Научные исследования

In-depth research (using questionnaires and interviews) into patients suffering from Visual Snow Syndrome, and establishes that the condition is a real and unique syndrome. It proposes diagnostic criteria for VS and explains what the core symptoms are and their prevalence. If you are interested in reading the research into VS, this would be the best starting place.

A poster presentation of earlier research conducted by Schankin et al that feeds into the above 2014 study.

Finds that changes in how the water flows through the brain are not responsible for Visual Snow Syndrome; this was significant as it has been shown that changes in water diffusion and perfusion in the brain are linked to migraine. Therefore, they suggested for the first time that VS should be treated separately from migraine with persistent aura.

Shows that Visual Snow Syndrome patients who also suffer from migraines have a greater likelihood of suffering from palinopsia, spontaneous photopsia, photophobia, nyctalopia and tinnitus. Therefore, they conclude that migraine aggravates VS symptoms. Additionally, they found that typical migraine aura does not impact VS symptoms, and since it is a common problem alongside the Syndrome, they conclude that the conditions may share pathophysiology (i.e. they may be caused by the same physical processes in the brain). Using PET scans, they also found that there was hypermetabolism in the right lingual gyrus and left cerebellar anterior lobe in the brains of VS patients. This is significant as it is the first objective finding in VS (i.e. we can see that there is actually something wrong!). Notably, the same parts of the brain have more blood moving through them during light sensitivity during a migraine, confirming overlap between migraine and VS. They also suggest that tinnitus, given how prevalent it is, may be another core symptom of Visual Snow Syndrome.

Explains how Visual Snow Syndrome behaves differently to persistent migraine aura, both in how the symptoms present themselves (VS affects the vision in a uniform manner, whereas migraine is homonymous) and the electrophysiological activity in the brain. They then review previous literature, explain what the symptoms of VS are and how it relates to migraine and typical migraine aura. In general, it gives a good overview of what Visual Snow Syndrome is and the important research that has been done into it – another good read!

This piece reviews all of the main literature on VS to date. Here’s its summary: “Recent evidence suggests visual snow is a complex neurological syndrome characterized by debilitating visual symptoms. It is becoming better understood as it is systematically studied. Perhaps the most important unmet need for the condition is a sufficient understanding of it to generate and test hypotheses about treatment.”

Only the first page or so is relevant, but it includes some brief thoughts from three reputable neurologists on Schankin et al’s 2014 study, as well as some suggested further reading.

Reviews the symptoms of 32 patients with Visual Snow Syndrome. Notably, it highlights the prevalence of tremor in VS patients, a symptom rarely mentioned in relation to the condition. They explore how colour filters can reduce the severity of VS symptoms, particularly filters that are in the yellow-blue spectrum. Since VS is associated with tinnitus, tremor, migraine, and palinopsia, and is related to colour-dependant processing (evidence by the impact that coloured filters have on symptoms), they conclude that VS may be the result of an imbalance of koniocellular and magnocellular pathway function creating a thalamocortical dysrhythmia that results in a disorder of visual processing. Unfortunately, the paper does not explain what this means. However, the koniocellular and magnocellular pathways are two distinct visual pathways carrying information from the retina to the brain. The koniocellular pathway is responsible for high-definition visual perception, and helps you identify shapes. The magnocellular pathway is less high-definition, and helps you perceive motion. The study is essentially saying that there is an imbalance between these two pathways, which disturbs key signals that travel between the thalamus and the cortex in the brain, leading to VS symptoms. It is difficult to understand, but to read more about thalamocortical dysrhythmia, click here.

Reviews and describes previous studies and literature regarding migraines generally as well as Visual Snow Syndrome. Notably, its expands upon the potential role of the lingual gyrus by suggesting that it is important in adjusting the brightness of light perception. It proposes that healthy subjects have an active system in the visual cortex which suppresses the symptoms experienced by VS patients – the lingual gyrus is thought to be key in this system. It is believed that since the lingual gyrus is overactive in VS patients, the suppression system malfunctions and fails to subdue VS symptoms. It also notes how in previous studies’ treatments, which can be useful in reducing migraine symptoms, are often ineffective for VS patients but are worth trying following a diagnosis. It suggests that Verapamil, a treatment for certain types of migraine, may be prescribed when other medicines fail.