underscore the need to balance safety with psychosocial well-being across care settings and beyond the patient-provider dyad. PATIENT AND PUBLIC CONTRIBUTION: This study was informed by the Patient-Oriented Research Agenda and developed through consultations with patients and family caregivers to identify priority areas for rehabilitation research. Priority areas identified that informed the current study were (1) the need to focus on the psychosocial aspects of recovery from illness and injury and (2) the importance of exploring patients' recovery experiences and needs across the continuum of care. The study protocol, ethics submission, analysis and manuscript preparation were all informed by healthcare providers with lived experience of working in COVID care settings.

Compartment syndrome: Neuromuscular complications and electrodiagnosis.

Compartment syndrome (CS) is a treatable condition characterized by elevated intracompartmental pressure and may be acute or chronic in nature. Sustained elevated compartment pressure can lead to ischemia and necrosis of muscle as well as injury to peripheral nerves, creating a deficit that may be neuropathic, myopathic, or mixed. While electrodiagnostic assessments are of limited utility in the diagnosis of acute/traumatic CS, they can assist with prognosticating return of function after surgical fasciotomy or in clarifying the injury pattern in cases in which a traumatic injury results in subsequent neuromuscular deficits. They can also be used to rule out conditions that mimic chronic exertional CS. During electrodiagnostic assessment, clinicians should be aware of patterns associated with muscle fibrosis vs denervation and use this information to assist with prognostication and appropriate counseling for patients regarding any interventional or adaptive treatments that may help restore function.

Effectiveness of Platelet-Rich Plasma Injections for Nonsurgical Management of Carpal Tunnel Syndrome: A Systematic Review and Meta-analysis of Randomized Controlled Trials.

OBJECTIVE: To systematically review and evaluate the efficacy and complication profile of platelet-rich plasma (PRP) injection into the carpal tunnel for management of carpal tunnel syndrome (CTS). DATA SOURCES: PubMed, MEDLINE, SCOPUS, EMBASE, Google Scholar, Cochrane Central Register of Controlled Trials, and Web of Sciences (from inception to January 1, 2019). STUDY SELECTION: Controlled trials addressing PRP for CTS. DATA EXTRACTION: Two reviewers independently screened the titles, abstracts, and full texts, extracting data from eligible studies. The outcomes of interest were the visual analog score (VAS) for pain and the Boston Carpal Tunnel Questionnaire (BCTQ), including the subscales of the symptom severity scale (SSS) and the Functional Status Scale (FSS). Other reported outcome measures and complications were analyzed descriptively. DATA SYNTHESIS: Four randomized controlled studies satisfied the inclusion criteria and analyzed a total of 191 cases with a final follow-up of either 3 or 6 months. Control groups included splinting in 2 studies, corticosteroid injection in 1 study, and saline injection in 1 study. There was a statistically and clinically significant improvement in the BCTQ (standardized mean difference=-2.06; 95% confidence interval [CI], -3.41 to -0.70; P=.003) between groups. Subgroup analysis showed significant improvement in SSS (standardized mean difference=-1.95; 95% CI, -3.65 to -0.25; P=.02) but not for FSS (standardized mean difference=-2.19; 95% CI, -4.77 to 0.40; P=.10). There was a similar improvement in VAS and nerve conduction studies in those receiving PRP compared to controls. Complication rate in the included studies was low with 4 of 97 participants receiving PRP injections experiencing transient pruritis, burning, or tingling. CONCLUSIONS: PRP represents a promising therapy for patients with mild to moderate CTS; however, included studies were limited as follow-up was short, the studies included patients that were heterogeneous, and the number of included studies was low. Further investigation is necessary to determine the true efficacy and effect of PRP and to better delineate the long-term results in patients with CTS.

Effect of shoulder and elbow position on ulnar nerve conduction.

