Posts Tagged ‘visual snow’


Open Journal Article: Mapping cortical hubs in tinnitus

2009 November 23



Subjective tinnitus is the perception of a sound in the absence of any physical source. It has been shown that tinnitus is associated with hyperactivity of the auditory cortices. Accompanying this hyperactivity, changes in non-auditory brain structures have also been reported. However, there have been no studies on the long-range information flow between these regions.


Using Magnetoencephalography, we investigated the long-range cortical networks of chronic tinnitus sufferers (n = 23) and healthy controls (n = 24) in the resting state. A beamforming technique was applied to reconstruct the brain activity at source level and the directed functional coupling between all voxels was analyzed by means of Partial Directed Coherence. Within a cortical network, hubs are brain structures that either influence a great number of other brain regions or that are influenced by a great number of other brain regions. By mapping the cortical hubs in tinnitus and controls we report fundamental group differences in the global networks, mainly in the gamma frequency range. The prefrontal cortex, the orbitofrontal cortex and the parieto-occipital region were core structures in this network. The information flow from the global network to the temporal cortex correlated positively with the strength of tinnitus distress.


With the present study we suggest that the hyperactivity of the temporal cortices in tinnitus is integrated in a global network of long-range cortical connectivity. Top-down influence from the global network on the temporal areas relates to the subjective strength of the tinnitus distress.

You can read the full article here:


Student Doctors & My Neurologist (2nd Correction)

2009 June 2

This last eight days has seen a lot of changes for me. Last Tuesday I had my last appointment with my neurologist. He has now done as much as he can to control the pain symptoms of my migraine. These come from damage to my neck. My prescription of the anti-epileptic drug Epilim (sodium valproate) has helped the pain migraines. But I still suffer a lot of debilitating non-pain migraine with aura. At least things are going in the right direction. Though I seem to again be in a cluster of attacks.

On a much more positive note, today I sat in with some student doctors. Some months ago my GP (family doctor) asked if I would do so. They asked me a lot of questions about the “complicated migraine” I suffer. This gave me an opportunity to also talk about the fact I am unable to visualise (see things in my “mind’s eye”). And that I have no visual episodic memory (memory for life events). I talk about this further in the Visualisation FAQs page, and the series linked to there. My hope is that this may bring it to the attention of neurology researchers.

If you have any combination of these symptoms, I would like to hear from you. You can either comment – there is a discussion at the end of “Cannot Visualise (Part Three)“. Or you can, if you prefer, e-mail me privately at – just remove the “nospam” part!

(I’ve corrected the e-mail address above.)

(Oops! I forgot to add the combination of symptoms. If you have any combination of these symptoms…):-

  • Migraine, and/or,
  • Persistent aura, and/or,
  • Visual snow, and/or,
  • Inability or poor ability to visualise, and/or,
  • Poor visual episodic memory.

Persistent Migraine Aura & Visual Snow (Part Three) (Last Edited: 2009 Nov 19)

2008 October 11

Go back to Part 2

This is the final part of a three part series. You can go back to part two from the links at the top and bottom of this page. Or you can jump to any part from the PMA & Visual Snow FAQs page link.

To finish this short series, I’ll relate my own experience. This list of symptoms may be of interest generally and to anyone with persistent aura or visual snow.

I’ve always or long had a few symptoms which I thought everyone had:

  • Swirling pink-purple and green patterns in the dark. These repeat with change. I don’t always get them and they don’t usually last long.
  • Spontaneous afterimages. These are rather like anyone would get if someone flashed a bright torch in their eyes at a distance. Except they pop up without any light source. They also take a while to disappear. The brightest and largest ones can last half an hour or more.
  • A rushing, whistling, whining sound in my ears. This is called tinnitus. In my case I get several distinct but faint sounds all across my stereo field.

Because these hadn’t caused any problems I hadn’t bothered with them. Then just under three months ago I suddenly got a lot more symptoms. My GP diagnosed persistent aura, including visual snow. My specialist has confirmed the diagnosis:

