Activation tests in the diagnosis of myasthenia gravis using repetitive stimulation

: 145 patients with confirmed myasthenia gravis were examined by repetitive stimulation at a frequency of 2-3 s-1. A decrement of the proximal muscles at rest was demonstrated in 116 (80%) of the patients and the deltoid muscle was most sensitive. In 29 patients without a significant decrement at rest activation test were supplemented. Prolonged maximum isometric contraction for a period of 1 minute revealed a subsequent decrement in 13 patients. The ischaemic test was positive in 5, incl. 1 where activation by isometric contraction was negative. The total number of patients, where impaired neuromuscular transmission was diagnosed by repetitive stimulation, increased to 130 (90%) when activation tests were used. The described activation tests are technically unpretentious, non-invasive and can be used in routine practice of any EMG laboratory.