Former Bantams skipper Stephen Darby has announced he is retiring from the sport after being diagnosed with motor neurone disease (MND).

Here are some key questions and answers about the condition:

- What is MND?

MND describes a group of diseases that affect nerves in the brain and spinal cord, called motor neurones, which send messages to the muscles.

As the messages stop reaching them, the muscles gradually weaken and waste away. This affects how a person talks, eats, drinks and breathes.

- What are the early signs of MND?

The symptoms of MND can appear gradually and may not be obvious at first.

They can include: weakness in the ankles or legs, slurred speech which can develop into difficulty swallowing, a weak grip, muscle cramps and twitches, weight loss and shrinking of arm and leg muscles.

- Who does the condition affect?

MND is very rare, affecting up to 5,000 adults in the UK at any one time.

It is more likely to occur in those who are over the age of 50, but can affect adults of all ages.

- What causes MND?

It is still not clear what causes MND but it is thought a combination of genetic and environmental factors may lead to its development. Research into the disease is ongoing.

- Is there a cure?

Not at the moment. The degenerative condition is always fatal and can significantly shorten life expectancy, but a few people do live for decades. Treatments like a feeding tube or mask to help the individual breathe air may be needed as the condition worsens over time.