Can epilepsy patients who don't respond to anticonvulsive drugs, benefit from transcranial electrical stimulation?
Rasmussen's encephalitis (RE) involves focal motor or generalised seizures that result in hemiparesis and cognitive decline (Rasmussen et al., 1958). RE is caused by repeated inflammation in the brain, which most commonly affects one hemisphere. RE is often diagnosed in early childhood and the patient progressively deteriorates approaching adulthood. An effective RE treatment is the surgical implants such as the deep brain and vagus nerve stimulation techniques. An alternative method is transcranial direct current stimulation (tDCS) which modulates cortical excitability (Nitsche et al., 2002). In this longitudinal experiment we evaluate the effectiveness and safety of tDCS as a non-invasive alternative treatment to surgical implants. We further compare the inhibitory effects of cathodal and anodal stimulation.
Five RE patients (mean age 19, 3 females) participated in the study. Patients primary caretakers were asked to keep a seizure diary for three months before and two months after the treatment, and record details of their seizures. Study consisted of three phases where participants received cathodal, anodal and sham stimulations subsequently.
3 patients received cathodal direct current stimulation (2.0 mA), and the remaining two received cathodal amplitude modulated (tACS) stimulation (0.85 mA peak-to-peak added to 1.15 mA, 12 Hz) for 30 minutes. We used a custom built stimulator with wet sponge electrodes called the tessaNova (Teknofil Ltd, Istanbul, Turkey). The active electrode was placed on the epileptogenic focus determined by participant's T2 weighted MRI scan, and the second electrode on the contralateral mastoid. Following a long break patients received anodal and sham stimulations as well.
Four patients (Patient 1-4) showed more than 50% decrease in seizure frequency after receiving cathodal direct current stimulation. One patient (Patient 1 and 2) ceased having seizures for 8 and 10 days respectively, despite having a 20-30 seizure/day prior to the treatment. Two patients showed increased reductions in seizure frequency after receiving cathodal tACS stimulation. Longest tDCS effect lasted one month. Anodal and sham stimulations did not have any effects on the seizure frequency. Altogether results demonstrate that cathodal tDCS and tACS as effective and safe non-invasive treatment alternatives to reduce cortical excitability and seizure frequency in patients with RE.
Topaloglu, P., Erdogan, E. T., Kurt, A., Kocagoncu, E., Kucuk, Z., Kinay, D., Yapici, Z., Aksu, S., Baykan, B., & Karamursel, S. (2016). Transcranial direct current stimulation improves seizure control in patients with Rasmussen encephalitis. Epileptic Disorders, 18, 58-66.