  • Something called Scheerer’s Phenomenon. This is where you see short-lived and fast-moving squiggles. These are normally seen against bright uniform fields like white walls or blue sky. You can see these normally without any pathology. Though not everyone does. They are how the brain interprets ‘gaps’ in the blood supply to the eyes caused by white blood cells. In my case it is constant in the right conditions.
  • Visual snow itself. At first I confused this with Scheerer’s Phenomenon. Visual snow is like the static you get on an analogue TV in a poor reception area. It’s been described as like “seeing the air” and is also called aeropsia. In my case I see it in dim or dark conditions and it is pronounced most times. It is constant in the right conditions in my case. Though it did go away for a few minutes one night recently.
  • Something I call sparklers. These are like exploding fireworks. In my case they take place at the centre of my vision. They usually happen when I go from looking at a bright scene to a darker one. Sometimes I see them while still in a bright scene. I get these most days. They last a second or two each time. They are usually green or orange in my case.
  • Fasciculation(?) Localised involuntary twitching or nerves or muscles. These vary from day to day in frequency. Each event can last a second or two or for several minutes. The actual frequency of twitching can be a twitch every second or two to many times a second.
  • Pinpoint flashes. These are hard to spot so I’m not sure how often I get them. They may be short lived spontaneous afterimages. The name I have given them describes them perfectly.
  • A kind of scintillating scotoma I call “aurora”. These look a bit like the Northern or Southern Lights. But they are colourless. I get my aurora in my right field (side) of vision in darkness. It happens most times I go from lit to dark conditions. It lasts a few minutes before fading away. It is dimmer than the scintillating scotoma I get before a hemiplegic migraine attack. It is reactivated by light, even with my eyes closed.
  • Another visual symptom I see in my centre of vision is something I call a “capillary”. This is because it resembles in many ways videos of red blood cells pumping through a capillary. Except that the ‘cells’ are white ringlets. They even pulse. I usually only see them in brightly lit conditions against a white field. Very rarely they end with a spontaneous afterimage. Worried about this, I asked my optometrist about them. After examining my eyes she said I had no damage. So it wasn’t a blood vessel bursting! Also there are no blood vessels in the centre of vision. These seem to happen more in my right eye.
  • I also get a single stationary ringlet in the centre of my vision. Recently this has lasted several days. I see it when I blink. I now realise it is in my right eye and is a spontaneous afterimage that won’t go away. Though it has faded again. Usually I see this rarely.

Some rare visual symptoms I get are:

  • Starbursts or rays. These look like short but very bright rays with patternation within them. They emerge from very bright usually point light sources such as the sun reflecting of a metal tap (faucet). They give the appearance of something like one of those floating seeds like from cotton. Except they shine. Very pretty!
  • Halos. A misty veil of light surrounding a bright light source in dark conditions. Though the scene itself is not misted.

Any of these symptoms can increase when I get a hemiplegic migraine attack.

I can also spontaneously get the other symptoms of such an attack without the usually scintillating scotoma or headache. These usually last just a minute or two and are much milder. Most common are a short, mild burning sensation in one or other hand. This is usually associated with paresthesia (numbness or pins and needles) in a proper attack. Or I can get tingling in my top teeth. Sometimes I also get mild photophobia or hyperacusis: intolerance to light or sound. Finally I sometimes get short lived strobing or pulsating headaches. These usually last only a few seconds and can sometimes be severe.

Each person’s symptoms may vary. I have come across a support forum for people who have or think they have visual snow and are worried by it. Before writing a permanent page here, this is the link to that forum:

Go back to Part 2



Tuesday Round-up for Friends

2008 October 7

Two medical related things happened this week.

First, my headache/migraine specialist replied to my letter. I’d written to him asking how I should update my Incapacity Benefit (IB) claim in my new questionnaire. I also updated him on my recent diagnosis of persistent aura (persistent aura without infarction, also known as persistent migraine aura). I’d also mentioned back spasms I’d had many years ago. I wrote to him before seeing my GP (family doctor) about the new lower back problem I’d started getting. So I didn’t include that in my letter.

So the second thing is that I saw my GP about that back pain.

I now think I understand where my specialist is coming from. I couldn’t understand why he was focussing on my neck and shoulder pain and mobility problems. I had been referred because of what my GP had thought were frequent and severe migraine. He replied that he is “one of a minority” who think that neck pain is the source of a wide range of headache problems, including migraine. Even though migraine clearly has a neurological pathway, he believes these are triggered by neck pain. Other opinion in medical science as I wrote about in my Saturday SeriesMigraines” includes the trigeminal nerve as “central to the mechanism”. But they don’t all agree that this is the cause of migraine onset.

He also said that persistent aura “is a well recognised condition” and that “neither the causes nor the remedies for it have been agreed in current medical practice”. But he did say that there is research into persistent aura to try to understand it better. He finished by saying that he thinks my headaches are therefore migraines. So I only need add the neck and shoulder pain and mobility to the new form if I think it adds to my inability to work beyond the migraines.

Which leads me on to my GP appointment. He examined my mobility and pain. It looks like I have, superficially at least, a similar problem in my lower back as my neck and shoulders. The nerve root is causing pain which limits my mobility. That pain then spreads to my general pelvic area and my legs as I stand or walk for any length of time. Sitting or lying down relieves the discomfort. He has prescribed physiotherapy as a first step. I am now waiting for the appointment for that to come through.


