'Visual Snow' May Be a Distinct Clinical Entity

LOS ANGELES – So-called visual snow, characterized by myriad persistent tiny dots throughout the visual field, commonly occurs in patients with migraine, but it is usually accompanied by other visual symptoms and appears to be a distinct entity, according to combined data from two cross-sectional studies.

In a two-part study among 240 patients with visual snow, nearly all had other visual symptoms such as after-images or poor night vision, reported lead investigator Christoph Schankin, Ph.D., a postdoctoral clinical research fellow at the University of California at San Francisco Headache Center. Slightly more than half also had migraine, but the visual snow did not have any of the features of typical aura. Also, only a small minority of affected patients had used illicit drugs.

"Visual snow is almost always associated with additional visual symptoms. It therefore represents a unique clinical syndrome – the visual snow syndrome," he said at the annual meeting of the American Headache Society. "It is distinct from visual aura in migraine; migraine with and without aura are common comorbidities, but we don’t actually know at the moment what is the pathological link between those two conditions. And the intake of illicit drugs is not relevant."

Dr. Schankin went one step further, proposing new diagnostic criteria for the visual snow syndrome: visual snow plus at least three additional visual symptoms out of nine identified in the study, in the context where these symptoms are not consistent with typical migraine aura and cannot be attributed to some other disorder.

A session attendee congratulated the investigators on the research, noting, "These patients, for those who haven’t seen them, are devastated and lonely. Some can’t drive, some can’t work, some can’t read books, some can’t use computers. They are a wreck ... and there is nobody out there who is owning this condition – I don’t know if it falls in the realm of neuro-ophthalmology or neurology or headache, and what to do with these poor folks. ...They have been banished to the realms of psychiatry and have been told they have functional disorders and other things, when it is very clearly a widespread neurological perceptual disturbance."

He said his own experience with affected patients affirms the existence of the visual snow syndrome. "The more you talk to them, the more you appreciate that they really do have these features in common ... So I just want to thank you for bringing attention to this sort of orphan disorder, and hope it raises awareness, and that some people will take interest in it and studying the biophysiology and treatment options."

Session chair Dr. R. Allan Purdy, a neurologist at Dalhousie University in Halifax, N.S., asked the neuro-ophthalmologists present to weigh in with their thoughts on the possible pathophysiology of visual snow.

"I think this is a somewhat migrainous phenomenon in people with very sensitive brains," one replied. "We have done EEGs on these people and they are normal, at least in adults that we have seen with this. It is definitely real – these people are not making this up. And we have seen quite a few of these cases in neuro-ophthalmology."

Another concurred, saying "I think it’s real." Moreover, in her opinion, the presence of visual snow alone would be sufficient for diagnosis. "I suspect it’s migrainous because most of these people have migraines. But it’s not aura. I don’t know really what it is. It’s incredibly frustrating because nothing works. You can try every antiepileptic known to mankind, and nothing works. So I agree that this is something we need to pay attention to and help these people."

Dr. Schankin noted that research on visual snow is scarce, and affected individuals suffer in part because of a lack of knowledge about the condition in the medical community. "Patients are commonly given the diagnosis of persistent migraine aura or a posthallucinogen perceptual disorder, especially after LSD intake," he noted.

He and his coinvestigators studied members of an online support group for visual snow (Eye on Vision). In the first part of the study, they analyzed data from an Internet survey among 120 patients that asked about visual symptoms. They were 26 years old on average and about two-thirds were men.

Results showed that in addition to visual snow, nearly all patients reported other visual symptoms, such floaters (73%); persistent visual images (63%); difficulty seeing at night (58%); tiny objects moving on the blue sky (57%); sensitivity to light (54%); trails behind moving objects (48%); bright flashes (44%); and colored swirls, clouds, or waves when their eyes were closed (41%).

Dr. Schankin noted that some of these symptoms map onto the well defined clinical phenomena of palinopsia (trailing and prolonged after-images), photophobia, and impaired night vision.

And others fall into a category of entoptic phenomena, or visual symptoms originating in the eyes themselves, namely, floaters (likely protein aggregations in the vitreous fluid that cast a shadow on photoreceptors); photopsia (bright flashes typically elicited by mechanical stimulation of the eyes); Scheerer’s phenomenon (small moving objects against the sky thought to be due to blood cells moving in the retinal vessels that cast a shadow on the photoreceptors); and self-light of the eye (the colored swirls, clouds, and waves), whose etiology is unknown.

