Direction-Changing Positional Nystagmus in Acute Otitis Media Complicated by Serous Labyrinthitis: New Insights into Positional Nystagmus.

To demonstrate characteristic nystagmus findings in acute otitis media (AOM) complicated by serous labyrinthitis and discuss the mechanism of direction-changing positional nystagmus (DCPN) in this condition.A patient with AOM complicated by serous labyrinthitis on the left side.Video nystagmography and 3D fluid attenuated inversion recovery (FLAIR) magnetic resonance imaging (MRI).Characterize positional nystagmus in a head-roll test observing the change of nystagmus direction in process of time and compare findings of temporal bone 3D FLAIR MRI.A previously healthy 50-year-old man who complained of acute otalgia, hearing loss, and vertigo was diagnosed with AOM complicated by serous labyrinthitis on the left side. A head-roll test performed on the day when vertigo developed showed persistent geotropic DCPN. While pre- and postcontrast T1-weighted MRI showed no signal abnormality in both inner ears, 10-minute delay postcontrast 3D FLAIR image showed enhancement in the inner ear on the left side. Four-hour-delay postcontrast 3D FLAIR images showed more conspicuous enhancement of the whole cochlea, vestibule, and semicircular canals on the left side.In AOM complicated by serous labyrinthitis, density of perilymph may increase due to direct penetration of cytokines and other inflammatory mediators from the middle ear into perilymph and breakdown of blood-labyrinth barrier that causes vascular leakage of serum albumin into perilymph. The density difference between perilymph and endolymph makes the semicircular canal gravity sensitive. A buoyant force is also generated by gravity, causing indentation of endolymphatic membrane in the ampulla and cupula displacement. Thus, at the early stage of serous labyrinthitis, a head-roll test may elicit persistent geotropic DCPN, of which the direction can be changed over time.