NIRS-Based Assessment of Cerebral Oxygenation During High-Definition Anodal Transcranial Direct Current Stimulation...

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 ± 12.5 years, Glasgow Coma Score before tDCS 13.2 ± 0.3) were treated with HD-tDCS at 21 days after TBI. The parameters were as follows: 1 mA, 9 V, and current density ~0.15 mA/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 15 min, 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 (30 min), 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.