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The Intensity of Downbeat Nystagmus during Daytime
Author(s) -
Spiegel Rainer,
Rettinger Nicole,
Kalla Roger,
Lehnen Nadine,
Straumann Dominik,
Brandt Thomas,
Glasauer Stefan,
Strupp Michael
Publication year - 2009
Publication title -
annals of the new york academy of sciences
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.712
H-Index - 248
eISSN - 1749-6632
pISSN - 0077-8923
DOI - 10.1111/j.1749-6632.2009.03865.x
Subject(s) - daytime , supine position , sitting , intensity (physics) , medicine , fixation (population genetics) , morning , audiology , physics , optics , atmospheric sciences , population , environmental health , pathology
On the basis of reports by patients with downbeat nystagmus (DBN) that their symptoms were worse during the morning but better during the daytime, we investigated whether the intensity of DBN changes during the daytime. DBN was measured at 9 am, 11 am, and 1 pm. The mean peak slow phase velocity (MPSPV) of DBN was determined in different eye positions, with and without fixation, as well as in three different body positions: sitting upright, lying supine with the nose up, and lying prone with the nose down. Twelve patients with DBN either due to cerebellar degeneration or of idiopathic etiology were examined. The major findings of this study were as follows. First, the intensity of DBN significantly decreased during the daytime. When measured in the sitting upright position and primary eye position, MPSPV decreased from 4.32 deg/sec (±SEM 1.02) at 9 am to 2.12 deg/sec (± 0.5) at 11 am ( P < 0.01) and stayed constant around 1.93 deg/sec (± 0.57) at 1 pm ( P < 0.01 from 9 am to 1 pm) and 2.08 deg/sec (± 0.75) at 3 pm ( P < 0.01 from 9 am to 3 pm). Second, this change did not depend on fixation during the measurements. Third, this effect was not influenced by the eye position during the measurements (upward, downward, or straight ahead). Our data show that the intensity of DBN decreases during the daytime. This decrease correlates with the symptoms of the patients. This change during daytime did not depend on visual fixation. Another possible mechanism is the modulation of DBN by head position relative to gravity, that is, by otolith input. This should be evaluated in further studies.