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jIdeofor K Ndulue, Sachin Kedar, David Whitney, James Shou, Diego Torres; The neuro-ophthalmology of orthostatic tremor. Invest. Ophthalmol. Vis. Sci. 2018;59(9):2184.
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Orthostatic tremor (OT) is a rare neurological disease due to abnormal activation of the ponto-cerebello-thalamo-cortical pathway producing a characteristic 13-18 Hz tremor of the extremities upon standing. We report the neuro-ophthalmic features in OT.
We studied 52 OT and 22 control subjects. We measured visual acuity; contrast sensitivity (CS; 5/2.5%), stereo-acuity, near point convergence (NPC), ocular alignment (distance and near) and thickness of retinal nerve fiber layer (RNFL) and ganglion cell layer (GCL-IPL) using Cirrus OCT. Ocular fixation (sitting and standing) and motility (range, saccade, pursuits, fast and slow vestibulo-ocular reflex (VOR) and VOR cancellation) was clinically assessed. NEI-VFQ-25 questionnaire was administered by in-person interview. Chi square was performed to compare categorical variables while Mann-Whitney test and Spearman’s correlation coefficients were used to asses for associations between continuous variables.
The OT cohort had 84% female subjects. Mean OT disease duration was 7.7 ± 5.6 years. We found no differences between OT and controls for visual acuity, contrast sensitivity, stereo-acuity and thickness of the RNFL and GCL-IPL layers. For distance, 6 (11.5%) OT and 2 (9%) control subjects had esophoria; 18 (35%) OT and 3 (14%) control subjects. At near, no OT or control subject had esophoria, however, 37 (71%) OT and 14 (64%) control subjects had exophoria. We found no difference in NPC, fusional convergence and divergence amplitudes, between OT and control. Forty-five OT (87%) developed orthostatic tremors within 5 minutes of standing. None of these subjects developed abnormal eye movements upon standing. There was no significant correlation between disease duration and visual acuity, contrast acuity, NPC, fusional convergence or divergence amplitudes, RNFL and GCL thickness. On NEI-VFQ-25, general health subscale score was significantly worse in OT patients compared to controls (median: 50 vs 75; p = 0.01). However, there was no significant difference in other subscale and overall composite score (OCS) between OT patients and control. Longer duration of OT correlated positively with a better OCS (r = 0.38; p < 0.00).
OT does not involve the afferent and efferent visual pathway. Lack of abnormalities of ocular motility and alignment suggest that ocular motility centers in the pontine tegmentum are spared in OT.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.
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