Aura-related brain activity triggers trigeminal axons, leading to migraine

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Aura-related brain activity triggers trigeminal axons, leading to

migraine

Last Updated: 2002-02-01 14:15:46 EST (Reuters Health)

By Karla Gale

NEW YORK (Reuters Health) - Cortical spreading depression (CSD)

associated with migraine aura activates trigeminal afferents to the

meninges, which in turn leads to the onset of vascular dilation and

headache, Harvard Medical School researchers suggest.

" Our work shows for the first time that endogenous brain electrical

events can evoke pain and produce dilation of blood vessels, " Dr.

A. Moskowitz told Reuters Health in an interview.

For their research, Dr. Moskowitz and his associates used a pinprick to

induce CSD in anesthetized rats after craniotomies were performed. They

discuss their findings in the February issue of Nature Medicine.

According to laser speckle-contrast imaging, blood flow in the cortex

and pial vessels increased about 3 minutes after inducing the CSD,

lasting no more than 2 minutes. These changes progressed across the

cortical surface in the ipsilateral hemisphere along with neuronal and

glial depolarization.

About 5 minutes after the CSD was evoked, blood flow increased in the

middle meningeal artery, lasting about 45 minutes. This response was

prevented by transecting the trigeminal branch innervating the meninges.

The CSD also led to unilateral leakage of plasma protein within the

overlying dura mater. Just as with the meningeal artery dilation, the

edema could be prevented by blocking trigeminal denervation.

Dr. Moskowitz elucidated these results, saying " The spreading depression

seems to be able to irritate and trigger the trigeminal fibers that are

on surface. This information travels centrally into nucleus chordalis. "

" From there, " he continued, " there's a series of transmissions to the

area in which pain is perceived and a transmission causing a reflex-like

event that causes dilation of the blood vessels in the meninges of the

dura mater. "

He suggested that other cortical events " that don't have quite as

distinct a signature as CSD " may operate in more silent areas of the

brain, leading to similar activity that triggers the trigeminal system

and resulting in migraine without aura.

" One can imagine how a variety of brain-related events, like sleep,

stress, or depression, can modulate activity in the cerebral cortex, and

thereby up-regulate or down-regulate events that could irritate the

trigeminal nerve endings, " the Harvard researcher concluded.

Nature Med 2002;8:136-142.