Diagnostic accuracy of voluntary and stimulated neuromuscular jitter studies in ocular myasthenia gravis

Giuseppe Cosentino PhD, Paolo Prunetti MD, Giulia Tammam MD, Chiara Zaffina MD, Matteo Gastaldi MD, PhD, Cristina Tassorelli PhD, Enrico Alfonsi MD, Massimiliano Todisco MD, PhD

Introduction/Aims There is a lack of studies comparing the accuracy of neuromuscular jitter analysis during voluntary activation (v-jitter study) versus axonal stimulation (s-jitter study). The study aimed to compare these two techniques in the same population of patients with suspected ocular myasthenia gravis (OMG).

Methods Fourteen control subjects (mean age: 55.5±15.2 years) and 34 patients with suspected OMG (mean age: 59±13.9 years) were prospectively evaluated. Twenty spike pairs and 30 individual spikes were analyzed during v-jitter and s-jitter study, respectively. Two different criteria for abnormal individual jitter values were evaluated: =/+ or > than 10% values exceeding the upper normal limit.

Results OMG was diagnosed in 19 patients based on clinical and laboratory findings, without considering jitter measurements. In most patients, v-jitter and s-jitter analyses provided comparable results. The maximum sensitivity (89%) was achieved with s-jitter study using the =/+10% criterion, while the maximum specificity (93%) was found with v-jitter study using the >10% criterion.

Discussion Both v-jitter and s-jitter studies showed good to very good accuracy for the diagnosis of OMG, in the absence of any statistically significant difference. Therefore, the patient's cooperation level and examiner's experience should guide the choice of performing v-jitter or s-jitter analysis in patients with suspected OMG.

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