Facioscapulohumeral dystrophy: jitter in facial muscles.

Motor end plate jitter was studied by single fibre EMG in the orbicularis oculi muscle of eight patients with facioscapulohumeral dystrophy activated by extramuscular nerve stimulation. The jitter was found to be slightly larger in comparison with the normal controls, although still within the normal limits in each patient. The findings are considered to indicate absence of any significant neuromuscular transmission disturbance, inflammatory or regenerative process, or reinnervation in progress. There was no evidence of muscle fibre conduction abnormality even in very weak muscle.