Per Wiki
In 1988, Biden suffered two brain aneurysms, one on the right side and one the left. Each required surgery with high risk of long-term impact on brain functionality. In February 1988, after suffering from several episodes of increasingly severe neck pain, Biden was taken by long-distance ambulance to Walter Reed Army Medical Center and given lifesaving surgery to correct an intracranial berry aneurysm that had begun leaking.[94][95] While recuperating, he suffered a pulmonary embolism, a major complication.[95]
Another operation to repair a second aneurysm, which had caused no symptoms but was at risk of bursting, was performed in May 1988.[95][96] The hospitalization and recovery kept Biden from his duties in the Senate for seven months.[52] Biden has had no recurrences or effects from the aneurysms since then.[95]
In retrospect, Biden’s family came to believe the early end to his presidential campaign had been a blessing in disguise, for had he still been campaigning in 1988, he might well not have stopped to seek medical attention and the condition might have become unsurvivable.