In the second part of the study, the investigators conducted telephone interviews with another 120 patients with visual snow to further explore the nature of symptoms and antecedent events. These patients were 31 years old on average and nearly evenly split between men and women.

Results showed that the textural patterns described for the snow varied considerably. The most common pattern reported was dots alternating from black (on light backgrounds) to white (on dark backgrounds) (48%), while some patients reported flashing dots, transparent dots, or other patterns. "We don’t know what that means – whether that has some pathophysiologic relevance," Dr. Schankin commented.

Analyses restricted to the subset reporting black and white dots showed that 98% had at least one additional visual symptom, and 93% had three or more. In this part of the study, another symptom identified was halos or starbursts, seen in 65% of cases.

Of the 40 patients with onset of visual snow later in life, 54% had a history of migraine. However, when asked about events in the week before the onset of visual snow, only 33% reported headache, and just 10% reported aura symptoms. But none had classic features of visual aura, such as unilaterality, zig-zag lines, or scotoma, during visual snow. Additionally, only 8% had used illicit drugs, mainly marijuana, in the week leading up to the start of visual snow, and none had significant ophthalmologic findings.

Dr. Schankin disclosed no relevant conflicts of interest.

LOS ANGELES – So-called visual snow, characterized by myriad persistent tiny dots throughout the visual field, commonly occurs in patients with migraine, but it is usually accompanied by other visual symptoms and appears to be a distinct entity, according to combined data from two cross-sectional studies.

In a two-part study among 240 patients with visual snow, nearly all had other visual symptoms such as after-images or poor night vision, reported lead investigator Christoph Schankin, Ph.D., a postdoctoral clinical research fellow at the University of California at San Francisco Headache Center. Slightly more than half also had migraine, but the visual snow did not have any of the features of typical aura. Also, only a small minority of affected patients had used illicit drugs.

"Visual snow is almost always associated with additional visual symptoms. It therefore represents a unique clinical syndrome – the visual snow syndrome," he said at the annual meeting of the American Headache Society. "It is distinct from visual aura in migraine; migraine with and without aura are common comorbidities, but we don’t actually know at the moment what is the pathological link between those two conditions. And the intake of illicit drugs is not relevant."

Dr. Schankin went one step further, proposing new diagnostic criteria for the visual snow syndrome: visual snow plus at least three additional visual symptoms out of nine identified in the study, in the context where these symptoms are not consistent with typical migraine aura and cannot be attributed to some other disorder.

A session attendee congratulated the investigators on the research, noting, "These patients, for those who haven’t seen them, are devastated and lonely. Some can’t drive, some can’t work, some can’t read books, some can’t use computers. They are a wreck ... and there is nobody out there who is owning this condition – I don’t know if it falls in the realm of neuro-ophthalmology or neurology or headache, and what to do with these poor folks. ...They have been banished to the realms of psychiatry and have been told they have functional disorders and other things, when it is very clearly a widespread neurological perceptual disturbance."

He said his own experience with affected patients affirms the existence of the visual snow syndrome. "The more you talk to them, the more you appreciate that they really do have these features in common ... So I just want to thank you for bringing attention to this sort of orphan disorder, and hope it raises awareness, and that some people will take interest in it and studying the biophysiology and treatment options."

Session chair Dr. R. Allan Purdy, a neurologist at Dalhousie University in Halifax, N.S., asked the neuro-ophthalmologists present to weigh in with their thoughts on the possible pathophysiology of visual snow.

"I think this is a somewhat migrainous phenomenon in people with very sensitive brains," one replied. "We have done EEGs on these people and they are normal, at least in adults that we have seen with this. It is definitely real – these people are not making this up. And we have seen quite a few of these cases in neuro-ophthalmology."

Another concurred, saying "I think it’s real." Moreover, in her opinion, the presence of visual snow alone would be sufficient for diagnosis. "I suspect it’s migrainous because most of these people have migraines. But it’s not aura. I don’t know really what it is. It’s incredibly frustrating because nothing works. You can try every antiepileptic known to mankind, and nothing works. So I agree that this is something we need to pay attention to and help these people."

