Neuromuscular ultrasound: Impact on diagnosis and management

[Vasculitic involvement of the skeletal muscle and the peripheral nervous system: clinical and neuropathologic perspective]

The peripheral nervous system is a classic target organ in systemic vasculitis. In addition, the skeletal muscle can also be affected. Myalgia, muscle weakness and sensory deficits are typical signs, which can lead to severe functional limitations and impaired of quality of life. Vasculitic involvement of the skeletal muscle (vasculitic myopathy [VM]) and peripheral nerves (vasculitic neuropathy [VN]) occurs predominantly in polyarteritis nodosa and small-vessel vasculitis. VM presents with elevated markers of inflammation and is typically characterized by immobilizing myalgia with normal creatine kinase activity and diffuse or patchy areas of hyperintensity on T2-weighted MRI ("MRI myositis without myositis"). In VN, sensor motor deficits predominantly affect the lower extremity in the area supplied by several peripheral nerves (e.g., mononeuritis multiplex) with acute to subacute history. The histopathological examination of nerve and muscle biopsies is the gold standard for the diagnosis of vasculitic manifestations and has a significant impact on the therapeutic approach.

Establishing Reference Values in the Neuromuscular Ultrasound Laboratory Using the e-Norms Method: A Feasibility Study

INTRODUCTION/AIMS

The standard procedure to establish reference values in a neuromuscular laboratory involves examining healthy controls, as nerve size varies with the population and muscle echo intensity (EI) is device-specific. We aimed to derive these reference values by extrapolation from a studied sample (the e-norms method), compare them with published reference values, and determine their diagnostic accuracy.

METHODS

We retrospectively analyzed data from consecutive patients who underwent nerve and/or muscle ultrasound in our ultrasound laboratory, which is a tertiary referral center for neuromuscular diseases in Southern Poland in the years 2018-2023. We plotted the cross-sectional area (CSA) of the nerve segments and EI of the individual muscles and derived descriptive statistics from the plateau of the e-norms curve. We compared the mean difference of the nerve size to other studies and determined the ability of the muscle EI to discriminate myopathic versus healthy subjects using receiver operator characteristics curves.

RESULTS

We analyzed 1124 nerves and 1154 muscles from 109 and 99 subjects, respectively. The derived reference values for nerve CSA were mostly concordant with other studies, including all nerve segments in the legs and with the exception of compression sites and the most proximal nerve segments in the arms. Using the reference values for muscle EI established with the e-norms method, we were able to discriminate myopathic from healthy subjects with 85% sensitivity and 92% specificity.

DISCUSSION

The e-norms is a feasible method to establish reference values in the neuromuscular ultrasound laboratory.

Comparing the Anatomy of the Lateral Femoral Cutaneous Nerve in Patients With and Without Meralgia Paresthetica: A Systematic Review and Meta-Analysis

The anatomical variations of the lateral femoral cutaneous nerve (LFCN) are well documented, with several studies hypothesizing that specific variants may increase the LFCN's susceptibility to meralgia paresthetica (MP). This systematic review and meta-analysis aimed to compare the prevalence of LFCN anatomical variations among limbs with and without MP. It also sought to determine if the LFCN's cross-sectional area (CSA) on ultrasound differed between limbs with and without MP. PubMed, SCOPUS, CINAHL, and Cochrane databases were used to query publications from inception to June 13, 2024. Included studies had a population of living patients, with or without the diagnosis of MP, and reported on the LFCN's exit from the pelvis, branching patterns, distance from the anterior superior iliac spine (ASIS), and/or CSA on ultrasound. Eighteen studies were included, nine retrospective and nine prospective, with a total of 1512 nerves. The LFCN in limbs with MP was closer to the ASIS (p < 0.01) and the MP limbs had a higher percentage of nerves exiting the pelvis lateral to or over the ASIS (p < 0.01) when compared to healthy limbs. The CSA was larger in the nerves affected by MP compared to the unaffected nerves (p < 0.01). The results demonstrate that specific anatomical variations of the LFCN, where the nerve courses in a more lateral or superficial position, may increase its susceptibility to developing MP. The differences in nerve CSA also show the potential utility of ultrasound as a diagnostic adjunct for MP.

Neuromuscular Ultrasound Training in Neuromuscular Fellowship Programs in Canada: Minding the Gap

INTRODUCTION/AIMS

Neuromuscular ultrasound (NMUS) is gaining prominence as a valuable tool for diagnosing neuromuscular disorders at the point of care. Neuromuscular disorder diagnostic criteria guidelines have begun incorporating NMUS findings. As interest grows, fellowship programs must consider incorporating training into their curricula. This study evaluated the current state of NMUS training, potential barriers, and interest in training across Canadian neuromuscular fellowship programs.

METHODS

A 23-question online survey was developed and distributed via email to all 10 neuromuscular fellowship program directors across Canada.

RESULTS

Seven (70%) programs responded to the survey. There was general agreement among programs on the value of NMUS, however, only one (14.3%) program reported they would consider recent graduates to be competent in NMUS. Critical barriers to incorporation of NMUS training included lack of a formalized curriculum, faculty expertise and time, and equipment. Two (28.6%) programs reported that accessibility of equipment and one (14.3%) that faculty expertise was not a barrier to NMUS training. Two (28.6%) programs have local NMUS training options available to fellows (in only one program is NMUS training mandatory). All programs expressed interest in additional training opportunities, and three (43%) programs reported taking steps toward incorporating NMUS training into their curricula.

DISCUSSION

NMUS training is in its infancy in Canada, with several common barriers identified across programs. There is universal interest in further NMUS training opportunities for fellows, highlighting the importance of a common approach to addressing the educational gap to support development of formalized NMUS training mechanisms in Canada.

