A 15-year-old, right-handed Hispanic boy with B-cell acute lymphoblastic leukemia (ALL) was transferred for acute onset of stroke-like symptoms. Appoximately 6.5 hours prior to arrival, the patient was in his normal state of health. At that time, he developed abrupt onset of headache and left arm tingling described as "ants crawling on my arm." He described associated dysarthria, dysphagia, and progression of symptoms over the first hour to include left lower extremity paresthesias. By the time of neurologic consultation, he reported some subjective improvement in left leg sensory deficits but was weak throughout his left hemibody. Past medical history was notable for B-cell ALL diagnosed 3 months earlier, for which the patient had undergone induction chemotherapy with vincristine, daunorubicin, pegylated asparaginase, and intrathecal methotrexate (IT-MTX) and cytarabine. He achieved remission and was being treated with consolidation chemotherapy consisting of systemic cyclophosphamide, cytarabine, mercaptopurine, vincristine, pegylated asparaginase, and IT-MTX. His most recent lumbar puncture with IT-MTX was 10 days prior to presentation, at which time CSF analysis had shown white blood cells 2/mm 3 , red blood cells 2/mm 3 , and unremarkable cytology (a few normal-appearing lymphocytes). Family history was negative for stroke. The patient denied current tobacco, alcohol, or drug use.Initial temperature was 98.9°F, blood pressure 112/52 mm Hg, heart rate 110, respirations 20, oxygen saturation 100% on room air. Examination demonstrated intact mental status. Cranial nerves were intact except for a left lower facial droop. Motor examination showed 5/5 strength throughout the right hemibody and 4/5 strength throughout the left. Deep tendon reflexes were 2ϩ throughout with flexor plantar responses. Sensation was decreased to pinprick over the left lower extremity from the thigh distally. Coordination was intact but gait was slightly wide-based.Initial laboratory assessment showed white blood cells 3,500/mm 3 , hemoglobin 7.4 g/dL, platelets 58,000/mm 3 , international normalized ratio 0.92, creatinine 0.4 mg/dL, all stable from prior values. Electrolytes were within normal limits. CT of the head was negative for acute abnormality.

SUMMARYTypical causes of internuclear ophthalmoplegia (INO) include arterial infarcts, demyelinating conditions, inflammation and trauma. We here report the unique case of a 33-year-old man with INO of the right eye caused by infarction of the right midbrain, confirmed by diffusion-weighted MRI. At presentation he displayed impaired adduction of the right eye with normal movement of the left. CT angiogram revealed an underlying developmental venous anomaly (DVA), raising the concern of venous infarction. His symptoms improved with aggressive management of blood pressure and risk factors. The patient had vascular risk factors-smoking, hypertension and dyslipidaemia-and we theorise that the hyalinised and inelastic walls of our patient's DVA were more vulnerable to the thrombogenic effects of his risk factors, predisposing him to this event. Venous infarcts owing to DVA are rare. To our knowledge INO secondary to venous infarct has not been reported, and should be considered in the differential of such cases. BACKGROUND