Stroke, as the name suggests, is a sudden event where the person may literally be 'struck down' at the tick of a clock by their neurological symptoms. Two major types of stroke exist, ischaemic (a lack of blood flow) and haemorrhagic (a bleed) and their treatments are therefore very different. Time is critical in stroke, and if suspected, emergency treatment is required.
Depending on where the stroke is in the brain, abilities of thinking, or cognition, can be affected, and may occur in combination with classic symptoms such as weakness, tingling or speech difficulty. Symptoms can include altered behaviour, memory loss, mood change, lowered awareness or insight into one's environment, and difficulty with functions such as language interpretation, concentration, and visual perception.
Recovery can be complex, and it takes a dedicated team of health professionals to treat someone who is hospitalised with a major stroke. Symptoms may improve depending on the extent of the stroke, and rehabilitation is often used to stimulate new connections within the brain in order to maximise recovery, sometimes over many months.
The time to act is in fact before stroke occurs - prevention is so important, and to consider discussing steps towards this with your doctor if any concerns.