Total group of migraine with aura patients (MAtot)
N1, P1 and N2 latencies were not significantly different between HV and MAtot (p > 0.05) (Table 2).
Table 2 Latencies (in milliseconds) of VEPs in healthy volunteers (HV), the total group of migraine with aura patients (MAtot) and its subgroups with pure visual aura (MA) or visual aura associated with paraesthesia and/or dysphasia (MA+). Data are expressed as means ± SD.
Electrophysiological parameters (ms) HV (n = 30) MAtot (n = 47) MA (n = 27) MA+ (n = 20)
N1 (N75) 76.5 ± 6.4 75.7 ± 5.2 75.4 ± 5.8 75.9 ± 4.6
P1 (P100) 103.5 ± 5.9 103.1 ± 6.7 102.9 ± 5.7 103.4 ± 8.0
N2 (145) 144.2 ± 10.4 141.7 ± 11.9 140.6 ± 9.6 142.6 ± 11.4
Table 3 N1–P1 VEP component amplitude (μV) and habituation slope in healthy volunteers (HV), the total group of migraine with aura patients (MAtot) and its subgroups with pure visual aura (MA) or visual aura associated with paraesthesia and/or dysphasia (MA+). Data are expressed as means ± SD
N1-P1 HV (n = 30) MAtot (n = 47) MA (n = 27) MA+ (n = 20)
1st amplitude block (μV) 6.97 ± 2.90 7.28 ± 3.23 6.53 ± 3.36 8.27 ± 2.83
2nd amplitude block (μV) 7.15 ± 3.02 7.39 ± 3.23 6.43 ± 3.29 8.69 ± 2.70
3rd amplitude block (μV) 6.87 ± 2.79 7.40 ± 2.96 6.49 ± 2.83 8.64 ± 2.74
4th amplitude block (μV) 6.55 ± 2.74 7.16 ± 3.17 6.12 ± 3.07 8.57 ± 2.81
5th amplitude block (μV) 6.25 ± 2.57 7.34 ± 3.00 6.49 ± 2.97 8.49 ± 2.70
6th amplitude block (μV) 5.97 ± 2.63 7.42 ± 3.02 6.65 ± 3.09 8.45 ± 2.64
Slope −0.50 ± 0.36 +0.006 ± 0.40 +0.01 ± 0.30 +0.0049 ± 0.18
Table 4 P1-N2 VEP component amplitude (μV) and habituation slope in healthy volunteers (HV), the total group of migraine with aura patients (MAtot) and its subgroups with pure visual aura (MA) or visual aura associated with paraesthesia and/or dysphasia (MA+). Data are expressed as means ± SD
P1-N2 HV (n = 30) MAtot (n = 47) MA (n = 27) MA+ (n = 20)
1st amplitude block (μV) 6.59 ± 3.16 7.00 ± 3.07 6.12 ± 2.65 8.18 ± 3.26
2nd amplitude block (μV) 6.49 ± 3.03 6.87 ± 3.26 5.88 ± 2.55 8.20 ± 3.70
3rd amplitude block (μV) 6.49 ± 2.94 6.62 ± 3.10 5.67 ± 2.66 7.91 ± 3.25
4th amplitude block (μV) 5.99 ± 2.85 6.32 ± 2.88 5.37 ± 2.36 7.60 ± 3.08
5th amplitude block (μV) 6.26 ± 2.59 6.84 ± 2.93 6.01 ± 2.45 7.96 ± 3.19
6th amplitude block (μV) 5.61 ± 2.86 6.50 ± 2.78 5.78 ± 2.70 7.47 ± 2.64
Slope −0.35 ± 0.73 −0.09 ± 0.42 −0.06 ± 0.47 −0.13 ± 0.35
In the rm-ANOVA model with N1–P1 peak-peak amplitude as dependent variable, multivariate test was significant for the “group” × “blocks” interaction effect (Wilks’ Lambda = 0.745, F5,71 = 4.862, p = 0.0007) (Table 3). After checking that the sphericity assumption was not violated (Mauchley Test: p = 0.104), univariate rm-ANOVAs for N1–P1 peak-peak amplitude confirmed the significant interaction factor effect (F5,375 = 5.261, p = 0.0001, partial η2 = 0.066, op = 0.988) observed (see above) at the multivariate test. Post-hoc analysis showed that VEP amplitudes differed between groups only in the last block (5.97 μV in HV vs. 7.42 μV in MAtot, p = 0.038, raw data are shown in Fig. 2). In HV, N1–P1 amplitude was significantly lower in the 6th compared to the 1st block (p = 0.0008). This was not so in MAtot, where this comparison did not reach the significance level (p = 0.994).
Fig. 2 Raw amplitudes (mean ± SEM) of N1-P1 (upper graphs) and P1-N2 (lower graphs) VEP components in 6 sequential blocks of 100 recordings. On the left healthy volunteers [HV, n = 30] are compared to the total group of migraine with aura patients [MAtot, n = 47]; on the right they are compared to the 2 subgroups of patients with pure visual aura [MA, n = 27] and patients with complex aura [MA+, n = 20]. ≠ p < 0.05 MAtot vs HV; *p < 0.05 MA+ vs MA; § p < 0.05 MA+ vs HV
In the rm-ANOVA model with P1-N2 peak-peak amplitude as dependent variable, multivariate test was not significant for the “group” × “blocks” interaction effect (Wilks’ Lambda = 0.869, F5,71 = 2.149, p = 0.069) (Table 4).
The linear regression N1–P1 slope of VEP amplitudes over all blocks differed significantly between the two groups (F1,75 = 24.493, p < 0.0001, partial η2 = 0.246, op = 0.998; raw data are shown in Fig. 3). The P1–N2 slope of the linear regression analysis was not different between groups (F1,75 = 3.312, p = 0.073, partial η2 = 0.042, op = 0.435; Fig. 3).
Fig. 3 Raw habituation slope of VEP N1-P1 and P1–N2 peak-to-peak amplitudes (mean ± SEM) over 6 sequential blocks of 100 averaged responses in healthy volunteers (HV, n = 30), patients with pure visual aura (MA, n = 27), patients with complex aura (MA+, n = 20) and the 2 latter groups combined (MAtot, n = 47)
In the MAtot group the N1–P1 amplitude slope correlated positively with the number of days elapsed since the last migraine attack (r = 0.351, p = 0.045). There were no other significant correlation between neurophysiological and clinical data.