Concerns have arisen over Sen. John McCain’s health after the lawmaker underwent a craniotomy this weekend, with medical experts saying the recovery time for his surgery may delay his return to Washington by a few weeks. While the Senate awaits his return to consider a bill to repeal the Affordable Care Act, neurosurgeons interviewed by The New York Times said the recovery time for such a procedure is usually several weeks—not one week, as a statement from McCain’s office implies. “Usually, a blood clot in this area would be a very concerning issue,” Dr. Nrupen Baxi, an assistant professor of neurosurgery at the Albert Einstein College of Medicine in New York City, told the Times. Other surgeons interviewed said the recovery time may depend on the cause of the clot, which could have been a stroke, a blow to the head, or brain changes tied to aging. McCain’s office has not provided details on what caused the blood clot but said the senator is in “good spirits” after undergoing a “minimally invasive” craniotomy.