Fourth Nerve Paresis plus Crossed Horner Syndrome in Acute Leukemia

Abstract

A 29-year-old patient with diplopia showed a unilateral fourth nerve palsy combined with a Horner syndrome on the opposite side. Magnetic resonance images disclosed a focal hemorrhage in the left dorsal midbrain, affecting the nucleus of the fourth nerve and adjacent oculosympathetic fibers. Further evaluations including a bone marrow biopsy confirmed acute lymphoblastic leukemia. The combination of ocular motor and oculosympathetic palsy has a distinct localizing value. Fourth nerve palsy ipsilateral to Horner syndrome locates lesion in the cavernous sinus, while contralateral fourth nerve palsy locates the lesion in the midbrain.