Persistent Migraine Aura & Visual Snow (Part Two) (Last Edited: 2009 Nov 19)

2008 October 4

Go back to Part 1 | Go on to Part 3

This is part two of a three part series. You can continue to part two from the links at the top and bottom of this page. Or you can jump to any part from the PMA & Visual Snow FAQs page link.

In part one we started by looking at persistent aura without infarction. This is also known as persistent migraine aura, or PMA. This is something I have been diagnosed with, along with something called visual snow. This week, we will look at visual snow.

What is Visual Snow?

Visual snow is one of the symptoms that can go with PMA. But PMA is not the only cause of visual snow. Another common cause is having used hallucinogenic drugs like LSD, MDMA (Ecstasy) and so on. In this case the cause is called hallucinogen persisting perception disorder, or HPPD.

HPPD can be triggered by just a single dose of an hallucinogen. And there can be some time between taking the last dose and the beginning of HPPD. This is why doctors will take a drug use history if visual snow is to be diagnosed. Like PMA, the way HPPD works is not known. Another name for visual snow in HPPD is aeropsia.

A third, but rarer cause of visual snow is optic neuritis. This is inflammation of the optic nerve caused by multiple sclerosis, or MS. It is important to get the cause of visual snow checked out, therefore. Though it is much more likely to result from HPPD or PMA. Visitors on forums have, anecdotally, blamed a range of other illnesses and causes. These may include Lyme disease, auto-immune disease, long use of a VDU, dehydration and so on. But none of these claims is supported by medical evidence.

This link gives a fair demonstration of what it is like to have visual snow (which is most obvious in near or total darkness):

How Good is Medicine at Diagnosing Visual Snow?

Anecdotally, from a forum I have visited (like PMA in many cases too), it can be hard to get a firm diagnosis of visual snow. Many doctors still seem to be unaware of the condition. Most people’s experience is one of being referred to an optometrist, and then eventually to an ophthalmologist or other specialist before diagnosis. Others find that they are told “it’s all in your mind” (as they can for PMA).

But there are a number of researchers looking into visual snow. So if you have it, or think you do, you may find them on a forum.

Other Symptoms

There are a number of other symptoms that often go with visual snow. These include:

  • Starbursts – rays that come from bright light sources,
  • Palinopsia – overly long or more frequent afterimages from looking at light sources,
  • Floaters – which most people can experience,
  • Trails – where moving objects appear to leave a visual wake,
  • Scheerer’s Phenomenon – or blue field entopic phenomenon; fast moving, wiggly white lines against a bright uniform background, which can also be common for non-visual snow sufferers,
  • Halos – mist like halos around bright lights especially at night,
  • Tinnitus – ringing, hissing or other noise in the ears,
  • Depersonalisation-derealisation – often described as “feeling weird” or “being spaced out”.

Those with visual snow can also have what are called secondary sequelae. This means symptoms that are caused by general anxiety about the main symptoms. These include:

  • Anxiety,
  • Panic attacks,
  • Depression.


There is no established treatment for visual snow. PMA sufferers may have success with some of the drugs used to treat that. The two most effective for both tend to be sodium valproate and topiramate. HPPD sufferers may respond to clonazepam. Here drug abstinence is also recommended. Again, the forum I visit lists other drugs and herbal remedies that may or may not work.

I can personally say that meditation is a big help when it comes to anxiety, panic attacks or depression. This is also helpful because in meditation we learn to control mental focus. This helps work past the visual symptoms that can otherwise be overwhelming.

At the time of writing, little research is being carried out into visual snow.

Go back to Part 1 | Go on to Part 3


Persistent Migraine Aura & Visual Snow (Part One) (Last Edited: 2009 Nov 19)

2008 September 27

This is part one of a three part series on persistent aura without infarction, also called persistent migraine aura (PMA), and on visual snow (VS).

You can continue to part two from the link at the bottom of this page. Or you can jump to any part from the PMA & Visual Snow FAQs page link.

In this series I have used reputable sources for the science of persistent aura and visual snow. I’ll include the sources in the final post.

What is Persistent Migraine Aura?

Persistent migraine aura, or PMA, used to be called prolonged migraine aura status. Its proper diagnostic name is persistent aura without infarction. “Without infarction” means without the death of brain cells (or other cells). It is a little understood medical condition. Its cause, called its pathogenesis, is unknown. This means that it is not known how its symptoms are caused. It is also not known what medical examinations are useful in diagnosing PMA. Though at least one medical site says:

  • Description: Aura symptoms persisting more than one week without radiographic evidence of infarction,
  • Diagnostic criteria: (A) The present attack in a patient with 1.2 Migraine* with aura is typical of previous attacks except that one or more aura symptoms persist for more than one week, and (B) Not attributed to another disorder.

