There were different types of backlash. In the science section of the Cultivation Encyclopaedia, the injuries accrued from backlash were divided into five general grades.
To Song Qingshu, it looked like the goateed elderly Daoist had suffered fourth-degree backlash. The spiritual pressure which had recoiled on him had rampaged through his body with no release outlet. In addition, the goateed elderly Daoist had circulated his own spirit energy in an effort to fight it, which had had the effect of driving the spiritual energy up into his head, thus causing it to swell.
If his condition wasn't treated in time, it was very likely that he would wind up in a coma and become a vegetable.