It looks like you're asking about "fortification spectra." This term is most commonly associated with migraine aura, specifically the visual disturbances that some people experience before or during a migraine attack.
What Are Fortification Spectra?
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They appear as shimmering, zigzagging lines that often start as a small flickering spot in the visual field and gradually expand outward.
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The patterns resemble the fortifications or walls of a medieval castle, hence the name.
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They can be colorful or black-and-white.
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Often, they are accompanied by a scotoma (blind spot) in part of the vision.
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Typically, these last 10–30 minutes before resolving.
Why Do They Occur?
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They result from cortical spreading depression—a wave of altered brain activity that moves across the visual cortex.
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This wave causes temporary changes in neurons and blood flow, leading to the visual phenomenon.
Are They Harmful?
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Fortification spectra themselves are not dangerous but can be an early warning of a migraine headache.
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In some cases, they can occur without headache, a condition known as ocular migraine or migraine aura without headache.
Would you like more information on how to manage migraines with aura?
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