Repetitive nerve stimulation in juvenile myasthenia gravis: Diagnostic strategy and area decrement value.

BACKGROUND: Juvenile myasthenia gravis (JMG) poses diagnostic challenges, and repetitive nerve stimulation (RNS) sensitivity in children lags behind that in adults. We aimed to characterize RNS-positive JMG and identify strategies to improve diagnostic yield. METHODS: We retrospectively analyzed 105 JMG children (January 2019-April 2025), comparing RNS-positive and RNS-negative groups on key clinical variables. RNS characteristics were further examined by onset site, nerve stimulated, stimulation frequency, and measurement parameter. RESULTS: (1) RNS-positive children were more likely to develop severe or refractory disease. (2) Ocular weakness was the predominant initial manifestation. The facial nerve showed the highest RNS positivity rate. (3) A decremental response was most frequently observed at 3 Hz stimulation, with 5 Hz stimulation serving as a useful supplementary frequency. (4) CMAP (compound muscle action potential) area decrement can be a valuable adjunct to amplitude decrement in suspected JMG cases. CONCLUSIONS: RNS is an essential diagnostic tool in JMG. To maximize diagnostic yield while accommodating children's cooperation levels, clinicians and technicians should adopt age-appropriate protocols-selecting optimal nerves for stimulation, applying complementary stimulation frequencies, and evaluating both amplitude and area decrements. Children with confirmed RNS positivity warrant close monitoring and timely therapeutic intervention.