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

Objective: 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. Patients: A patient with AOM complicated by serous labyrinthitis on the left side. Intervention: Video nystagmography and 3D fluid attenuated inversion recovery (FLAIR) magnetic resonance imaging (MRI). Main outcome measures: 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.

Results: 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.

Conclusions: 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.