Direction-changing positional nystagmus towards the uppermost ear was noted in 8 of 14 normal subjects and in 7 of 16 patients with Meniere's disease given glycerol (1.5 g/kg). The slow phase velocities of the nystagmus reached a muximum about 3 hours after the oral administration of glycerol.
Positional nystagmus was suspected of originating from changes in the specific gravity of the endolymph caused by the infiltration of glycerol into the endolymphatic space, which may indicate that glycerol can pass through the bloodlabyrinth barrier.
It may be useful in the investigation of this barrier in patients with Meniere's disease to observe positional nystagmus in response to the glycerol test.
