Each eye is examined with the other covered (this is called ductions). The patient is unable to adduct either the left or the right eye. If you watch closely you can see nystagmus upon abduction of each eye. When both eyes are tested together (testing versions) you can see the bilateral adduction defect with nystagmus of the abducting eye. This is bilateral internuclear ophthalmoplegia often caused by a demyelinating lesion effecting the MLF bilaterally. The adduction defect occurs because there is disruption of the MLF connections between the internuclear abducens nucleus and the lower motor neurons in the oculomotor nucleus that innervate the medial rectus muscle. NeuroLogic Exam has been supported by a grant from the Slice of Life Development Fund at the University of Utah, the Department of Pediatrics and the Office of Education at the University of Nebraska Medical Center. Viewing the video requires installation of the free QuickTime Plug-in.
