Differentiating Decompensated Superior Oblique Muscle Dysfunction From Ischemic Fourth Cranial Nerve Palsies (.pdf)

Isolated fourth cranial nerve palsies are commonly caused by decompensation of a dysfunctional superior oblique muscle ('decompensated palsies'). The differentiation of this cause from palsy caused by presumed microvascular ischemia ('ischemic palsy') at the time of initial diagnosis has value. The diagnosis a decompensated palsy is traditionally suggested by finding abnormally high vertical fusional vergences. This study was undertaken to discover if abnormally high fusional vergences are reliable in this task and whether there are other clinical characteristics that could fortify the differentiation between these two causes.