INTRODUCTION: The aims of this study were to determine the effect of shoulder and elbow position on ulnar nerve conduction studies (NCS), and the length of reserve that asymptomatic individuals have in their ulnar nerves. METHODS: Healthy subjects (n = 22) underwent ulnar NCS in 4 positions of shoulder abduction and elbow flexion. RESULTS: The mean increase in nerve conduction velocity (NCV) from the slack position of shoulder adducted and elbow extended to the stretch position of shoulder abducted and elbow flexed was 2.9 m/s (P < 0.01). Using this difference, the mean length of reserve in the ulnar nerve along the limb was found to be 28.3 (SD=13.8) mm. Shoulder abduction increased the mean NCV 0.8 m/s (P = 0.03) independent of elbow flexion. CONCLUSIONS: This study demonstrates an ulnar nerve reserve in healthy patients that is taken up with shoulder abduction and elbow flexion and suggests shoulder position should be standardized during ulnar NCS. Muscle Nerve, 2019.

Optimal E2 (reference) electrode placement in fibular motor nerve conduction studies recording from the tibialis anterior muscle.

INTRODUCTION: In this study we aimed to determine the contribution of the E2 (reference electrode) to the compound muscle action potential (CMAP) amplitude during fibular motor recording to the tibialis anterior (TA) when E2 is placed over routine referential vs. alternative sites. METHODS: The CMAP was obtained from 10 healthy subjects, using the active electrode (E1) over sites routinely used as E2 for the TA, whereas the E2 was over the contralateral knee. The same procedure was performed with the E1 over alternative E2 sites. RESULTS: Significant electrical signal was captured over routine E2 placement sites. Among the tested alternative E2 sites, the ipsilateral patella (especially its medial aspect) was the most electrically silent. DISCUSSION: Using alternative E2 sites with near isoelectric recordings can optimize near-field potential measurement in the fibular motor recording to the TA and represents a more accurate way of measuring nerve and muscle function. Muscle Nerve 59:249-253, 2019.

How Much Sciatic Nerve Does Hip Flexion Require?

Measured nerve conduction velocity in the fibular nerve increases across the knee during hip flexion. This is due to stretching of sciatic and fibular nerves. We modeled the additional nerve length required for the sciatic nerve to course around the flexed hip, based upon distance between the hip and the sciatic nerve on magnetic resonance imaging (MRI). The median distance from the femoral head to the sciatic nerve was 41 mm. The model predicted that 64 mm of sciatic nerve is required for hip flexion. This impacts our understanding of lower limb nerve conduction studies and clinical straight leg raising tests.

Postpolio syndrome and the late effects of poliomyelitis. Part 1. pathogenesis, biomechanical considerations, diagnosis, and investigations.

Postpolio syndrome (PPS) is characterized by new muscle weakness and/or muscle fatigability that occurs many years after the initial poliomyelitis illness. Many theories exist regarding the pathogenesis of PPS, which remains incompletely understood. In contrast, the late effects of poliomyelitis are often a consequence of biomechanical alterations that occur as a result of polio-related surgeries, musculoskeletal deformities, or weakness. Osteoporosis and fractures of the polio-involved limbs are common. A comprehensive clinical evaluation with appropriate investigations is essential to fulfilling the established PPS diagnostic criteria. PPS is a diagnosis of exclusion in which a key clinical feature required for the diagnosis is new muscle weakness and/or muscle fatigability that is persistent for at least 1 year. Electromyographic and muscle biopsy findings including evidence of ongoing denervation cannot reliably distinguish between patients with or without PPS. Muscle Nerve 58:751-759, 2018.

Post-polio syndrome and the late effects of poliomyelitis: Part 2. treatment, management, and prognosis.

Post-polio syndrome (PPS) is characterized by new muscle weakness and/or muscle fatigability that occurs many years after the initial poliomyelitis illness. An individualized approach to rehabilitation management is critical. Interventions may include rehabilitation management strategies, adaptive equipment, orthotic equipment, gait/mobility aids, and a variety of therapeutic exercises. The progression of muscle weakness in PPS is typically slow and gradual; however, there is also variability in both the natural history of weakness and functional prognosis. Further research is required to determine the effectiveness of selected medical treatment. Muscle Nerve 58:760-769, 2018.