Acute onset of upbeat nystagmus, exotropia, and internuclear ophthalmoplegia--a tell-tale of ponto-mesencephalic infarct.

Two patients were assessed for acute onset of diplopia. Clinical examination revealed upbeat nystagmus, exotropia, and internuclear ophthalmoplegia (INO). Both patients had vascular risk factors; acute ischemic stroke affecting ponto-mesencephalic junction was suspected. Magnetic resonance imaging confirmed strategic location of the acute infarct affecting the medial longitudinal fasciculus, adjacent occulomotor nuclei, and paramedian tract. We propose that constellation of acute onset of upbeat nystagmus, INO, and exotropia in patients with vascular risk factors might be unequivocal manifestation of the ponto-mesencephalic stroke.