INTENSITY DEPENDENCE OF AUDITORY-EVOKED POTENTIALS IS PRONOUNCED IN MIGRAINE - AN INDICATION OF CORTICAL POTENTIATION AND LOW SEROTONERGIC NEUROTRANSMISSION

Migraine is associated with stimulus hypersensitivity, increased evoke d cortical responses, and abnormal 5-HT levels in peripheral blood. We studied cortical auditory evoked potentials (AEPs) between attacks in 35 patients suffering from migraine without aura (MO, n = 25) or with aura (MA, n = 10) and in 25 healthy volunteers. Binaural tones were d elivered at 40, 50, 60, and 70 dB sensation level (SL) in a pseudorand omized order. The intensity dependence of the auditory N1-P2 component was significantly greater in MO (p = 0.003) and MA (p = 0.02) patient s than in healthy controls, resulting in a much steeper amplitude/stim ulus intensity function slope. When three sequential blocks of 40 aver aged responses were analyzed at the 40- and 70-dB SL intensities, N1-P 2 amplitude decreased in second and third blocks at both intensities i n controls, but increased in migraineurs, a difference that was signif icant in both blocks for the 70-dB SL stimulus. The strong interictal dependence of AEPs on stimulus intensity may thus be due to potentiati on (instead of habituation) of the response during repetition of the h igh-intensity stimulation. In concordance with previous studies of vis ual evoked potentials, these results confirm that migraine is characte rized between attacks by an abnormality of cortical information proces sing, which might be a consequence of low 5-HT transmission and favor cortical energy demands.