Dr Rudd: says a positive attitude will help recovery

"It does seem to be the case that it's more difficult to get over second and subsequent strokes, compared to the first one, but it does depend on how severe the stroke is, and how the patient reacts to the stroke."

If a person suffers one stroke, they have a 40% chance of having a second one within five years, according to Philip Bath, Stroke Association professor of stroke medicine at the University of Nottingham.

He told BBC News Online the risk would be 15 times that of someone who has not had a stroke.

In addition to her suspected stroke before Christmas, Princess Margaret is known to have had a stroke in 1998.

Effect of a stroke

A stroke occurs because part of the brain is deprived of oxygen either because a blood vessel becomes blocked or bursts.

The resulting effects of the stroke vary enormously depending on which area of the brain is affected.

When stroke patients are admitted to hospital, they receive acute stroke care.

Patients are likely to be asked to make lifestyle changes, such as giving up smoking, cutting back on alcohol, losing weight, reducing cholesterol and doing more exercise.

Doctors may also prescribe aspirin or cholesterol or blood pressure lowering drugs.

Tests are also carried out to see if the arteries in the neck are narrowed, which could mean patients need surgery.

Professor Bath said modern medicine had "quite a potent package" to treat strokes.

After her second suspected stroke in January, it was reported Princess Margaret was having problems swallowing, a side effect suffered by 45% of a stroke victims.

Strokes can damage the complex system if nerves and muscles which control swallowing.

Food can "go down the wrong way" and get into the lungs causing coughing or choking, and in severe cases chest infections and pneumonia.

Dehydration risk

Catherine Collins, chief dietician at St George�s Hospital in London said stroke patients often had trouble controlling liquids in their mouths.

Therefore, there was a risk of dehydration unless fluids were actively administered.

She said losing as little as 2% of the body's normal fluid content made patients drowsy or confused.

Problems eating solids can lead to malnutrition and secondary problems such as reduced resistance to infection and pressure sore risk.

Swallowing is tested as soon as the stroke patient gets to hospital.

Neurologist Professor Peter Sandercock, a stroke expert from the University of Edinburgh, told the BBC: "Patients are normally tested at the bedside.

"If swallowing really is a problem then what we would do is a clinical x-ray, giving them a fluid which appears dark on x-ray.

"Then we can see if they cannot swallow or if fluid is going down the wrong way."

If there are problems, the patient can be fed by mouth, by a tube going into the nose and down to the stomach, or directly into the stomach.

When problems do not clear up in a few days, patients are assessed by speech and language therapists and dieticians.

In January, Princess Margaret was cared for at the exclusive King Edward VII Hospital, where basic rooms cost �365 a night.

An intensive therapy unit can cost from �798 a night, with special nurses, physiotherapy and escorts which the Princess is likely to need, costing extra.

Patients at the hospital, a favourite of the Royal family, are offered luxuries including a comprehensive wine list, and meals are served course by course "to ensure the food is fresh".

But it also offers top-class medical care and one of the highest nurse to patient ratios in the country.