Sustained visual cortex hyperexcitability In Migraine with Persistent Visual Aura

[shaolinbomber]

http://brain.oxfordj...awr157.full.pdf

Here's another good article I found about the newer types of diagnostic tools they are using in neurology to identify the problems with disorders involving persisting visual disturbances.

Also notice that on all of the readings from the mEEG done on all of the test groups who complained of visual disturbances, the Persistent Visual Aura crowd (I believe HPPDers can be summed in with this group) had the highest readings of cortical excitability.

"

The present finding of persistent hyperexcitability across

ictal-interictal phases suggests that sustained cortical spreading

depression reverberations might be the culprit in persistent visual

aura. We hereby provide two possible reasons why a vicious cycle

of sustained cortical spreading depression is formed in persistent

visual aura. First, persistent potentiation in persistent visual aura

may lead to enduring and excessive neuronal stress, and the accumulation

of metabolites such as lactate and protons that may

induce repetitive cortical spreading depression (Scheller et al.,

1992). Given the protective nature of habituation, persistent potentiation

leads to brain sensory overload, depletes the cortical

energy reserve and finally leads to neuronal stress and a biochemical

shift that triggers cortical spreading depression (Coppola et al.,

2009; Rankin et al., 2009). On the other hand, the excitatory

waves piloting each cortical spreading depression propagation

and the detrimental effects of repetitive cortical spreading depression

upon intracortical inhibition (Kruger et al., 1996) may

upregulate cerebral excitability and eventually increase vulnerability

to cortical spreading depression (Holland et al., 2010).

The association between cortical spreading depression and

hyperexcitability here is further supported by a clinical observation

that 45% of patients with persistent visual aura had worsening

headache during aura persistence (Wang et al., 2008).

Despite PET evidence of sustained metabolic activation in the

medial occipital cortex with persistent visual aura, there was no

corresponding metabolic change during a typical migraine aura

(Andersson et al., 1997). Therefore, single cortical spreading depression

propagation per se (hence migraine aura) cannot explain

the persistent potentiation in persistent visual aura. The culprit

should be, again, the complex interaction between cortical spreading

depression reverberations and central excitability. The entanglement

between central excitability and cortical spreading

depression reverberations may further explain the lack of correlation

between magnetoencephalography and most clinical measures."

CONCLUSION

"Persistent visual aura is characterized by persistent hyperexcitability

of the visual cortex without interictal-ictal variation, compatible

with the excitatory effect of sustained reverberations of cortical

spreading depression. Our magnetoencephalography data on the

excitability changes in the visual cortex differentiates persistent

visual aura from other migraine disorders (migraine with aura,

migraine without aura and chronic migraine). Therefore, while belonging

to the migraine spectrum, persistent visual aura may be considered a distinct disorder."