Laughlin, Ruple S.

Purpose: Hereditary transthyretin amyloidosis (ATTRv) is a progressive multisystem disease in which median mononeuropathy at the wrist (MNW) is common and often precedes systemic involvement. Nerve conduction studies (NCS) have historically been the gold standard for MNW, but neuromuscular ultrasound (NMUS) is complementary. The aim of this study was to compare NMUS with electrodiagnostic (EDX) testing for the diagnosis of MNW in patients with symptomatic ATTRv. Methods: A retrospective review was performed of patients 18 years and older with ATTRv confirmed by genetic testing who underwent both EDX testing and NMUS of the median nerve between 2019 and 2025. Demographic, NMUS, and EDX data were collected. Results: Data from 15 upper limbs in 10 patients were analyzed. Median nerve cross‐sectional area at the wrist was significantly greater than reference values ( P = 0.041). MNW was identified in 80% of wrists by NMUS and 100% by NCS, with no significant difference between modalities. Median nerve cross‐sectional area at the wrist did not significantly correlate with MNW severity determined by NCS ( r = −0.018; P = 0.941) or with any NCS parameters (all P > 0.080). Concurrent polyneuropathy was diagnosed in 60% of patients, but there was no association between polyneuropathy and MNW detection by either modality ( P > 0.197). Conclusions: NMUS and NCS demonstrate comparable diagnostic accuracy for MNW in ATTRv. Given its noninvasive nature and efficiency, NMUS may serve as an adjunct to classic EDX testing in this population.

Purpose: Neuromuscular ultrasound, including cross-sectional area measurements, adds diagnostic value to the clinical and electrodiagnosis evaluation of ulnar neuropathy at the elbow. Previously published reference values for ulnar nerve size vary widely. Our objective was to establish age-specific reference values for ulnar nerve cross-sectional area at multiple sites in asymptomatic adults for our laboratory. Methods: Healthy adult subjects without neuromuscular symptoms or disease were recruited from our tertiary referral electromyogram laboratory and staff. Ulnar nerve cross-sectional area measurements were made in short axis at the wrist, forearm, cubital tunnel, retrocondylar groove, 2 cm proximal to the medial epicondyle, and mid-upper arm with the elbow flexed to 90°. Dynamic neuromuscular ultrasound evaluated for subluxation and dislocation at the medial epicondyle. Results were stratified by age group (younger than 40, 40–60, and older than 60 years) with at least 20 subjects per sex per group, as well as by sex, body mass index, and handedness. The upper limit of normal was established as two standard deviations above the mean. Results: One hundred forty-two subjects (ages 18–84, mean 47.7 years) were included. Cross-sectional area significantly increased with age at all sites except the wrist. Cross-sectional area cut-offs at the retrocondylar groove were 10.0, 10.9, and 11.4 mm 2 , respectively, by age group. Ratios comparing retrocondylar groove and cubital tunnel to arm and forearm were calculated. Thirty-two percent had subluxation or dislocation in at least one limb. Conclusions: Age-specific cross-sectional area cut-offs and ratios may facilitate a more nuanced interpretation and diagnostic value when used in conjunction with clinical and electrodiagnosis evaluation of ulnar neuropathy at the elbow.

ABSTRACT Introduction/Aims Neuromuscular ultrasound (NMUS) is becoming increasingly incorporated as a complementary tool in electrodiagnostic (EDX) medicine. Competency assessment is critical to ensure adequate quality, appropriate application, and accurate interpretation. The primary objective was to develop a competency‐based assessment tool of foundational NMUS skills among postgraduate medical trainees in a single center. Methods The assessment included written (28 multiple‐choice, short answer, or yes/no) questions and practical skills (15 prompts) sections recommended by a published consensus‐based survey to include the knowledge and skills necessary to achieve minimal competency for unsupervised practice of NMUS for common conditions. The written portion included interpretation of basic pathology. Core practical content focused on the most evaluated structures in the Mayo EDX laboratory: the median and ulnar nerves and diaphragm muscle. The practical portion was administered by a single examiner and scored with a five‐point competency‐based rating. Four experienced educators used the Angoff standard setting method to set passing scores for each section. Results Subjects included three EMG‐track clinical neurophysiology fellows who completed a NMUS lecture series with supervised hands‐on scanning and a 2‐week intra‐lab NMUS elective during fellowship. Composite scores ranged from 89% to 97%. All subjects met minimum passing scores for each section (77% and 88% for the knowledge and skills sections, respectively). Discussion This NMUS competency assessment was successfully implemented and may be incorporated into postgraduate medical trainee evaluation to ensure minimal competency in evaluation of carpal tunnel syndrome, ulnar neuropathy at the elbow, and diaphragm function. This effort integrates quality NMUS evaluations into clinical practice.

