Abstract
Purpose: :
Flicker is known to induce higher metabolic demands and alter blood flow in both retina and brain. People with migraine often report aversiveness to flickering lights, and show abnormal performance on visual psychophysical measures involving flickering stimuli in between attacks whilst asymptomatic. It is unclear whether these functional deficits arise from the brain, retina or both. In this study, we consider whether people with migraine show retinal and/or brain electrophysiological abnormalities with flickering stimuli.
Methods: :
Transient (1 Hz, 250 ms) and steady-state (8 Hz, 480 ms) full-field (31°) pattern reversal electroretinograms (PERG) and visual evoked responses (PVER) were recorded simultaneously in 21 migraine patients (12 without aura, 9 with aura) at least 7 days post-migraine and in 28 age-similar (18-45 years) non-headache controls. Monocular checkerboard stimulation (mean luminance 52 cd/m², check size 0.8°, contrast 96%) was used. A total of 200 artefact-free signals were collected at 1 kHz, amplified and bandpass filtered (1.25-100 Hz). For transient waveforms, we extracted the peak-to-trough amplitude of the PERG N95 and PVER P100 components. Steady-state amplitudes were analysed in the frequency domain after discrete Fourier transform to isolate the second harmonic (16 Hz).
Results: :
PERG amplitudes did not differ significantly between groups (mean µV ± SEM; transient control 9.5 ± 0.3, migraine 10.0 ± 0.5; steady-state control 3.4 ± 0.1, migraine 3.3 ± 0.1). Likewise the 18% reduction in the transient PVER amplitude was not statistically significant (control 11.6 ± 0.7, migraine 9.5 ± 0.7). However, the mean steady-state PVER amplitude was significantly lower by 35% in the migraine group (control 4.1 ± 0.3, migraine 2.7 ± 0.2, F(1,47) = 7.6, p<0.01).
Conclusions: :
To our knowledge, this study is the first to demonstrate normal retinal function simultaneous with abnormal cortical function on steady-state recording in people with migraine in between attacks. The mechanism underlying the cortical abnormality that becomes apparent with flickering stimuli is unclear.
Keywords: electrophysiology: clinical • electroretinography: clinical