Bret Michaels's health has taken a turn for the worse, PEOPLE has learned: After an excruciating headache late Thursday night, the star was rushed to an undisclosed hospital where doctors discovered he suffered a massive subarachnoid hemorrhage (bleeding at the base of his brain stem), according to a source close to the situation. Michaels, 47, is currently in critical condition. "After several CAT scans, MRIs and an angiogram, [doctors] decided to keep Michaels in the ICU and are running several tests to determine the cause. [It] will be touch and go for the next few days while he is under intense observation," the source says. Reps confirm this report is accurate, and tell PEOPLE, "We will have no additional information until further testing is done."