The finding that migraine patients show signs of lactic acidosis, thus suggesting abnormalities in the functioning of the TCA, has led researchers to further investigate the TCA, for example, for pyruvate, SDH, nicotinamide adenine dinucleotide cytochrome c reductase, succinate cytochrome c reductase, NADH dehydrogenase and CS, in order to investigate the relationship between migraine and the TCA (Figure 3) (Stuart and Griffiths, 2012). This evidence concerns the gene CS and migraine disorder.