Brown's syndrome with contralateral inferior oblique overaction: a possible mechanism.

The simultaneous occurrence of Brown's syndrome in one eye and inferior oblique overaction in the other eye is an infrequently reported association. Review of our series of 38 cases of Brown's syndrome disclosed six patients with overaction of the contralateral inferior oblique, of whom four stepped out to contralateral superior oblique palsy. We propose that these patients initially have bilateral Brown's syndrome in infancy, and spontaneous resolution occurs in one eye only. While Brown's syndrome is present the antagonist inferior oblique muscle undergoes isometric contracture. With spontaneous resolution of Brown's syndrome a relative imbalance of forces occurs, with the superior oblique muscle now being relatively paretic compared with the contracted and fibrotic inferior oblique. Up-shoot in adduction then becomes apparent.