Optimizing Electrodiagnostic Studies: The Role of Clinical History in Improving Diagnostic Concordance-A Retrospective Study

Background: Electrodiagnostic (EDx) studies are crucial for diagnosing neuromuscular diseases and are considered a complement to neurological examinations. Their effectiveness is highly dependent on the quality of the initial clinical diagnosis, medical history, and physical examination. This study aims to evaluate the concordance between clinical diagnoses and EDx findings, and to identify the primary specialties and clinical data justifying EDx referrals. Methods: This retrospective study included data from referral forms and EDx reports for nerve conduction studies and electromyography at Hospital General de México "Dr. Eduardo Liceaga" from January 2022 to January 2023. Statistical analyses involved descriptive statistics, Cohen's Kappa coefficient, and binary logistic regression to assess diagnostic concordance and the influence of clinical symptoms. Results: Out of 1065 referral requests, 61.8% had their clinical diagnosis confirmed through EDx studies. Most requests originated from orthopedics (25.7%), rheumatology (17.5%), and neurology (17.4%). Although 79.5% of requests included symptoms, only 32.1% included a physical examination. Common diagnoses included radiculopathy (34.6%), polyneuropathy (22.7%), and carpal tunnel syndrome (22.4%). Concordance between clinical and electrophysiological diagnoses had a coefficient of 0.578 (95% CI: 0.537-0.619; p < 0.001). Pain and weakness were significantly associated with diagnostic confirmation (pain: OR 3.1; 95% CI: 1.79-5.48; p < 0.001; weakness: OR 2.46; 95% CI: 1.35-4.48; p = 0.003). Neurology had the highest concordance (0.853; 95% CI: 0.829-0.878), while neurosurgery had the lowest (0.502; 95% CI: 0.378-0.627). Conclusions: EDx studies are valuable, yet their concordance with clinical diagnoses is limited. The experience of the requesting physician significantly impacts diagnostic accuracy. Enhancing referral information is essential for improving EDx study effectiveness and reducing unnecessary procedures, thereby improving patient outcomes and managing costs.

Education Research: Feasibility, Reliability and Educational Value of Neuromuscular Ultrasound Training in a Canadian Neurology Residency Program: A Pilot Study

Background and Objectives

Point-of-care neuromuscular ultrasound (NMUS) is increasingly used in the evaluation of peripheral nervous system disorders; however, there remains a gap in education and training for neurology residents. We evaluated whether neurology residents can feasibly be trained in basic NMUS skills and nerve cross-sectional area (CSA) measurement and whether they value incorporation of this training into their curriculum.

Methods

Participants included neurology residents (postgraduate years 1-5) at the University of Alberta (Edmonton, Alberta, Canada). All completed pretraining and posttraining surveys using a Likert scale, rating their confidence in independently performing NMUS and their degree of agreement regarding the educational value of NMUS training. Residents underwent training (7 hours) comprising 1 didactic and 2 hands-on sessions, detailing NMUS of median, ulnar, and fibular nerves. Participants could then opt-in to a posttraining testing session where CSA measurements (mm2) of the median, ulnar, and fibular nerve at multiple sites were independently performed on 3 healthy volunteers and compared with measurements obtained by the trainer.

Results

Eighteen residents participated in training and pretraining/posttraining surveys. Nine completed the testing component. Nerve CSA measurement reliability between the trainer and trainees across all nerve sites combined was very good (intraclass correlation coefficient [ICC] 0.93, 95% CI 0.83-0.96) but varied by nerve and site. ICC was good to very good (0.62-0.95) except for the ulnar nerve-distal forearm/wrist (0.39-0.58) and fibular nerve-fibular head (0.12) sites. The coefficient of variation (CoV) across all sites was 19.6% (95% CI 17.3-21.8) and best for the median nerve-wrist site at 15.5% (9.8-20.8). The mean absolute difference between trainer and trainee measurements was low (<0.5 mm2 across all sites). Comparing pretraining and posttraining survey responses, there was a significant increase in agreement that basic NMUS operational skills were obtained and in confidence in independently measuring each nerve. NMUS training was considered a valuable component of a neurology residency program curriculum (median rating: strongly agree).

Discussion

Neurology residents across stages of training can acquire basic NMUS and CSA measurement skills of the median and ulnar nerves after 2 half-days of training and value incorporation of NMUS training in their educational curriculum.

Ways to think about vasculitic neuropathy

PURPOSE OF REVIEW

Vasculitis as a pathomechanism for neuropathy can be isolated to the peripheral nervous system, a part of a systemic autoimmune condition or a component of another syndrome. This review aims to discuss the broad range of diagnoses in which vasculitic neuropathy can be encountered, highlight the progress in imaging techniques in identifying vasculitis, and the new drugs developed for other autoimmune diseases that may be applied to neurological conditions.

RECENT FINDINGS

Advances in imaging modalities, ultrasound, MRI and FDG-PET scanning for neuromuscular applications has redefined many aspects of vasculitic neuropathies. The benefit of dividing vasculitides by vessel size is becoming less absolute as diagnostic approaches advance. MRI and FDG-PET are widely used in diagnosis, defining extent of involvement of disease and monitoring. In neuralgic amyotrophy, the identification of hourglass-like constrictions on imaging has changed the treatment paradigm to include surgical interventions. These diagnostic approaches are supported by new immunomodulating and immunosuppression techniques.

SUMMARY

Vasculitic neuropathies are a broad group of conditions with a range of causes and associations. Increased use of imaging techniques impacts our traditional definitions and classifications. The growth in treatment options for other autoimmune conditions are likely to infiltrate the neurological landscape.

Another step forward for neuromuscular ultrasound

See article on pages 295–302 in this issue.