Application Value of the Motor Unit Number Index in Patients With Kennedy Disease

The aim of this study was to evaluate the usefulness of the motor unit number index (MUNIX) technique in Kennedy disease (KD) and test the correlation between the MUNIX and other clinical parameters. The MUNIX values of the bilateral deltoid, abductor digiti minimi (ADM), quadriceps femoris (QF), and tibialis anterior (TA) were determined and compared with the course of the disease. The MUNIX sum score was calculated by adding the MUNIX values of these 8 muscles. Disability was evaluated using the spinal and bulbar muscular atrophy functional rating scale (SBMAFRS). The MUNIX scores of patients with KD were negatively correlated with the course of the disease (p < 0.05), whereas their motor unit size index (MUSIX) scores were positively correlated with the course the of disease (p < 0.05). MUNIX sum scores were correlated with SBMAFRS scores (r = 0.714, p < 0.05). MUNIX was more sensitive than compound muscle action potentials or muscle strength as an indicator of neuron loss and axonal collateral reinnervation. The MUNIX sum score is an objective and a reliable indicator of disease progression, and it is a potential choice for therapeutic clinical trials. The MUNIX can assess the functional loss of motor axons and is correlated with disability. The MUNIX sum score may be especially suitable as an objective parameter.

Short-interval intracortical inhibition and facilitation targeting upper and lower limb muscles

Transcranial magnetic stimulation (TMS) can be used to study excitability of corticospinal neurons in human motor cortex. It is currently not fully elucidated if corticospinal neurons in the hand vs. leg representation show the same or different regulation of their excitability by GABAAergic and glutamatergic interneuronal circuitry. Using a paired-pulse TMS protocol we tested short-interval intracortical inhibition (SICI) and short-interval intracortical facilitation (SICF) in 18 healthy participants. Motor evoked potentials were evoked in one hand (abductor digiti minimi) and one leg muscle (tibialis anterior), with systematic variation of the intensities of the first (S1) and second (S2) pulse between 60 and 140% resting motor threshold (RMT) in 10% steps, at two interstimulus intervals of 1.5 and 2.1 ms. For the hand and leg motor representations and for both interstimulus intervals, SICI occurred if the intensities of S1 < RMT and S2 > RMT, while SICF predominated if S1 = S2 ≤ RMT, or S1 > RMT and S2 < RMT. Findings confirm and extend previous evidence that the regulation of excitability of corticospinal neurons of the hand versus leg representation in human primary cortex through GABAAergic and glutamatergic interneuronal circuits is highly similar, and that corticospinal neurons of both representations are activated by TMS transsynaptically in largely identical ways.

A Comparison Between the Adductor Pollicis Muscle and the Abductor Digiti Minimi Muscle Using Electromyography AF-201P in Rocuronium-Induced Neuromuscular Block: A Prospective Comparative Study

Background The AF-201P, a new electromyography (EMG)-based neuromuscular monitor has been developed recently. The aim of this clinical study was to compare two ulnar nerve innervated muscles: the adductor pollicis (AP) muscle and the abductor digiti minimi (ADM) muscle during the recovery from rocuronium-induced neuromuscular block by using EMG AF-201P. Methods Twenty patients undergoing surgery with general anesthesia were enrolled in the study. During total intravenous general anesthesia, train-of-four (TOF) and post-tetanic counts (PTC) responses following 0.9 mg/kg rocuronium administration were concurrently monitored at the AP and the ADM muscles with EMG AF-201P on the opposite arms. At the end of the surgery, sugammadex 2 mg/kg was administered when TOF counts of 2 was observed at both muscles. The primary outcome of the study was time from administration of rocuronium to first appearance of PTC response (first PTC). The secondary outcomes of the study were time from administration of rocuronium to first reappearance of TOF response (first TOF), time from first PTC to first TOF (PTC-TOF time), time to reappearance of TOF counts of 2, and time from administration of sugammadex to TOF ratio ≥ 0.9. Agreement between the two muscles was assessed using the Bland-Altman analysis. Data are expressed as mean ± standard deviation. Results Nineteen patients were included in the analysis. Time for appearance of the first PTC was significantly faster at the ADM muscle than the AP muscle (32.4 ± 13.1min vs 24.4 ± 11.4min, p = 0.006). Interval time between the first PTC and the first TOF was significantly longer with the ADM muscle than the AP muscle (19.4 ± 7.3min vs 12.4 ± 10.6min, p = 0.019). There were no significant differences in time to TOF counts of 2 and sugammadex-facilitated recovery between the two muscles. Bland-Altman analyses showed acceptable ranges of bias and limits of agreement of the two muscles. Conclusions The ADM muscle showed a good agreement with the AP muscle during rocuronium-induced neuromuscular block but faster recovery of PTC response when using EMG. Trial registration : UMIN-CTR (Registration No. UMIN000044904). Registered 19 July 2021 -Retrospectively registered,

