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December 1991

Superior Oblique Myokymia: Quantitative Characteristics of the Eye Movements in Three Patients

Author Affiliations

From the Departments of Neurology (Drs Leigh, Tomsak, and Dell'Osso and Mr Seidman) and Ophthalmology (Dr Tomsak), Case Western Reserve University, University Hospitals, and Department of Veterans Affairs Medical Center, Cleveland, Ohio.

Arch Ophthalmol. 1991;109(12):1710-1713. doi:10.1001/archopht.1991.01080120094034

• Using the magnetic search coil technique, we measured horizontal, vertical, and torsional rotations of both eyes of two patients with idiopathic superior oblique myokymia, and of the affected eye in a third patient. Superior oblique myokymia was strictly monocular and consisted of an initial intorsion and depression of the affected eye and subsequent oscillations with torsional and vertical components. The peak-to-peak torsional and vertical amplitudes of the oscillations were less than 1°, but peak velocities frequently exceeded 4°/sec in both planes. Fourier analysis indicated two features: (1) a broad range of frequencies up to about 50 Hz, indicating irregular oscillations; and (2) a superimposed larger-amplitude oscillation in the range from 1.5 to 6 Hz. Taken with electromyographic data from other studies, these results indicate that superior oblique myokymia reflects spontaneous discharge of trochlear motor neurons that have undergone regenerative changes.

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