Teaching NeuroImages: Acute Parinaud syndrome.

An 82-year-old man with atrial fibrillation, nonadherent to rivaroxaban, presented with sudden bilateral ptosis. Examination demonstrated bilateral ptosis (figure 1), pupils midline, fixed midsize, not reactive to light but constricting to accommodation, impaired vertical eye movements, paresis of superior greater than inferior rectus, and upgaze convergence nystagmus. MRI showed infarction of bilateral third nerve nuclei and mesial thalami consistent with an artery of Percheron infarct (figure 2), presumed cardioembolic origin. Artery of Percheron is a single P1 branch that supplies the bilateral paramedian thalami and rostral midbrain. Infarcts may present with vertical gaze palsy, memory impairment, and impairment of arousal. AUTHOR CONTRIBUTIONS Emily Swinkin drafted the manuscript, edited images for the publication, and revised the manuscript. Esther Bui conceptualized the study, obtained images for the manuscript, and revised the manuscript for intellectual content.