A Case of Persistent Direction-Changing Positional Nystagmus with Sudden Sensorineural Hearing Loss

Sudden sensorineural hearing loss (SSNHL) often accompanies vertigo. A 52-year-old man with SSNHL showed persistent geotropic direction-changing positional nystagmus (DCPN) in the head-roll test, which was at first thought to occur due to “a light cupula in the horizontal semicircular canal on the affected side.” Six days later, the positional nystagmus changed to left beating direction fixed nystagmus (paralytic nystagmus). Furthermore, two months after discharge, the nystagmus changed to transient geotropic DCPN (“canalolithiasis” in the horizontal semicircular canal on the affected side), and subsequently turned again into persistent apogeotropic DCPN, thought to be caused by “cupulolithiasis;” this pattern persists until now. In the early stage, increase in the protein content of the endolymph, caused by the inner ear damage associated with SSNHL, may have increased the specific gravity of the endolymph, with consequent decrease in the relative specific gravity of the cupula, resulting in a “light cupula.” Thereafter, a possible gradual otolithic production of endolymph may have caused the mixed phenomenon of both “canalolithiasis” and “cupulolithiasis.” Finally, only “cupulolithiasis” has persisted for more than 3 months, and exercise therapy aimed at releasing the attached otolith onto the cupula, has not been entirely effective. These phenomena were thought to reflect a more severe chronic degenerative stage of SSNHL with vertigo than cupulopathy alone. Brain MRI showed no abnormal findings, while MRA showed serpiginous vertebrobasilar arteries. Hemodynamic vertebrobasilar insufficiency may cause peripheral hypoperfusion in the labyrinth, which could affect the density or viscosity of the endolymph. We speculate that disruption of endolymphatic homeostasis in SSNHL could have been involved in the transition of the nystagmus patterns in this case.