Study on variation trend of repetitive nerve stimulation waveform in amyotrophic lateral sclerosis

Quantitative evaluation of factors influencing the 3 Hz repetitive nerve stimulation test in patients with amyotrophic lateral sclerosis

INTRODUCTION/AIMS

Previous studies have suggested that treatments targeting the neuromuscular junction (NMJ) may play a role in the treatment of amyotrophic lateral sclerosis (ALS). However, factors impacting repetitive nerve stimulation (RNS), a technique to evaluate NMJ function, have yet to be fully elucidated. We aimed to identify independent factors contributing to the decremental response of the accessory nerve and evaluated its value in ALS clinical practice.

METHODS

A total of 626 patients who were diagnosed with ALS and underwent 3 Hz RNS tests on the accessory nerve were enrolled. Data on their clinical and electrophysiological indicators were divided into a training set (collected from June 2016 to December 2022) and a test set (collected from January to August 2023). Stepwise regression was used in independent variable selection and model building.

RESULTS

Forty-two percent of patients had a decrement larger than 10% and 24% had a decrement larger than 15%. Onset age, sex, onset site, forced vital capacity (FVC) and motor unit potential (MUP) duration were independent factors contributing to the results of the RNS test. MUP duration had the greatest impact on decremental response, followed by FVC and onset age. The decremental response in females was larger than in males. Upper limb onset was found to contribute more to the decrement than lower limb or bulbar onset.

DISCUSSION

In patients with ALS, NMJ safety factor is reduced during re-innervation. Decremental response is affected by multiple factors, which needs to be considered in clinical trials targeting the NMJ in these patients.

Study on the Diagnostic Value of Neuroelectrophysiological Examination in Patients with Amyotrophic Lateral Sclerosis

Objective

Amyotrophic lateral sclerosis (ALS) is a progressive neurodegenerative disease with unknown causes involving upper and lower motor neurons. Our study aimed to explore the diagnostic value of neuroelectrophysiological examination in patients with amyotrophic lateral sclerosis.

Methods

A total of 64 patients admitted to our hospital from January 2014 to December 2020 were selected as ALS group. Additionally, 64 normal healthy people in the same period were selected as the control group. Electrophysiological tests were performed on all personnel involved in the study, and the results and parameter changes of different personnel were compared and analyzed.

Results

There was a statistical difference between the EMG data of clinically confirmed ALS and the proposed ALS and possible ALS (p < 0.05). The abnormality of confirmed ALS was particularly obvious, and the overall abnormal rate of EMG in ALS was 85%. The CMCT of the upper and lower limbs of clinically diagnosed ALS, suspected ALS, and possible ALS were longer than that of the normal group (p < 0.05). There was no significant statistical difference between clinically diagnosed ALS and suspected ALS (p > 0.05), and there was a difference between clinically diagnosed ALS and possible ALS (p < 0.05). In ALS group, the frequency of F wave decreased, which may be related to the involvement of F wave conduction pathway and the degree of lower motor neuron involvement (p < 0.05). In addition, the amplitudes of F and H waves increased, which was related to the involvement of upper motor neurons (p < 0.05). In ALS group, SCV was hardly involved, and CMAP decreased significantly, which was positively correlated with the degree of muscular atrophy and muscle strength decline (p < 0.05). The sensitivity of electrophysiological detection was 76.56%, the specificity was 78.33%, and the AUC was 0.8578.

Conclusion

Patients with clinically suspected ALS should undergo electrophysiological testing as soon as possible, which is conducive to the early diagnosis and differential diagnosis of ALS. This trial is registered with ChiCTR2100046535.

