BASIC AND CLINICAL ASPECTS OF VERTIGO AND DIZZINESS Prognosis of Idiopathic Downbeat Nystagmus Judith Wagner, a,c Nadine Lehnen, a,c Stefan Glasauer, b Michael Strupp, a and Thomas Brandt a a Department of Neurology, Klinikum Grosshadern, Ludwig-Maximilians University, Munich, Germany b Bernstein Center for Computational Neuroscience, Munich, Germany Downbeat nystagmus (DBN) is a common form of acquired involuntary ocular oscilla- tion overriding fixation. Little is known about the natural evolution of DBN in idiopathic cases. Therefore, eye movements were recorded in seven patients with idiopathic DBN by search-coil technique over a course of up to six years. Neither the slow-phase velocity (SPV) nor the dependency of the SPV on gaze position as an indicator of dysfunction of the oculomotor velocity-to-position integrator changed significantly over the time course investigated in this study. Key words: downbeat nystagmus; scleral search coil; flocculus Introduction Downbeat nystagmus (DBN) is a frequent form of acquired involuntary ocular oscillation overriding fixation. It is commonly caused by cerebellar disorders involving the (para-) floccu- lar lobe, such as cerebellar degenerative disease and posterior fossa infarction, and—rarely— brainstem lesions. In many cases, no underlying pathology can be detected, the so-called idio- pathic DBN. 1 In the case of secondary DBN, the prognosis depends on the course of the underlying disease. However, little is known about the natural evolution of DBN in idio- pathic cases. Therefore we recorded eye move- ments in seven patients with idiopathic DBN by search-coil technique over a course of up to six years. We show that neither the slow-phase velocity (SPV) nor the dependency of the SPV on gaze position as an indicator of dysfunction of the oculomotor velocity-to-position integra- tor 2 changes significantly over the time course investigated in this study. Address for correspondence: Judith Wagner, M.D., Department of Neurology, Ludwig-Maximilians University, Klinikum Grosshadern, Marchioninistraße 15, D-81366 Munich, Germany. judith.wagner@ med.uni-muenchen.de c Contributed equally Patients and Methods Seven patients with idiopathic DBN (three men, mean age at the time of the first record- ing 68 years) took part in the study. Three- dimensional eye and head movements were recorded at 1 kHz with dual search coils (Skalar, Delft, The Netherlands; Remmel Systems, Ash- land, Massachusetts, USA) placed on the left eye and the forehead at different points in time during a period of 2 to 6 years (mean 4 years). The three-dimensional SPV of DBN and its dependency on eye position were evaluated in different eye positions, as described previously. 2 Tests were performed in darkness, with a laser target point being visible throughout the whole experiment and with a flashed target that was visible for less than 100 ms. T-test for dependent samples was used to detect differences in SPV and its dependency on eye position between the first and last recording. Results Out of seven patients, two had three record- ings (baseline, two, and five years) and five had two recordings (baseline and two, three, five, or six years afterward). The individual Basic and Clinical Aspects of Vertigo and Dizziness: Ann. N.Y. Acad. Sci. 1164: 479–481 (2009). doi: 10.1111/j.1749-6632.2009.03767.x C  2009 New York Academy of Sciences. 479