or VISUAL AURA*
Scintillating scotoma is the most common visual aura preceding migraine. It is also called 'fortification spectrum' and 'teichopsia'.
It is generally accepted that Dr Hubert Airy (1838-1903) was the first to describe this condition in a paper presented to the Royal Society in February 1870, using the term fortification spectrum. His paper was undoubtedly one of the most influential publications on migraine of all time.
However the earliest reference to this phenomenon is by Dr John Fothergill (1712-1780). He was responsible for the earliest English language description of migraine in a paper read before the Select Society of Licentiates on 14th December 1778. Referring to the visual changes he wrote: "objects swiftly changing their apparent position, surrounded by luminous angles, like those of a fortification."
This complex condition has been fully described in my April 2006 newsletter Headaches, Migraine and Diet, which should be read in conjunction with this present newsletter.
Aura is experienced by 10-20% of migraineurs. Aura is defined as focused symptoms that grow over 5-15 minutes and generally last about an hour. In most cases, the migraine headache follows the aura. However the two events can happen at the same time, or the aura may develop after the headache starts. The aura can occur in the absence of headache.
With the aura of migraine, visual symptoms are the most common and include the following:
Description of Scintillating Scotamata
A scintillating scotoma usually begins as a small spot of pulsating light, which may flicker, near the centre of the visual field, though rarely exactly central, generally off to one side. This gradually increases in size, expanding into one or more shimmering arcs of white or coloured flashing lights. As the arc of light gradually enlarges, it becomes more obvious and may take the form of a definite zigzag pattern. Inside the arc is the scotoma, with varying degrees of loss of vision within it. The vision beyond the borders of the expanding scotoma remains normal. From beginning to end (when it gradually fades away) is generally about 60-90 minutes.
There may be associated nausea, fatigue and dizziness.
Once the scotoma has resolved, vision returns completely to normal, and there are no lasting symptoms.
Where Does the Scotoma Come From?
The visual anomaly results from abnormal functioning of portions of the occipital cortex, at the back of the brain.
It is not in the eyes or any component of the eyes such as the retina. The scintillating scotoma can be 'seen' with the eyes closed.
There is no accepted cause of scintillating scotoma.
Migraine is caused by abnormal brain activity, which can be triggered by a number of factors. It is generally accepted by the experts that the attack begins in the brain and involves nerve pathways and chemicals. The changes affect the blood flow in the brain and surrounding tissues.
The following can be triggers to a migraine attack and thus can be triggers for the scintillating scotoma or scotomata.
(National Library of Medicine: www.nlm.nih.gov/medlineplus).
Symptoms of scintillating scotoma typically appear gradually as described above and rarely last more than 90 minutes, leading into the headache of classic migraine with aura, or resolving without consequences in the absence of headache. The scotoma typically resolves within the stated timeframe leaving no subsequent symptoms.
It may be difficult to read while the scotoma is present.
It is dangerous to drive a vehicle or operate machinery while the scotoma is present.
Normal central vision may return several minutes before the scotoma disappears.
*Copyright 2012: The Huntly Centre.
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