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The threshold for phosphenes is lower in migraine
S K Aurora1, K M A Welch, F Al-Sayed
1Headache Research Center, Henry Ford Health Sciences Center, Detroit, MI, USA. sheena.aurora@swedish.org
Cephalalgia : an International Journal of Headache
|April 29, 2003
Summary
Migraine patients, particularly those with aura, show heightened occipital cortex excitability. This neurophysiological finding using transcranial magnetic stimulation (TMS) supports theories of visual disturbances in migraine with aura.
Area of Science:
- Neuroscience
- Neurology
- Clinical Neurophysiology
Background:
- Migraine with aura (MwA) is often associated with visual disturbances.
- Previous preliminary studies suggested occipital cortex hyperexcitability in MwA.
- A blinded study was needed to confirm these findings in MwA and migraine without aura (MwoA) compared to controls.
Purpose of the Study:
- To investigate and compare occipital cortex excitability in MwA, MwoA, and normal controls (NC).
- To utilize transcranial magnetic stimulation (TMS) to objectively measure cortical excitability thresholds.
Main Methods:
- A blinded study comparing 10 MwA, 10 MwoA, and 10 NC.
- Transcranial magnetic stimulation (TMS) applied to the occipital scalp.
- Determined phosphene generation threshold intensity and visual phenomena elicitation.
Main Results:
- Significantly higher proportion of subjects with phosphene generation in MwA (100%) and MwoA (60%) compared to NC (30%) [P = 0.003].
- Significantly lower threshold levels for phosphenes in MwA (42.8%) compared to NC (57.3%) [P = 0.0001].
- Confirmed differences in occipital cortex excitability thresholds between migraineurs and controls.
Conclusions:
- The study provides direct neurophysiological evidence of occipital cortex hyperexcitability in migraineurs.
- Findings correlate with clinical observations and theories of visual disturbances in migraine.
- TMS offers a quantifiable method to assess cortical excitability in migraine.