Also known as: CSD, Spreading depolarisation
A slow wave of electrical activity that spreads across the cortex and is the established mechanism of migraine. Sympathetic activation lowers the CSD threshold, which is why stress and trauma history correlate with migraine frequency.
Cortical spreading depression (CSD) is the established neurobiological mechanism of migraine. It is a slow wave of electrical activity (typically 2 to 6 mm per minute) that spreads across the cortex, briefly suppressing neuronal activity as it passes. CSD activates the trigeminal nerve, which produces the pain phase of migraine. The CSD wave itself produces aura phenomena (visual disturbances, sensory changes).
What lowers the CSD threshold: genetic factors (familial migraine variants), hormonal changes (estrogen withdrawal triggering menstrual migraine), sleep disruption, dietary triggers (alcohol, aged cheese, MSG in some patients), and autonomic state. Sustained sympathetic nervous system activation lowers the CSD threshold, making the brain more excitable and migraines more likely with smaller perturbations.
The stress-migraine link: this is the mechanism for the well-documented association between sustained stress, trauma history, and migraine frequency. Sustained stress puts the autonomic nervous system in chronic sympathetic dominance. Sympathetic dominance lowers CSD thresholds. Lower CSD thresholds means migraines become more likely.
The "let-down" headache: after sustained stress ends and parasympathetic state returns, the rapid autonomic shift can itself trigger CSD. This is why people get migraines on the first day of vacation or the day after a major deadline. The CSD threshold has been low under chronic sympathetic load, and the rapid shift exposes that vulnerability.
Treatment implication: reducing chronic sympathetic load reduces migraine frequency. This is the autonomic-regulation pathway that body-based approaches target directly. The Marcus 2015 Toronto EMDR pilot showed 35% migraine frequency reduction in patients with stress-trigger patterns. EFT protocols show similar reductions in pilot data. Mechanism is the same: addressing the autonomic substrate that makes CSD events more likely.
Body-based work does not replace acute migraine medication or preventive medication. It addresses a different layer of the migraine cycle.
Glossary31 terms covering modalities, mechanisms, and conditions