Table 1.
Neurophysiological and Functional Imaging in Migraine
| Technique | Episodic Migraine | Chronic Migraine | Interpretation/Implication |
|---|---|---|---|
| Neurophysiological Techniques | |||
| Magnetic Suppression of Perceptual Accuracy (MSPA) | Letter reporting accuracy decreased by magnetic pulse, but not as much as in controls † | Letter reporting accuracy not decreased by magnetic pulse, in contrast to episodic migraine and controls † | Intracortical inhibitory mechanisms may be more impaired in chronic migraine than episodic migraine, leading to a greater increase in baseline cortical excitability † |
| Magnetoencephalography (MEG) | Intermittent excitability associated with migraine attack ‡‡ | Persistent excitability during and between attacks ‡‡ | Different pathophysiologic mechanisms underlie episodic and chronic migraine ‡‡ |
| Functional Imaging Techniques | |||
| Positron Emission Tomography (PET) | Increased activity in brainstem (pons) and selected cortical areas during migraine‡,§ | Increased activity in pons, right temporal cortex; decreased activity in selected cortical areas, caudate nuclei; all findings in the interictal period † | Certain brain regions (eg, pons, rostral medulla) may be overactive during attacks‡,§ of episodic migraine but continuously overactive † in chronic migraine |
| Activity in dorsal rostral pons, anterior cingulate cortex, and cuneus correlated with pain scores; activity in anterior cingulate cortex and pulvinar correlated with paresthesia scores ¶ | Pulvinar, cingulate and cuneus activity likely linked to affective component of pain; pons activity may be associated with migraine pathophysiology ¶ | ||
| Magnetic Resonance Imaging (MRI; relaxation rates R2, R2' and R2*) | Significant increase in R2' and R2* values in periaqueductal gray matter vs controls, not different from chronic migraine †† | Significant increase in R2' and R2* values in periaqueductal gray matter vs controls, not different from episodic migraine †† | Iron homeostasis in the periaqueductal gray may be persistently impaired in migraineurs, perhaps caused by repeated attacks †† |
| No differences in R2' and R2* values in red nucleus and substantia nigra vs controls †† | Significant decrease in R2' and R2* values in periaqueductal gray matter, red nucleus, and substantia nigra compared with the episodic migraine and controls †† | May be due to hyperoxia associated with head pain during an attack †† | |