Dr. Schankin noted that research on visual snow is scarce, and affected individuals suffer in part because of a lack of knowledge about the condition in the medical community. "Patients are commonly given the diagnosis of persistent migraine aura or a posthallucinogen perceptual disorder, especially after LSD intake," he noted.

He and his coinvestigators studied members of an online support group for visual snow (Eye on Vision). In the first part of the study, they analyzed data from an Internet survey among 120 patients that asked about visual symptoms. They were 26 years old on average and about two-thirds were men.

Results showed that in addition to visual snow, nearly all patients reported other visual symptoms, such floaters (73%); persistent visual images (63%); difficulty seeing at night (58%); tiny objects moving on the blue sky (57%); sensitivity to light (54%); trails behind moving objects (48%); bright flashes (44%); and colored swirls, clouds, or waves when their eyes were closed (41%).

Dr. Schankin noted that some of these symptoms map onto the well defined clinical phenomena of palinopsia (trailing and prolonged after-images), photophobia, and impaired night vision.

And others fall into a category of entoptic phenomena, or visual symptoms originating in the eyes themselves, namely, floaters (likely protein aggregations in the vitreous fluid that cast a shadow on photoreceptors); photopsia (bright flashes typically elicited by mechanical stimulation of the eyes); Scheerer’s phenomenon (small moving objects against the sky thought to be due to blood cells moving in the retinal vessels that cast a shadow on the photoreceptors); and self-light of the eye (the colored swirls, clouds, and waves), whose etiology is unknown.

In the second part of the study, the investigators conducted telephone interviews with another 120 patients with visual snow to further explore the nature of symptoms and antecedent events. These patients were 31 years old on average and nearly evenly split between men and women.

Results showed that the textural patterns described for the snow varied considerably. The most common pattern reported was dots alternating from black (on light backgrounds) to white (on dark backgrounds) (48%), while some patients reported flashing dots, transparent dots, or other patterns. "We don’t know what that means – whether that has some pathophysiologic relevance," Dr. Schankin commented.

Analyses restricted to the subset reporting black and white dots showed that 98% had at least one additional visual symptom, and 93% had three or more. In this part of the study, another symptom identified was halos or starbursts, seen in 65% of cases.

Of the 40 patients with onset of visual snow later in life, 54% had a history of migraine. However, when asked about events in the week before the onset of visual snow, only 33% reported headache, and just 10% reported aura symptoms. But none had classic features of visual aura, such as unilaterality, zig-zag lines, or scotoma, during visual snow. Additionally, only 8% had used illicit drugs, mainly marijuana, in the week leading up to the start of visual snow, and none had significant ophthalmologic findings.

Dr. Schankin disclosed no relevant conflicts of interest.

LOS ANGELES – So-called visual snow, characterized by myriad persistent tiny dots throughout the visual field, commonly occurs in patients with migraine, but it is usually accompanied by other visual symptoms and appears to be a distinct entity, according to combined data from two cross-sectional studies.

In a two-part study among 240 patients with visual snow, nearly all had other visual symptoms such as after-images or poor night vision, reported lead investigator Christoph Schankin, Ph.D., a postdoctoral clinical research fellow at the University of California at San Francisco Headache Center. Slightly more than half also had migraine, but the visual snow did not have any of the features of typical aura. Also, only a small minority of affected patients had used illicit drugs.

"Visual snow is almost always associated with additional visual symptoms. It therefore represents a unique clinical syndrome – the visual snow syndrome," he said at the annual meeting of the American Headache Society. "It is distinct from visual aura in migraine; migraine with and without aura are common comorbidities, but we don’t actually know at the moment what is the pathological link between those two conditions. And the intake of illicit drugs is not relevant."

Dr. Schankin went one step further, proposing new diagnostic criteria for the visual snow syndrome: visual snow plus at least three additional visual symptoms out of nine identified in the study, in the context where these symptoms are not consistent with typical migraine aura and cannot be attributed to some other disorder.

