Inferior oblique muscle palsy with "paradoxical" v-pattern strabismus.

Background and purpose: A- and V-patterns are commonly encountered with cyclovertical muscle palsies. Inferior oblique (IO) muscle palsy produces and A-pattern caused mainly by the decreasing abducting action of the IO in upgaze and an increasing abduction action of the superior oblique in downgaze. V-pattern association with an IO palsy has not been, to our knowledge, reported before. The purpose of our paper is to report on a patient iwth IO palsy and a paradoxical V-pattern and explain the proposed pathophysiology behind the V-pattern.

Case report: We report a 67 year old female with a 3 year history of diplopia. She met the Bielschowsky/Parks three step test to identify an IO muscle palsy, and she showed all the usual criteria of an IO muscle palsy except for a paradoxical V-pattern.

Conclusion: Many forces affect patterns in cyclovertical muscle palsies. A V-pattern in IO palsy can be explained by the spread of comitance resulting in inhibitional innervational pseudo-palsy of the superior rectus muscle resulting in V-exotropia or in inhibitional palsy of the contralateral superior oblique muscle resulting in V-esotropia.