Electro-oculographic findings pre- and post-cochlear implantation.

Vestibular symptoms following cochlear implantation are relatively rare, in spite of well-documented evidence of a significant surviving vestibular neuron population in profoundly deaf individuals. This report details the electro-oculographic (EOG) findings before and after insertion of the Nucleus 22-channel cochlear implant in 25 adults. These findings are correlated to the clinical course of these patients.

Changes in the time constants of the vestibulo-ocular reflex and optokinetic afternystagmus following unilateral ablative vestibular surgery.

Changes in the time constants and gains of the vestibulo-ocular and optokinetic systems were studied in seven patients. Angular acceleration pulse and optokinetic stimuli were administered to three normal subjects and also to seven patients at specific intervals after unilateral ablative vestibular surgery. The gains and the time constants of the two systems were compared. Regression analysis showed that the vestibulo-ocular and optokinetic time constants for slow phase eye movements away from the ablated ear declined significantly after surgery in the patient group, but that the gains did not. A theory based upon variability of system parameters by the CNS is outlined to explain the changes in the dynamics of the two systems after surgery. The data from this study suggest that the time constant may be a useful parameter in clinical vestibular testing.

The reproducibility of caloric tests of vestibular function in young and old subjects.

The test-retest repeatability of the hot caloric response alone and of the hot and cold caloric responses combined, was evaluated in 29 subjects, over a 6-month period. The subjects were from two different age groups, 20-30 years (15 subjects) and 65-75 years (14 subjects). Intersubject variability was statistically significant in both age groups, though of greater magnitude in the older subjects. Once a vestibular caloric response baseline was established, for any given subject, there was reasonably reliable test-retest repeatability over time, in both age groups, with coefficients of reliability greater than 0.90.

Diagnoses in a dizziness unit.

Data are given on 2,515 patients who attended the Dizziness Unit on 3,113 visits. The sex incidence was 58% female, 42% male, and the sex preference most marked in the psychogenic group from ages 20 to 50. Dizziness is mainly a condition of middle-age; with a steadily aging population we can expect a disproportionate increase in patients with dizziness. Psychogenic dizziness was the commonest of all diagnoses (21.1%), followed closely by "undiagnosed"; together, these two comprised 40% of all diagnoses. Obviously, they deserve more clinical attention than such relatively rare conditions as delayed endolymphatic hydrops (0.5%) or inner ear fistula (0.4%). For all diagnostic categories, on repeated visits the original diagnosis was changed in about one-third of cases. Diagnostic conversion was most frequent in "undiagnosed", at a level of 58%.