Diagnostic characteristics of nerve conduction study parameters for vasculitic neuropathy.

INTRODUCTION/AIMS: In vasculitic neuropathy (VN), a 50% side-to-side difference in the amplitude of compound muscle action potentials and sensory nerve action potentials is considered meaningful, but unequivocal evidence is lacking. The aim of this study is to characterize electrodiagnostic features that best distinguish VN from other axonal polyneuropathies. METHODS: We conducted a case-control study between January 2000 and April 2021. We reviewed the records of patients with VN who had bilateral nerve conduction studies (NCS) and evaluated different electrodiagnostic models to help distinguish VN from non-inflammatory axonal polyneuropathies. RESULTS: We identified 82 cases, and 174 controls with non-inflammatory axonal neuropathies. The amplitude percent difference Z-score model showed the best discriminatory capability between cases and controls (area under the curve [AUC] 0.87; 95% confidence interval [CI] 0.82, 0.93), and the number of nerves tested did not significantly influence the model. Individually, the ulnar motor nerve (AUC 0.86; 95% CI 0.77, 0.94) and median motor nerve (AUC 0.85; 95% CI 0.77, 0.94) showed the best discriminatory capability. A 50% amplitude difference between at least two bilateral nerves, either in the upper (AUC 0.85; 95% CI 0.77, 0.93) or lower (AUC 0.79; 95% CI 0.71, 0.87) extremity showed good discriminatory threshold for detecting VN. DISCUSSION: The best electrodiagnostic criteria for VN utilizes z-scores of percent differences in nerve amplitudes, but this approach may be difficult to implement at the bedside. Alternately, a 50% amplitude difference in at least two nerves is a reasonable approximation.

Comparison of the United Kingdom and United States approaches to approval of new neuromuscular therapies.

Many novel therapies are now available for rare neuromuscular conditions that were previously untreatable. Hereditary transthyretin amyloidosis and spinal muscular atrophy are two examples of diseases with new medications that have transformed our field. The United States and the United Kingdom have taken disparate approaches to the approval and coverage of medications, despite both providing incentives to develop therapies targeting rare diseases. The US requires less evidence for approval when compared with medications for common diseases and does not have a mechanism to ensure or even encourage cost-effectiveness. The Institute of Clinical and Economic Review provides in-depth cost-effectiveness analyses in the US, but does not have the authority to negotiate drug costs. In contrast, the UK has maintained a similar scientific threshold for approval of all therapies, while requiring negotiation with National Institute for Health and Care Excellence to ensure that medications are cost-effective for rare diseases. These differences have led to approval of medications for rare diseases in the US that have less evidence than required for common diseases. Importantly, these medications have not been approved in the UK. Even when medications meet traditional scientific thresholds, they uniformly arrive with high list prices in the US, whereas they are available at cost-effective prices in the UK. The main downsides to the UK approach are that cost-effective medications are often available months later than in the US, and some medications remain unavailable.

Patients who meet electrodiagnostic criteria for CIDP rarely present with a sensory predominant DSP phenotype.

INTRODUCTION: It is unknown how often patients with electrodiagnostic evidence of chronic inflammatory demyelinating polyradiculoneuropathy (CIDP), a potentially treatable condition, present with a distal symmetric polyneuropathy (DSP) phenotype. METHODS: We reviewed the records of patients who presented to our electrodiagnostic laboratory between January 1, 2011, to December 31, 2019, and fulfilled electrodiagnostic criteria for CIDP to identify those who presented with a sensory predominant DSP phenotype. RESULTS: One hundred sixty-two patients had a chronic acquired demyelinating neuropathy, of whom 138 met criteria for typical or atypical CIDP. Nine of these patients presented with a sensory predominant DSP phenotype, among whom six were eventually diagnosed with distal acquired demyelinating symmetric (DADS) neuropathy; one with Polyneuropathy, Organomegaly, Endocrinopathy, Monoclonal protein, Skin changes (POEMS) syndrome; and two with idiopathic DSP. The prevalence of acquired chronic demyelinating neuropathies among all patients presenting with a DSP phenotype was estimated to be 0.34%. DISCUSSION: Patients who meet electrodiagnostic criteria for CIDP rarely present with a sensory predominant DSP phenotype, and electrodiagnostic testing rarely identifies treatable demyelinating neuropathies in patients who present with a DSP phenotype.

A Self-Study Curriculum in Electromyography and Nerve Conduction Studies for Residents and Fellows.

INTRODUCTION: To our knowledge, there are no freely available curricula for a focused resident or fellow rotation in electromyography and nerve conduction studies that address the Accreditation Council for Graduate Medical Education (ACGME) milestones for neurology, physical medicine and rehabilitation, clinical neurophysiology, or neuromuscular medicine. Thus, we created this curriculum to help trainees develop a basic understanding of clinical electrodiagnostic studies. The program objectives map to many of the relevant ACGME milestones, primarily those pertaining to medical knowledge, patient care, and practice-based learning and improvement. METHODS: The curricular materials include an interactive, hyperlink-driven slide show with 19 educational modules, subdivided further into basic and advanced topics. We also created a 50-question multiple-choice test, paired each question with key concepts, and provided instructions on using the test results to develop a trainee-specific learning plan. RESULTS: Residents and fellows have been using this curriculum at the University of Michigan since 2007. The mean and median scores of 80 trainees who took the 50-item test between 2007 and 2016 were 80% and 82%, respectively, with a standard deviation of 10%. In annual surveys of neurology residents, this electromyography rotation has consistently had the highest mean approval rating of all clinical rotations in the training program. DISCUSSION: This curriculum is a complete, self-contained learning resource that may be used alone or to supplement a supervised apprenticeship for trainees who want to learn to perform electrodiagnostic studies independently. The content ensures that trainees demonstrate mastery of many of the ACGME milestones for their field.

Nerve conduction studies are safe in patients with central venous catheters.

INTRODUCTION: It is unknown if central venous catheters bypass the skin's electrical resistance and engender a risk of nerve conduction study-induced cardiac arrhythmia. The objective of this study is to determine if nerve conduction studies affect cardiac conduction and rhythm in patients with central venous catheters. METHODS: Under continuous 12-lead electrocardiogram monitoring, subjects with and without central venous catheters underwent a series of upper extremity nerve conduction studies. A cardiologist reviewed the electrocardiogram tracings for evidence of cardiac conduction abnormality or arrhythmia. RESULTS: Ten control subjects and 10 subjects with central venous catheters underwent the nerve conduction study protocol. No malignant arrhythmias or conduction abnormalities were noted in either group. CONCLUSIONS: Nerve conduction studies of the upper extremities, including both proximal stimulation and repetitive stimulation, do not appear to confer increased risk of cardiac conduction abnormality in those patients with central venous catheters who are not critically ill or have a prior history of arrhythmia. Muscle Nerve 56: 321-323, 2017.