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Repetitive Nerve Stimulation Exhibits Positive Association with Inpatient Diagnosis of Myasthenia Gravis

Findings from retrospective study show that repetitive nerve stimulation is a highly sensitive and specific test for the diagnosis of myasthenia gravis in an inpatient setting, with its results being more rapidly available in comparison with antibody testing.

Results from confirmatory antibody testing in myasthenia gravis are often delayed, but the approach of using repetitive nerve stimulation has shown the potential of being more effective in rapidly confirming a diagnosis of MG in the inpatient setting, according to new study results.1

A statistically significant association was shown in a retrospective analysis with 32 hospitalized patients between positive repetitive nerve stimulation and diagnosis of myasthenia gravis (MG; P = .0002).1 The overall sensitivity and specificity of repetitive nerve stimulation in the analysis from the inpatient population was 83.3% and 96.2%, respectively.

Katherine Clifford, MD, neurologist and resident physician, Stanford Medicine, and colleagues presented the data at the 2022 American Association of Neuromuscular & Electrodiagnostic Medicine Annual Meeting, held September 21-24, in Nashville, Tennessee. Of the total identified hospitalized patients, 6 had a greater than 10% decrement on slow repetitive nerve stimulation, confirming neuromuscular junction pathology dysfunction.1 Five of the participants were diagnosed with MG and 1 patient was diagnosed with Lambert-Eaton myasthenic syndrome.

The patients with normal repetitive nerve stimulation (n = 26), all of them except 1 participant had alternative causes of weakness. That patient was then later diagnosed as seronegative MG based on clinical improvement with acetylcholinesterase inhibitors.

Clifford and colleagues wrote, “Sensitivity and specificity of repetitive nerve stimulation is typically reported from outpatient centers, and we hypothesized that these values might not apply to hospitalized patients with higher grades of weakness.”

The study performed a retrospective analysis of adult patients who had inpatient repetitive nerve stimulation at Stanford Medicine between 2016 to 2021. In the study's research, repetitive nerve stimulation from at least at 1 site and a neurological evaluation was included along with performing descriptive statistics and Fisher exact analysis.

In their demographic data, the median patient age was revealed to be 64 years old, the range was set between 29 and 89 years of age. The number of females that participated in the study was more than half the total number of participants (56%). In addition, 12 of 32 (38%) required intubation or nivolumab (Opdivo; Bristol Myers Squibb) for respiratory failure and required a feeding tube.1 As for the limitations of the study, Clifford et al noted that they used preexisting data, the site selection for repetitive nerve stimulation was not expansive, and there was a small number of patients with an ultimate diagnosis of MG collected for the analysis.

In previous studies, a broad range of diagnostic sensitivity of repetitive nerve stimulation was yielded, ranging from 30% to 90% for generalized MG and 10% to 60 for ocular MG, without a differentiation between inpatient and outpatient cohorts.1 Repetitive nerve stimulation could serve as a first line diagnostic test for inpatient settings given that the diagnostic sensitivity of repetitive nerve stimulation increases with the severity of MG.

Clifford and colleagues wrote, “repetitive nerve stimulation is a highly sensitive and specific text in both aiding in the inpatient diagnosis of MG and in ruling out a neuromuscular junction pathology in patients presenting with varying patterns of acute neuromuscular weakness.” Therefore, by using repetitive nerve stimulation, the approach offers rapid results which would then aid patients in a timelier diagnosis in comparison with antibody testing.

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REFERENCES
1. Clifford K, Wu C, Post D, Shaik R, Muppidi S. Repetitive Nerve Stimulation in the Inpatient Diagnosis of Myasthenia Gravis. Presented at: AANEM 2022; September 21-24; Nashville, TN. Abstract 40.