Next few weeks are key to the recovery process
Quite rightly, Sir Alex Ferguson's family have not disclosed details about his condition following the haemorrhage he suffered. However, the most common form for a man of his age with a history of cardiovascular issues - Sir Alex had a pacemaker fitted in 2003 - is intracerebral, in which there is bleeding within the brain tissue, causing irreparable damage to those cells.
In Sir Alex's case, his surgeons have decided to operate almost certainly because they felt the size of the blood clot was causing damage to the remaining brain tissue. This is often life-saving surgery and aims to reduce any long-term disability Sir Alex might suffer with this form of stroke.
A patient will have suffered the symptoms of a stroke before they have alerted the emergency services. The medical team will stabilise their breathing and then perform a scan to determine if a blood vessel has blocked or burst.
In this instance, it was the latter and bleeding was sufficient to require surgery and the critical care that followed.
Once this first phase of treatment is completed, the medics will try to uncover what caused the bleeding. This is critical to prevent any further bleeding.
There are three potential causes. There may be an abnormality within the brain tissue, a weakening of the blood vessels, or the blood may not be clotting properly. The diagnosis will vary from one patient to another.
For the first few days after the operation, the focus is on the patient's life support.
A prognosis is very hard to give in the first days and often for some weeks.
If they survive without signs of improvement after several months, then it is unlikely an individual will return to their former health. However, in the immediate aftermath there is everything to fight for and the potential for a full recovery, albeit sometimes after a long period of rehabilitation.
Peter Hamlyn is a consultant neurosurgeon