Modulation of visual cortical excitability in migraine with aura: effects of 1 Hz repetitive transcranial magnetic stimulation

Abstract

Recent studies showed hyperexcitability of the occipital cortex in subjects affected by migraine with aura. It has been shown that 1 Hz repetitive transcranial magnetic stimulation (rTMS) reduces excitability of visual cortex in normal subjects. The aim of the study was to investigate the effects of low frequency (1 Hz) rTMS on visual cortical excitability by measuring changes in phosphene threshold (PT) in subjects with migraine with aura. Thirteen patients with migraine with aura and 15 healthy controls were examined. Using a standardized transcranial magnetic stimulation protocol of the occipital cortex, we assessed the PT (the lowest magnetic stimulation intensity at which subjects just perceived phosphenes) before and after a 1-Hz rTMS train delivered at PT intensity for 15 min. The difference in the proportion of subjects reporting phosphenes in migrainer and control groups was significant (migrainers: 100% vs controls 47%; P<0.05), and 1 Hz rTMS over the occipital cortex led to a significantly increased visual cortex excitability expressed as a decrease in PT in subjects affected by migraine with aura. Conversely, after a 1-Hz TMS train normal subjects showed increased PT values, which suggests a decreased visual cortex excitability. Our findings confirm that the visual cortex is hyperexcitable in migrainers and suggest a failure of inhibitory circuits, which are unable to be upregulated by low frequency rTMS.

Electrophysiological response patterns of primary sensory cortices in migraine

“…This finding would suggest that a lower preactivation level effectively characterises the migrainous brain, although a "dysexcitability" of intracortical inhibitory interneurons cannot be excluded. As a matter of fact, low-frequency rTMS was shown to have a paradoxical effect on the migraine cortex [92], which may suggest that the effect of TMS depends on the excitability level of the underlying cortex.…”

A double dissociation between striate and extrastriate visual cortex for pattern motion perception revealed using rTMS

“…By applying TMS pulses at a frequency of 1 Hz it is possible to induce a temporary reduction of excitability in the stimulated region of cortex as measured by the relative strength of TMS stimulation required to elicit a certain cortical response pre-and post-rTMS stimulation [Fitzgerald et al, 2006]. This effect has been demonstrated specifically in visual cortex [Brighina et al, 2002;Fierro et al, 2005]. Offline 1 Hz rTMS has also been used to demonstrate that striate cortex is involved in the dichoptic (separate stimuli to each eye) combination of two components into a plaid percept [Saint-Amour et al, 2005].…”

Motor and Occipital Cortex Excitability in Migraine Patients

“…Motor symptoms in some migraine subtypes have also drawn attention to the hyperexcitability of motor cortex. [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20] Transcranial magnetic stimulation (TMS) is a non-invasive tool to investigate physiology and excitability of both motor-and occipital cortices. 11,[21][22][23][24][25] The changes in motor threshold, latency and amplitude of motor evoked potential, central motor conduction time and cortical silent period after magnetic ABSTRACT: Objective: We evaluated motor and occipital cortex excitability in migraine patients using transcranial magnetic stimulation.…”