| Abstract #769, Date 2/17/99, Session Y2, Poster (J34) |
| Otoneurological findings and pathophysiology of large vestibular aqueduct syndrome |
| *K. Funabiki, Y. Naito, I. Honjo (Kyoto University Graduate School of Medicine) |
Four patients with large vestibular aqueduct syndrome were included in this study. Three of the patients underwent endolymphatic sac closure surgery in the ear with worse hearing. In these patients, positional nystagmus evoked with the operated ear up was remarkably diminished, but that with the unoperated ear up continued to be evoked even after surgery, indicating that the positional vertigo in LVA patients is caused by the labyrinth which is situated superiorly in lateral head position. The frequency of vertigo attacks accompanying hearing deterioration was reduced after surgery in two patients. Another patient suffered from vertigo attacks even after surgery, which occurred along with the deterioration of hearing in the unoperated ear. In one patient who exhibited left beating spontaneous nystagmus and the deterioration of hearing in the left ear, VOR gain with horizontal rotaion toward left was relatively higher than that toward right. The electrolyte compositions of the endolymphatic sac fluid was measured in two patients who underwent surgery. In Patient 1, the concentrations of sodium (Na), potassium (K) and chlorine (Cl) of the fluid sampled from the endolymphatic sac were 140 mEq/l, 5.1 mEq/l and 109 mEq/l respectively. In this patient, the ratio of electrolyte concentration (Na : K : Cl) of the endolymphatic sac fluid (1 : 0.04 : 0.78) was similar to that of the perilymph (1 : 0.05 : 0.84) sampled during cochlear implantation performed simultaneously. Findings for endolymphatic sac fluid in Patient 2 (Na : K : Cl = 1 : 0.03 : 0.81) were very similar to those in Patient 1. These results suggest that hearing loss and vertigo attacks in patients with LVA may be caused by a mixture of endolymph and perilymph due to rupture of the membrane separating these two compartments. |