Hyponatremia: Bret Michaels' Latest Brain Bleed Hurdle

Bret Michaels has experienced another medical complication, a condition known as hyponatremia, according to a statement posted Tuesday on the website of the 47-year-old reality TV star and former Poison frontman.

The condition, defined by abnormally low levels of salt in the blood can lead to seizures and brain swelling, and is the latest development in the health problems that have affected Michaels since his hospitalization last Friday for what his publicist confirmed was 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 critical condition in the intensive care unit of an undisclosed hospital. The statements also indicated that doctors had not yet located the source of the bleeding in his brain.

Neurologists said it is overwhelmingly likely that the complication arose from Michaels' brain bleed.

"It is not at all unexpected that Mr. Michaels has hyponatremia," said Dr. Wendy Wright, an assistant professor of neurology and neurosurgery at Emory University Hospital in Atlanta, and a specialist in hyponatremia after brain injury. "There are several potential causes that tend to involve chemical imbalances in the brain, leading to either a slight increase in total body fluid -- making the relative amount of sodium in the body seem lower -- or a loss of sodium in the urine."

Dr. Vivek Deshmukh, director of cerebrovascular and endovascular neurosurgery at George Washington University in Washington, D.C., said hyponatremia is "very commonly seen" in subarachnoid hemorrhage patients, and the risk of the complication is in fact one of the reasons that doctors monitor these patients so closely in the intensive care unit.

Deshmukh also said it is unlikely that the condition will affect Michaels' prognosis, though the occurrence of such sodium fluctuations may prolong a patient's hospitalization.

"Hyponatremia that is detected early should not be associated with any long-term complications and the overall prognosis remains unchanged," he said. "Treatment is typically straightforward and requires simply replacing the sodium in the blood."

Wright said, however, that determining exactly how this new complication will factor in to Michaels' chances of a normal recovery are as yet unclear.

"We do not have much information at this time about Mr. Michaels' clinical condition to understand how significant a setback this is," she said. "Best case scenario, this would be something that was found pre-emptively, will be treated sufficiently and will not cause any further harm to Mr. Michaels."

Bret Michaels May Have Dodged Bullet, Doctors Say

If the condition had gone undetected, however, Michaels could have been at risk of such serious side effects as seizures, brain swelling and neurological decline. "Some of these side effects can be permanent," Deshmukh said.

Wright said swelling would pose the greatest threat. "Swelling of the brain would typically present as progressive loss of consciousness, or even coma," she said. "The treatment is to correct the hyponatremia, but even treating the sodium levels too rapidly can have complications."

Still, Tuesday's statement on Michaels' website said he was remaining positive and responding well to tests and treatments, and that he remained hospitalized and conscious in critical but stable condition.

"Even though today was a minor setback, doctors remain hopeful for a full recovery and plan to release more specific information next Monday," it read.

Doctors have yet to detail exactly what caused the bleeding in the first place. However, some neurologists have said they are optimistic that Michaels would survive the ordeal -- although the recovery process could take several weeks to months. In a bit of hopeful news, Michaels' father reported that his son could talk Friday, albeit with slurred speech.

He was also reportedly experiencing blurred vision.

"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 balloonlike 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," Deshmukh said. "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."

ABC News' Sheila Marikar contributed to this report.