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Case Reports
. 2018 Aug 13:3:148-150.
doi: 10.1016/j.cnp.2018.07.001. eCollection 2018.

Stimulated single-fiber electromyography (sSFEMG) in Lambert-Eaton syndrome

Vincenzo Todisco  1 , Giovanni Cirillo  1   2 , Rocco Capuano  1 , Alessandro d'Ambrosio  1 , Gioacchino Tedeschi  1 , Antonio Gallo  1
Affiliations
Case Reports

Stimulated single-fiber electromyography (sSFEMG) in Lambert-Eaton syndrome

Vincenzo Todisco et al. Clin Neurophysiol Pract. .

Abstract

Objective: To report the clinical features and the neurophysiological approach of a patient with Lambert-Eaton myasthenic syndrome (LEMS), highlighting the diagnostic role of the stimulated single fiber electromyography (sSFEMG).

Case report: A 60-year-old woman presenting with the LEMS triad (proximal and axial weakness, autonomic dysfunction and areflexia) was evaluated by neurophysiological tests (electroneuromyography, repetitive stimulation test (TSR), voluntary and stimulated SFEMG). We reported: 1) increase of compound muscle action potential (CMAP) amplitude (>60%) following brief isometric exercise compared to the rest (baseline); 2) decremental/incremental response of CMAP amplitude at low- (3 Hz) and high-frequency (30 Hz) repetitive stimulation test (RST), respectively; 3) increased neuromuscular jitter and blocking at voluntary single-fiber electromyography (vSFEMG); 4) stimulation rate-dependent reduction of the neuromuscular jitter and blocking at sSFEMG. Diagnosis was confirmed by serological demonstration of circulating voltage gated calcium channels (VGCC) antibodies.

Significance: The present case highlights the role of the sSFEMG in the diagnosis of LEMS, underling the stimulation rate-dependency of both neuromuscular jitter and blocks.

Keywords: Lambert-Eaton myasthenic syndrome (LEMS); Neuromuscular jitter; Stimulated single fiber electromyography (sSFEMG).

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Figures

Fig. 1
Fig. 1
Neurophysiological tests in LEMS. Representative neurophysiological diagnostic approach in patients with LEMS. (A) the baseline low amplitude of the median nerve compound muscle action potential (CMAP) from right abductor pollicis brevis (APB) was significantly increased after brief isometric exercise; (B) in the same muscle, low- (LF) and C) high-frequency (HF) repetitive stimulation test (RST) showed significant decremental (B) and incremental response (C), respectively.
Fig. 2
Fig. 2
Frequency-dependent neuromuscular jitter in LEMS. Stimulated single-fiber electromyography (sSFEMG) demonstrated a frequency-dependent reduction of the neuromuscular jitter values at the increase of the stimulation rate.
See this image and copyright information in PMC

References

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