EM	episodic migraine
CM	chronic migraine
PCr	phosphocreatine
Pi	inorganic phosphate
TP	total phosphorus signal
PCr/Pi, PCr/ATP	a reduced ratio indicates energy deficit
ATP	adenosine triphosphate
In bold	brain areas affected by reduced glucose metabolism and shared by insulin resistance, migraine and AD subjects.
*	Lai KL et al enrolled patients with CM without medication overuse headache, major depression or prior preventive treatment.
**	A higher headache frequency was associated with smaller grey matter volume in the anterior cingulate cortex and hippocampus in EM and CM
***	According to current literature, most studies have chosen the occipital cortex as the region of interest, as aura, most commonly with visual symptoms, is attributed to this area in patients suffering from this type of migraine [83]
****	The orbitofrontal cortex includes the Brodmann areas 10, 11 and 47 [84]
*****	The inferior frontal gyrus includes the Brodmann areas 44, 45 and 47 [85]
†	In comparing the brains of CM patients with EM patients, Valfrè et al reported that CM patients had significant grey matter reductions in these areas.
††	The lateral orbital gyrus includes the Brodmann area 47 [86] Mackey, Sott; Petrides, Michael (2006). "Chapter 2: The orbitofrontal cortex: sulcal and gyral morphology and architecture". In Zald, David H.; Rauch, Scott (eds.). The Orbitofrontal Cortex. New York: Oxford University Press. p. 34
†††	Chronic migraine patients had smaller frontal regions than episodic migraine patients.
††††	This study on young women with Polycystic Ovary Syndrome reported a direct association between mild insulin resistance and brain glucose hypometabolism, which was independent of overweight or obesity.