Internuclear ophthalmoplegia of abduction. Isolated impairment of phasic ocular motor activity in supranuclear lesions.

Abduction saccadic movement slowed to either side without any limitation in the end position occurred in a patient. This ocular motor abnormality constituted a mirror image of the well-known internuclear ophthalmoplegia of abduction. Intermuclear ophthalmoplegia of either type demonstrates that a lesion between the center for conjugate gaze and the ocular motor nuclei can impair phasic activity of the eye muscles without reducing their tonic function.