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THE PARAMETERS OF SINGLE FIBRE EMG To detect abnormal neuromuscular transmission, two parameters are analysed: ‘jitter’ as an indicator of irregularity of neuromuscular transmission, and ‘blocking’ as an indicator of failure of transmission (Stålberg and Trontelj 1994). Each lower motor neurone arising from an anterior horn of the spinal cord connects with a number of muscle fi bres via the terminal branches of its axon. With discharge of the motor neurone, all the connected muscle fi bres fi re more or less simultaneously. Conduction of the discharge along the axon is fast but neuromuscular transmission from axon terminal to the muscle fi bre at the motor end plate is slower. And the transmission time across the motor end plate varies from one end plate to another. Even in the same motor end plate, it can differ from one fi ring to another. This variation is what is meant by jitter (Fig. 1a). While the variation in transmission time is least during regular fi ring of a muscle fi bre, it increases with irregular fi ring, and is most pronounced when the motor end plate is defective, as in myasthenia gravis HOW TO DO IT