Isolated vertical ophthalmoplegia caused by bilateral rostroventral midbrain infarction.

Abstract

Midbrain infarctions involve the oculomotor nerve, usually in association with other neurological deficits. Sometimes infarcts are so small that they only cause isolated palsies of the oculomotor nerve, or only one or two extraocular muscles. Several cases of partial oculomotor palsies caused by small lesions of the oculomotor fascicles in the midbrain have been reported, on the basis of which, models of the spatial arrangement of oculomotor nerve fascicles have been proposed [1–12]. We report a case of isolated vertical ophthalmoplegia and pupillary abnormality caused by bilateral rostroventral midbrain infarction. From the neurological findings that correlated with radiographic findings, bilateral oculomotor nerves were considered to be impaired at the level of infranuclear fascicles. The findings of our case provide new insight into the rostrocaudal distribution of the fascicles of the oculomotor nerve. An 82-year-old man with a 15-year history of hypertension presented with bilateral vertical ophthalmoplegia. Eight days before admission, he suddenly developed lethargy and was slightly disoriented. The pupils were round and isocoric (4 mm) under moderate lighting conditions and reacted sluggishly to light, which suggests the involvement of the pupillomotor system bilaterally to some extent considering his age. Vertical eye movements were completely lost in both directions. Horizontal eye movement was intact for both smooth pursuit and saccades. No diplopia, nystagmus, or ptosis was noted. The oculocephalic reflex (OCR) in both vertical directions and Bell’s phenomenon were bilaterally absent, suggesting infranuclear partial oculomotor palsies. Hess charts could not be performed because he had difficulty in comprehending instructions. He had normal motor, cerebellar, and sensory functions without pathological reflexes. All of his laboratory data were within normal limits. The findings of transthoracic echocardiogram, electrocardiogram, and 24-h Holter monitoring were normal. Carotid ultrasonography only showed an isoechoic plaque (1.5 mm) in the left common carotid artery. Brain MRI conducted on admission 8 days after the onset of symptoms revealed an acute cerebral infarction extending from the bilateral ventromedial parts of the upper midbrain to the left ventromedian area of the thalamus (Fig. 1). MR angiography revealed no marked stenosis or aneurysm of main arteries. Although angiographic evidence was not available, the infarct was probably caused by occlusion of the left paramedian thalamic artery. The patient was treated with an antiplatelet medication and discharged 12 days after admission with improvement of vertical ophthalmoplegia. Our patient presented with bilateral vertical ophthalmoplegia and pupillary abnormality without ptosis or horizontal eye movement disorders. The rostral interstitial nucleus of the medial longitudinal fasciculus (riMLF), which is closely associated with vertical gaze, was not damaged, as determined from MRI findings [13]. The absence of both vertical OCR and Bell’s phenomenon strongly suggests infranuclear oculomotor palsies. The neurological and radiological findings are consistent with partial fascicular oculomotor palsies sparing the fascicles innervating the medial rectus and levator palpebrae muscles. The precise spatial arrangement of oculomotor nerve fascicles is not yet elucidated. On the basis of the combination of neurologically proven oculomotor dysfunctions, H. Naruse (&) Y. Nagashima R. Maekawa Y. Shiio Department of Neurology, Tokyo Teishin Hospital, 2-14-23, Fujimi, Chiyoda-ku, Tokyo 102-8798, Japan e-mail: hinaruse-tky@umin.ac.jp