Neuro-Vestibular Diagnostics

Arbeitsgruppenleiter
Dr. Jörn Pomper

Mitarbeiter
Lena Gebert
Sebastian Scheidt
Melanie Wallscheid

The complaint of dizziness is highly prevalent but remains often an enigma to the physician in daily practice. Serious diseases potentially accompanied by dizziness like stroke, multiple sclerosis or brain tumors can easily be identified by brain imaging or other standard neurological techniques without the necessity to understand how dizziness evolves. The treatment of the underlying disease mostly relieves dizziness. The majority of patients suffering from dizziness, however, do not have an observable lesion. Here, the aim is to understand and to treat the underlying deficits within a pathophysiological framework of dizziness. Basically, we consider a disturbance of the perception of one’s own orientation relative to the outside world  the core pathologic correlate of the subjective experience of dizziness. Hence, affections of any neural system contributing to this perceptual stability would, in principle, be capable to elicit dizziness. Traditionally, emphasis has been placed on the vestibular system that is reflected in the current diagnostic repertoire. The integrity of semicircular canals, primary afferents and the vestibulocerebellum is evaluated by vestibular stimulation and the recording of eye movements dependent on vestibular stimulation. Currently used stimulation methods encompass caloric and rotatory stimuli with distinct accelerations (chair rotation, head-impulse-test). Eye movements are recorded by means of electrooculography, videooculography or search coils dependent on the problem to clarify. The integrity of otolith organs and their central connections is examined by applying acoustic or vibratory stimuli and evaluating evoked myogenic potentials of neck or facial muscles (cVEMP, oVEMP). Quantitative head-impulse-measurements using search coils and both VEMPs constitute innovative techniques that have extended our diagnostic repertoire and provided new explanations of some forms of previously mysterious forms of dizziness. The usage of these up-to-date techniques in the evaluation of patients suffering from dizziness is one of our group’s interests. To this end, we have established normative data over the last years. These new tests have allowed us to increase the percentage of patients in whom specific forms of dizziness can be diagnosed. On the other hand, a significant group of patients remains, in whom the dizziness remains „idiopathic“, i.e. unexplained. Objective measurements of deficits or proven concepts are scarce. Psychogenic origins and circumscribed deficiencies in sensorimotor processing are discussed but remain controversial. In order to make headway, the laboratory explores the possibility that some forms of idiopathic dizziness may be a consequence of dysfunctional sensorimotor processing related to perceptual stability. We apply and extent psychophysical techniques, many of them developed at the DCN during the last years. Psychophysical data are compared with validated questionnaires to infer their potential relevance for dizziness and their relationships to psychopathological conditions. For example, we conducted a study in patients with chronic dizziness in which we could not verify one of the widely assumed hypotheses of a maladjusted efference copy involved in visual perception.