Clinical Reasoning: A 12-Year-Old Girl With Acute Onset Diplopia, Dizziness and Upbeat Nystagmus.

We report a case of a 12-year-old girl who presented with acute onset diplopia, dizziness and upbeat nystagmus. On examination, she had right internuclear ophthalmoplegia (INO) with right eye hypertropia and exotropia and impaired convergence. In addition, she also had spontaneous primary position symmetric upbeat nystagmus. In this report, we discuss the clinical approach with meticulous neuro-ophthalmologic examination and neuroanatomical localization in pediatric patients with acute onset diplopia.