Migraine-linked characteristics of transcranial magnetic stimulation-induced phosphenes.

Transcranial magnetic stimulation is used to explore visual cortex hyperexcitability in migraine. We hypothesized that the phosphene threshold in subjects suffering from migraines with and without aura would be lower than in controls, and this phenomenon could be linked to higher pain and disability levels. We also implied that subjects with lower phosphene threshold could see more phosphenes of different colors and shapes. Our primary objective was to compare the phosphene threshold between migraine without aura, migraine with aura, and control groups and investigate which factors contribute to different phosphene parameters in migraineurs. Secondary objectives were to compare color, shape, and number of phosphenes between groups and assess pain and disability level correlation with the phosphene characteristics. Phosphene threshold in migraine without aura, migraine with aura, and control groups were 68 ± 9.5% vs. 75 ± 12%, vs. 80 ± 11%, respectively. Other phosphene parameters (number, color and shape) did not differ between groups. Average pain level during the attack did not correlate with phosphene threshold significantly, though the non-significant trend for negative correlation of migraine disability assessment scale score and a phosphene threshold has been found the higher was migraine disability assessment scale value, the lower was phosphene threshold (ß = -0.255; P = 0.139). Other variables: gender, age, migraine subtype, migraine duration and use of hormone contraceptives - were not related to the phosphene threshold value. Our study provides additional data on visual cortex hyperexcitability in migraineurs, regarding transcranial magnetic stimulation with a figure-of-eight coil. Visual cortex excitability might be linked to higher disability.

Intermittent Theta-Burst Stimulation Over the DorsoLateral PreFrontal Cortex (DLPFC) in Healthy Subjects Produces No Cumulative Effect on Cortical Excitability.

Background: Intermittent Theta Burst Stimulation (iTBS) is a design of repetitive Transcranial Magnetic Stimulation (rTMS) and could be a candidate to replace rTMS in the treatment of depression, thanks to its efficacy, shorter duration, and ease of use. The antidepressant mechanism of iTBS, and whether this mechanism is mediated by a modulation of cortical excitability, remains unknown. Methods: Using a randomized double-blind, sham-controlled trial, 30 healthy volunteers received either iTBS or a sham treatment targeting the left DorsoLateral PreFrontal Cortex (L-DLPFC), twice a day over 5 consecutive days. Cortical excitability was measured before and after the 5 days of stimulation. Results: No difference in cortical excitability was observed between active or sham iTBS. Conclusion: Our study does not support any effect on cortical excitability of repetitive iTBS targeting the L-DLPFC.