Pupil-sparing complete third nerve palsy from cryptogenic midbrain stroke in an otherwise-healthy young adult with patent foramen ovale

Although pupil-sparing in acute unilateral complete third nerve palsy is often a sign of ischemic nerve injury, it is not specific for injury outside of the midbrain. This report documents acute pupil-sparing complete third nerve palsy in an otherwise healthy young adult with patent foramen ovale and associated atrial dilatation who suffered cryptogenic focal midbrain stroke, presumably from a paradoxical embolism. The patent foramen ovale was surgically closed. Over the next several months neurological recovery was complete except for diplopia and relatively comitant hypotropia, which responded well to conventional strabismus surgery.