ABSTRACT Introduction/Aims In severe ulnar neuropathy at the elbow (UNE), occasionally surgeons will employ an end‐to‐side (ETS) nerve transfer of the anterior interosseous nerve (AIN) motor branch of pronator quadratus (PQ) to the ulnar motor component distally (AIN ETS). We used an ultrasound (US)‐guided near‐nerve monopolar needle stimulation of the AIN to determine the specific contribution of the transferred PQ motor branch to the ulnar‐innervated hand intrinsic muscles following AIN ETS in patients with UNE. Methods After inserting the monopolar needle under US guidance, direct stimulation of the AIN was performed while recording from the abductor digiti minimi (ADM), first dorsal interosseous (FDI), and flexor pollicis longus (FPL). The presence or absence of a compound muscle action potential (CMAP) was noted from each muscle. Results The technique was used in two patients with chronic UNE, one with a cubital tunnel decompression and AIN ETS and the other with a decompression alone. In the patient with decompression and AIN ETS, direct stimulation of the AIN revealed a low amplitude CMAP recorded from the FDI and FPL, suggesting AIN axonal contribution to FDI in the setting of prior AIN ETS. In the patient with decompression alone, near‐nerve stimulation generated an expected CMAP in the FPL but no response in the hand intrinsics. Discussion This study may demonstrate the utility of US‐guided near‐nerve monopolar needle AIN stimulation and suggests that it is a reliable technique to isolate the AIN contribution to hand intrinsic reinnervation following AIN ETS.

ABSTRACT Background Monoclonal gammopathy‐associated myopathies (MGAMs) include light chain (AL) amyloid myopathy, sporadic late‐onset nemaline myopathy (SLONM), and vacuolar myopathy with monoclonal gammopathy and stiffness (VAMMGAS). These subtypes usually occur separately, although rare overlap has been described. We report a patient with monoclonal gammopathy and concurrent SLONM and excessive glycogen accumulation, resembling VAMMGAS but with distinct features. Methods Case report with clinical, electrophysiological, pathological, and therapeutic characterization of a patient with IgG‐kappa monoclonal gammopathy and coexisting SLONM and glycogen accumulation within muscle fibers. Results A 69‐year‐old man developed subacute progressive axial and limb weakness, head drop, dysphagia, and weight loss. Examination showed proximal/distal weakness, neck extensor weakness, and lumbar hyperlordosis. EMG revealed myopathic motor unit potentials without electrical myotonia or complex repetitive discharges. Serum studies identified IgG‐kappa monoclonal protein with elevated kappa light chain and ratio. Muscle biopsy demonstrated nemaline rods (1% of fibers) and scattered fibers with non‐rimmed vacuoles (0.3% of fibers) containing PAS‐positive, diastase‐labile material consistent with concurrent SLONM and glycogen storage myopathy‐like pathology. Genetic testing for congenital nemaline and glycogen storage myopathies was negative. Plasma‐cell directed therapy with daratumumab, lenalidomide, and dexamethasone led to rapid functional improvement and M‐protein reduction. Further gains followed autologous stem cell transplantation. Conclusion This case expands the MGAM spectrum, highlighting co‐occurrence of SLONM and an excessive glycogen accumulation responsive to immunotherapy and transplantation. These findings suggest a spectrum of related disease processes. Recognition of this combined pathology is clinically important, as affected patients may benefit from targeted immunotherapy or stem cell transplantation.

ABSTRACT Background and Aims Chronic inflammatory demyelinating polyradiculoneuropathy ( CIDP ) is a common, treatable, autoimmune, neuropathy frequently misdiagnosed. The complex electrodiagnostic ( EDX ) criteria required for diagnosis are challenging to apply in routine practice. This study evaluates the effectiveness of a machine‐assisted EDX tool in real‐time identification of demyelinating nerve conduction studies ( NCS ) stipulated by 2021‐ EAN / PNS CIDP criteria in conjunction with an online CIDP clinical probability calculator. Methods We prospectively evaluated 100 consecutive patients with referral or EDX diagnosis of polyradiculoneuropathy beginning January 1, 2024. Fifty patients were included, each from Jacksonville and Rochester Mayo Clinics. Routine electromyography ( EMG ) reports were compared to a machine‐assisted support tool applying 2021‐ EAN / PNS CIDP EDX criteria to NCS assessing demyelination. The EDX ‐assistant performance was compared to the final clinical diagnosis and our previously reported online CIDP clinical prediction tool ( https://news.mayocliniclabs.com/cidp‐calculator/ ). Results Among 100 patients (60% male; median age 64), 30 had a final clinical CIDP diagnosis with 29 having intravenous immunoglobulin follow‐up; 27 (93%) improved and 2 (7%) stabilized. Routine EMGs reported demyelination in 14 of 30 (47%), with 46% sensitivity and 79% specificity. The EDX ‐assistant identified CIDP demyelination in 28 of 30 (93%), with 93% sensitivity and 57% specificity. The clinical calculator detected CIDP in 30 of 30 (100%) with 86% specificity, increasing to 94% after excluding false positives lacking demyelinating features on the EDX tool. Interpretation A real‐time machine‐assisted EDX support tool, used with a clinical web‐based calculator, streamlines CIDP assessment by improving standardized identification of 2021‐EAN/PNS CIDP demyelinating NCS criteria and aiding clinical decisions.