NIRS-Based Assessment of Cerebral Oxygenation During High-Definition Anodal Transcranial Direct Current Stimulation in Patients with Posttraumatic Encephalopathy

Abstract

The aim was to evaluate the changes in brain tissue oxygenation, assessed by near-infrared spectroscopy (NIRS) during high-definition transcranial direct current stimulation (HD-tDCS) in patients with posttraumatic encephalopathy (PTE). Fifty-two patients with PTE after diffuse, blunt, non-severe traumatic brain injury (TBI) (14 women and 38 men, 31.8±12.5years, Glasgow Coma Score before tDCS 13.2±0.3) were treated with HD-tDCS at 21days after TBI. The parameters were as follows: 1mA, 9V, and current density ~0.15mA/cm2. The duration of HD-tDCS was 30 min. The anodal and cathodal electrodes were placed over the left M1 and contralateral supraorbital region, respectively. HD-tDCS was delivered by a direct current stimulator with a pair of surface sponge electrodes (S=3 cm2). Regional cerebral oxygen saturation (SctO2) in the frontal lobes was measured simultaneously and bilaterally by the cerebral oximeter. SctO2 values were compared before stimulation, by the 15th minute and at the end of the tDCS. Significance was preset to p<0.05. Results. Before the stimulation, SctO2 values varied between 53% and 86% (74±7.1%) without significant difference between hemispheres (p=0.135). After 15min, a significant (p<0.0000001) decrease in regional SctO2 on the anodal side was observed (mean 54.5±5.6%). On the cathodal side, SctO2 remained unchanged. At the end of the stimulation (30min), differences between the hemispheres in SctO2 remained statistically significant (p<0.05). Conclusions. In patients with PTE complicated by TBI, HD-tDCS causes a statistically significant (p<0.05) decrease in regional SctO2 on the anodal side.