Noninvasive Brain Stimulation Protocols in the Treatment of Epilepsy: Current State and Perspectives

Abstract

Summary:In epileptic seizures, there is an enhanced probability of neuronal networks to fire synchronously at high frequency, initiated by a paroxysmal depolarisation shift. Reducing neuronal excitability is a common target of antiepileptic therapies. Beyond or in addition to pharmacological interventions, excitability-reducing brain stimulation is pursued as an alternative therapeutic approach. Hereby, noninvasive brain stimulation tools, such as transcranial magnetic stimulation (TMS) and transcranial direct current stimulation (tDCS), have gained increased interest as efficient tools to modulate cortical excitability and activity. In animal models, stimulation-induced cortical excitability diminution has been shown to be suited to reduce seizures. Clinical studies conducted to date, however, have shown mixed results. Reasons for this, as well as possible optimization strategies that might lead to more efficient future stimulation protocols, will be discussed.

Emerging subspecialties in Neurology

“…However, the poor correlation between real seizure frequency and those reported by patients makes the boundary of a possible placebo effect difficult to find. 5 There is also increasing evidence that transcranial stimulation might improve selective skills in cognitive disorders such as Alzheimer disease. These findings are very preliminary, since improving performances in a single task does not necessarily represent a global cognitive enhancement.…”

Neurostimulation, neuromodulation, and the treatment of epilepsies

“…A repetitive protocol in which one session of tDCS is applied daily over the course of several days or weeks may prolong these effects even longer. The optimal protocol for tDCS has yet to be established, with important questions regarding optimal stimulation duration, repetition rate, reference electrode position, and stimulation strength still unanswered (Nitsche and Paulus, 2009). …”

“…The coil delivers the magnetic current through the skull which induces an electric current in the brain that elicits action potentials in cortical neurons approximately 1.5-2.0 cm beneath the scalp (Epstein et al, 1990). Animal studies showed that if the electrical current repetitively activated these cortical neurons, long-lasting changes in cortical excitability will have occurred, leading to the discovery of rTMS (Nitsche and Paulus, 2009). The type of excitability change is determined by the frequency of the repeated pulses, such that low-frequency rTMS (≤ 1 Hz) reduces cortical excitability and high-frequency rTMS (> 1 Hz) increases cortical excitability (Pascual-Leone et al, 1998) but these changes are not necessarily synonymous with increased inhibition or excitability, respectively.…”

Transkranial likestrømsstimulering ved kroniske smerter

“…Tidlige faser av kliniske studier har vist at behandlingen potensielt kan brukes ved epilepsi (19,20), alvorlig depresjon (21,22) og rusavhengighet (23)(24)(25). I tillegg kan stimuleringen fasilitere motorisk funksjon etter hjerneslag (26,27) og hukommelsesfunksjon ved Alzheimers sykdom (28).…”