Ultra-early amplitude decrement after repetitive nerve stimulation supports early neuromuscular junction injury in amyotrophic lateral sclerosis: a prospective cross-sectional study

The dying-back hypothesis holds that the damage to neuromuscular junctions and distal axons in amyotrophic lateral sclerosis occurs at the earliest stage of the disease. Previous basic studies have confirmed early damage to neuromuscular junctions, but it is difficult to obtain such evidence directly in clinical practice. In this prospective cross-sectional study, we recruited 22 patients with early amyotrophic lateral sclerosis with disease duration < 12 months and with clinical symptoms limited to the upper limbs. We also recruited 32 healthy controls. Repetitive nerve stimulation was performed, and patients were followed for 12 months. We found a significant change in the response to repetitive nerve stimulation in amyotrophic lateral sclerosis patients without spontaneous electromyographic activity. Patients that were prone to denervation had an increased decrement response of target muscles after repetitive nerve stimulation. These results suggest that changes in response to repetitive nerve stimulation may occur before denervation in amyotrophic lateral sclerosis patients. The damage to lower motor neurons is more obvious in patients with a higher percentage of repetitive never stimulation-related amplitude decrements. This study was approved by the Institutional Ethics Committee of Peking University Third Hospital (approval No. M2017198) on August 24, 2017.

Progressive muscle weakness and amyotrophy during pregnancy as the first manifestation of systemic lupus erythematosus: A case report and review of literature

BACKGROUND

Systemic lupus erythematosus is a common autoimmune disease involving multiple systems. Clinical involvement of the central and peripheral nervous systems is not unusual, but peripheral neuropathy in systemic lupus erythematosus with chronic inflammatory demyelinating polyneuropathy is uncommon. Our study aimed to illustrate the clinical features, diagnosis, and treatment of systemic lupus erythematosus combined with chronic inflammatory demyelinating polyneuropathy, and to aid in the identification of peripheral neuropathy in systemic lupus erythematosus.

METHODS

This article reports a case of systemic lupus erythematosus with onset in pregnancy, with chronic inflammatory demyelinating polyneuropathy as the first manifestation. We then analyze the identification of common peripheral neuropathy in systemic lupus erythematosus in detail, based on a literature review of confirmed cases of systemic lupus erythematosus combined with chronic inflammatory demyelinating polyneuropathy.

RESULTS

A 34-year-old woman presented progressive muscle weakness and muscular atrophy in the extremities during pregnancy, 3 years previously. At 4 months after onset, she had completely lost the ability to hold objects and walk, and had slight numbness in the limbs, without paresthesia. Her condition was misdiagnosed as "motor neuron disease" at the time. Three years after onset, her condition was revisited because of nephrotic syndrome, and she was diagnosed with nephrotic syndrome and peripheral nerve injury caused by systemic lupus erythematosus. After immunosuppressive treatment with corticosteroids and intravenous cyclophosphamide, her symptoms of muscle weakness were markedly improved. This article summarizes the characteristics of systemic lupus erythematosus combined with chronic inflammatory demyelinating polyneuropathy that have been reported in the literature, from the aspects of morbidity, disease progression, nerve injury, laboratory examinations, and treatment response.

CONCLUSIONS

Our identification of a common peripheral neuropathy in systemic lupus erythematosus will help to improve clinicians' understanding of various peripheral neuropathies in systemic lupus erythematosus. It will also aid in the early diagnosis and treatment of such patients, thus improving their long-term prognosis.

Persistent neuromuscular junction transmission defects in adults with spinal muscular atrophy treated with nusinersen

Objective

Spinal muscular atrophy (SMA) is a motor neuron disease caused by low levels of survival motor neuron (SMN) protein. Prior work in models and patients has demonstrated electrophysiological and morphological defects at the neuromuscular junction (NMJ). Therapeutic development has resulted in clinically available therapies to increase SMN protein levels in patients and improve muscle function. Here we aimed to investigate the effect of SMN restoration (via nusinersen) on NMJ transmission in adults with SMA.

Methods

Participants undergoing nusinersen treatment underwent 3 Hz repetitive nerve stimulation (RNS) of the spinal accessory nerve to assess compound muscle action potential amplitude decrement. Maximum voluntary isometric contraction (MVICT), Revised Upper Limb Module (RULM), and 6 min walk test (6MWT) were assessed for correlations with decrement.

Results

Data from 13 ambulatory (7 men/6 women, mean age 40±11 years) and 11 non-ambulatory (3 men/8 women, mean age 38±12 years) participants were analysed. Cross-sectional analyses of RNS decrement were similar at 14 months of nusinersen (−14.2%±11.5%, n=17) vs baseline (−11.9%±8.3%, n=15) (unpaired t-test, p=0.5202). Longitudinal comparison of decrement in eight participants showed no change at 14 months (−13.9%±6.7%) vs baseline (−16.9%±13.4%) (paired t-test, p=0.5863). Decrement showed strong correlations with measures of MVICT, RULM and 6MWT but not age or disease duration.

