Ivan diagnosed days after birth

There are several types of cerebral palsy and how badly a person is affected in their daily lives depends on which part of the brain is damaged.

Between around a quarter and a third of children and adolescents, and about one in 10 adults, will also have epilepsy, according to the charity Scope.

Some people with cerebral palsy suffer only minor problems but, as in Ivan's case, others have severe disabilities.

The condition's major effect is that it causes movement problems such as difficulties walking, feeding, talking or using the body.

Some people are unable to sit up without support and require help with feeding.

Depending on which part of the brain is damaged, there may be problems with sight, hearing, perception and accompanying learning difficulties.

People with cerebral palsy often have difficulty controlling their facial expressions.

The main types of cerebral palsy include spastic cerebral palsy, where some of the muscles in the body are tight, stiff and weak.

Athetoid (dyskinetic) cerebral palsy is when control of muscles and posture is disrupted by spontaneous and unwanted movements.

In ataxic cerebral palsy, a sufferer can have problems with balance, shaky movements of hands or feet, and difficulty with speech.

Mixed cerebral palsy is when there is a combination of two or more of the above conditions.

The symptoms of cerebral palsy can take a few months to develop.

David Cameron has said he and his wife Samantha noticed that Ivan was having sudden jerky movements within days of his birth.

About one in 400 babies born in the UK each year will have cerebral palsy and symptoms include stiffness or floppiness of the limbs.

Seven out of 10 cases of the condition are spastic cerebral palsy, where the limbs become stiff and may be drawn in towards the body.

In athetoid cerebral palsy (10% of cases), the person may have involuntary writhing movements.

The first symptoms of cerebral palsy that parents may notice is problems with feeding, such as gagging on food or vomiting.

A youngster may also be slow to crawl or walk and have weakness in their limbs, slowness of speech and a delay in developing social skills with other children or family members.

It used to be thought that cerebral palsy was caused by problems during labour or birth but it is now generally accepted that this only relates to about one in 10 cases.

The most common cause of cerebral palsy is when the developing brain becomes damaged while the baby is growing in the womb.

This may be caused by genetic problems, malformations of the brain and conditions that affect the mother, such as rubella or toxoplasmosis - which is caught from a parasite in undercooked meat, raw meat and cat faeces.

Infections when a baby is young (such as encephalitis or meningitis) can also lead to cerebral palsy.

The condition cannot be cured but treatments and physiotherapy, occupational therapy and speech therapy can help reduce its impact.

Epilepsy, which affects more than 450,000 people in the UK, is defined by having recurrent seizures (sometimes called fits).

A seizure is caused by a sudden burst of excess electrical activity in the brain, which causes disruption to the way messages pass along the body's systems.

The number and type of seizures will vary from person to person and there are many different associated syndromes, some of which are very rare.

Scientists know about 40 different types of seizure and a person may have more than one type.

Sometimes the reasons for epilepsy are known - such as brain damage suffered during a difficult birth or a stroke which starves the brain of oxygen.

However, most people with the condition (60%) will not know the reason behind their epilepsy.

There is no current cure for epilepsy but medication can help control seizures and allow people to live as normal a life as possible.