A detailed analysis of long-term outcomes following reconstruction for congenital thumb hypoplasia

This retrospective study analyses long-term outcomes of reconstruction for congenital thumb hypoplasia Grades 2 and 3 A. In 22 thumbs (mean follow-up 9 years), instability of the metacarpophalangeal joint was found in 20 thumbs regardless of the method of reconstruction, double breasting of local tissue with or without adductor pollicis advancement or use of a slip of flexor digitorum superficialis to supplement local tissue. There was a trend towards a greater global strength, higher Kapandji score and better subjective function score when the abductor digiti minimi was used as an opposition transfer as compared with the flexor digitorum superficialis. Results for motion and subjective parameters were consistent with comparable studies though these comparisons are compromised by different methods of classification and assessment. Consistent application of an expanded Blauth grading system and a formal hypoplastic thumb score will improve the ability to compare pre- and postoperative status, different techniques and results from different centres. Level of evidence: IV

Functional reconstructions using only ulnar nerve and ulnar nerve-innervated muscles for traumatic musculocutaneous, median and radial nerve palsies

A 20-year-old right-handed fisherman experienced a severe injury in a high-energy traffic accident. These injuries included a shaft fracture of the right humerus, open comminuted fracture of the right forearm and multiple peripheral nerve palsies involving the musculocutaneous, median and radial nerves. Six months after the initial treatment, the patient was referred to our hand surgeons for further treatment. Several operations for functional reconstruction using only the ulnar nerve and ulnar nerve-innervated muscles were performed: the main procedures included a partial ulnar nerve transfer for elbow flexion, flexor carpi ulnaris transfer for reconstruction of wrist and finger extension and opponensplasty using the abductor digiti minimi. Three years after the initial injury, the patient had relatively good function including elbow flexion and stable side pinch and grasp. Functional reconstruction using a combination of the ulnar nerve and ulnar nerve-innervated muscles may be useful in specific cases involving multiple peripheral nerve injuries.

Lambert-Eaton Myasthenic Syndrome Presenting as Cerebellar Symptoms

A 79-year-old man visited neurology clinic due to gait ataxia and vertigo for 10 months. Neurologic examination revealed saccadic pursuit, mild dysmetria, impaired tandem gait, and areflexia that recovers after exercise. The amplitude of compound muscle action potentials recorded on the abductor digiti minimi increased up to 6,639.4% during repetitive nerve stimulation at 50 Hz stimulation. This case demonstrates that clinicians should consider Lambert-Eaton myasthenic syndrome as a differential diagnosis when a patient complains of gait ataxia and vertigo.

Changes in Corticospinal Circuits During Premovement Facilitation in Physiological Conditions

Changes in corticospinal excitability have been well documented in the preparatory period before movement, however, their mechanisms and physiological role have not been entirely elucidated. We aimed to investigate the functional changes of excitatory corticospinal circuits during a reaction time (RT) motor task (thumb abduction) in healthy subjects (HS). 26 HS received single pulse transcranial magnetic stimulation (TMS) over the primary motor cortex (M1). After a visual go signal, we calculated RT and delivered TMS at three intervals (50, 100, and 150 ms) within RT and before movement onset, recording motor evoked potentials (MEP) from the abductor pollicis brevis (APB) and the task-irrelevant abductor digiti minimi (ADM). We found that TMS increased MEPAPB amplitude when delivered at 150, 100, and 50 ms before movement onset, demonstrating the occurrence of premovement facilitation (PMF). MEP increase was greater at the shorter interval (MEP50) and restricted to APB (no significant effects were detected recording from ADM). We also reported time-dependent changes of the RT and a TMS side-dependent effect on MEP amplitude (greater on the dominant side). In conclusion, we here report changes of RT and side-dependent, selective and facilitatory effects on the MEPAPB amplitude when TMS is delivered before movement onset (PMF), supporting the role of excitatory corticospinal mechanisms at the basis of the selective PMF of the target muscle during the RT protocol.

Compartimentalización Neuromuscular de los Músculos Vastus Medialis y Abductor Digiti Minimi en Personas Jóvenes

There is evidence that supports that the recruitment of motor units within the same muscle presents a certain heterogeneity. This heterogeneity in activation has led to the hypothesis that certain muscles could be organised neuromuscularly as functional compartments, beyond the existence that is demonstrable at a morphological level. This would imply that the motor unit grouped in certain muscle regions would show different activation levels that differ from the motor units located in other zones of the same muscle. Several studies have evidenced the existence of differential recruitment of the muscles on the trunk and limbs, demonstrated the existence of functional compartmentalization in that. This thesis sought to demonstrate the existence of a functional compartmentalization in Vastus Medialis and Abductor Digiti Minimi muscles in young people.