The aim of this study is to investigate the effects of cathodal transcranial direct current stimulation in the management of seizures in subjects with focal refractory epilepsy.

Hypothesis: Epilepsy is the most common neurological disorder globally, affecting approximately 50 million people worldwide. Of these, approximately 20% present with intractable or refractory epilepsy, where the frequency of seizures cannot be controlled adequately with anti-epileptic drugs (AEDs), leading to great neurobiological, cognitive, psychological and social consequences. Transcranial Direct Current Stimulation (tDCS) is a non-invasive brain stimulation (NIBS) technique that can effectively modulate (up- or down-regulate) cortical excitability of targeted brain regions. It has the potential of downregulating the neuronal activity, through the cathodal stimulation of the epileptic focal area and thus, reducing the frequency of seizures. Previous studies have shown that cathodal tDCS is a safe and effective treatment modality of treatment to reduce the frequency of seizures in patients with refractory epilepsy. However, the level of evidence of its effects in the management of seizures frequency is still low. In the present work, the investigators aim to evaluate the effects of tDCS in the management of seizures in patients with refractory epilepsy and its impact on cognitive function and quality of life.

Objective: The main aim of this randomized controlled trial is to determine if cathodal tDCS is effective in reducing the frequency of seizures in refractory epilepsy and, to determine if this reduction will positively impact the participants cognitive status and quality of life.

Methods: This is a prospective, randomized, placebo-controlled, double-blind, single-center study. The participants in the study will be randomized to either the intervention - tDCS group or sham group. Each individual will undergo 15 consecutive sessions of real cathodal tDCS stimulation or sham-stimulation. The primary outcome measure will be the frequency of seizures, measured by a seizure diary; changes in interictal epileptiform discharges on the Electroencephalogram (EEG); and functional connectivity changes in the epilepsy focal area, measured by resting-state Functional Resonance Image (rs-fMRI). Secondary outcomes include quality of life and cognition. Outcome measures will be done prior to intervention; immediately after intervention, at 1 month-follow up and again at 3-months follow up.

Inclusion Criteria:

• confirmed diagnosis of focal refractory epilepsy
• participants must be 18 years or older
• must be on a stable medication regimen
• seizures frequency equal or greater than 1 seizure/month
• participants or their caregivers must be able to use a seizures diary

Exclusion Criteria:

• participants younger than 18 years old
• diagnosis of generalized epilepsy
• participants who are still making changes to medication regimen
• participants who are pregnant
• participants who have any kind of intracranial implants
• seizure frequency less than 1/month
• participants with skin abnormalities or rash on the scalp
• participants or caregivers that are unable to use a seizures diary

The tDCS machine is equipped with a sham option, determined by a code, that will not be disclosed to the participants, outcome assessor and principal investigator until the moment of data analysis. Randomization will be done through envelopes that will contain the codes of types of stimulation (real vs sham), which will be prepared by a third party.