Description of the Neurovisual and Radiological Specificities of Patients With Visual Snow

Visual snow syndrome (SNV) is characterized by a continuous grainy or pixelated visual sensation additional to the perceived image. Patients often report a feeling similar to seeing noise from cathode-ray televisions.

The prevalence is not well known but about 2% of the population could be reached. Although benign and stable, this pathology is often troublesome in everyday life.

Its precise etiology remains unknown to this day. Ophthalmologic explorations do not reveal any significant abnormalities. Neurologically, "standard" examinations appear normal. Only the examinations carried out in the context of research have been able to highlight anomalies such as an imbalance between visual cortical inhibition and excitation as well as a high spontaneous neural triggering and hypermetabolism of the associative visual cortex (functional MRI, PET- MRI). In addition, the Visual Evoked Potentials show a lack of habituation, testifying to cortical hyperexcitability.

To our knowledge, no specific neurovisual study focusing on the functions involved in the processing of visual information has been carried out to date. We propose the realization of a complete evaluation made up of existing tasks as well as the adaptation of some of them specific to SNV.

The posterior abnormalities currently highlighted by imaging have been carried out in examinations not available on a daily basis. A non-invasive brain MRI study will be carried out in our patients using more recent techniques (MRI with arterial spin labelling or ASL for Arterial Spin Labelling, and diffusion tensor imaging or DTI for Diffusion Tensor Imaging) in order to search for possible posterior lesions and clinical radiological correlations.