Conclusion

Adults with SMA had significant NMJ transmission defects that were not corrected with 14 months of nusinersen treatment. NMJ defects were negatively associated with physical function, and thus may represent a promising target for additive or combinatorial treatments.

Diagnosis of Myasthenia Gravis

The diagnosis of autoimmune Myasthenia Gravis (MG) remains clinical and rests on the history and physical findings of fatigable, fluctuating muscle weakness in a specific distribution. Ancillary bedside tests and laboratory methods help confirm the synaptic disorder, define its type and severity, classify MG according to the causative antibodies, and assess the effect of treatment objectively. We present an update on the tests used in the diagnosis and follow-up of MG and the suggested approach for their application.

[A case of facial-onset sensory and motor neuronopathy (FOSMN) with cerebellar ataxia and abnormal decrement in repetitive nerve stimulation test]

A 59-year-old woman presented with a 7-year history of facial numbness on the left side, and gradual worsening of symptoms. Over several years, facial muscle weakness, dysarthria, tongue atrophy and fasciculation had progressed. Then, she developed cerebellar ataxia affecting the left extremities, in addition to earlier symptoms. Brain MRI revealed cerebellar atrophy, and ^99mTc-SPECT depicted cerebellar hypoperfusion. A repetitive nerve stimulation test (RNS) indicated abnormal decrement in the nasalis and trapezius muscles on the left side. Facial-onset sensory and motor neuronopathy (FOSMN) was diagnosed. Administration of intravenous immunoglobulin resulted in improvement of some symptoms. Although cerebellar ataxia is not a common symptom of FOSMN, a case showing TDP-43-positive glial cytoplasmic inclusions in cerebellar white matter has been reported. Therefore, it is possible that FOSMN may cause cerebellum impairment in some patients. Furthermore, RNS positive rate in the trapezius muscle is known to be high in amyotrophic lateral sclerosis (ALS) patients. It is speculated that RNS of the affected muscles in FOSMN may show abnormal decrement by the same mechanisms as ALS.

Can the Large-Scale Decrement in Repetitive Nerve Stimulation Be Used as an Exclusion Criterion for Amyotrophic Lateral Sclerosis?

Objective: The objectives of this work were to identify the characteristics of repetitive nerve stimulation (RNS) in patients with amyotrophic lateral sclerosis (ALS) and further verify the electrophysiological exclusion criteria of ALS.

Methods: A total of 150 patients with ALS who were admitted to the Department of Neurology of Renmin Hospital of Wuhan University from January 2015 to December 2018 were enrolled. Clinical and electrophysiological data of the enrolled patients were collected. The differences in the amplitudes of the compound muscle action potential (CMAP) between the trapezius muscle (Trap) and the abductor digiti minimi (ADM) in low-frequency RNS were compared. Furthermore, we analyzed the associations between decremental responses and gender, onset age, duration of disease, onset site, Amyotrophic Lateral Sclerosis Functional Rating Scale—Revised (ALSFRS-R), disease progression rate, and CMAP amplitude.

Results: A significant decrement (≥20%) in at least one muscle was observed in 11.3% of the ALS patients, while decrements (≥10%) in at least one muscle were observed in 41.3%. The decremental percentage in the trapezius muscle was significantly higher than that in the abductor digiti minimi (P < 0.001). The onset age, duration of disease, onset site, and disease progression rate did not affect decremental responses. The decremental responses in RNS were more significant in ALS patients with low ALSFRS-R scores (P = 0.01). Moreover, there was a positive linear correlation between the CMAP amplitude and the decremental percentage of Trap and ADM in ALS patients.

Conclusions: CMAP decremental responses in RNS were common in ALS patients, suggesting abnormalities of neuromuscular junctions (NMJs). It is worthy of further discussion whether to consider a decrement >20% in RNS as a diagnostic exclusion criterion for ALS.