*”1.2 Migraine” means migraine with aura under today’s medical diagnostic criteria, the IHS Members Handbook (1997/1998). See the sources list at the end of this post for a download location. The International Headache Society (IHS) now classifies it as type 1.5.3.

Neurological symptoms that can be associated with PMA include:

  • Visual snow,
  • Vision loss,
  • Increased afterimages,
  • Tinnitus,
  • and others.

Medication that has been tried for treatment includes:

  • acetazolamide (also called Diamox),
  • valproate (also called valproic acid, sodium valproate or Epilim),
  • lamotrigine (also called Lamictal, Lamogine or Lamictin),
  • topiramate (also called Topamax),
  • furosemide (also called frusemide or Lasix).

This, from PubMed the USA’s National Institute of Health, says something of the current state of understanding:

“To the best of our knowledge, persistent visual symptoms, lasting months or years without evidence of infarction, a rare complication of migraine with aura, has been reported in only 20 patients. We report the case of a 43-year-old woman with a 31-year history of migraine with typical visual aura. At presentation, she experienced a visual aura in her right hemifield followed by a pulsating headache. The visual symptoms persisted.”

It is my experience, from my own research and talking on forums, this laughably underestimates the prevalence of persistent aura. Though another record did conclude:

“This case {of hemiplegic migraine} illustrates the potential for permanent neurological deficits to occur as a sequelae {sic} of HM in the absence of infarction, and highlights potentially important pathophysiological and treatment implications.”

A third says:

“Migraine with aura is a common disorder in industrialised countries, affecting up to 5% of the adult population. Although migraine aura is usually a benign disorder, in rare instances it can be the cause of serious neurologic {sic} complications … Other complications are … persistent auras without infarction. These disorders are of both clinical and scientific interest, as they throw light on the complex and not yet fully understood relationship between migraine with aura, stroke and epilepsy.”

Go on to Part 2


Tuesday Round-up for Friends

2008 September 9

I’m back on Epilim (sodium valproate) after seeing my doctor on Friday. I showed him how the Wikipedia suggests the symptoms I have are visual snow. I showed him how visual snow can be symptomatic of persistent migraine aura (pma). And how it can in that circumstance be treatable with Epilim. And I said how a support forum I had contacted agreed that my symptoms matched theirs generally. And that many of them had been diagnosed with pma. He agreed with my assessment that it’s likely Epilim had been masking the visual symptoms. Also, given how my migraine rate shot up again on coming off, that it had been somewhat effective. So now we’ll see what happens. If Epilim is effective in my case, we’d expect:

  • My frequency of migraine to reduce,
  • My visual snow and related symptoms to reduce,
  • And possibly the severity of migraines to reduce.

Time will tell.



Tuesday Round-up For Friends

2008 August 19

I saw my optometrist. (Apparently, there’s a difference between optician, optometrist and ophthalmologist in increasing order of qualifications.) She could find no physical problem with my eyes or eyesight. So she said I should go back to my doctor. She said, though admitting she’s no expert, she suspects the visual phenomena relate to migraines.

On that subject, the sweet little things have gone up quickly in frequency since June. Again. Back now to almost one every other day as at their peak. So far I cannot find anything from my exhaustive migraine diary to show a trigger. But then I have two kinds of headache/migraine according to my specialist.

Still, at least between times it gives me some time to study the Buddhist sutras. And to practise mindfulness. I have chosen the lineage of Zen Master Thich Nhat Hanh. Thay (teacher) was the first I read online. Thay’s writings are wonderfully clear. I am fortunate and grateful to have found his books. I hope one day to be able to hear a talk from him. And to be able to learn from a teacher in his lineage.

Perhaps these migraines are a blessing in disguise?


Tuesday Round-up For Friends

2008 August 12

I saw my doctor on Monday about the “visual snow” I’m seeing before my eyes. I figured the best thing to do was just go with that. I thought if I loaded him with a mass of “symptoms” he might just ignore me. He gave me a quick eye exam, and suggested I see my optician. So I’m booked to do so on Friday. I’ll see what she finds.

As I expected, the back spasms I had in my late teens and early twenties weren’t in my medical records. So that’s something I’ll have to make sure my specialist knows about next time I see him. That won’t be until November now. Whether that makes any practical difference now, who can say?


Tuesday Round-up For Friends

2008 August 5

Hello. This is the first of what will be my Tuesday round-up of what’s happened in my presently boring life. It’s mainly for friends and family. Whether it’s of any interest to anyone (or anyone else) I don’t know, but here goes anyway.

If friends and family could read this and give their thoughts privately, I will be grateful. Others may find it interesting (if long) if they have “visual snow or static”.

Read the rest of this entry ?