SLC4A4 and familial hemiplegic migraine: More recently, a mutation in SLC4A4 [14] encoding the Na+-HCO3- cotransporter NBCe1 has been identified in sisters with FHM, and a mutation in SLC1A3 [15] encoding the glial glutamate transporter EAAT1 has been identified in one patient with pure hemiplegic migraine.