Superior oblique myokymia. An electromyographical analysis.

In a patient with superior oblique myokymia, the causative pathological motor unit was found by electromyography in the superior oblique eye muscle. Firing of this unit was somewhat irregular, but often assumed a nearly constant frequency around 35/s, so that the mechanical effect was mainly a tonic deviation rather than a tremor. Single discharges, analysed by computer averaging, showed a peculiar shape, prolonged duration, and high voltage, supranuclear control of the pathological unit was defective, although not completely lacking.