Abstract Details

Title Visual contrast threshold at 15 Hz is able to confirm visual snow syndrome in individual patients

Topic Headache

Presentation(s) S20 - Headache Imaging and Physiology and Episodic Syndromes Associated with Migraine (4:14 PM-4:25 PM)

Poster/Presentation
Number 005

Background Patients with VS suffer from a continuous TV snow-like visual disturbance in the entire visual field that might reduce the contrast perceived. Currently, the only objective measure is hypermetabolism of the lingual gyrus found at the group level. In clinical practice, however, individual patients present with subjective symptoms, and objective measures are lacking to confirm the diagnosis.

Objective To confirm the presence of visual snow syndrome (VS) in the individual patient. We tested the hypothesis that patients with VS have an increased threshold for detecting visual contrasts.

Design/Methods Twenty patients with VS were compared to 20 age-, gender-, migraine- and aura-matched controls. Subjects were randomly presented vertically left or right tilted bars flickering at six different frequencies (15Hz, 20Hz, 25Hz, 30Hz, 35Hz, 40Hz). The contrast threshold was measured in a two-alternative adaptive forced-choice procedure (QUEST) for the discrimination between the two image orientations. The threshold was defined as the log10 (Michelson-Contrast) necessary to achieve the correct response in 75% of the cases.

Results The 75% contrast threshold at 15 Hz was significantly higher in VS patients compared to controls (0.601 Wilks-Lambda p=0.007; -1.94±0.13 vs. -2.26±0.37, T=-3.71, p=0.001, MANOVA). The AUC for the ROC curve of 75% contrast threshold at 15 Hz was 0.73±0.09. A contrast threshold of -2,00 is able to support the diagnosis of VS in an individual patient with a sensitivity of 80% and a specificity of 70%.

Conclusions The visual 75% contrast threshold measured at 15 Hz is the first technical test that might be able to confirm the hitherto purely subjective and history-driven diagnosis of VS in an individual patient.

Authors/Disclosures
Christoph J. Schankin, MD (Department of Neurology, Inselspital, Bern University Hospital) PRESENTER	The institution of Dr. Schankin has received personal compensation in the range of $500-$4,999 for serving as a Consultant for Lilly. The institution of Dr. Schankin has received personal compensation in the range of $500-$4,999 for serving as a Consultant for Teva. The institution of Dr. Schankin has received personal compensation in the range of $500-$4,999 for serving on a Scientific Advisory or Data Safety Monitoring board for Lilly. The institution of Dr. Schankin has received personal compensation in the range of $500-$4,999 for serving on a Scientific Advisory or Data Safety Monitoring board for Lundbeck. The institution of Dr. Schankin has received personal compensation in the range of $500-$4,999 for serving on a Scientific Advisory or Data Safety Monitoring board for Novartis. The institution of Dr. Schankin has received personal compensation in the range of $500-$4,999 for serving on a Scientific Advisory or Data Safety Monitoring board for Teva. The institution of Dr. Schankin has received personal compensation in the range of $500-$4,999 for serving on a Speakers Bureau for Grünenthal. The institution of Dr. Schankin has received personal compensation in the range of $500-$4,999 for serving on a Speakers Bureau for Lilly. The institution of Dr. Schankin has received personal compensation in the range of $500-$4,999 for serving on a Speakers Bureau for Novartis. The institution of Dr. Schankin has received personal compensation in the range of $5,000-$9,999 for serving on a Speakers Bureau for Teva. The institution of Dr. Schankin has received personal compensation in the range of $500-$4,999 for serving on a Speakers Bureau for Lundbeck. Dr. Schankin has stock in Zynnon.
	No disclosure on file
	No disclosure on file
	No disclosure on file
Andreas Straube	Andreas Straube has received personal compensation in the range of $500-$4,999 for serving on a Scientific Advisory or Data Safety Monitoring board for TEVA. Andreas Straube has received personal compensation in the range of $500-$4,999 for serving on a Speakers Bureau for TEVA. Andreas Straube has received personal compensation in the range of $500-$4,999 for serving as an Expert Witness for Novartis.

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