A session attendee congratulated the investigators on the research, noting, "These patients, for those who haven’t seen them, are devastated and lonely. Some can’t drive, some can’t work, some can’t read books, some can’t use computers. They are a wreck ... and there is nobody out there who is owning this condition – I don’t know if it falls in the realm of neuro-ophthalmology or neurology or headache, and what to do with these poor folks. ...They have been banished to the realms of psychiatry and have been told they have functional disorders and other things, when it is very clearly a widespread neurological perceptual disturbance."

He said his own experience with affected patients affirms the existence of the visual snow syndrome. "The more you talk to them, the more you appreciate that they really do have these features in common ... So I just want to thank you for bringing attention to this sort of orphan disorder, and hope it raises awareness, and that some people will take interest in it and studying the biophysiology and treatment options."

Session chair Dr. R. Allan Purdy, a neurologist at Dalhousie University in Halifax, N.S., asked the neuro-ophthalmologists present to weigh in with their thoughts on the possible pathophysiology of visual snow.

"I think this is a somewhat migrainous phenomenon in people with very sensitive brains," one replied. "We have done EEGs on these people and they are normal, at least in adults that we have seen with this. It is definitely real – these people are not making this up. And we have seen quite a few of these cases in neuro-ophthalmology."

Another concurred, saying "I think it’s real." Moreover, in her opinion, the presence of visual snow alone would be sufficient for diagnosis. "I suspect it’s migrainous because most of these people have migraines. But it’s not aura. I don’t know really what it is. It’s incredibly frustrating because nothing works. You can try every antiepileptic known to mankind, and nothing works. So I agree that this is something we need to pay attention to and help these people."

Dr. Schankin noted that research on visual snow is scarce, and affected individuals suffer in part because of a lack of knowledge about the condition in the medical community. "Patients are commonly given the diagnosis of persistent migraine aura or a posthallucinogen perceptual disorder, especially after LSD intake," he noted.

He and his coinvestigators studied members of an online support group for visual snow (Eye on Vision). In the first part of the study, they analyzed data from an Internet survey among 120 patients that asked about visual symptoms. They were 26 years old on average and about two-thirds were men.

Results showed that in addition to visual snow, nearly all patients reported other visual symptoms, such floaters (73%); persistent visual images (63%); difficulty seeing at night (58%); tiny objects moving on the blue sky (57%); sensitivity to light (54%); trails behind moving objects (48%); bright flashes (44%); and colored swirls, clouds, or waves when their eyes were closed (41%).

Dr. Schankin noted that some of these symptoms map onto the well defined clinical phenomena of palinopsia (trailing and prolonged after-images), photophobia, and impaired night vision.

And others fall into a category of entoptic phenomena, or visual symptoms originating in the eyes themselves, namely, floaters (likely protein aggregations in the vitreous fluid that cast a shadow on photoreceptors); photopsia (bright flashes typically elicited by mechanical stimulation of the eyes); Scheerer’s phenomenon (small moving objects against the sky thought to be due to blood cells moving in the retinal vessels that cast a shadow on the photoreceptors); and self-light of the eye (the colored swirls, clouds, and waves), whose etiology is unknown.

In the second part of the study, the investigators conducted telephone interviews with another 120 patients with visual snow to further explore the nature of symptoms and antecedent events. These patients were 31 years old on average and nearly evenly split between men and women.

Results showed that the textural patterns described for the snow varied considerably. The most common pattern reported was dots alternating from black (on light backgrounds) to white (on dark backgrounds) (48%), while some patients reported flashing dots, transparent dots, or other patterns. "We don’t know what that means – whether that has some pathophysiologic relevance," Dr. Schankin commented.

Analyses restricted to the subset reporting black and white dots showed that 98% had at least one additional visual symptom, and 93% had three or more. In this part of the study, another symptom identified was halos or starbursts, seen in 65% of cases.

Of the 40 patients with onset of visual snow later in life, 54% had a history of migraine. However, when asked about events in the week before the onset of visual snow, only 33% reported headache, and just 10% reported aura symptoms. But none had classic features of visual aura, such as unilaterality, zig-zag lines, or scotoma, during visual snow. Additionally, only 8% had used illicit drugs, mainly marijuana, in the week leading up to the start of visual snow, and none had significant ophthalmologic findings.

Dr. Schankin disclosed no relevant conflicts of interest.