The objective of this project is to improve diagnosis and treatment of patients with otoneurologic disorders. Three interrelated aspects of the projects are described. The investigators will continue to study dizzy patients with addition of these cases to their large database. This study will include precisely computer-controlled stimuli in a series of tests that measure various aspects of the vestibular systems. Eye movement and posture data are collected and analyzed on line. Results are entered into the database and continued refinement and identification of new cases of dizziness are ongoing in this project. In the second group of experiment, the investigators will study patients with familial periodic ataxia in which the disorder has been linked to a region on chromosome 19p. Experiments will be conducted to narrow this defect, possibly to a potassium channel disorder. The investigator's have collected several families with familial disorders and are following them clinically as well as evaluating them with molecular biology techniques. The third set of studies will correlate the pathology seen by light microscopy in the inner ear, nerve and brain stem with the data collected over several years on the patients in the clinical laboratory database. It is anticipated that 8-10 previously well studied patients will be available each year, as a result of death due to natural causes, for postmortem evaluations for their vestibular systems.