Litchy, William J.

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.

ABSTRACT Background Agrin‐congenital myasthenic syndrome ( AGRN ‐CMS) is a rare, heterogeneous genetic disorder of the neuromuscular transmission that can present from infancy to adulthood. The clinical phenotype includes distal weakness mimicking distal myopathies. Additionally, electromyography and muscle biopsy may demonstrate myopathic features, increasing the diagnostic challenge. Mitochondrial dysfunction has not been reported in the muscle of AGRN ‐CMS patients. Methods We report the clinical, electrophysiological, radiological, myopathological, and genetic findings of a patient with AGRN‐ CMS. Results A 47‐year‐old male presented at age 18 with sudden onset of eyelid ptosis, weakness, and fatigue, followed by dysphagia, dyspnea on exertion, exercise intolerance, and myalgias. Three sisters had similar symptoms. Neurological examination showed lower limb weakness, predominantly affecting the calf muscles with associated atrophy. Tendon reflexes were normal but absent at the ankles. Creatine kinase levels were normal. Electromyography demonstrated myopathic changes in distal muscles with fibrillation potentials in the gastrocnemius. 2 Hz‐Repetitive nerve stimulation of the fibular nerve revealed a 32% decrement in the extensor digitorum brevis without facilitation. Tibialis anterior biopsy showed non‐specific myopathic changes, neurogenic features, and histological evidence of mitochondrial dysfunction, as suggested by the scattered cytochrome c oxidase‐negative fibers. Whole exome sequencing detected a homozygous pathogenic AGRN variant (c.5012G>A, p.Arg1671Gln). No pathogenic or suspected pathogenic variants were detected in muscle mitochondrial DNA or in nuclear genes affecting mitochondrial function. Conclusions This patient expands the pathological spectrum of AGRN ‐CMS to include mitochondrial dysfunction and highlights the importance of low‐frequency repetitive nerve stimulation in the assessment of patients with distal weakness for differentiating myopathies from CMS.

This case report describes a 65-year-old man who experienced complete remission of cavin-4 immunoglobulin G (IgG) rippling muscle disease after receiving rituximab therapy.

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 Introduction/Aims Accurate needle electromyography (EMG) of the short head of the biceps femoris (SHBF) is often important to localize nerve damage when proximal to the fibular head. Techniques have been proposed for accurate SHBF EMG; however, needle placement accuracy is low and with the risk of inadvertent needle placement into the long head (LHBF) potentially resulting in false localization and inappropriate operative management. This study aimed to define the optimal window for accurate SHBF needle EMG placement through ultrasound (US) investigation of the anatomical relationships of the SHBF, LHBF, and common fibular nerve (CFN) in the distal posterolateral thigh. Methods Forty lower limbs from 20 healthy adults were evaluated using US. Distances from the popliteal crease (PC) to the SHBF and LHBF myotendinous junctions and position of the CFN in the popliteal fossa were recorded. The “SHBF window” was defined as the region where the SHBF muscle body is present in the absence of the LHBF. Results The SHBF was located anterolateral to the LHBF tendon/muscle and the CFN medial to the SHBF in all limbs. The average distances from the PC to SHBF and LHBF muscles were 0.6 and 6.4 cm, respectively. The optimal “SHBF window” was identified to be 3–4 cm (2–3 fingerbreadths) proximal to the PC, anterolateral to the LHBF tendon in the distal thigh. Discussion SHBF examination within this optimized window results in increased accuracy of needle placement, aiding in the electrodiagnostic localization of fibular nerve lesions.