Christoph Schankin, MD, a fellow in the Department of Neurology, University of California, San Francisco, Headache Center recently discussed visual snow at the 54th Annual Scientific Meeting of the American Headache Society. Sometimes patients with visual snow are diagnosed with persistent migraine aura or a perceptual disorder stemming from hallucinogen use. Also called positive persistent visual disturbance, people with visual snow see tiny, typically black and white dots in their visual field. The dots are always present, and patients have said that the colors can change quickly and often. At times, bright flashes, photophobia, floaters, color swirls and impaired night vision occur.
Results from Dr. Schankin’s study showed that 40 of the 57 patients with black and white visual snow said their visual symptoms occurred later in life. Seventeen of the patients had symptoms for as long as they could remember. Of the 40 patients who had had late-onset visual snow, 33% said they had experienced a headache during the week of onset, and 10% reported a visual aura. Of the participants studied, more than 54% had experienced migraine headaches, and 35% had typical migraine aura. Dr Schankin, and his colleagues made clear however that visual snow is a unique clinical syndrome – distinct from visual aura in migraine. Dr. Schankin said “However, migraine and migraine with aura are comorbidities, and we don’t know at the moment what the pathophysiological link is between these conditions.” Neurology Reviews August 2012