[Neuro-otological study of Laurence-Moon-Biedl syndrome].

Two siblings of Laurence-Moon-Biedl (L-M-B) syndrome with nystagmus and/or sensorineural hearing loss were reported. One sibling had a slight hearing impairment as well as gaze and rebound nystagmus. The auditory brainstem responses (ABR) showed increased latencies of wave V on both ears. The optokinetic nystagmus (OKN) was limited toward the both horizontal sides. Nystagmus was superimposed on the eye tracking movement. Ocular hypermetria was observed, with bilateral weakness of caloric responses and even a failure of visual fixation suppression. Another sibling had a left-beating spontaneous nystagmus. The latencies of wave V of ABR were prolonged in both ears. The leftward OKN was limited and bilateral saccadic pursuits observed on eye tracking test. These results suggest that cerebellar of brain-stem lesions may be involved in L-M-B syndrome.

Effects of sodium bromate on ionic concentrations and osmolalities of the cochlear fluids in guinea pigs.

Effects of sodium bromate on cochlear potentials and electrolyte composition of the cochlear fluids in guinea pigs were investigated following administration of sodium bromate into the cochlea, using perilymphatic perfusion. Cochlear microphonics and the whole nerve action potential of the auditory nerve were markedly suppressed. The K+ and Cl- activities in the endolymph as well as the endocochlear dc potential (EP) decreased significantly and irreversibly, in proportion to the concentration of sodium bromate. A negative EP never developed during the monitoring of 120 min. Microsamples of the endolymph showed substantial decreases of K+ and Cl- concentrations and an increase in the concentration of Na+. Osmolality of the endolymph was much lower than that of the perilymph. The severe edema of the stria vascularis and collapse of Reissner's membrane were histologically evident. These events suggest a breakdown of the endolymph-perilymph barrier, coincident with an inhibition of the strial active transport, as a result of the ototoxic action of sodium bromate. The possible ion and water movement across the endolymph-perilymph barrier in the presence of sodium bromate is discussed.

Effect of glycerol on inner ear fluid electrolytes and osmolalities in guinea pigs.

Endolymph of the scala media (SM) and perilymph of the scala vestibuli (SV) and scala tympani (ST) were collected from the basal turn of anesthetized guinea pigs before and after intravenous administration of glycerol (3 g/kg). Sound-evoked responses were recorded during the test periods. Blood, CSF, and perilymph of the ST were also collected continuously after the injection. The osmolalities and chloride concentrations of the collected samples were determined. In another experiment, the continuous changes of potassium and chloride concentrations in endolymph and perilymph of the ST before and after the injection were measured by ion-selective electrodes. The osmolalities in CSF and perilymph lagged behind the increase in serum osmolality. The osmolalities in endolymph and perilymph increased gradually after the injection, reached maximum values after 90 minutes, and then decreased. The changes in chloride and potassium concentrations in endolymph and perilymph had similar tendencies. But the increases in chloride concentrations in perilymph of the SV and ST were much less than that in endolymph. We propose that most of the osmolality increase in perilymph is due to glycerol or other osmotically active substances and that the osmolality increase in endolymph is due to water shift.