gms | German Medical Science

Objective: Transcranial direct current stimulation (tDCS) induces polarity specific changes of cerebral blood flow. The pathophysiological mechanism of this phenomenon is still not fully understood. Possible mechanisms are either a modulation of cortical neuronal activity or a direct impact on the vessel wall musculature. We evaluated the influence of tDCS on cerebral vasospasm (VSP) in a double blood injection subarachnoid hemorrhage (SAH) model in rats.

Methods: SAH was induced in 63 Sprague Dawley male rats using the double-hemorrhage SAH-model. The rats were assigned to the tDCS-group (anodal 24/cathodal 26) or to the control-group (no tDCS) consisting of 13 rats. TDCS was applied one to 4 times per day (day 3 and 4) after SAH induction via an epicranial electrode placed over the right hemisphere. MRI including a TOF-(time of flight) sequence was performed on day 1(baseline), on day 2 after the second injection and on day 5 for the assessment of VSP of large basal arteries. Three VSP severity grades (mild, moderate and severe) were differentiated. TDCS was than correlated with the incidence and severity of VSP.

Results: A total of 72 rats were analyzed, 63 rats in the SAH-group and 9 rats in the sham-group. No VSP was seen in the sham-group. In the SAH-group VSP was visible on day 2 in 77.7% (49/63) of the rats, among which were 26.6% (13/49) rats with severe, 2.1% (1/49) with moderate and 71.3% (35/49) with mild VSP. On day 5 VSP was seen in 85.7% (54/63) of the rats. Severe VSP was detected in 66.6% (36/54), moderate in 20.4% (11/54) and mild in 13% (7/54) of the rats. There was a significant difference concerning the overall VSP incidence on day 2 (anodal 75%, cathodal 80.8% and control 84.7%) between the different SAH-groups (Fisher's exact test, p=0.41). However, comparing the VSP incidence on day 2 and 5 we found an increase in VSP incidence in the anodal- and in the control-group, whereas the VSP incidence in the cathodal-group remained stable. We found no significant difference in respect to the frequency of stimulation and VSP severity.

Conclusion: A polarity specific association is found between tDCS and the VSP incidence in a SAH model in rats: anodal tDCS results in an increased incidence of VSP whereas cathodal tDCS keeps the VSP incidence stable. Future experiments have to show wether longer or more frequent cathodal tDCS can induce a reduction of the VSP incidence.