Extrastriate brain regions likely to be associated with cortical spreading depression have demonstrated a relationship with changes in cerebral blood flow (CBF) in the interictal state for those with episodic migraine. Arterial spin labeling magnetic resonance imaging (ASL-MRI) is sufficiently sensitive to detect CBF abnormalities among those in the interictal state, according to a study recently published in Headache. 

This cross-sectional study included 17 individuals with episodic migraine (4.0±3.8 monthly migraines; mean age 32.7±9.9 years; 13 women) and 19 healthy controls (mean age 31±9.3 years). Among those with episodic migraine, 13 had migraine with aura and 4 had migraine without aura. These individuals were assessed during the interictal phase for CBF at the University Hospital in Zürich, Switzerland, with no migraines reported within ±2 days of the scan. To compare intergroup global CBF, the study researchers extracted each group’s mean CBF over 90 cortical brain regions, comparing healthy controls with both the episodic migraine group and the migraine-with-aura subgroup using unpaired two-tailed t-tests.

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Those with episodic migraine demonstrated hyperperfusion in the right middle temporal visual area (MT+) compared with controls (Cohen’s d 0.99; mean CBF for episodic migraine 40.9±9.4 mL/100g/min; mean CBF for controls 33.1±5.9 mL/100g/min). Those in the migraine-with-aura subgroup showed hyperperfusion in the superior temporal gyrus and right MT+ (unpaired 2-sample 1-sided t-test, t=–4.33 and t=–6.03, respectively; P <.001). Cohen’s d effect size for MT+ was 1.34 (mean CBF for migraine-with-aura vs controls, 43.3±8.6 vs 33.1±5.9 mL/100g/min), and for the superior temporal gyrus was 1.28 (mean CBF for migraine-with-aura vs controls, 47.4±6.4 vs 40.1±4.9 mL/100g/min). Those with episodic migraine showed a positive correlation between anxiety and CBF in the right angular gyrus and left parietal operculum (parameter estimates+90% confidence intervals were 3.72+0.79 and 2.51+0.56, respectively).  

Limitations to this study include exclusive investigation of episodic migraine during the interictal state, a lack of information on changes to dynamic blood flow throughout the migraine cycle, a lack of screening for allodynia, an inability to answer whether hyperperfusion occurred, small sample sizes for migraine with and without aura, a lateralization of between-group differences to the right hemisphere, and a lack of information on photophobia during attacks.

The study researchers conclude that “[in] the interictal state, hyperperfusion was found in the supposed region of [cortical spreading depression] onset, located occipito-temporally.” They further conclude that “ASL-MRI is a sensitive method to identify local abnormalities in CBF in episodic [migraine with aura] especially in the interictal state.”

Reference

Michels L, Villanueva J, O’Gorman R, et al. Interictal hyperperfusion in the higher visual cortex in patients with episodic migraineHeadache. 2019;59(10):1808-1820.