Analysis of characteristic eye movement abnormalities in internuclear ophthalmoplegia

Quantitative electro-oculographic recording techniques were used to analyze four characteristic eye movement abnormalities in 21 patients with internuclear ophthalmoplegia (INO). The frequency of each of the abnormalities was determined to suggest a pattern that is the most sensitive in detecting the syndrome of INO. Slowing of the adducting saccade was the most frequently found abnormality, being present in all patients. The other characteristic eye movement disorders were found less frequently: dissociated nystagmus at 30 degrees of eccentric gaze, dysmetria of the abducting eye, and limitation of adduction. The most sensitive pattern for detecting an INO seems to be slowing of the adducting saccade combined with either dissociated nystagmus or dysmetria of the abducting eye. Limitation of adduction was seen much less frequently.