[Acute peripheral vestibular lesions. Monocular subjective visual vertical and cyclodeviation]

Independent Measures of Utricular Function: Ocular Vestibular Evoked Myogenic Potentials Do Not Correlate With Subjective Visual Vertical or Fundus Photographic Binocular Cyclorotation

Ocular vestibular evoked myogenic potentials (oVEMPs), subjective visual vertical (SVV), and fundus photographically measured binocular cyclorotation (BCR) are diagnostic tests to assess utricular function in patients with vertigo or dizziness. In 138 patients with chronic vertigo or dizziness, we asked whether the asymmetry ratio of oVEMP (normal, right side pathological, left side pathological) could predict the SVV deviation (normal, rightward deviation, leftward deviation) or BCR (normal, cyclorotation to the right, cyclorotation to the left). There was no correlation between oVEMP and SVV and between oVEMP and BCR, while SVV and BCR correlated highly. Although both oVEMP and SVV measure aspects of utricular function, our findings demonstrate that oVEMP and SVV are not redundant and may reflect different utricular pathologies. The role of fundus photographic BCR may be relegated to only confirm unclear SVV results in vestibular diagnostic workup.

[Vestibular compensation : basic principles and clinical significance]

The vestibular system has the ability to repair deficits due to functional lesions, which is known as vestibular compensation. For successful function the performance of different receptors is less important than the bilateral balance of neuronal activity between the vestibular nuclei complexes. In this review based on data from animal experiments and clinical observations, the mechanisms of vestibular compensation, its time course and its clinical significance are described. Most of the clinical features can be explained by neuronal operations known from animal experiments. It must be emphasized that vestibular compensation is not a static phenomenon but a fluctuating process which can be influenced by therapeutic procedures. Vestibular compensation for static phenomena can be almost completely carried out, but for dynamic features only incompletely. These factors should be taken in account for diagnosis, therapy and assessment of vestibular disturbances.