Stimulation single fibre EMG concentric needle

Stimulation single fibre EMG recording kindly donated by Dr. Spas Getov, SpR in clinical neurophysiology, Kings College Hospital. Patient referred with question of myaesthenia gravis. Intermittent diplopia and ptosis, positive AChR antibodies. Stimulating facial nerve at zygomatic arch with monopolar needle at 10 Hz. Recording orb. oculi with concentric facial needle electrode. The large potential in centre of the screen shows increased jitter and blocking. Stimulation intensity was increased to confirm that this was not due to sub-optimal stimulation of the axon. Potentials obtained with concentric needles are often superimpositions of two or more single fibre potentials, as is probably the case here. Nonetheless concentric needle single fibre EMG can detect increased jitter and blocking, although the sensitivity may be a little lower than with single fibre needle electrodes.