The nystagmus blockage syndrome.

A previously unrecognized form of nystagmus associated with esotropia was described in the German literature by Adelstein and Cüppers in 1966 as the nystagmus blockage syndrome. Even though widely publicized in the European ophthalmic literature, this entity has remained virtually unrecognized in this country. We have identified the nystagmus blockage syndrome in 12 of 247 consecutive patients with congenital esotropia. The following characteristic features were encountered: onset of esotropia in early infancy, pseudoabducens paralysis, head turn toward the side of the fixating eye, absence of nystagmus with the fixating eye in adduction, and appearance of a manifest jerky nystagmus as the fixating eye moves into primary position and abduction. It has been suggested that the nystagmus is actively blocked by convergence innervation, the esotropia thus being caused by sustained convergence and secondary changes in the medial rectus muscles. The differential diagnosis includes crossed fixation and bilateral sixth nerve paralysis.