Could cathodal transcranial direct current stimulation modulate the power spectral density of alpha-band in migrainous occipital lobe?

OBJECTIVE: To identify the correlation between cathodal transcranial direct current stimulation (tDCS) and the power spectral density (PSD) of alpha-band on the occipital lobe of migraineurs. METHODS: Firstly, a cross-sectional study was performed to compare the PSD of alpha-band in the occipital cortex of 25 migraineurs versus 10 healthy volunteers in resting state and during repetitive light stimuli (RLS). Secondly, the patients participated in 12 sessions of cathodal (n = 11) or sham tDCS (n = 10) over the primary visual cortex (V1) to investigate the alpha-band PSD. RESULTS: The alpha-band PSD on the occipital cortex was higher in migraineurs than healthy subjects in resting state and lower during the first train of RLS. Cathodal tDCS over the V1 reduced the alpha-band occipital activity in resting state but did not interfere with the functional responses to RLS when light stimulation was turned on. CONCLUSIONS: Our findings suggest that the occipital cortex of migraineurs is hypoactive in the baseline condition, but becomes hyperactive when stimulated by light. Cathodal tDCS over the V1 decreases baseline alpha PSD in patients, possibly modulating the involved neuronal circuitries, but it cannot interfere once photic stimulation starts.

Transcranial direct current stimulation in the prophylactic treatment of migraine based on interictal visual cortex excitability abnormalities: A pilot randomized controlled trial.

PURPOSE: The aims of this paper are (i) to compare the excitability of visual cortex in migraine patients with healthy volunteers; and (ii) if an abnormal excitability has been found, to modulate cortical excitability in migraine patients with transcranial direct current stimulation (tDCS) and observe their clinical and neurophysiological effects. METHODS: The study was divided into two steps. A cross-sectional study (step 1) was conducted to compare the cortical excitability of 23 migraineurs (11 with and 12 without aura) on 11 healthy individuals. On step 2, a randomized, double blinded, controlled pilot trial was carried on with 19 migraineurs, randomly divided into: experimental and control group. During 12 sessions, experimental and group received active tDCS to visual cortex and control group received sham tDCS. The headache diary was applied for a total of 90days (before, during and after tDCS sessions). Phosphene threshold (PT) induced by transcranial magnetic stimulation was recorded to measure the excitability of the visual cortex before and after each session. RESULTS: Step 1 showed higher level of cortical excitability between migraineurs when compared to healthy volunteers; therefore, cathodal tDCS was applied over visual cortex in step 2. After tDCS application, a significant decrease was observed in a number of migraine attacks, painkiller intake and duration of each attack just in experimental group. The analysis of PT indicated no difference in cortical excitability after tDCS. CONCLUSIONS: Findings of the study suggested that inhibitory tDCS on visual cortex might be an alternative and non-pharmacological treatment for migraine prophylaxis. However the clinical improvements of patients after tDCS treatment are not correlated with changes in cortical excitability.