Bret Michaels has suffered a setback on the road to his recovery from a brain hemorrhage last week.
While doctors have told ABC News that a "full recovery" may still be possible for the rocker and reality star, he has experienced a side effect called hyponatremia, a lack of sodium in the body which could lead to seizures.
The former Poison frontman, 47, remains in intensive care and is said to be in critical, but stable condition.
The setback comes after Michaels' publicist confirmed last week that Michaels had suffered a massive subarachnoid hemorrhage, or bleeding at the base of his brain stem. On Sunday, statements posted on the star's official website indicated that he was still in the intensive care unit at an undisclosed hospital and in critical condition. The statements also indicated that doctors had not yet located the source of the bleeding in his brain.
Doctors have yet to detail exactly what caused the bleeding in the first place. However, some neurologists were optimistic that Michaels would survive the ordeal -- although the recovery process could take several several weeks to months. In a bit of hopeful news, Michaels' father reported that his son was able to talk on Friday, albeit with slurred speech.
He was also reportedly experiencing blurred vision.
"The long-term prognosis from subarachnoid hemorrhage depends mostly on how poor the patient's condition was on arrival," said Dr. Wendy Wright, an assistant professor of neurology and neurosurgery at Emory University Hospital in Atlanta. "We do know that Mr. Michaels' condition is still being described as critical; that is an automatic label for anyone who is diagnosed with subarachnoid hemorrhage, due to the severe, life-threatening nature of this disease. However, the fact that he is conscious does suggest a better prognosis than if he were comatose.
"Based on how he is being described now, I would like to remain optimistic that he will survive this potentially devastating diagnosis."
"The fact that he's made it to a hospital and is apparently in some sort of reasonable condition... that's a good sign." Said Dr. Arno Fried, chairman of Neurosurgery at Hackensack University Medical Center in Hackensack, N.J. "I would describe [Michaels' condition] as guarded. If the bleed has not caused too much damage, the possibility of recovery is quite good."
Bret Michaels' Subarachnoid Hemorrhage: Aneurysm to Blame?
Dr. Daniel Barrow, who is chairman neurosurgery at Emory University Hospital, agreed that the latest reports suggest that Michaels' condition could be far worse.
"If he is hospitalized and speaking, he is in a much, much better category with regard to the possibility of a good recovery," Barrow said. "The best outcome is that he will be able to resume all of his previous activities with no complications. That is conceivable."
But, Barrow said, "There are many hurdles to cross before [Michaels] is out of the woods."
Bret Michaels: Aneurysm, or Just a Bleed?
Part of determining exactly what these hurdles are depends on doctors' ability to determine the nature of the bleeding. Neurologists have said an aneurysm -- a balloon-like bulge in an artery that has the potential to rupture -- is a possible cause.
"Generally speaking, subarachnoid hemorrhage that is not the result of a ruptured brain aneurysm carries a much more favorable prognosis," said Dr. Vivek Deshmukh, director of Cerebrovascular and Endovascular Neurosurgery at George Washington University in Washington, D.C. "In Mr. Michaels' case, the fact that he is awake and talking is a very good sign.
"The report that Mr. Michaels is awake enough to respond to questions means that he is not at the end of the scale that has the worst outcome," said Dr. Alan Hoffer, director of Neurotrauma at the University Hospitals Case Medical Center in Cleveland, Ohio. But, he added, "The presence of cranial nerve deficits, implied by his difficulty with vision and speech, means that he is likely in the middle of the scale."
The prognosis could be much worse if an aneurysm is, indeed, to blame. Dr. Nicholas Bambakidis, director of Cerebrovascular and Skull Base Surgery at University Hospitals Case Medical Center, said that many aneurysm patients suffer irreversible brain damage as a result of the hemorrhage itself.
"In cases in which there is no neurological damage initially, then patients must face the risk of the treatment, which consists of surgery to repair the aneurysm by closing it off such that blood no longer enters it," Bambakidis said. "If all goes well, patients then face a risk of stroke due to spasm in their normal blood vessels, which is caused by some type of reaction to the initial hemorrhage we do not fully understand , which and can occur up to three weeks after the bleeding.
Bret Michaels, Diabetic, Battled Appendicitis Too
"Though we do have medications and treatments aimed at reducing this risk ... they are not always effective and up to 20 percent of patients can have a serious stroke despite our best efforts."
Dr. Carmelo Graffagnino, director of the Duke Neurosciences Critical Care Unit in Durham, N.C., said that aneurysm or not, the initial severity of the bleed is also an important factor.
"The likelihood of further short term complications depends on how much blood was released during the subarachnoid bleed," Graffagnino said. He said that the fact that Michaels is a diabetic could make his care more complex and increase the likelihood he could experience "complications and slowed recovery."
The latest medical woes for Michaels came just days after an emergency appendectomy he received after falling ill before a concert April 11.
Besides his active performing career, Michaels can be seen each week as a top contender on Donald Trump's NBC reality show "The Celebrity Apprentice," competing against singer Cyndi Lauper and media maven Sharon Osbourne, to name a few of the remaining competitors. He previously starred in VH1's "Rock of Love With Bret Michaels."
Sheila Marikar contributed to this report.