Repetitive nerve stimulation of anconeus in the assessment of neuromuscular transmission disorders.

Repetitive nerve stimulation of the anconeus muscle is described. Control studies showed the test to be reliable and well tolerated over a range of stimulus frequencies and train lengths. Sixty-one patients with primary disorders of neuromuscular transmission were tested. Repetitive nerve stimulation of anconeus was abnormal in 2 of 21 patients with ocular myasthenia, but showed a significant decrementing response in 16 of 30 patients with generalized myasthenia gravis. In comparison with other muscles, repetitive nerve stimulation of anconeus was more sensitive than abductor digiti minimi, but equally sensitive as deltoid. The test may also be used to help characterize other disorders of neuromuscular transmission such as congenital myasthenia or the Lambert-Eaton myasthenic syndrome. Compared with single fibre EMG on extensor digitorum communis, repetitive stimulation of anconeus was usually, but not always, a less sensitive method of detecting a neuromuscular transmission disorder.